National Instruments RMX-4120, RMX-4121, RMX-4122, RMX-4124, RMX-4125 User Manual
...
RMX
RMX Programmable Power Supplies User Manual
RMX-4120
RMX-4121
RMX-4122
RMX-4123
RMX-4124
RMX-4125
RMX-4126
RMX-4127
RMX Programmable Power Supplies User Manual
February 2017
375744C-01
About the RMX User Manual
This manual is intended for users of the Regulated DC Power Supply and their instructors.
It is assumed that the reader has knowledge about electrical safety standards and the electrical
aspects of regulated DC power supplies.
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Indicates general danger, warning, or caution. When this symbol is marked on the
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Off (supply).
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Contents
Chapter 1
Installation and Preparation
Attaching the Connector Cover ........................................................................................ 1-1
Connecting the Power Cord.............................................................................................. 1-1
RMX-4120/4121/4122/4123 (750 W Models)......................................................... 1-2
Necessary Cable ............................................................................................... 1-2
RMX-4124/4125/4126/4127 (1500 W Models)....................................................... 1-2
Necessary Cable ............................................................................................... 1-3
Switchboard Breaker Requirements ................................................................. 1-3
Connection Procedure............................................................................................... 1-4
Turning the Power On ...................................................................................................... 1-6
Turning the POWER Switch On .............................................................................. 1-6
Inrush Current................................................................................................... 1-7
Turning the POWER Switch Off .............................................................................. 1-7
Rack Mounting ................................................................................................................. 1-8
Load Considerations ......................................................................................................... 1-8
Loads with Peak Current or Pulse-Shaped Current.................................................. 1-8
Loads that Generate Reverse Current to the Power Supply ..................................... 1-9
Loads with Accumulated Energy ............................................................................. 1-9
Load Cables ...................................................................................................................... 1-10
Protecting Against Noise .......................................................................................... 1-11
Cabling Considerations When Using Remote Sensing ............................................ 1-11
Connecting to the Output Terminals ................................................................................ 1-12
Attaching the Output Terminal Cover ...................................................................... 1-15
Sensing.............................................................................................................................. 1-17
Local Sensing ........................................................................................................... 1-19
Remote Sensing ........................................................................................................ 1-19
Connecting an Electrolytic Capacitor Across the Load.................................... 1-22
Inserting a Mechanical Switch Between the RMX Programmable
Power Supply and the Load.............................................................................. 1-22
Accessories ....................................................................................................................... 1-23
Parallel Operation Signal Cable ............................................................................... 1-23
Chapter 2
Basic Functions
Measured Value Display and Setting Display .................................................................. 2-1
Measured Value Display .......................................................................................... 2-1
Power Display................................................................................................... 2-1
Setting Display ......................................................................................................... 2-2
Overvoltage Protection and Overcurrent Protection Setting Display....................... 2-2
System Configuration Setting Display ..................................................................... 2-2
Panel Operations............................................................................................................... 2-3
© National Instruments | v
Contents
Measured Value Display, Setting Display, and Set OVP/OCP Display...................2-3
Fine Adjustment................................................................................................ 2-3
Output Operations............................................................................................................. 2-3
Output State at Power-up .......................................................................................... 2-4
Operation Overview.......................................................................................................... 2-4
CV Power Supply and CC Power Supply.........................................................................2-7
Crossover Point................................................................................................. 2-8
CV Mode and CC Mode Operation Examples .........................................................2-8
Example 1 .........................................................................................................2-8
Example 2 .........................................................................................................2-8
Using the RMX Programmable Power Supplies as a CV or CC Power Supply ..............2-9
Protection Functions and Alarms......................................................................................2-11
Alarm Occurrence and Clearing Alarms ..................................................................2-12
Alarm Occurrence............................................................................................. 2-12
Clearing Alarms................................................................................................2-13
Alarm Signal ..................................................................................................... 2-13
Protection Function Activation ................................................................................. 2-14
Setting limitation functions...............................................................................2-14
CONFIG Settings.............................................................................................................. 2-20
Specifying CF01 to CF36, CF 41 to CF52 CONFIG Settings.......................... 2-24
Specifying CF00/CF40 CONFIG Settings ....................................................... 2-25
CONFIG Parameter Details .............................................................................. 2-25
Preset Memory Function................................................................................................... 2-39
Saving Settings to Preset Memory............................................................................2-39
Recalling Preset Memory Entries ............................................................................. 2-40
Locking Panel Operations (Key Lock) .............................................................................2-41
Bleeder On/Off Feature .................................................................................................... 2-41
Fall Time................................................................................................................... 2-44
Switching from Remote Mode to Local Mode ................................................................. 2-44
Factory Default Settings (Initialization) ........................................................................... 2-45
Chapter 3
External Control
Overview........................................................................................................................... 3-1
