Vicor Mini MegaPAC AC-DC Switcher User Manual

USER GUIDE | UG:110

Mini MegaPACTM
AC-DC Switcher

November 2013

Contents Page

Overview 1
of Product

Mechanical 2
Considerations

MegaPAC 3
Do’s and Don’ts

Technical Description 3

Configuring and 5
Reconfiguring
MegaPACs

ConverterPAC 6
Description

Part Numbering 8

ConverterPAC Output 9
and Connector Pin
Identification

Quick Install 10
Instructions

Mechanical Drawings 13

Interface Connections 14

Specifications 20

Output Studs 21

Connector Kit Contents 21

Current Share Boards 22

Low Leakage Version 25

Overview

The Mini MegaPAC AC-DC switcher allows users to instantly configure high eciency,
o-line power supplies that operate on either 115 or 230 Vac (47-500 Hz),
or 260-380 Vdc. Although small in size, (3.4"H x 6.0"W x 9.5”L), (85,8 x 153,4 x 241,3 mm),
the Mini MegaPAC provides up to 1,000 W of output power. The chassis has five slots
and can provide up to ten isolated outputs.

A complete power supply is configured at the factory by selecting and inserting up
to five same length slide-in output assemblies called ConverterPACs. ConverterPACs
incorporate one or two VI-200/VI-J00 and/or Maxi Vicor DC-DC converters and are
available in a wide array of output voltages and power levels. The net result is a power
supply that oers the advantages of a custom supply, but is assembled from standard
and modular building blocks. For detailed information about the ConverterPACs, refer
to the ConverterPAC data sheets. The ConverterPACs used in the Mini MegaPAC use VE­2xx and VE-Jxx modules. In addition, there is a four output model called a FlexPAC that
uses discrete circuits to support low power needs.

Manufactured at Westcor, a division of Vicor, the entire family of MegaPAC power
supplies is completely user-configurable. If output requirements change, i.e., more
power or a dierent output voltage is needed, upgrading is easy: simply unlock a single
screw and replace the slide-in ConverterPAC assembly with one of the same length
and has the desired voltage power rating. For additional flexibility, ConverterPACs
can be connected in parallel to increase output power (booster ConverterPACs), or in
series for higher voltages (total output voltage should not exceed 400 V). The driver
is to the le of the boosters when looking at the output end of the supply. A user­friendly interface provides control and output sequencing capability, in addition to
useful status indicators. Please consult our Applications Engineering Department if you
have other special requirements. Using the VSPOC configurator tool available on

vicorpower.com, anybody can now configure a Mini MegaPAC (and other Westcor

power supplies) online.

UG:110 vicorpower.com Applications Engineering: 800 927.9474 Page 1

Standard Features

n Input voltage: 90-132 or 180-264 Vac, 47-500 Hz, or 260-380 Vdc

n Output power: 1,000 W @ 115 Vac or 230 Vac

n Outputs: 5 slots (up to 10 outputs)

n Full power output to 45°C; half power to 65°C

n Fan cooled

n Conducted EMI meets EN55022 Class A and B

n AC Power OK status signal

n RoHS compliant available

n Output Sequencing and General Shutdown (Consult Applications Engineering

for automatic sequencing circuitry)

n Autosense (Refer to Page 10 and Page 14 for more information on Autosense)

n Overcurrent protection standard on all outputs

n Output overvoltage protection on all ConverterPAC outputs with VI-200 module

n Output overtemperature limiting on all ConverterPAC outputs with VI-200 module

n Size: 3.4"H x 6.0"W x 9.5”L (85,8 x 153,4 x 241,3 mm)

n Safety Agency Approvals: CE Mark, cTÜVus

Optional Features

n DC OK status signal

n Reversed fan airflow direction

n Extended temperature range DC-DC converters

n Current share boards - see Pages 22-24

n Low leakage version - see Page 25

Mechanical Considerations

The Mini MegaPAC can be mounted on any of four surfaces using standard 8-32 or
4 mm screws. The chassis comes with four mounting points on each surface; maximum
allowable torque is 20 lb-in. The maximum penetration is 0.15 in (3,8 mm).

When selecting a mounting location and orientation, the unit should be positioned so
air flow is not restricted. Maintain a 2" (5,1 cm) minimum clearance at both ends of the
Mini MegaPAC and route all cables so airflow is not obstructed. The standard unit draws
air in at the fan side and exhausts air out the load side. If airflow ducting is used, avoid
sharp turns that could create back pressure. The fan moves approximately 30 CFM of air.

Avoid excessive bending of output power cables aer they are connected to the
Mini MegaPAC. For high-current outputs, use cable-ties to support heavy cables and
minimize mechanical stress on output studs. Be careful not to short-out to neighboring
output studs. The Mini MegaPAC is supplied with serrated, flanged hex-nuts on all
output studs. Therefore, thread locking compounds or lock washers are not required.
The maximum torque recommended on flanged nuts is 45 lb-in. Never loosen the inner
nut on a ConverterPAC. This nut supports the hardware inside the ConverterPAC and is
factory torqued.

