OPERATOR’S MANUAL
MST SERIES
POWER MODULE
DIGITALLY CONTROLLED POWER MODULE SYSTEM
1/9 RACK SIZE 200 WATT POWER MODULES
FOR USE WITH KEPCO POWER MODULE CONTROLLERS
MODELS
KEPCO INC.
An ISO 9001 Company.
MST 6-20M, MST 15-12M,
MST 25-8M, MST 36-5M,
MST 36-5MF, MST 55-3.5M,
MST 75-2.5M, MST 100-2M
MST 150-1.2M
IMPORTANT NOTES:
1) This manual is valid for the following Model and associated serial numbers:
MODEL SERIAL NO. REV. NO.
2) A Change Page may be included at the end of the manual. All applicable changes and
revision number changes are documented with reference to the equipment serial numbers. Before using this Instruction Manual, check your equipment serial number to identify
your model. If in doubt, contact your nearest Kepco Representative, or the Kepco Documentation Office in New York, (718) 461-7000, requesting the correct revision for your
particular model and serial number.
3) The contents of this manual are protected by copyright. Reproduction of any part can be
made only with the specific written permission of Kepco, Inc.
Data subject to change without notice.
KEPCO®
©2013, KEPCO, INC
P/N 228-1736 REV 3
KEPCO, INC. ! 131-38 SANFORD AVENUE ! FLUSHING, NY. 11355 U.S.A. ! TEL (718) 461-7000 ! FAX (718) 767-1102
email: hq@kepcopower.com
! World Wide Web: http://www.kepcopower.com
THE POWER SUPPLIER™
Declaration of Conformity
Application of Council directives:
Standard to which Conformity is declared:
EN61010-1:2001 (Safety requirements for electrical equipment for measurement,
control and laboratory use - Part 1)
Manufacturer's Name and Address:
Importer's Name and Address:
Type of Equipment:
Model No.:
73/23/EEC (LVD)
93/68/EEC (CE mark)
KEPCO INC.
131-38 SANFORD AVENUE
FLUSHING, N.Y. 11355 USA
P
O
C
E
V
I
T
A
T
N
E
S
E
R
P
E
R
Component Power Supply
[PRODUCT MODEL NUMBER]
Y
Year of Manufacture:
I, the undersigned, declare that the product specified above, when used in conjunction with the conditions of conformance set forth in the product instruction manual, complies with the requirements of the
Low Voltage Directive 73/23/EEC, which forms the basis for application of the CE Mark to this product.
Place: KEPCO Inc.
131-38 Sanford Ave.
Flushing, N.Y.11355 USA
Saul Kupferberg
(Full Name)
Date:
228-1348 DC-COMP/INST 061813 A
VP OF SALES
(position)
Conditions of Conformance
MST “Modular” products
When this product is used in applications governed by the requirements of the EEC, the following restrictions and conditions apply:
1. For European applications, requiring compliance to the Low Voltage Directive, 73/23/EEC, this power
supply is considered a component product, designed for “built in” applications. Because it is incomplete in construction, the end product enclosure must provide for compliance to any remaining electrical safety requirements and act as a fire enclosure. (EN61010-1:2001 Cl. 6, Cl. 7, Cl.8, and Cl. 9)
2. This power supply is designed for stationary installation, with mains power applied via a KEPCO Rack
Adapter.
3. This power supply is considered a Class 1 (earthed) product. It is intended for use as part of equipment meant for test, measurement and laboratory use, and is designed to operate from single phase,
three wire power systems. This equipment must be installed in a specifically designed KEPCO rack
adapter and within a suitably wired equipment rack, utilizing a three wire (grounded) mains connection.
See wiring section of this manual for complete electrical wiring instructions. (EN61010-1:2001
Cl.6.10.1)
4. This power supply has secondary output circuits that are considered hazardous.
5. The output wiring terminals of this power supply have not been evaluated for field wiring and, therefore, must be properly configured by the end product manufacturer prior to use.
6. This power supply employs a supplementary circuit protector in the form of a fuse mounted within its
enclosure. The fuse protects the power supply itself from damage in the event of a fault condition. For
complete circuit protection of the end product, as well as the building wiring, it is required that a primary circuit protection device be fitted to the branch circuit wiring. (EN61010-1:2001 Cl. 9.5)
7. Hazardous voltages are present within this power supply during normal operation. All operator adjustments to the product are made via externally accessible switches, controls and signal lines as specified within the product operating instructions. There are no user or operator serviceable parts within
the product enclosure. Refer all servicing to qualified and trained Kepco service technicians.
B 228-1364 COND/CONFORM 061813
SAFETY INSTRUCTIONS
1. Installation, Operation and Service Precautions
This product is designed for use in accordance with EN 61010-1 and UL 3101 for Installation Category 2,
Pollution Degree 2. Hazardous voltages are present within this product during normal operation. This
product is designed for use in a KEPCO Rack Adapter product. Operation of this product without a rack
adapter should never be attempted. The product should never be operated with the cover removed
unless equivalent protection of the operator from accidental contact with hazardous internal voltages is
provided.
!
!
!
There are no operator serviceable parts or adjustments within the product enclosure.
Refer all servicing to trained service technician.
Source power must be removed from the product prior to performing any servicing.
This product is designed for use with nominal a-c mains voltages indicated on the
rating nameplate.
2. Grounding
This product is a Class 1 device which utilizes protective earthing to ensure operator safety.
The PROTECTIVE EARTHING CONDUCTOR TERMINAL must be properly con-
!
nected prior to application of source power to the product (see instructions on installation herein) in order to ensure safety from electric shock.
PROTECTIVE EARTHING CONDUCTOR TERMINAL - This symbol indicates the
point on the product to which the protective earthing conductor must be attached.
EARTH (GROUND) TERMINAL - This symbol is used to indicate a point which is
connected to the PROTECTIVE EARTHING TERMINAL. The component installer/
assembler must ensure that this point is connected to the PROTECTIVE EARTHING TERMINAL.
CHASSIS TERMINAL -This symbol indicates frame (chassis) connection, which is
supplied as a point of convenience for performance purposes (see instructions on
grounding herein). This is not to be confused with the protective earthing point, and
may not be used in place of it.
3. Electric Shock Hazards
This product outputs hazardous voltage and energy levels as a function of normal operation. Operators
must be trained in its use and exercise caution as well as common sense during use to prevent accidental
shock.
This symbol appears adjacent to any external terminals at which hazardous voltage
!
228-1369 SAFETY - (MST) 061813 C/(D Blank)
levels as high as 500V d-c may exist in the course of normal or single fault conditions.
This symbol appears adjacent to any external terminals at which hazardous voltage
levels in excess of 500V d-c may exist in the course of normal or single fault conditions.