About the J1 Connector ....................................................................................................3-1
Attaching the J1 Cable Core ..................................................................................... 3-2
About the J2 Connector ....................................................................................................3-5
Output Terminal Insulation............................................................................................... 3-7
When the Output Terminal is Not Grounded (Floating)........................................... 3-7
When the Output Terminal is Grounded................................................................... 3-9
Cautions When Controlling the Output with an External Voltage (Vext)................ 3-11
Controlling the Output Voltage ........................................................................................ 3-12
Control Using an External Voltage (Vext) ............................................................... 3-12
External Voltage (Vext) Connection ................................................................ 3-13
Control Using an External Resistance (Rext) ........................................................... 3-13
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RMX Programmable Power Supplies User Manual
External Resistance (Rext) Connection............................................................ 3-14
Controlling the Output Current......................................................................................... 3-14
Control Using an External Voltage (Vext) ............................................................... 3-15
Control Using an External Resistance (Rext) ........................................................... 3-16
External Resistance (Rext) Connection............................................................ 3-16
Controlling the Output On and Off States ........................................................................ 3-17
External Contact Connection.................................................................................... 3-18
Long-Distance Wiring ...................................................................................... 3-18
Controlling Output Shutdown .......................................................................................... 3-19
Output Shutdown Connection .................................................................................. 3-19
Long-Distance Wiring ...................................................................................... 3-20
Controlling the Clearing of Alarms .................................................................................. 3-20
Alarm Clear Connection ........................................................................................... 3-21
Long-Distance Wiring ...................................................................................... 3-22
External Monitoring ......................................................................................................... 3-22
Monitor Output Rating ............................................................................................. 3-22
External Monitoring of the Operation Status ................................................... 3-23
Chapter 4
Parallel/Series Operation
Master-Slave Parallel Operation....................................................................................... 4-1
Features of the RMX Programmable Power Supplies During
Master-Slave Parallel Operation............................................................................... 4-1
Voltage Display and Current Display............................................................... 4-1
Connection (Master-Slave Parallel Operation)......................................................... 4-3
Connecting the Signal Cables (Parallel Operation).......................................... 4-3
Connecting the Load (Parallel Operation) ........................................................ 4-4
Settings (Master-Slave Parallel Operation) .............................................................. 4-6
Setting the Master Unit, the Slave Units, and the Number of Units in
Parallel Operation (Including the Master Unit) ................................................ 4-6
Setting the Voltage and Current ....................................................................... 4-6
Setting the Overvoltage Protection (OVP) and Overcurrent Protection (OCP)
of the Master Unit............................................................................................. 4-6
Starting Master-Slave Parallel Operation ................................................................. 4-7
Turning Power On ............................................................................................ 4-7
Turning Power Off............................................................................................ 4-7
Series Operation ............................................................................................................... 4-8
Features of the RMX Programmable Power Supplies During Series Operation...... 4-8
Voltage Display and Current Display............................................................... 4-8
External Control ............................................................................................... 4-8
External Monitoring ......................................................................................... 4-8
Remote Sensing ................................................................................................ 4-9
Alarm ................................................................................................................ 4-10
Connection (Series Operation) ................................................................................. 4-10
Connecting the Load (Series Operation) .......................................................... 4-10
© National Instruments | vii
Contents
Settings (Series Operation) ....................................................................................... 4-11
Setting the Voltage and Current........................................................................ 4-11
Setting the Overvoltage Protection (OVP) and Overcurrent Protection (OCP).. 4-11
Starting (Series Operation) .......................................................................................4-11
Turning the Power On and Off ......................................................................... 4-11
Turning the Output On and Off ........................................................................ 4-11
Chapter 5
Maintenance
Calibration Overview........................................................................................................ 5-1
Calibration Procedure ....................................................................................................... 5-1
Installation ................................................................................................................ 5-1
Launch ...................................................................................................................... 5-1
Calibration Items....................................................................................................... 5-2
Basic Instructions...................................................................................................... 5-3
Save Calibration........................................................................................................ 5-3
Backup Calibration Data to a XML File...........................................................5-3
Send Calibration Data from a XML File .......................................................... 5-3
Revision History ............................................................................................... 5-3
System Requirements ....................................................................................... 5-4
Hardware Requirements ...................................................................................5-4
Environment......................................................................................................5-4
Cleaning ............................................................................................................ 5-4
Connection ................................................................................................................5-5
Appendix A
Specifications
Appendix B
Troubleshooting
Appendix C
NI Services
Index
viii | ni.com
1
Installation and Preparation
This chapter describes how to turn on an RMX programmable power supply, what kind of load
cables to use, and how to connect cables to the output connectors.