Avoid applications in which the unit is exposed to excessive shock or vibration levels. In
such applications, a shock absorption mounting design is required.

UG:110 vicorpower.com Applications Engineering: 800 927.9474 Page 2

MegaPAC Do’s and Don’ts

n For units without Autosense, do not leave ConverterPAC Sense lines open. Always

terminate them to their respective output locally or at the load. Use twisted pair 22-24
AWG wire. If ConverterPAC has Autosense, no local sense connection is required. See
Page 10 and Page 14 for more information on Autosense.

n If needed, use Connector Kit # 19-130040 for the Mini MegaPAC.

n Always fill all output slots of the MegaPAC. If a slot is not filled with a

ConverterPAC, it should be filled with an airblock. Airblocks are plastic assemblies
whose main function is to fill up an empty slot. Any airflow escape from an empty
slot significantly degrades thermal performance, and can result in overheating and

damage to the power supply.

n Do not unplug ConverterPACs while input power is applied. They are not

designed for hot-plug applications.

n Do not restrict airflow to the unit. The fan draws air into the unit and forces it out at

the output power terminals.

n Single output ConverterPACs should NOT be paralleled directly together.

n For power expansion, use booster ConverterPACs. Viewing the unit from the output

terminal side, always insert boosters to the right side of the driver. For booster arrays,
do not power up with bus bars removed.

n Always ensure that output hex-nuts are properly torqued before applying

power to supply.

n Do not use boosters as independent outputs. Disconnecting bus bars will damage

booster ConverterPACs.

n Run the output (+/–) power cables next to each other to minimize inductance.

n Wait 5 minutes aer shutting o power before inserting or removing ConverterPACs.

n The MegaPACs do not have user-serviceable components. They must be returned to

the factory for repairs. Contact Customer Service for a RMA number before returning
the unit. Do not attempt to repair or modify the power supply in any manner other
than the exchange of ConverterPACs as described in this User Guide.

n Insert proper fault protection at power supply input terminals (i.e., a fuse).

n Use proper size wires to avoid overheating and excessive voltage drop.

n Never loosen the inner nut on a ConverterPAC. Verify output nuts are tight

before powering up.

n Output voltages over 60 Vdc, whether from individual modules or series arrays, are

considered as hazardous secondary outputs under UL60950. Appropriate care must
be taken in design implementation of the supply.

n Only use the regular length ConverterPACs in the Mini MegaPAC. One cannot use any

of the Extended Length ConverterPACS in the Mini MegaPAC. The ELs are only used
in the EL (Low Noise) products.

Technical Description

The Mini MegaPAC chassis consists of an o-line single phase AC front end, EMI filter,
cooling fan, customer interface and associated housekeeping circuits. Input AC mains
voltage (L1/N, L2 and GND) is applied to a terminal block. The input current is passed
through an EMI filter designed to meet EN55022 Class A and B. At start-up, inrush
current is limited by an NTC thermistor prior to being passed to the power rectifiers.
The power rectifiers and filter capacitors are arranged in a conventional full wave bridge

UG:110 vicorpower.com Applications Engineering: 800 927.9474 Page 3

rectifier/voltage doubler configuration. This operates as a full wave bridge rectifier on
230 Vac, or can be manually strapped for operation as a voltage doubler on 115 Vac,
delivering unregulated 300 Vdc to a high voltage backplane. The backplane supplies
power to a variety of ConverterPAC assemblies that provide the desired low voltage,
regulated outputs.

Voltage conversion in the output assemblies is achieved by Vicor's family of
Zero-Current-Switching (ZCS) DC-DC converters. These are forward converters in which
the main switching element switches at zero current. This patented topology has a
number of unique attributes: low switching losses; high frequency operation resulting
in reduced size for magnetics and capacitors; excellent line and load regulation; wide
adjustment range for output; low EMI/RFI emission and high eciencies.

At initial power-up, the Mini MegaPAC outputs are disabled to limit the inrush current
and to allow the DC bus potential to settle out to the correct operating level. A low­power flyback converter operating with PWM current-mode control converts the high
voltage DC bus into regulated low voltage to power the internal housekeeping circuits
and DC cooling fan. When operating on 115 Vac, the internal housekeeping Vcc comes
up within two seconds aer the application of input power. On 230 Vac, it comes up
within 500 ms. Once the bus potential is within operating parameters, the AC Power OK
signal asserts to a TTL "1" indicating that the input power is OK, and allows the power
outputs to come up within <50 ms later. An auxiliary Vcc output of 5 Vdc sourcing up to

0.3 A is provided for peripheral use on interface connector J10-9.

An output Enable/Disable function is provided by using an optocoupler to control the
Gate In pins of the ConverterPAC assemblies. If the Enable/Disable control pin is pulled
low, the optocoupler turns on, pulling the Gate In pin low and disabling the output.
The typical delay associated for an output to come up when measured from release of
the Enable/Disable pin is 5-10 ms. The General Shutdown function controls all outputs
simultaneously and works in a similar manner.