TABLE OF CONTENTS
SECTION PAGE
SECTION 1 - INTRODUCTION
1.1 Scope of Manual ..................................................................................................................................... 1-1
1.2 Description .............................................................................................................................................. 1-1
1.3 Specifications .......................................................................................................................................... 1-1
1.4 Features .................................................................................................................................................. 1-3
1.4.1 Control/Programming......................................................................................................................... 1-3
1.4.2 Status Indicators................................................................................................................................ 1-6
1.4.3 Front Panel Meters ............................................................................................................................ 1-6
1.4.4 Output Enable/Disable and Polarity Reversal.................................................................................... 1-6
1.4.5 Protection........................................................................................................................................... 1-6
1.4.6 Series Configurations ........................................................................................................................ 1-6
1.4.7 Parallel Configuration ........................................................................................................................ 1-7
1.5 Options .................................................................................................................................................... 1-7
1.6 Accessories ............................................................................................................................................. 1-7
SECTION 2 - INSTALLATION
2.1 Unpacking and Inspection ....................................................................................................................... 2-1
2.2 Terminations and Controls ...................................................................................................................... 2-1
2.3 A-C Input Requirement............................................................................................................................ 2-1
2.4 Cooling .................................................................................................................................................... 2-1
2.5 Preliminary Check-out ............................................................................................................................. 2-3
2.5.1 Required Equipment .......................................................................................................................... 2-3
2.5.2 Initial Setup........................................................................................................................................ 2-3
2.5.3 Checkout Procedure.......................................................................................................................... 2-5
2.6 Installation/Removal ................................................................................................................................ 2-7
2.6.1 Changing Control Bus Address (Node or Channel Number) ............................................................. 2-7
2.6.2 Installation.......................................................................................................................................... 2-9
2.6.3 Removal............................................................................................................................................. 2-10
2.7 Grounding................................................................................................................................................ 2-10
2.7.1 Safety Grounding............................................................................................................................... 2-10
2.7.2 D-C (Output) Grounding .................................................................................................................... 2-10
2.8 Power Module to Load Interface ............................................................................................................. 2-11
2.9 Connection, General ............................................................................................................................... 2-12
2.9.1 Load Connection with Local Error Sensing........................................................................................ 2-12
2.9.2 Load Connection with Remote Error Sensing.................................................................................... 2-13
SECTION 3 - OPERATION
3.1 Introduction to Controlling the MST Power Module Output ..................................................................... 3-1
3.1.1 Status Flags (Error Messages).......................................................................................................... 3-1
3.1.2 Timing Requirements for a Valid Status ............................................................................................ 3-1
3.2 Operating Modes..................................................................................................................................... 3-2
3.2.1 Voltage Mode..................................................................................................................................... 3-2
3.2.2 Current Mode..................................................................................................................................... 3-2
3.3 Output Polarity Reversal ......................................................................................................................... 3-2
3.4 Output Enable and Disable ..................................................................................................................... 3-4
3.5 Parallel Operation.................................................................................................................................... 3-5
3.6 Series Operation ..................................................................................................................................... 3-5
3.7 Fault Protection ....................................................................................................................................... 3-6
3.7.1 Fault Recovery................................................................................................................................... 3-6
3.7.2 Tracking Overvoltage and Overcurrent Detectors ............................................................................. 3-6
3.7.3 Overtemperature Detectors ............................................................................................................... 3-7
3.7.4 A-C Loss Detector ............................................................................................................................. 3-7
3.7.5 Open Sense/Power Wire Protection .................................................................................................. 3-7
3.8 Calibration ............................................................................................................................................... 3-8
MST SERIES 061813 i
TABLE OF CONTENTS
SECTION PAGE
3.8.1 Equipment Required ......................................................................................................................... 3-8
3.8.2 +5 Volts Reference Adjust (R49) ...................................................................................................... 3-9
3.8.3 Output Voltage (EO) Zero Adjust (R11) ............................................................................................ 3-10
3.8.4 Current Sense Zero Adjust (R50) ..................................................................................................... 3-10
3.8.5 Output Current I
3.8.6 Voltage Reference Adjust (R47) ....................................................................................................... 3-11
3.8.7 Current Reference Adjust (R48) ....................................................................................................... 3-11
3.8.8 Current (I
O
Zero Adjust (R51) ................................................................................................ 3-10
O
) Full Scale Adjust (R52) ................................................................................................. 3-11
ii MST SERIES 061813
LIST OF FIGURES
FIGURE TITLE PAGE
1-1 MST Power Supply .............................................................................................................................. iv
1-2 MST Power Supply, Mechanical Outline Drawing ................................................................................ 1-4
1-3 Remotely Controlled Power Supply Configurations Using Kepco Products ......................................... 1-5
2-1 Front and Rear Views of the MST Power Module................................................................................. 2-2
2-2 DC Output Connector Configuration for Preliminary Checkout............................................................. 2-3
2-3 Initial Checkout Setup ........................................................................................................................... 2-4
2-4 Configuration and Calibration Controls and Testpoints ........................................................................ 2-9
2-5 Output Impedance vs. Frequency......................................................................................................... 2-11
2-6 Connector Locations and Pin Assignments .......................................................................................... 2-13
3-1 Calibration Test Set-up ......................................................................................................................... 3-9
LIST OF TABLES
TABLE TITLE PAGE
1-1 MST Model Parameters ........................................................................................................................1-1
1-2 MST General Specifications .................................................................................................................1-2
1-3 Accessories ...........................................................................................................................................1-7
2-1 Functions of Internal Controls ...............................................................................................................2-1
2-2 Front Panel Controls and Indicators .....................................................................................................2-2
2-3 Rear Terminations ................................................................................................................................2-3
2-4 Node Address Selection .......................................................................................................................2-8
2-5 DC Output Connector Pin Designations ...............................................................................................2-12
3-1 Error Messages .....................................................................................................................................3-1
3-2 Maximum External Capacitance Values to Ensure Dry Switching ........................................................3-3
MST SERIES 061813
iii
FIGURE 1-1. MST POWER SUPPLY
iv MST SERIES 061813
FIGURE 0-1.
SECTION 1 - INTRODUCTION
1.1 SCOPE OF MANUAL
This manual contains instructions for the installation, operation, and maintenance of the MST
series of 200 Watt, voltage and current stabilized d-c power supplies (power modules) manufactured by Kepco, Inc., Flushing, New York, U.S.A.
1.2 DESCRIPTION
The Kepco MST 200 Watt Series (Figure 1-1) consists of eight, single-output models as shown
in Table 1-1. MST Series Power Modules employ a switch mode preregulator for high efficiency
and power density, with linear output stabilization for accuracy and resolution. MST Power Supplies (Modules) are of a modular, plug-in design whose 7" x 1-3/4” cross-section allows nine
independently controlled modules to be mounted abreast in a standard (19" x 7" x 20.9") Kepco
Model RA 55 rack adapter or 5 modules in a standard (9.6” x 7” x 20.9”) Kepco Model CA 400
case.
The MST Power Module is controlled digitally via the IEEE 1118 2-wire serial bus (“Bitbus”) with
12 bits of resolution over the entire voltage and current ranges. Voltage and current are displayed on LED panel meters, and read back over the control bus with an accuracy of 0.06%.
Operating status is displayed on front panel LED indicators and read back over the bus.
An MST Power Module can be installed without powering down the system. Employing current-sharing for parallel operation, they may be “hot-swapped” for redundant (N+1) applications.
MST Power Supplies can be operated with universal a-c input power sources (90-264Vac,
47-63Hz) and incorporate power factor correction (0.98) to meet EN 61000-3-2. MST Power
Modules can also be configured in series for higher than rated output voltages (500V d-c maximum).
TABLE 1-1. MST MODEL PARAMETERS
OUTPUT
VOLTAGE
MODEL
MST 6-20M 0-6 20 16 12 2.5 5 50 51%
MST 15-12M 0-15 12 9.6 7.2 5 10 100 61%
MST 25-8M 0-25 8 6.4 4.8 5 10 100 62%
MST 36-5M 0-36 5 4.0 3.0 5 10 100 63%
MST 55-3.5M 0-55 3.5 2.8 2.1 5 10 100 64%
MST 75.2.5M 0-75 2.5 2.0 1.5 7.5 15 150 64%
MST 100-2M 0-100 2.0 1.6 1.2 7.5 15 150 66%
MST 150-1.2M 0-150 1.2 1.0 0.7 7.5 20 200 66%
Adjustment
Range
(V d-c)
OUTPUT CURRENT
Maximum (Amps)
45° C55° C65° C
Source
(max.)
RIPPLE
(mV p-p)
SW
(max.)
NOISE
(mV p-p)
(Spike)
20MHz
EFFICIENCY
(100% Load
120V a-c)
1.3 SPECIFICATIONS
The MST Series electrical and mechanical specifications are listed in Tables 1-1 and 1-2.
MST SERIES 061813 1-1
.
TABLE 1-2. MST GENERAL SPECIFICATIONS
SPECIFICATIONS RATING/DESCRIPTION
INPUT
A-C Voltage
Frequency
Input Current maximum 3.6A rms 90V a-c Input
Current Harmonics Within EN 61000-3-2 limits Any source condition, rated load
Efficiency minimum See Model Table 1-1 120V a-c, rated output Load
EMI FCC Class A, CISPR 11 Class A Conducted Emissions
Leakage Current
Power Factor 0.98 min. All source conditions, full load
EMC Complies with IEC 61326-1, Class A
Source Effect Voltage 0.001%
Load Effect
Temperature Effect Voltage 0.01%/ °C
Time Effect (drift) Voltage 0.01%
Programming
Resolution
Data Read Back
Accuracy
Transient Recovery Time 100 Microseconds
Turn On/Off Overshoot None Any source/load condition
Error Sense 0.5V maximum/wire Any source/load condition
Temperature 0 ° to +65° C, start from –20°C (see Table 1-1) Operating
Humidity 0 to 95% RH Non-condensing Operating &
Shock 20G 11 msec ±50% half sine 3 axes, 3 shocks each axis,
Vibration 5 – 10Hz 10mm double amplitude
Altitude Sea level to 10,000 ft. Any source/load condition
Isolation (Output – Case) ±500 V d-c
Display Voltage 3.5 Digit LED, red
(1) Current mode regulation is subject to an additional 0.015% settling effect as well as a d-c offset of up to 3mA based on compliance voltage
nominal 100-250V a-c Single phase
range 90-264 Va-c Brownout Voltage
nominal 50-60 Hz At >63 Hz, input leakage current
range 47 – 63 Hz (400 Hz)
120V a-c,
240V a-c,
Current 0.005%
Voltage ±0.002% or 0.5mV, whichever is greater
Current
Current 0.02%/ °C
Current 0.02%
Voltage 12 Bits, 0.024% % of E
Current 12 Bits, 0.024% % of I
Voltage 0.1% % of E
Current 0.12% % of I
Current 3.5 Digit LED, red
<0.5 mA
60Hz
<1.0 mA
50Hz
OUTPUT
±0.005%
(500 Microseconds for MST 6-20M)
MISCELLANEOUS
–40° to +85° C Storage
10 – 55 Hz 2G
(1)
exceeds specifications
90 – 132, 176 – 264V a-c,
any load condition
10% to 100% Load at E
any source condition
10% to 100% Load at I
Return to within stabilization
band from 50% load step
Storage
non-operating
Non-operating, 1 hour each axis
CONDITION
≤ 85Vrms
MAX
MAX
Any source/load condition
(0 – 45° C)
0.5 – 8.5 hours
Any source/load condition
MAX
MAX
MAX
MAX
Front panel,
For reference only
,
1-2 MST SERIES 061813
TABLE 1-2. MST GENERAL SPECIFICATIONS (CONTINUED)
SPECIFICATIONS RATING/DESCRIPTION
Status Indicators Voltage Mode Green LED
Current Mode Amber LED
Current Share Amber LED
Output Enabled Green LED
Polarity Reversed Green LED
Output Fault Red LED
Output Enable Built in power and sense relay
Polarity Reversal Built in power and sense relay
Parallel Connection N+1 redundancy, forced current share Currents divided equally
Overvoltage protection Tracks output setting, power shutdown
Overtemperature Thermostat
Open sense wire Automatic detection with power shutdown
Backup current limit Tracks output current at 110%
PHYSICAL
Type of Construction
Cooling Internal D-C Cooling Fans Exhaust to rear
Module
Dimensions
Weight
Load Connection
Source Connection
English 7” x 1.83” x 20”
Metric 178 x 46.5 x 508 mm
English 8 lbs.