Note Protection provided by this equipment may be impaired if it is used in a
manner not described in the manual.
Attaching the Connector Cover
RMX programmable power supplies are supplied with a connector cover that fits over the entire
sensing, J1, and J2 connectors. For safety reasons, be sure to attach the connector cover when
you use the RMX programmable power supply.
Figure 1-1. Connector Cover
Connecting the Power Cord
This product is a piece of equipment that conforms to IEC Overvoltage Category II (equipment
that consumes energy supplied from a fixed installation).
A power cord is not included with the RMX-4124/4125/4126/4127. Use a power cord that
conforms to this product’s rated AC input voltage, input current, and configured for the
plug type. Refer to your product specifications for details.
Caution Risk of electric shock. This product is a piece of equipment that conforms
to IEC Safety Class I (equipment that has a protective conductor terminal). Be sure
to earth ground the product to prevent electric shock. The product is grounded
through the power cord ground wire. Connect the protective conductor terminal to
earth ground.
© National Instruments | 1-1
Chapter 1 Installation and Preparation
RMX-4120/4121/4122/4123 (750 W Models)
Necessary Cable
• North America—Extra Hard Usage Cord, min. 300 V, 60 C, 14 AWG, 3 Conductor cord,
3 m or less, with a NEMA 5-15P to C14.
• Europe—HAR Marked, min. 300 V, 60 C, 2.5mm2, 3 Conductor cord, 3 m or less, with a
plug configured for the country of use to C14.
• International—Certified for country of use, min. 300 V, 60 C, 2.5mm
3 m or less, with a plug configured for the country of use to C14.
The power cord can be used to disconnect the RMX programmable power supply from the
AC power line in an emergency. Connect the plug to an easily accessible power outlet so that the
plug can be removed from the outlet at any time. Be sure to provide adequate clearance around
the power outlet.
1. Check that the AC power line meets the nominal input rating of the product. The product
can receive a nominal line voltage in the range of 100 VAC to 240 VAC at 50 Hz or 60 Hz.
2. Check that the POWER switch is turned off.
3. Connect the power cord to the AC inlet on the rear panel.
4. Insert the power plug into a grounded outlet.
2
, 3 Conductor cord,
RMX-4124/4125/4126/4127 (1500 W Models)
Caution Risk of electric shock. Before you connect the power cord, turn off the
switchboard breaker (a switch that cuts off the power supply from the switchboard).
Risk of fire. Connection to the switchboard must be performed by a person who has
knowledge about electrical safety standards and the electrical aspects of regulated
DC power supplies. The switchboard breaker must meet the requirements shown
below.
Caution Inside the product, protective circuits are connected to match the polarity
of the input terminal. Be sure to connect the L, N, and (GND) terminals of the product
to the matching terminals on the switchboard.
In an emergency, turn off the switchboard breaker to disconnect the product from the AC power line.
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RMX Programmable Power Supplies User Manual
RMX-4125
Switchboard
N
L
N
L
Breaker indication example
For the
RMX-4125 only
30 A
Power cord
RMX-4125
dedicated breaker
Necessary Cable
• Vinyl cabtire cable (VCTF): Nominal cross-sectional area 5.5 mm2, 3 core
• Finished diameter: 10.5 to 14.4 mm in diameter
• Rated voltage: 250 V or higher
• Input terminal end: 14 mm of insulation stripped from conductor for the L and N wires.
Crimping terminal: (round, M4) that fixes the cable insulation in place
for the GND wire
• Length: 3 m or less
Switchboard Breaker Requirements
• Installation must be done in accordance with national wiring rules, such as NFPA 70 "NEC"
and CSA C22.1 "CEC".
• Rated current: 30 A (for safety, breakers whose rated current exceeds 30 A cannot be used)
• Do not power any other equipment from the switchboard breaker.
• Keep the breaker readily accessible at all times.
• Indicate that the breaker is dedicated for use with this product and that it is used to
disconnect the product from the AC power line.
Figure 1-2. Switchboard Diagram
© National Instruments | 1-3
Chapter 1 Installation and Preparation
Crimping terminal (round, M4)
When crimping the core wire, use a
crimping terminal and tool that can
also grip the insulation.
Connection Procedure
1. Check that the AC power line meets the nominal input rating of the product. The product
can receive a nominal line voltage in the range of 100 VAC to 240 VAC at 50 Hz or 60 Hz.
2. Check that the POWER switch is turned off.
3. Attach a crimping terminal to the GND wire.
Figure 1-3. Attaching the Crimping Terminal
4. Connect the power cord and the included INPUT terminal cover to the AC INPUT terminal
on the rear panel. Be sure to connect the AC INPUT L, N, and (GND) terminals correctly.
Pass the power cord through the INPUT terminal cover, and fix the cord in place using the
cable gland.
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RMX Programmable Power Supplies User Manual
STRIP-GAUGE
14 mm
Correct
Incorrect
Incorrect
The stripped wire is
touching the chassis.
The wire strands are
touching the chassis.
INPUT terminal cover
INPUT terminal cover
INPUT terminal cover
AC INPUT terminal
L: Black or brown
N: White or blue
(GND)
Screw
: Green or green and yellow
Power cord
Power cord
Power cord
Screw
Use this screw to fix the
wire in place.
Screw M4
Remove the first
14 mm of the wire’s
covering, and then
insert the wire here.
AC INPUT terminal
Cable gland:
Turn left to unlock
Cable gland:
Turn right to lock
Cable gland: Supports wires from 10.5 to 14.4 mm in diameter
Figure 1-4. Connecting the Power Cord
5. Attach an appropriate crimping terminal to the switchboard end of the power cord.
6. Turn off the switchboard breaker.
7. Connect the L, N, and (GND) wires of the power cord to the matching terminals on the
switchboard.
© National Instruments | 1-5
Chapter 1 Installation and Preparation
Turning the Power On
Turning the POWER Switch On
Caution Risk of electric shock. Regardless of whether load cables are connected to
the output terminals, be sure to attach the OUTPUT terminal cover before turning the
POWER switch on.
You can use the CONFIG settings to set how the RMX programmable power supplies
start when you turn the POWER switch on. Depending on the setting, the output may
be turned on automatically when the POWER switch is turned on. If you connect a
load without setting OVP and OCP to appropriate values, the load may be damaged
if the output is programmed to automatically turn on when the power is switched on.
When you turn the POWER switch on for the first time after purchase, the RMX programmable
power supply will be programmed with its factory default settings. Refer to Chapter 2, Factory
Default Settings (Initialization), for more information about these settings. Each subsequent
time you turn the power supply on, it starts with the panel settings (excluding the output on/off
setting) that were in use immediately before the POWER switch was turned off.
You can use the CONFIG setting CF02 to select how the RMX programmable power supply
starts when the POWER switch is turned on. Refer to Chapter 2, CF02 Power-on Status
Parameter, for more information about this setting.
1. Check that the power cord is connected correctly.
2. Check that the OUTPUT terminal cover is attached. Refer to the Attaching the Output
Terminal Cover section for more information about attaching the terminal cover. When the
product is shipped from the factory, the OUTPUT terminal cover is not attached.
3. Turn the POWER switch on. All the LEDs light, and then the voltmeter and the ammeter
display the following sequence of information: the rated voltage and rated current, the
firmware version number, the build number, and then the selected interface. Each item is
displayed for approximately 1 second. After a few seconds, the RMX programmable power
supply enters the operation standby state during which the output value is displayed.
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RMX Programmable Power Supplies User Manual
Figure 1-5. Power On Information Display
Inrush Current
When the POWER switch is turned on, an inrush current of up to 70 A can momentarily flow
into the rear AC input of the programmable power supply. Check that sufficient current capacity
is available in the AC power line or the switchboard, particularly if you are using multiple RMX
programmable power supplies and turning on their POWER switches simultaneously.
Turning the POWER Switch Off
Flip the POWER switch to the side to turn RMX programmable power supplies off. The RMX
programmable power supplies save the panel settings (except the output on/off setting) that were
in use immediately before the POWER switch was turned off.
You can use CONFIG settings CF02 to select how the RMX programmable power supply starts
when the POWER switch is turned on. Refer to Chapter 2, CF02 Power-on Status Parameter,
for more information about this setting.
If the POWER switch is turned off immediately after the settings have been changed, the last
settings may not be stored.
Caution After you turn the POWER switch off, wait at least 10 seconds after the
panel display turns off before you turn the POWER switch back on. Repeatedly
turning the POWER switch on and off at short intervals can cause damage to the
inrush current limiter. Furthermore, this will shorten the service life of the POWER
switch and the internal input fuse.
© National Instruments | 1-7
Chapter 1 Installation and Preparation
Load current with peaks Pulse-shaped load current
Set constant current
Ammeter reading (mean value)
Set constant current
Ammeter reading (mean value)
Rack Mounting
You can use brackets or slide rails to mount the RMX programmable power supply to a rack.
When you mount an RMX programmable power supply to a rack, install the optional support
angles (NI P/N) to support the device.