Metric 3.6 Kg.
Enclosed, plug-in style includes status LEDs, two digital
meters, handle and ON/OFF switch
Mates with Positronic POW-R-LOK Series 6 pin connector, Kepco P/N 143-0458 (See Figure 2-6 and Table 2-5),
Mates with Molex Minifit, Jr. Series 10 pin connector,
Kepco p/n 143-0544 (See Figure 2-6)
Mating connectors provided with
MST compatible rack adapters
Mates with a-c backplane in
MST compatible rack adapters
CONDITION
Latched, reset
by cycling source
power off
Refer to Figure 1-2
1.4 FEATURES
1.4.1 CONTROL/PROGRAMMING
Control of the MST Power Module is via the IEEE 1118 2-wire serial bus operating at 375KHz;
as many as 27 separate modules of either the MST, MAT, MBT or BOP Series design can be
addressed via the bus (see Figure 1-3). Decoders for RS232, IEEE-488 and VXI are available in
modular form and stand-alone types. As shown in Figure 1-3, the following controllers are available to control of MST (and MAT) Power Modules directly from a computer.
a. Controller Model TMA PC-27 plugs into a half-card slot of a DOS-based PC and allows key-
board control of the MST via the IEEE 1118 bus.
b. Controller Model TMA 4882-27 is free-standing and allows host computers designed for
RS232 or IEEE 488 bus communication to control the MST via the IEEE 1118 bus.
c. Controller Model TMA-VXI-27 plugs into a slot in a VXI chassis and allows VXI-based com-
puters to control the MST via the IEEE 1118 bus.
d. Controller Model MST 488-27 plugs into a slot in a Model RA 55 Rack Adapter and allows
host computers designed for RS232 or IEEE 488 bus communication to control the MST via
the IEEE 1118 bus.
e. The MST Power Module can also be directly controlled via the keypad of the MBT Series
(“G” Option) Power Supply via the IEEE 1118 bus.
MST SERIES 061813 1-3
FIGURE 1-2. MST POWER SUPPLY, MECHANICAL OUTLINE DRAWING
1-4 MST SERIES 061813
MST SERIES 061813 1-5
FIGURE 1-3. REMOTELY CONTROLLED POWER SUPPLY CONFIGURATIONS USING KEPCO PRODUCTS
1.4.2 STATUS INDICATORS
Six status indicators at the front panel provide operational information (see Table 2-2):
• VOLTAGE MODE
• CURRENT MODE
• CURRENT SHARE
• OUTPUT ENABLED
• POLARITY REVERSED
•OUTPUT FAULT
1.4.3 FRONT PANEL METERS
Two digital meters at the front panel provide displays of output voltage and current. These displays show 3.5 digits and are provided for reference only, accurate to 0.5% (typical) for voltage
and 1.5% (typical) for current.
1.4.4 OUTPUT ENABLE/DISABLE AND POLARITY REVERSAL
The MST Power Module features integral relays to enable/disable the output and to allow polarity reversal. Separate relays are provided for power and sense connections. Disabling the MST
as a voltage source means opening the connection between the power supply and its load. Disabling the MST as a current source means shorting the power supply's output terminals. The
polarity reversal relays provide for two-quadrant operation.
1.4.5 PROTECTION
The MST Power Module incorporates the following protection circuits which cause the MST to
automatically isolate the load and force power module output voltage and current to zero.
• Overvoltage protection: Tracks output voltage; activated if the output goes out of tolerance (see PAR. 3.7.2).
• Overcurrent protection: Tracks output current; activated if the output goes out of tolerance (see PAR. 3.7.2).
• Overtemperature: Activated when the internal temperature exceeds a safe operating
threshold (see PAR. 3.7.3).
• AC loss: Activated if loss of source power detected (see PAR. 3.7.4).
• Open power lead and sense wire: Activated if an open sense wire or open power lead is
detected (see PAR. 3.7.5).
1.4.6 SERIES CONFIGURATIONS
The output of the MST Power Module “floats;” so that MST Power Modules can be connected in
series to obtain higher output voltages, up to a maximum of ± 500 Volts referenced to the chassis (see PAR. 3.6).
1-6 MST SERIES 061813
1.4.7 PARALLEL CONFIGURATION
A parallel configuration may be employed for higher output current and for N + 1 redundant,
“hot-swap” applications. When connected in a parallel configuration, MST Power Modules
employ forced current sharing to ensure equal distribution of the load among all power modules,
improving performance, reducing component stress, and increasing reliability (see PAR. 3.5).
1.5 OPTIONS
The F option (F appended to the Model Number, e.g., MST 6-20MF) incorporates additional filtering to provide significant output noise reduction in the range of 1KHz to 10MHz. Contact
Kepco Sales Engineering for additional information regarding performance and availability.
1.6 ACCESSORIES
The MST Power Module is designed for installation in Kepco Rack Adapter Model RA 55 which
accommodates nine 1/9 rack size power modules. With a 1/9 rack Controller module installed,
the RA55 will accommodate eight 1/9 rack power modules. Connecting cables and IEEE 1118
bus daisy chain terminations are supplied with the RA 55 Rack Adapter. Additional accessories
are listed in Table 1-3.
TABLE 1-3. ACCESSORIES
ACCESSORY PART NUMBER
MATING CONNECTOR
(DC OUTPUT)
LOAD CONNECTOR PINS 107-0327 Replacement pins for DC OUTPUT connector.
LOAD CABLE 118-0849 Allows output load connections of up to 20 Amperes to MST
INPUT POWER/COMMUNICATION
CABLE
142-0372
118-0850 Allows power and communication connections to MST
Mates with DC OUTPUT connector, Kepco P/N 143-0457
(Positronic POW-R-LOK Series 6 pin connector).
power module not installed in RA 55 Rack Adapter (for
advanced troubleshooting). Cable length is approximately 7
feet, terminated at one end with mating connector for MST
module output connector. The opposite end is terminated
with two hook lugs for the power connections, as well as a
ring lug for the load sharing connection. Error sensing is
established at the hook lug terminals. This cable is typically
used in conjunction with 118-0850 Input Power/Communication Cable.
power module not installed in RA 55 Rack Adapter (for
advanced troubleshooting). Cable length is approximately 7
feet, terminated at one end with mating connector for MST
module a-c input/control bus connector. The opposite end of
the cable is split into two terminations, one a NEMA 5-20P
a-c mains plug and the other a 9-pin D-sub connector that
mates with the control bus connector of RA 55 (as well as
CA 400, MST 488-27 or TMA 4882-27). This cable is typically used in conjunction with 118-0849 Output Load Cable.
USE
MST SERIES 061813 1-7/(1-8 Blank)
SECTION 2 - INSTALLATION
2.1 UNPACKING AND INSPECTION
This instrument has been thoroughly inspected and tested prior to packing and is ready for
operation. After careful unpacking, inspect for shipping damage before attempting to operate.
Perform the preliminary operational check as outlined in PAR. 2.5. If any indication of damage is
found, file an immediate claim with the responsible transport service.
If the Power Modules are shipped pre-installed in the RA 55 Rack Adapter, each
module is secured to the RA 55 Rack Adapter by two shipping screws. These
screws must be removed from the bottom of the rack adapter, otherwise the modules cannot be removed from the rack adapter.
2.2 TERMINATIONS AND CONTROLS
a. Internal Calibration Controls: Refer to Figure 2-4 and Table 2-1.
b. Front Panel: Refer to Figure 2-1 and Table 2-2.
c. Rear Panel: Refer to Figure 2-1 and Table 2-3.
TABLE 2-1. FUNCTIONS OF INTERNAL CONTROLS
NOTE
REFERENCE
DESIGNATION
R49 +5 V REF This is a primary adjustment for the analog circuits.
R11
R51
R50 Current Sensing Zero This adjustment calibrates the current monitor amplifier to zero.
R52 Full Scale Current Adjust This adjustment calibrates the programmed full scale value.
R47
R48
CONTROL PURPOSE
EO Zero
IO Zero
V
REF
I
REF
This control is used to adjust the output voltage of the Power Module to
zero. E
This control is used to adjust the output current of the Power Module to
zero. I
This is a full scale voltage adjustment.
This is a current read back accuracy adjustment.
calibrates the Power Module in the Voltage mode.
O Zero
calibrates the Power Module in the Current mode.
O Zero
2.3 A-C INPUT REQUIREMENT
MST Power Modules operate from single-phase a-c mains power over the specified voltage and
frequency ranges without adjustment or modification.
2.4 COOLING
The power transistors and rectifiers in the MST Power Module are maintained within their operating temperature range by means of internal heat sink assemblies cooled by internal fans.
PANEL OPENINGS AND THE TOP OF THE CASE MUST BE KEPT CLEAR FROM
OBSTRUCTIONS TO INSURE PROPER AIR CIRCULATION. Maximum ambient temperature
for installed MST modules is 45°C. See technical manuals for RA 55 or CA 400 rack adapters
MST SERIES 061813 2-1
for detailed cooling requirements. Periodic cleaning of the power module interior is recommended.
TABLE 2-2. FRONT PANEL CONTROLS AND INDICATORS
CONTROL/INDICATOR FUNCTION
POWER switch Turns a-c power ON/OFF. CAUTION: DO NOT repeatedly toggle the POWER
On/Off switch as this may cause unit to fault.
VOLTAGE MODE indicator - green LED Goes on to indicate MST is operating as a voltage source (see PAR. 3.2.1).
CURRENT MODE indicator -amber LED Goes on to indicate MST is operating as a current source (see PAR. 3.2.2).
POLARITY REVERSED indicator - green LED Goes on when negative output programmed while the output is enabled.(see
OUTPUT ENABLE indicator - green LED Goes on to indicate power relays are closed and output regulator is enabled
OUTPUT FAULT indicator - red LED Goes on to indicate internal power module fault detected (see PAR. 3.7).
CURRENT SHARE indicator - amber LED Goes on to indicate that unit is operating as “slave” module when used in a
VOLTS meter Displays output voltage.
AMPS meter Displays output current.
PAR. 3.3).
(see PAR. 3.4).
parallel configuration (see PAR. 3.5).
FIGURE 2-1. FRONT AND REAR VIEWS OF THE MST POWER MODULE
2-2 MST SERIES 061813
TABLE 2-3. REAR TERMINATIONS
REAR TERMINATION FUNCTION
AC Input/Control Bus connector Connects the MST Power Module to single-phase a-c power, safety ground, and two-
wire IEEE 1118 bi-directional Control Bus.
DC output connector Connects the MST Power Module output lines, sensing lines, frame ground lines and
current share bus to the load.
2.5 PRELIMINARY CHECK-OUT
2.5.1 REQUIRED EQUIPMENT
• Host computer w/communication cable for selected controller
• Kepco Controller (See PAR. 1.4.1).
• RA 55 or CA 400 rack adapter; alternative is to use Input Power/Communication Cable
(see Table 1-3)
• Load Interface Cable or mating load connector (see Table 1-3)
• Digital Voltmeter (DVM)
• Switch (SPST) rated 32V d-c, 1A
2.5.2 INITIAL SETUP
Initial set-up is as follows (See Figure 2-3):
1. Connect the Unit under test (UUT) to the computer/controller interface (refer to the appropriate Controller Instruction Manual and to the Rack Adapter (RA 55 or CA 400) Instruction
Manual for source power connections). NOTE: An Alternative configuration using the Input
Power Communication cable in place of the rack adapter may be used.
2. Install the MST Power Module into a vacant rack adapter slot (see PAR. 2.6.2).
3. Configure the Load Interface Cable as shown in Figure 2-2. If the Load Interface Cable is not
available, wire load mating connector as shown in Figure 2-2.
FIGURE 2-2. DC OUTPUT CONNECTOR CONFIGURATION FOR PRELIMINARY CHECKOUT
CAUTION: DO NOT repeatedly toggle the power ON/OFF switch as this may cause unit to fault.
4. Apply a-c power first to the MST power module(s) by setting Power ON/OFF switch on front
panel to ON., then apply a-c power to the Controller.
5. Set switch S1 (Figure 2-3) to CLOSE SENSE position.
MST SERIES 061813 2-3
NOTE: If the sequence in step 4, above, is reversed (i.e., a-c power applied to the Controller
first and MST power modules last), the operator must send an IEEE 488 Device Clear
command via the Host Computer prior to issuing other commands.
For proper time delays between commands refer to PAR. 3.1.2. For details on the CIIL or SCPI
commands, refer to the Instruction Manual for the applicable controller (see PAR. 1.4.1).
FIGURE 2-3. INITIAL CHECKOUT SETUP
2-4 MST SERIES 061813
2.5.3 CHECKOUT PROCEDURE
The following checkout procedure requires commands to be issued by the host computer in
order to program the power module or read back information (voltage, current or status) from
the power module; it does not include the IEEE 488 Bus Commands.
NOTE: The following procedure provides specific SCPI and CIIL commands where necessary
to implement the applicable step. These commands are for a Model MST 36-5M Power
Module set to Control Bus Address 1 (the factory default setting); for addresses other
than 1, change commands accordingly (see applicable Controller Instruction Manual
for details).
1. Issue commands from the host computer to initialize the Power Module.
SCPI COMMAND CIIL COMMAND
*RST DCL
NOTE: Both SCPI and CIIL commands must be issued in the proper syntax; incorrect syntax
can result in the Power Module being “locked out” from accepting further commands. If
this occurs, initialize the power module (see step 1 above). If the “locked out” condition
persists, turn off MST power for approximately 10 seconds, then reapply power. (Refer
to applicable Controller Instruction Manual for details regarding syntax.)
2. Issue commands from the host computer to set the MST Power Module to Voltage Mode,
program output voltage to +E
, current limit to I
MAX
and enable the output.
MAX
SCPI COMMANDS CIIL COMMANDS
FUNC1:MODE VOLT
VOLT1 36; CURR1 5; OUTP ON
NOTE: E
is the maximum output voltage of the unit listed in Table 1-1; I
MAX
FNC DCS :CH1 SET VOLT 36 SET CURL 5
CLS :CH1
is the maxi-
MAX
mum output current of the unit as listed in Table 1-1 for 45° C.
3. Verify that VOLTAGE MODE and OUTPUT ENABLED indicators on front panel are on and
VOLTS meter on front panel indicates E
MAX
.
4. Connect DVM across pins 5 (+) and 2 (–) of the DC Output connector (Figure 2-3) and verify
that DVM reads +E
MAX
.
5. Issue commands from the host computer to read back voltage; verify that readback voltage
is +E
MEAS1:VOLT? FNC DCS VOLT :CH1
MAX
.
SCPI COMMANDS CIIL COMMANDS
INX VOLT
FTH VOLT
6. Set switch S1 (Figure 2-3) to OPEN SENSE position. Verify that front panel OUTPUT
ENABLED indicator is off, and VOLTS meter reads 0V.
7. Issue commands from the host computer to check Status and verify status reads DEV Load
Path Fault (CIIL) or Relay Error (SCPI); refer to PAR. 3.1.1.
MST SERIES 061813 2-5
8. Verify that DVM connected across pins 5 and 2 of DC Output connector reads 0V.
9. Set switch S1 to CLOSE SENSE position and issue commands from the host computer to
set the MST Power Module to Voltage Mode, program output voltage to –E
to I
and enable the output.
MAX
SCPI COMMANDS CIIL COMMANDS
, current limit
MAX
FUNC1:MODE VOLT
VOLT1 –36; CURR1 5; OUTP ON
FNC DCS :CH1 SET VOLT –36 SET CURL 5
CLS :CH1
10.Verify that VOLTAGE MODE, POLARITY REVERSED and OUTPUT ENABLED indicators
on front panel are on and VOLTS meter on front panel indicates E
MAX
.
11. Connect DVM across pins 5 (+) and 2 (–) of the DC Output connector (Figure 2-3) and verify
that DVM reads –E
MAX
.
12.Issue commands from the host computer to read back voltage; verify that readback voltage
is –E
MEAS1:VOLT? FNC DCS VOLT :CH1
MAX
.
SCPI COMMANDS CIIL COMMANDS
INX VOLT
FTH VOLT
13.Set switch S1 (Figure 2-3) to OPEN SENSE position. Verify that front panel OUTPUT
ENABLED indicator is off, and VOLTS meter reads 0V.