NI recommends that you keep all pieces that you remove from a RMX programmable power
supply during installation. You will need these pieces if you remove the device from a rack.
When using several RMX programmable power supplies together for master-slave parallel or
series operation, mount them to a rack before use.
Load Considerations
Note The output can become unstable if the following types of loads are connected.
Loads with Peak Current or Pulse-Shaped Current
The front panel of the RMX power supply only displays averaged voltage and current values.
If the supply is connected to a load that draws current in spikes or pulses it is possible that the
front panel will display a current reading lower than the programmed current setpoint. In reality,
the spikes or pulses in the load current are exceeding the programmed current setpoint causing
the supply to switch instantaneously into constant-current mode and causing the output voltage
to drop.
For these types of loads, you must increase the set constant current or increase the current
capacity.
Figure 1-6. Loads with Peak Current or Pulse-Shaped Current
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RMX Programmable Power Supplies User Manual
IO
RD
EO
Equivalent circuit of the RMX-4122
Regenerative load
＋
0
Reverse current
-IO
+IO
Irp
RD (in Ω) ≤
RD: Reverse current bypass dummy load
E
O: Output voltage
Irp: Maximum reverse current
EO (in V)
Irp (in A)
Load
Output current
Loads that Generate Reverse Current to the Power Supply
RMX programmable power supplies cannot sink reverse current from the load. Therefore, if a
regenerative load (such as an inverter, converter, or transformer) is connected and tries to sink
power into the terminals of the power supply, the output voltage will increase and can become
unstable. This can cause a malfunction.
For these types of loads, connect a resistor (R
) as shown in the following figure to bypass the
D
reverse current. However, the amount of current to the load decreases by Irp.
Figure 1-7. Loads with Accumulated Energy
Caution Use a resistor with sufficient rated power for R
. If a resistor with
D
insufficient rated power for the circuit is used, the resistor will burn out.
Loads with Accumulated Energy
Connecting a load with accumulated energy, such as a battery, to an RMX programmable power
supply may cause current to flow from the load to the internal circuit. This current may cause
damage or reduce the life of the load.
For this type of load, connect a reverse-current-prevention diode (D
programmable power supply and the load in series as shown in the following figure.
) between the RMX
RP
This cannot be used in conjunction with remote sensing.
RMX-4122
Figure 1-8. Loads with Accumulated Energy
D
RP
Load with accumulated energy
DRP: Reverse-current-protection diode
© National Instruments | 1-9
Chapter 1 Installation and Preparation
Caution To protect the load and the RMX programmable power supplies, use a D
RP
that conforms to the following specifications.
• Reverse voltage withstand capacity–At least twice the rated output voltage of the RMX
programmable power supply.
• Forward current capacity–Three to ten times the rated output current of the RMX
programmable power supply.
• A diode with small loss.
• Be sure to take into account the heat generated by D
. DRP will burn out with inadequate
RP
heat dissipation.
Load Cables
Caution Risk of fire. Use load cables whose capacity is adequate for the
RMX programmable power supply’s rated output current. The output connector and
its surrounding area become hot. Use cables whose covers have heat resistance at
85 °C and higher.
Caution Risk of electric shock. Use the cable which has higher withstanding
voltage than the specified insulation voltage of the product to secure the double
insulation or reinforced insulation.
The current capacity of a load cable is dependent on the maximum allowable temperature of the
cable's insulation.
A cable’s temperature is determined by the resistive loss based on the current, the ambient
temperature, and the cable’s external thermal resistance. The following table shows the current
capacity of heat-resistant vinyl wires that have a maximum allowable temperature of 60 °C,
assuming that a wire is stretched out horizontally in air in an ambient temperature of 30 °C.
The current capacity must be reduced under certain conditions, such as when vinyl cables that
have a low heat resistance are used, when the ambient temperature is 30 °C or greater, or when
cables are bundled together and little heat is radiated.