14.Verify that DVM connected across pins 5 and 2 of DC Output connector reads 0V.
15.Set switch S1 to CLOSE SENSE position and issue commands from the host computer to
set the MST Power Module to Current Mode, program output current to I
limit to +E
MAX
.
and voltage
MAX
SCPI COMMANDS CIIL COMMANDS
FUNC1:MODE CURR
CURR1 5; VOLT1 36
FNC DCS :CH1 SET CURR 5 SET VLTL 36
16.Verify that CURRENT MODE indicator on front panel is on and AMPS meter on front panel
indicates I
MAX
.
17.Issue commands from the host computer to read back current; verify that read back current
is I
MEAS1:CURR? FNC DCS CURR :CH1
MAX
.
SCPI COMMANDS CIIL COMMANDS
INX CURR
FTH CURR
2-6 MST SERIES 061813
2.6 INSTALLATION/REMOVAL
The MST Power Module is designed to be rack-mounted in an RA 55 Rack Adapter. Refer to
Figure 1-2 for outline dimensions. For installation in confined spaces, care must be taken that
the surrounding environment does not exceed the maximum specified ambient temperature
(45° C); see PAR. 2.4. The MST Power Module may be shipped either individually, or already
installed in an RA 55 Rack Adapter. Follow power module installation procedures in RA 55
Instruction Manual.
2.6.1 CHANGING CONTROL BUS ADDRESS (NODE OR CHANNEL NUMBER)
Each MST Power Module connected to the IEEE 1118 bus must have a unique address (also
referred to as node or channel number). The address from 1 to 31 is selected by DIP selector
switch S1 accessed through the top of the unit (see Figure 2-4) and can be changed in accordance with Table 2-4. This address is set at Kepco to 1.
NOTE: Although 31 unique addresses are provided, the maximum number of instruments which
can be managed by the Kepco Controller is 27.
MST SERIES 061813 2-7
TABLE 2-4. NODE ADDRESS SELECTION
SELECTOR SWITCH SECTION
DECIMAL
ADDRESS
100001
200010
300011
400100
500101
600110
700111
801000
901001
1001010
1101011
1201100
1301101
1401110
1501111
1610000
1710001
1810010
1910011
2010100
2110101
2210110
2310111
2411000
2511001
2611010
2711011
2811100
2911101
3011110
3111111
A3S1-4
(A4)
A3S1-3
(A3)
(SIGNAL LINE)
A3S1-2
(A2)
A3S1-1
(A1)
A3S1-0
(A0)
NOTE: If the Power Module is already installed in a Rack Adapter and it is necessary to
change the control bus address, the Power Module must first be removed from the
Rack Adapter as described in PAR. 2.6.3 below.
2-8 MST SERIES 061813
FIGURE 2-4. CONFIGURATION AND CALIBRATION CONTROLS AND TESTPOINTS
2.6.2 INSTALLATION
To install the MST Power Module in the RA 55 Rack Adapter or CA 400 case, proceed as follows:
1. The factory setting for the control bus address is 1; if address 1 is already in use, refer to
PAR. 2.6.1 to change the address setting.
NOTE: If the Power Module is already installed in a Rack Adapter and it is necessary to
change the control bus address, the Power Module must first be removed from the
Rack Adapter as described in PAR. 2.6.3 below.
2. To ensure full engagement of the module interconnect to the RA 55 Rack Adapter or CA 400
case, pull out the two slotted captive thumb screws (at the front of the Module) and turn
counterclockwise until the threads engage.
MST SERIES 061813 2-9
3. Align slots of the Module with the guides of the Rack Adapter and insert Module into Rack
Adapter slot. Secure with the two thumb screws (maximum torque applied to thumb screws
is 10 foot-lbs).
2.6.3 REMOVAL
To remove the Power Module from the RA 55 Rack Adapter or CA 400 case, proceed as follows:
When removing a Module from a Rack Adapter under power, the Module POWER switch
must be placed in the OFF position prior to extraction.
1. Loosen the two slotted captive thumb screws that hold the Module in place in the Rack
Adapter until they disengage from the Rack Adapter.
2. Extract the module from the Rack Adapter using the front panel handle.
2.7 GROUNDING
Interconnections linking a stabilized Power Module to an a-c power source and a load are critical for both performance considerations and safety requirements. For optimum performance
certain rules must be observed. These rules are described in detail in the following paragraphs.
CAUTION
2.7.1 SAFETY GROUNDING
National and international safety standards set procedures for the grounding of a metal cover
and chassis of an instrument connected to an a-c power source.
When properly installed in the RA 55 Rack Adapter, the Power Module chassis is connected to
the RA 55 safety ground terminal via the GROUND pins of the AC/Control Bus connector (Figure 2-6). For operation of the MST Power Module outside the RA 55 Rack Adapter, consult
Kepco Applications Engineering for assistance.
RA 55 RACK ADAPTER MUST ALWAYS BE GROUNDED WHEN CONNECTED TO AN A-C
POWER SOURCE.
2.7.2 D-C (OUTPUT) GROUNDING
D-C output connections are those between the Power Module and the load, including remote
sensing connections. Despite precautions to eliminate noise such as shielding and twisted wirepairs, output connections may pick up radiated noise of a wide frequency. To minimize such
undesired effects, one side of the Power Module output/load may be grounded. Pin 4 of the DC
Output connector is connected to chassis (frame) ground. Although the d-c output is isolated
from chassis or ground up to ± 500 V d-c, in certain applications the user may elect to terminate
either the positive or negative terminals to chassis ground in order to optimize system performance.
WARNING
2-10 MST SERIES 061813
Successful d-c grounding depends on careful analysis of the system operation; only general
guide lines are provided here. One of the major points, however, is to avoid ground loops.
Ground loops are created when two or more points of different ground potentials in the output
circuit are grounded. An undesired signal (noise) is developed that is superimposed on the load
(output potential). A way to avoid ground loops is to check for points of resistance to ground. Differences in ground potential can be avoided if the output circuit is completely isolated. A single
point can then be selected along the Power Module output circuit and returned to ground with a
single wire. This method is dependent on the specific application.
2.8 POWER MODULE TO LOAD INTERFACE
The general function of a voltage or current stabilized Power Module is to deliver rated output to
the load. The load may be fixed or variable; resistive, capacitive, or inductive; and may be
located close to or far away from the Power Module. The Power Module is designed for varied
applications. The aim of the following paragraphs is to instruct the user in the interface of the
Power Module to the load.
The perfect interface between a Power Module and load insures optimum performance. To
approach this state of operation, one must be familiar with certain requirements, such as interconnection guidelines, Ohm's Law and a-c theory.
Load Wire Selection - A stabilized d-c Power Module is not an ideal voltage or current source
with zero output impedance (voltage mode) or infinite output impedance (current mode): All voltage sources have some amount of impedance which increases with frequency and all current
sources have impedance which decreases with frequency (see Figure 2-5).
FIGURE 2-5. OUTPUT IMPEDANCE VS. FREQUENCY
MST SERIES 061813 2-11
A practical model for a voltage-stabilized Power Module includes a series inductance representing d-c and low frequency source impedance. Load leads should have minimum voltage drops
(error sensing discussed in PAR. 2.10 below) and minimum inductance (error sensing does not
compensate for this). Similarly a model for a current stabilized Power Module includes a parallel
capacitor representing the d-c and low frequency source impedance. These considerations are
important if:
• The load is constantly changing value.
• The load is switched “on” and “off.”
• The output of the Power Module is step programmed.
• The load is reactive.
• Dynamic output response of the Power Module is of concern.
2.9 CONNECTION, GENERAL
All input and output connections between the Power Module and RA 55 Rack Adapter are made
automatically when the Power Module is fully seated in a Rack Adapter slot. Refer to the Rack
Adapter Instruction Manual for instructions on connecting RA 55 output connectors to the load,
a-c input power, and control signals.
The d-c output connector, labeled DC OUTPUT, is located on the back of chassis (Figure 2-6).
For the DC Output Connector pin designations on MST units refer to Table 2-5.
TABLE 2-5. DC OUTPUT CONNECTOR PIN DESIGNATIONS
MST SIGNAL CONNECTOR PIN
Output Terminal 1 (+) 6
Output Terminal 2 (–) 3
Sense Terminal 1 (+) 5
Sense Terminal 2 (–) 2
Current Share Bus 1
Module Chassis 4
NOTE: The polarity for the terminals indicated above are for output enabled and polarity
not reversed (normal).
2.9.1 LOAD CONNECTION WITH LOCAL ERROR SENSING
The most basic power supply/load interface is a 2-wire connection between the power supply
output terminals and the load. This connection method employs local error sensing which consists of connecting the error sense leads (pins 5 and 2) directly to the power supply output (pins
6 and 3). Its main virtue is simplicity: since voltage regulation is maintained at the power supply
output, the regulation loop is essentially unaffected by the impedances presented by the load
interconnection scheme. The main disadvantage is that it cannot compensate for losses introduced by the interconnection scheme and, therefore, regulation degrades directly as a function
of distance and load current. The main applications for this method are for powering primarily
resistive and relatively constant loads located close to the power supply, or for loads requiring
stabilized current exclusively. The load leads should be tightly twisted to reduce pick-up.
2-12 MST SERIES 061813
2.9.2 LOAD CONNECTION WITH REMOTE ERROR SENSING
If the load is located at a distance from the power supply terminals, or if reactive and/or modulated loads are present, remote error sensing should be used to minimize their effect on the voltage stabilization. A twisted shielded pair of wires from the sensing terminals directly to the load
will compensate for voltage drops in the load interconnection scheme (up to 0.5V maximum per
wire); the termination point of the error sensing leads should be at or as close as practical to the
load. For these conditions it is also recommended that some amount of local decoupling capacitance be placed at the error sense termination point to minimize the risk of unwanted pick-up
affecting the remote error sense function. For very long power module/load interconnecting
cables and/or reactive loads, it may be necessary to add decoupling capacitors between the
power and sense terminals at the power module side of the cable to suppress oscillation due to
cable inductance. A general recommendation is to install a network of one (1) 10µF, 6.3V capacitor paralleled by one (1) 0.1µF ceramic capacitor across each output sense pair (pins 6 to 5 and
3 to 2, respectively).
NOTE: As electrolytic capacitors are normally polarized make sure that the positive (+) terminal
of each one are respectively connected to the +V (pin 6) and -S (pin 2) pins.
FIGURE 2-6. CONNECTOR LOCATIONS AND PIN ASSIGNMENTS
MST SERIES 061813 2-13/(2-14 Blank)
SECTION 3 - OPERATION
3.1 INTRODUCTION TO CONTROLLING THE MST POWER MODULE OUTPUT
The MST family of Power Modules is designed for remote operation only. Operating the power
supply requires a series of commands to be sent to the Power Module from a host computer, via
a selected IEEE 1118 bus compatible Controller (see PAR. 1.4.1). The commands may either be
pre-programmed or sent individually using a keyboard, depending upon the controller selected.
The MST Power Module responds to both SCPI (Standard Commands for Programmable
Instruments) and CIIL (Control Interface Intermediate Language) commands. SCPI and CIIL
provide a common language conforming to IEEE 488.2 for instruments. For an explanation of
SCPI and CIIL commands and program syntax, refer to the applicable controller Instruction
Manual.
3.1.1 STATUS FLAGS (ERROR MESSAGES)
The MST Power Module supplies information to the controller regarding its operating condition
when queried via the STAT:QUES:COND? command in SCPI, or via the STA command in CIIL.
A listing of the standard error messages for both SCPI and CIIL appear in the Instruction Manuals for the various Kepco Controllers (see PAR.1.4.1). Table 3-1 lists the “catastrophic” status
messages of both SCPI and CIIL, along with the related MST Power Module condition.
TABLE 3-1. ERROR MESSAGES
CIIL ERROR MESSAGE SCPI STATUS MESSAGE POWER MODULE CONDITION
DEV Power Loss POWER LOSS OVERVOLTAGE / OVERCURRENT (See PAR. 3.7.2)
SOURCE POWER LOSS (See PAR. 3.7.4)
DEV Crowbarred None Not Supported
DEV Over Temperature OVERTEMPERATURE OVERTEMPERATURE (See PAR. 3.7.3)
DEV Overload OVERLOAD OPERATION IN MODE OTHER THAN PRO-
GRAMMED MODE (See PAR’s. 3.2.1, 3.2.2)
DEV Voltage Comparison Error VOLTAGE ERROR OUTPUT NOT AT PROGRAMMED VALUE
DEV Current Comparison Error CURRENT ERROR OUTPUT NOT AT PROGRAMMED VALUE
DEV Relay Not Opened
DEV Relay Not Closed
DEV Polarity Error
DEV Load Path Fault RELAY ERROR OPEN SENSE LEAD OR OPEN POWER LEAD
RELAY ERROR DEFECT IN ISOLATION OR POLARITY RELAY
OPERATION
CONDITION (See PAR. 3.7.5)
3.1.2 TIMING REQUIREMENTS FOR A VALID STATUS
After sending a command that might affect the output of the Power Modules or their relays, it is
recommended that the Status command be sent. For detailed information on this command
refer to the applicable controller Instruction Manual. For the Controller/MST system status command to be valid, the required time delay before sending the command is as follows:
• After an Open, Close (CIIL only), OUTP ON or OFF (SCPI only), Change of Polarity, or
Change of Mode, wait approximately 300 milliseconds.
MST SERIES 061813 3-1
• After a Confidence Test command or an Internal Self Test, wait approximately 400 milliseconds.
• After a Reset command, wait approximately 300 milliseconds.
3.2 OPERATING MODES
MST power modules permit the user to select the operating mode as either Voltage Mode or
Current Mode, depending upon the characteristics of the load being driven by the power module. The following paragraphs describe the characteristics and method of selecting the operating mode; note the following:
• only one operating mode may be selected at a time.
• operating mode selection affects only the operation of the fault detector and not the rectangular operating characteristic of the power module.
• the MODE indicators on the front panel indicate the real-time operating mode of the
Power Module.
3.2.1 VOLTAGE MODE
In this mode, the Power Module is programmed to behave as a voltage source. The user programs an operating voltage XX with a current limit YY based on the required voltage stabilization point and the maximum anticipated load current. The Power Module is now programmed to
provide a stabilized output voltage XX to a load impedance greater than or equal to XX/YY; the
VOLTAGE MODE indicator LED is on for these load conditions.
Load impedances below XX/YY are considered to be overloads, and the Power Module will
modulate the output voltage between zero and XX as necessary to maintain the load current at
YY. Operation with load impedances below XX/YY will result in the CURRENT MODE indicator
LED going on and the VOLTAGE MODE indicator going off; a status query at his point will indicate a device overload condition. Increasing the load impedance to a value greater than or
equal to the critical value indicated above will result in automatic return to normal operation.
3.2.2 CURRENT MODE
In this mode, the Power Module is programmed to behave as a current source. The user programs an operating current YY with a voltage limit XX based on the required current stabilization point and the maximum anticipated load voltage. The Power Module is now programmed to
provide a stabilized output current YY to a load impedance less than or equal to XX/YY; the
CURRENT MODE indicator LED is on for these load conditions.
Load impedances greater than XX/YY are considered to be overloads, and the Power Module
will modulate the output current between zero and YY as necessary to maintain the load voltage
at XX. Operation with load impedances greater than XX/YY will result in the VOLTAGE MODE
indicator LED going on and the CURRENT MODE indicator going off; a status query at his point
will indicate a device overload condition. Decreasing the load impedance to a value less than or
equal to the critical value indicated above will result in automatic return to normal operation.
3.3 OUTPUT POLARITY REVERSAL
MST Power Modules are designed to permit reversal of output terminal polarity via a remote
command. Polarity reversal is achieved via relay switching of both power and signal lines, and
can be employed in both Voltage and Current operating modes. Polarity reversal can be pro-
3-2 MST SERIES 061813
grammed in advance of output activation (Standby) or “on-the-fly” (Active) while the output is
enabled; both methods employ a “dry-switching” scheme in order to extend relay life.
For programming polarity reversal in Standby mode, the user simply issues the polarity reversal
command prior to enabling the output; the Power Module will then present reversed output
polarity when enabled.
For polarity reversal while the output is enabled, the action is somewhat more complex although
essentially transparent to the user. Upon receipt of a polarity reversal command, the Power
Module control circuit stores the previous output settings (mode, voltage and current setpoints,
etc.). The output of the Power Module is immediately programmed to zero volts and zero amps.
A time-out delay of 2 seconds maximum is employed to allow for discharge of any load capacitance through the Power Module's return supply; during this time-out interval, the power supply
waits for the output to reach zero volts. When zero volts is established, or at the end of the 2
second time-out, the relays are switched. The output is then reprogrammed to the stored settings and operation continues. During this sequence, error message generation is inhibited.
Restoration of the output to normal polarity follows a similar path.
NOTE: The “return supply” current incorporated into MST Power Modules is limited to a maxi-
mum value which may in some cases be inadequate to fully discharge all external load
capacitance. To ensure dry relay switching for all output conditions, the user must
ensure that the external load capacitance can be discharged completely within the 2
second time-out interval by the available current, or dry switching will not take place.
The maximum external capacitance value that can be discharged within the 2 second
time-out interval is calculated as follows (see Table 3-2):
IT×
-----------
C
≤
V∆
where C = Maximum external capacitance allowed to maintain dry switching (Farads)
I = Return supply current (Amps)
V = Output voltage (Volts)
T = Time (Sec) = 2 seconds
CAUTION: FAILURE TO OBSERVE THE “DRY SWITCHING” CRITERIA NOTED ABOVE
WILL CAUSE DAMAGE TO THE RELAYS AND VOID THE KEPCO WARRANTY.