Table 1-1. Current Capacity of Heat-resistant Vinyl Wires
Nominal
Cross-sectional
Area
2 mm
3.5 mm
5.5 mm
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2
2
2
AWG (Reference
Cross-sectional
Area)
Allowable
Current
(Ta = 30 °C)
Recommended
Current
14 (2.08 mm2) 27 A 10 A
12 (3.31 mm2) 37 A —
10 (5.26 mm2) 49 A 20 A
RMX Programmable Power Supplies User Manual
Table 1-1. Current Capacity of Heat-resistant Vinyl Wires (Continued)
Nominal
Cross-sectional
Area
2
8 mm
2
14 mm
2
22 mm
2
30 mm
2
38 mm
2
50 mm
2
60 mm
2
80 mm
2
100 mm
2
125 mm
2
150 mm
2
200 mm
AWG (Reference
Cross-sectional
Area)
Allowable
Current
(Ta = 30 °C)
Recommended
Current
8 (8.37mm2) 61 A 30 A
6 (13.3 mm2) 88 A 50 A
4 (21.15 mm2) 115 A 80 A
2 (33.62 mm2) 139 A —
1 (42.41 mm2) 162 A 100 A
1/0 (53.49 mm2) 190 A —
2/0 (67.43 mm2) 217 A —
3/0 (85.01 mm2) 257 A 200 A
4/0 (107.2 mm2) 298 A —
— 344 A —
— 395 A 300 A
— 469 A —
Protecting Against Noise
When connecting wires that have the same heat resistance, separating the wires as much as
possible to increase heat radiation enables a greater amount of current to flow. However, wiring
the + (positive) and - (negative) output wires of the load cable side by side or bundling them
together will minimize unwanted noise on the output. The currents shown in Table 1-1 are
allowable currents that have been reduced in consideration of the potential bundling of load
cables. Use these values as a guideline when connecting load cables.
Cabling Considerations When Using Remote Sensing
As you increase the current setpoint or increase the resistance of your load cabling, the voltage
drop between the RMX power supply and your load will increase. This results in the voltage at
your load being smaller than the programmed voltage setpoint. Refer to Appendix A,
Specifications, to see the maximum voltage drop each RMX power supply's remote sense
terminals can compensate for. If the voltage drop exceeds this level, use shorter load cables or
cables with a greater cross-sectional area.
© National Instruments | 1-11
Chapter 1 Installation and Preparation
- (negative) terminal + (positive) terminal
Chassis terminal
Connecting to the Output Terminals
Caution Risk of electric shock. Turn the POWER switch off before you touch the
OUTPUT terminals. Even if you turn the output off or turn the POWER switch off,
if the bleeder on/off setting (CF11) is set to “OFF,” the voltage that was present when
the output was on will remain at the output terminals. Turn the bleeder circuit on
before you touch the output terminals. Regardless of whether load cables are
connected to the output terminals, be sure to attach the OUTPUT terminal cover
before turning the POWER switch on. Confirm that the voltage between any output
terminal and ground is lower than the isolation voltage of the RMX programmable
power supply.
Figure 1-9. RMX-4125 Output Terminal
1. Turn the POWER switch off. Check that there is no voltage across the output terminals.
2. Connect one end of the included chassis connection wire to the chassis terminal, and then
connect the other end of the wire to the negative or positive output terminal.
Note For safety reasons, connect one of the output terminals to the chassis terminal
unless your application requires the output terminals to be floating.
Use the screw on the RMX to connect the wire to the chassis terminal. Use the screw on the
output terminal to connect the wire to the output terminal.
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RMX Programmable Power Supplies User Manual
Chassis
connection wire
Screw (M3)
Screw (M4)
Chassis
connection wire
Screw (M3)
Screw (M4)
Figure 1-10. RMX-4120/4121/4124/4125
Figure 1-11. RMX-4122/4123/4126/4127
3. Attach crimping terminals to the load cables.
The output terminals have holes for connecting the load cables. Use crimping terminals that
are appropriate for the bolts that you are using.
4. Use the included bolt set to connect the load cables to the output terminals.
Connect the positive cable to the positive output terminal and the negative cable to the
negative output terminal. The orientation of the crimping terminals will vary depending on
the wire diameter of the load cables used.
© National Instruments | 1-13
Chapter 1 Installation and Preparation
Spring washer
Washer
Nut
Bolt (M8)
Crimping terminal
Attach the cable to the inner side
of the crimping terminal.
Attach the cable to the outer side
of the crimping terminal.
Spring washer
Washer
Nut
Bolt (M5)
Screw (M4)
Figure 1-12. Connection Using M8 Bolt Set for RMX-4120/4121/4124/4125
Figure 1-13. Connection Using M5 Bolt Set for RMX-4122/4123/4126/4127
Crimping terminal
Note If you do not connect load cables in the correct orientation, you will not be
able to attach the OUTPUT terminal cover.
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RMX Programmable Power Supplies User Manual
R
line up the half of the cover.
Attaching the Output Terminal Cover
You can adjust the diameter of the holes that the load cables pass through by changing the
positions in which the top and bottom halves of the OUTPUT terminal cover are put together.
There are two available positions. Use the appropriate position for the load cables that you are using.
• For cables that are up to 10 mm in diameter: Put the top and bottom halves of the OUTPUT
terminal cover together so that the hole diameter is small.
• For cables that are between 10 mm and 18 mm in diameter: Put the top and bottom halves
of the OUTPUT terminal cover together so that the hole diameter is large.
1. Remove the screw that is attached next to the output terminals on the RMX. Use this screw
to attach the OUTPUT terminal cover.
2. Place the bottom half of the OUTPUT terminal cover underneath the load cables connected
to the output terminals.
Figure 1-14. Attaching Bottom Half of the OUTPUT Terminal Cover
emove the screws, and then
Note The top and bottom halves of the OUTPUT terminal cover have different
shapes.
3. Align the tabs of the top half of the OUTPUT terminal cover with those of the bottom half.
Align the tabs of the OUTPUT terminal cover according to the load cable diameter.
© National Instruments | 1-15
Chapter 1 Installation and Preparation
Top half of the cove
Align the protrusion of
the top half of the cover
with the top section
of the protrusion of the
bottom half.
Bottom half of the cover
For thick load cables
Cover hole diameter:
10 mm to 18 mm
Cover hole diameter:
Up to 10 mm
For thin load cables
Top half of the cover
Align the protrusion of
the top half of the cover
with the middle section
of the protrusion of the
bottom half of the cover.
Bottom half of the cover
Middle
section
Top section
After you have lined up the top and bottom halves
of the cover, use the screws to fix the cover in place.
Screws (M3)
Figure 1-15. Aligning Both Halves of the OUTPUT Terminal Cover
4. Push the OUTPUT terminal cover against the rear panel, and then use the RMX screws to
fix the cover in place. Ensure that the screws are securely fastened.
Figure 1-16. Attaching the OUTPUT Terminal Cover
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RMX Programmable Power Supplies User Manual
Sensing
When RMX programmable power supplies are shipped from the factory, the connector is
attached to the sensing terminals. RMX programmable power supplies are supplied with a
connector cover that fits over the entire sensing, J1, and J2 connectors. For safety reasons,
be sure to attach the connector cover when you use the RMX programmable power supply.
If they are damaged or lost, contact National Instruments.
Figure 1-17. Connector Cover
Figure 1-18. Terminal Connector
Caution Risk of electric shock and damage to internal circuits.
Never wire the sensing terminals while the POWER switch is turned on.
Use sensing cables that provide reinforced or double insulation with a capacity
greater than or equal to the isolation voltage of the RMX programmable power
supply. For uncovered sections of the shielded cables, use insulation tubes to secure
reinforced or double insulation with a capacity greater than or equal to the isolation
voltage of the RMX programmable power supply.
The sensing terminals are at approximately the same electric potential as the negative
output terminal. Insert the cables so that the wire strands do not touch the chassis
when they stick out of the sensing terminal. Also, insert the cables so that the stripped
wires do not stick out of the terminal.
© National Instruments | 1-17
Chapter 1 Installation and Preparation
Strip 7 mm (0.28 inches) of the
cable covering, and then insert
the cable here.
Incorrect
Incorrect
Correct
The wire itself is
in contact with
the chassis.
Wire scraps are
in contact with
the chassis.
Strip gauge
7 mm (0.28 inches)
Use this screw to fix the cables
cables in place so that they do
not come loose.
Local sensing jumpers
Even if you turn the output off or turn the POWER switch off, if the bleeder on/off
setting (CF11) is set to oFF, the voltage that was present when the output was on will
remain at the output terminals. Set the bleeder on/off setting to on before you touch
the sensing terminals.
Regardless of whether local sensing or remote sensing is used, be sure to attach the
sensing terminal cover before turning the POWER switch on.
If the sensing cables come loose, the output voltage across the load may become unstable, and
an excessive voltage may be applied to the load. If an appropriate OVP trip point is set, the OVP
will trip before an excessive voltage is generated.
When you are finished with remote sensing, return to local sensing mode.
Figure 1-19. Sensing Cable Connections
Terminal Function
-S Negative remote sensing terminal.
-LS Negative local sensing terminal connected to the negative output terminal
— Not connected.
+LS Positive local sensing terminal connected to the positive output terminal.
+S Positive remote sensing terminal.
Sensing cable: AWG28 to AWG16
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Table 1-2. Sensing Terminals and Functions
RMX Programmable Power Supplies User Manual
+
–
+LS
+S
-LS
-S
Output terminal
Chassis terminal
Sensing terminal
RMX
Load
Use twisted-pair wires for the load cables.
Make the cables as short as possible.
Local Sensing
By factory default, RMX programmable power supplies are set to local sensing (the rear panel
sensing connector is hard wired). The sensing point during local sensing is the output terminal.
This method does not compensate for the voltage drop across the load cable, so use this method
when the load current is small or when you do not need to consider the load effect voltage.