In order to allow for settling time, the user should wait approximately 300 milliseconds after
completion of polarity reversal before sending a status query in order to avoid erroneous fault
messages.
TABLE 3-2. MAXIMUM EXTERNAL CAPACITANCE VALUES TO ENSURE DRY SWITCHING
MODEL
MST 6-20M 400 125,000
MST 15-12M 400 50,000
MST 25-8M 250 20,000
MST 36-5 165 8,800
MST 55-3.5 110 4,000
RETURN SUPPLY CURRENT
(MILLIAMPS)
MAXIMUM EXTERNAL CAPACITANCE *
(µF)
* Values shown for worst case: T = 2 seconds and
MST SERIES 061813 3-3
∆V = maximum voltage.
TABLE 3-2. MAXIMUM EXTERNAL CAPACITANCE VALUES TO ENSURE DRY SWITCHING
MODEL
MST 75-2.5 60 1,600
MST 100-2 44 880
MST 150-1.2 30 400
* Values shown for worst case: T = 2 seconds and
RETURN SUPPLY CURRENT
(MILLIAMPS)
3.4 OUTPUT ENABLE AND DISABLE
Enabling or disabling the output of an MST Power Module differs, depending upon whether it is
operating as a voltage source or current source. The difference is determined by the opposite
impedance characteristics of an ideal voltage vs. ideal current source. This section defines the
“disable” function in terms of ideal voltage or current source characteristics, and details the
exact method by which MST Power Modules provides the disable function.
For both voltage and current sources the “disable” condition is always represented by a “noload” (zero load power) impedance. Regardless of whether the MST is operating in voltage or
current mode (see PAR. 3.2), the “disable” condition must ensure that the MST provides zero
power to the load, while ensuring full compliance to the load when subsequently enabled. The
correct implementation of the disable function, whether for voltage mode or current mode, is
automatic.
The definition of an ideal voltage source is a source which will supply stable voltage (Vo) into
any load impedance within the limits of its compliance current range (RL = Vo/IMAX). For an
ideal voltage source a no-load condition is then defined as infinite impedance, since this is the
only load condition at which the delivered power (Vo x Io) is zero. MST Power Modules provide
this function by opening all power relays, thus providing an open circuit to the load from the stabilizer output. Enabling the voltage source is accomplished by closing the appropriate relay contacts, depending upon selected output polarity, thus connecting the stabilizer output to the load.
MAXIMUM EXTERNAL CAPACITANCE *
(µF)
∆V = maximum voltage.
The definition of an ideal current source is a source which will supply stable current (Io) into any
load conductance within the limits of its compliance voltage range (GL = Io/VMAX). For an ideal
current source a no-load condition is then defined as infinite conductance (zero impedance)
since this is the only load condition at which the delivered power is zero. MST Power Modules
provide this function by closing all four power relays, thus placing a short circuit (RL=0) at the
output of the load stabilizer. While “disabled,” output current from the MST load regulator continues to circulate within the power module and through the shorted power relays. Enabling the
current source is accomplished by opening the appropriate relays contacts, depending upon the
selected output polarity, thus allowing the output current to flow through the load.
As with the output polarity reversal function described in PAR. 3.3, a “dry switching” scheme is
employed during the disable and enable functions. For both voltage and current modes of operation, the CIIL command to enable the output at the load is Close (CLS), and to disable the output at the load is Open (OPN); the corresponding SCPI commands are OUTP ON and OUTP
OFF, respectively.
3-4 MST SERIES 061813
3.5 PARALLEL OPERATION
MST Power Modules are specifically designed for operation in parallel, either for increased
power or for fault redundancy. The output stabilizer incorporates an active load-sharing scheme
to ensure equal distribution of load current among all paralleled modules, resulting in reduced
operating stress and higher reliability. The load-share circuitry employed is a single-wire type
with the positive error sense connection providing the signal return path.
To determine the number of Power Modules needed for a specific application, the user divides
the total required load current (including any transient peaks) by the Power Module’s rated current, rounding the result up to the next whole number if necessary. This method determines “N”,
the minimum number of power modules needed to support the load. For redundant applications
this number is increased based on the desired redundancy factor (N+1, N+2, etc.). For nonredundant applications, the user can reduce overall power system operating stress by increasing the number of modules above N.
For parallel operation, all Power Modules should be same model. The module d-c outputs and
error sense leads are wired in parallel to the load; the load share terminals from each DC Output
connector are daisy-chained together. The user must ensure that the load and sense wiring minimizes loop inductance to prevent stray pickup from injecting noise into the load share signals.
Twisted pairs (shielded, if necessary) should be used for both power and error sense leads
when remote error sensing is used, with all error sensing lines terminated to the same physical
location; if possible, the user should employ local error sensing.
Program each module for Voltage Mode operation at identical output voltage and current limit.
The load sharing circuitry will automatically select the “load master” as the module with the highest “effective” voltage supplying power to the output bus; all other modules operate as slaves
and are indicated as such by the CURRENT SHARE indicator LED on the front panel of the
power module. Since MST Power Modules are enabled sequentially, the enabled modules will
generate output voltage errors until the minimum number of modules (N) are turned on; the user
should ignore these error flags until all modules are enabled (SCPI provides a method of masking these flags using software). The same is true if modules are disabled sequentially.
3.6 SERIES OPERATION
MST Power Modules are designed to allow series operation to achieve higher output voltage if
desired. Series operation requires detailed investigation into all possible output conditions which
may result from either normal or abnormal operation to ensure that the power supplies are not
exposed to undue stress, especially voltage. This need is increased for MST Power Modules
which, because of the sequential turn-on characteristic, may be exposed to greater risk during
output enabling and disabling sequences. Users wishing to operate MST Power Modules in
series are directed to contact Kepco Applications Engineering for specific guidance.
MST SERIES 061813 3-5
3.7 FAULT PROTECTION
In addition to providing protection against externally generated faults, MST Power Modules
incorporate fault protection circuitry which protects the load in the event of an internal failure or
malfunction which may result in loss of output control. The fault classifications are output overvoltage, output overcurrent, internal overtemperature, source power loss and open sense wire.
A description of the fault detectors associated with these faults is provided in the following paragraphs.
The response of the Power Module to any of these faults (except for open sense/power lead) is
a fault shutdown procedure consisting of the following:
• All output power and signal relays are immediately opened, isolating the Power Module
from the load;
• Output voltage and current are programmed to zero;
• The dc-dc converter which powers the output stabilizer is latched off;
• A fault status flag is sent to the Controller indicating a catastrophic failure. Upon receiving a fault status flag, the Controller removes that Control Bus address from the look-up
table, preventing further commands from being directed to the faulty power module.
If an open sense lead or open power lead condition is detected, the fault shutdown procedure is
as follows:
• All output power and signal relays are immediately opened, isolating the Power Module
from the load;
• Output voltage and current are programmed to zero;
• A fault message is sent to the controller (Load Path Fault in CIIL, Relay Error in SCPI).
3.7.1 FAULT RECOVERY
Recovery from a fault status flag condition (described above) requires that the user cycle source
power off for a minimum of 5 seconds. After reapplication of source power, a device reset command (RST) must be sent to the module’s Control Bus address to restore the address to the
look-up table. This procedure eliminates any possibility of casual reapplication of a Power Module to the system load after symptoms of a catastrophic module failure have been detected.
3.7.2 TRACKING OVERVOLTAGE AND OVERCURRENT DETECTORS
The output stabilizer control circuitry of the MST Power Module includes separate overvoltage
and overcurrent tracking amplifiers. These devices monitor the actual output voltage and current
supplied by the Power Module and compare them to the programmed voltage and current values. In the event that either parameter exceeds the programmed limit by an amount equal to
10% of the Power Module’s rated voltage or current, the circuit initiates a fault shutdown procedure including a Device Power Loss status flag. The tolerance of the fault thresholds are ±3%.
3-6 MST SERIES 061813
3.7.3 OVERTEMPERATURE DETECTORS
Any one of a number of internal or external conditions (i.e., elevated ambient temperature,
clogged vent holes, cooling fan failure, etc.) can cause elevation of internal heat sink temperatures to unsafe levels. If unattended, the resultant temperature rise of the power devices will
lead to eventual destructive failure. MST Power Modules incorporate two internal thermostatic
switches to detect unsafe internal operating temperatures. One is located on the heat sink
related to the input preregulator and dc-dc converter, while the second monitors the heat sink
related to the output stabilizer. If the temperature of either heat sink rises above a predetermined safe temperature, the related thermostat will change state, initiating a fault shutdown and
generating a Device Overtemperature status flag. The thermostat will reset upon return of the
heat sink to acceptable operating temperature, however the module recovery procedure (see
PAR. 3.7.1) must still be performed.