Figure 1-20. Local Sensing
Remote Sensing
Remote sensing is a feature that reduces the effect of voltage drops across load cabling
resulting in a more accurate voltage being applied at the terminals of the load.
Refer to Appendix A, Specifications for the maximum voltage drop each RMX power supply's
remote sense terminals can compensate for. Select a load cable that has sufficient current
capacity to prevent the voltage drop in the load cable from exceeding the compensation voltage.
Refer to the Load Cables section for more information about the cables.
When using remote sensing, the output terminals compensate for the voltage drop across the load
cabling by increasing the output voltage above the programmed setpoint until the sense leads
detect the programmed setpoint at the load itself. This requires the output terminals to generate
a voltage that is greater than the programmed voltage level. If you are performing remote sensing
with the voltage close to the maximum output voltage of the power supply, the total output is
still limited by the maximum output voltage at the terminals of the power supply (105% of the
rated output voltage). If the signal doesn’t seem to be stable, an electrolytic capacitor may be
required at the sensing point (across the load).
To minimize noise on the output signal, use twisted-pair wires or 2-core shielded wires. Connect
the ground of your shielded wire to the ground of the RMX programmable power supply or the
load.
© National Instruments | 1-19
Chapter 1 Installation and Preparation
Band
Figure 1-21. Remote Sensing
RMX
Output terminal
Chassis terminal
Sensing terminal
+S
+LS
-LS
-S
Use twisted-pair wires for the load cables.
Make the cables as short as possible.
+
+
Load
–
For the sensing cables, use twisted-pair
wires or shielded wires.
C
–
Connect an
electrolytic
capacitor
across the load
as necessary.
1. Turn the POWER switch off.
2. Remove the sensing connector from the rear panel sensing terminals.
3. Remove the local sensing jumpers from the sensing connector.
4. Remove 7 mm of the wire covering. Connect the negative sensing cable to -S and the
positive sensing cable to +S.
Use cable screws to securely fix the cables in place so that they do not come loose.
5. Pinch the tip of the band, and remove the band from the connector cover.
Figure 1-22. Bottom Cover with Band
6. As shown in the figure, create a ring 40 mm away from the connector, and fasten with the band.
Make the ring as small as possible, and fasten the band as tight as possible. The band can
be reused. Do not cut the extraneous portion of the band.
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RMX Programmable Power Supplies User Manual
through the hole by holding this area with
a pair of tweezers.
Figure 1-23. Sensing Wire Assembly
40 mm
You can pull out the band that you passed
7. Firmly attach the sensing connector to the sensing terminals.
8. Fasten the lower side of the connector cover to the panel with the included screws, and then
insert the tip of the band into the hole of the cover. Finally, bring the top and bottom sides
of the connector cover together, and fasten with the included screws.
Figure 1-24. Connector Cover Assembly
9. Turn the power switch on.
© National Instruments | 1-21
Chapter 1 Installation and Preparation
Load
S
+
–
C
+
–
+S
–S
+
–
Connecting an Electrolytic Capacitor Across the Load
If the cabling is largely inductive, it may be necessary to connect an electrolytic capacitor across
the load. If you run into this problem, the following symptoms may appear:
• The output of the power supply is oscillating. If very long wires are used to connect the
load, the inductive and capacitive components of the cable can cause phase shifting that
results in oscillation at the output. You can reduce this effect by shortening the load cables.
However, if this does not rectify the problem, connect and electrolytic capacitor across the
load.
• If the load current is changing rapidly in a pulse-shaped pattern, the output voltage may
fluctuate due to inductance in the cabling. You can reduce the inductance component by
twisting the load cables, which stabilizes the voltage. However, if this does not rectify the
problem, connect an electrolytic capacitor across the load.
Table 1-3. Electrolytic Capacitor with RMX Programmable Power Supplies
RMX-4120
RMX-4124
RMX-4121/
RMX-4125
RMX-4122/
RMX-4126
RMX-4123/
RMX-4127
36 V or more 96 V or more 276 V or more 780 V or more
Capacitance: 0.1 μF to a few hundred μF.
Withstand voltage: At least 120% of the rated output voltage of the RMX programmable
power supply.
Inserting a Mechanical Switch Between the RMX Programmable Power Supply and the Load
If you want to connect and disconnect the load using a mechanical switch that is inserted
between the RMX programmable power supply and the load, be sure to include switches in the
sensing cables as shown in the following figure. Also make sure to turn on and off the load cable
and sensing cables simultaneously. Before you turn the mechanical switch on or off, be sure to
turn the output or the POWER switch off.
Figure 1-25. Mechanical Switch in a Sensing Cable
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