3.7.4 A-C LOSS DETECTOR
Although MST Power Modules are designed to provide a minimum of 21.5 milliseconds of output hold-up time (one full cycle of 47Hz power), loss of source power for extended periods will
eventually result in complete Power Module shutdown. Additionally, certain power loss intervals
can create a condition where the internal bias supply for the digital control circuitry decays partially, but not enough to force a system interrupt and reset; when this occurs, it is possible that
digital communication and processing can be corrupted without warning or notice. To prevent
this, MST Power Modules incorporate a power loss detector which will initiate a fault shutdown
with an accompanying Device Power Loss status flag if the internal bulk d-c storage capacitor
voltage falls to a level where quality of the internal bias voltages is questionable.
3.7.5 OPEN SENSE/POWER WIRE PROTECTION
In the event that the error sense leads (+S, -S) become disconnected from the power leads, the
output voltage will attempt to rise uncontrollably; the MST Power Module fault detection circuitry
continuously monitors the error sensing leads to protect against this occurrence. If an open
sense lead or power lead condition is detected, the fault detector immediately issues a string of
commands which reset the output status to Voltage Mode, Output Disabled (all output relays
open) and programs the output voltage and current limit to zero. At the same time, a fault message is sent to the controller (Load Path Fault in CIIL, Relay Error in SCPI). Once the open
sense or power lead condition is corrected, the power module is ready to accept additional commands without any further recovery measures; manual reset is not required.
The open sense/power wire protection circuitry can also be triggered by a power lead voltage
drop in excess of the 0.5V maximum specified headroom. If the error sense lead connections
appear to be correct, the user should double-check the size of the power leads to verify adequate margin. Contact Kepco Applications Engineering for assistance if necessary.
MST SERIES 061813 3-7
3.8 CALIBRATION
Calibration of the MST Power Module is recommended for any of the following conditions.
• The unit has been moved.
• Operating environment (temperature, humidity, etc.,) has been altered.
• Periodic maintenance determined by user.
• Inaccurate measurements are suspected.
Perform the procedures outlined below in sequence (see Figure 2-4 for the location of calibration controls). Calibration adjustments are recommended only when the test point value
exceeds the indicated tolerance on the measured value. Note that the measured value tolerance is generally an order of magnitude looser than the adjustment tolerance. This avoids
unnecessary recalibration, while providing a precision adjustment if calibration is required.
NOTE: E
is the maximum output voltage of the unit listed in Table 1-1; I
MAX
mum output current of the unit as listed in Table 1-1 for 45° C.
3.8.1 EQUIPMENT REQUIRED
Calibration of MST Series Power Modules requires the following equipment:
• Host computer
• RA 55 or CA 400 Rack Adapter, or Input Power/Communication Cable (see Table 1-3)
• Controller Module (Kepco MST 488-27 or TMA Series)
• Digital Voltmeter (DVM): 6½ digit display, 10 µV resolution
• Precision Current Shunt: R
where: E
= rated Power Module output voltage (e.g., 36V for MST 36-5)
MAX
I
= rated Power Module output current (e.g., 5A for MST 36-5)
MAX
NOTE: To avoid errors due to temperature drift of the shunt, a power rating of
greater than 10 times actual dissipation is recommended. The above calculation results in a maximum shunt power dissipation of less than 4W, a 100W
shunt is adequate for all models)
< 0.02 (EMAX / IMAX)Ω
SHUNT
is the maxi-
MAX
• Miscellaneous programming interface cables, load cables, etc.
Install the MST Series power module under test (UUT) in the calibration test set-up shown in
Figure 3-1
3-8 MST SERIES 061813
FIGURE 3-1. CALIBRATION TEST SET-UP
3.8.2 +5 VOLTS REFERENCE ADJUST (R49)
This procedure establishes the +5V reference voltage used by the analog circuits.
1. Disconnect the load and turn on the UUT. Proceed to step 3 if VOLTAGE MODE indicator is
on.
MST SERIES 061813 3-9
2. If the CURRENT MODE indicator is on, issue a command from the host computer to set the
UUT to Voltage mode. Verify that VOLTAGE MODE indicator is on.
3. Issue a command from the host computer to reset the UUT. This causes the UUT to be programmed to zero volts.
4. Connect the voltmeter to test connector J5, pins 1 (REF) and 6 (GND) (see Figure 2-4) and
verify meter reads between 5.00000V ± 500µV volts. If meter reading is outside these limits,
adjust potentiometer R49 for reading of +5.00000V ± 50µV.
3.8.3 OUTPUT VOLTAGE (E
) ZERO ADJUST (R11)
O
This procedure adjusts the offset of the voltage comparison amplifier to be zero for a programmed output voltage of zero.
1. Configure DC OUTPUT connector as shown in Figure 2-3 and close S1.
2. With the load disconnected, issue a command from the host computer to enable the output
(output relays closed). Verify OUTPUT ENABLED and VOLTAGE MODE indicators are on.
3. Connect DVM to DC output connector (see Figure 2-3) pin 5, Sense 1 (+) and pin 2, Sense 2
(–) and verify that output is 0V ± 500µV.
4. If the measured output is outside these limits adjust potentiometer R11 for reading of
0.00000V ± 50µV.
3.8.4 CURRENT SENSE ZERO ADJUST (R50)
This procedure adjusts the current sensing amplifier to zero with no current flowing through the
current sensing resistor.
1. Issue command from the host computer to reset the UUT.
2. Verify VOLTAGE MODE indicator is on.
3. Connect voltmeter to test connector J5, pins 4 (CSNS - Current Sense) and 6 (GND) and
verify meter reads 0.00000V ± 500µV. If meter reading is outside these limits, adjust potentiometer R50 for 0.00000V ± 50µV.
3.8.5 OUTPUT CURRENT I
ZERO ADJUST (R51)
O
This procedure adjusts the offset of the current comparison amplifier to be zero for a programmed output current of zero.
1. Issue commands from the host computer to set the UUT to Current Mode, program output
current to 0.0A, voltage limit to E
and disable the output.
MAX
2. Verify CURRENT MODE indicator is on and OUTPUT ENABLED indicator is off.
3. Connect voltmeter to test connector J5, pins 4 (CSNS - Current Sense) and 6 (GND) and
verify voltmeter reads 0.0000V ± 500µ V. If voltmeter reading is outside these limits, adjust
potentiometer R51 for 0.0000V ± 100µV.
3-10 MST SERIES 061813
3.8.6 VOLTAGE REFERENCE ADJUST (R47)
This procedure adjusts the internal full scale reference voltage to produce the full scale output
voltage E
when the full scale voltage is programmed.
MAX
1. Issue commands from the host computer to set the UUT to Voltage Mode, program current
limit to I
, output voltage to E
MAX
and enable the output.
MAX
2. Verify VOLTAGE MODE and OUTPUT ENABLED indicators are on.
3. Connect the voltmeter to DC output connector (see Figure 2-3) pin 5, Sense 1 (+) and
pin 2, Sense 2 (–) and verify measured value is within ± 1 LSB (1/4096) of E
sured value exceeds the acceptable range, adjust potentiometer R47 to E
R47 adjustment tolerance of ± 0.5 LSB (1/8192) of E
3.8.7 CURRENT REFERENCE ADJUST (R48)
This procedure establishes the maximum value of the internal current reference voltage so that
the readback current matches the programmed current.
1. Turn off UUT and connect precision shunt across DC Output connector pin 6, Output 1 (+),
and pin 3, Output 2 (–).
2. Turn on UUT.
MAX
. If mea-
MAX
, within the
MAX
.
3. Issue commands from the host computer to set the UUT to Current Mode, program output
current (I
4. Verify that CURRENT MODE and OUTPUT ENABLED indicators are on.
5. Issue commands from the host computer to read back current.
6. Verify that the read back value (step 5) is within ± 1 LSB (4096) of the programmed value
(step 3). If readback value exceeds acceptable range, adjust R48 for readback value within
±0.5 LSB (1/8192) of the programmed value.
3.8.8 CURRENT (I
This procedure adjusts the gain of the current sensing amplifier so that the actual full scale output current matches the programmed output current.
1. Issue commands from the host computer to set the UUT to Current Mode, program output
current (I
operating for a minimum of 20 minutes in Current Mode with output disabled to avoid drift
due to temperature fluctuations.
2. Enable the output and verify that CURRENT MODE and OUTPUT ENABLED indicators are
on.
3. Record the output current as measured across the external shunt.
) to 0.99 x I
O
) FULL SCALE ADJUST (R52)
O
) to 0.99 x I
O
, voltage limit to E
MAX
, voltage limit to E
MAX
and enable the output.
MAX
and disable the output. The unit must be
MAX
MST SERIES 061813 3-11
4. Issue commands from host computer to read back current.
5. Compare the read back current (step 4) to the measured current (step 3). Verify that measured current is equal to readback current within the acceptable range of ± 1 LSB (1/4096) of
I
. If the acceptable range is exceeded, adjust R52 until measured current is within ±0.5
MAX
LSB (1/8192) of read back current, repeating steps 1 through 5 as necessary.
3-12 MST SERIES 061813
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