The ride-through (hold-up) time is the amount of time the load can be supported before
loss of output regulation aer the loss of input power. Detecting the loss of input power
takes a finite time period aer which the AC Power OK signal goes from a TTL “1” to “0.”
This signal is available for use within 1.2 seconds aer initial power-up and can be used
to indicate an impending loss of power. A minimum of 3 ms of warning time is given.
Following the loss of input power, the outputs are disabled when the bus voltage falls
below its operating threshold.

Figure 1.

Mini MegaPAC Architecture

High Voltage
Unregulated Bus

Power
Input

EMI Filter

DC
Fan

AC/DC Power Rectification,
Input Voltage Strapping,
Inrush Current Limiting

Housekeeping
Circuits

Customer Interface
(Optoisolators)

Logic Power
Supply

DC Bus Sense

Control

DC/DC Output
ConverterPAC #1

DC/DC Output
ConverterPAC #2

DC/DC Output
ConverterPAC #3

DC/DC Output
ConverterPAC #4

DC/DC Output
ConverterPAC #5

Power Output

Power Output

Power Output

Power Output

Power Output

UG:110 vicorpower.com Applications Engineering: 800 927.9474 Page 4

Configuring and Reconfiguring MegaPACs

Most ConverterPACs of the same length can be easily added, replaced, or moved by
sliding the assemblies in or out of a MegaPAC chassis. (Currently, the exceptions
are the FinPACs which can only be used in the PFC MegaPAC-High Power and the
UniPACs which can only be used in the 4 kW MegaPAC). They are driver ConverterPACs
and can be inserted into any available slot. For outputs greater than 200 Watts, a
driver ConverterPAC and one or more booster ConverterPACs will be used. Arrays of
drivers and boosters should be configured so all boosters are placed in the slots to the
immediate right of the driver when looking at the output end of the MegaPAC.

Prior to removing or installing ConverterPACs, you must remove power from the
MegaPAC and wait five minutes. Failure to do so can result in personal injury or
damage to the supply.

Take standard ESD precautions when handling ConverterPACs.

Removing ConverterPACs

ConverterPACs can be removed by loosening the captive screw at the base. Once
this screw has been loosened, the ConverterPAC will slide out of the chassis. Once a

ConverterPAC has been removed, the empty slot MUST be filled with either another
ConverterPAC or an airblock. If the slot is le empty, it will provide an airflow escape

and cause failure to the power supply.

Installing ConverterPACs as Drivers

ConverterPACs can be installed in empty slots by simply sliding in the new
ConverterPAC and securing the screw at the base. Power and interface connections can
be made aer the ConverterPAC has been installed.

Installing Booster ConverterPACs to Increase Output Power

ConverterPACs can be paralleled for more power. Additional power to an output is
obtained by connecting one or more Boosters in parallel with a single Driver. The
Driver can be placed in any open slot. All Boosters should be inserted in the slots to
the immediate right of the driver when viewed from the output end of the MegaPAC.
Figure 2 shows a driver placed in slots # 1 and 3 boosters placed in slots # 2 to 4. Aer
inserting the Driver and Boosters, they are paralleled using bus bars across the positive
and negative output studs. Drivers should not be paralleled with each other. Bus bars
between a Driver and Booster(s) should never be disconnected. (For help in identifying
Boosters and Drivers, refer to the Part Numbering section on Page 8). Please note that
total output voltage should not exceed the converter baseplate-output isolation rating of
400 V. For detailed guideline on how outputs should be placed in series, please refer to
the Applications Note (Creating High Voltage Outputs) available on the website
at www.vicorpower.com.

Figure 2.

Paralleling ConverterPACs

Bus Bars for Paralleling

Loosen screw to

remove ConverterPAC

123

Driver

Boosters

UG:110 vicorpower.com Applications Engineering: 800 927.9474 Page 5

4

5

Remote Sense

Output Adjust

- Vout

+ Vout

DC OK (Power Good)

VI-J00

Remote Sense
Output Adjust

- Vout

+ Vout

DC OK (Power Good)

Remote Sense

Output #2 Adjust

Output #2

Output #1

Remote Sense

Output #1 Adjust

Remote Sense
Output Adjust

- Vout

+ Vout

DC OK (Power Good)

+ Vout

- Vout

Remote Interface

Voltage Limit Adjust

Current Limit Adjust

VI-200

ModuPAC

JuniorPAC

ConverterPAC Functional Description

ConverterPACs are the family of slide-in output assemblies used in MegaPAC power
supplies. Most ConverterPACs of the same length are interchangeable within a MegaPAC
and between AC input MegaPAC chassis. They can be added, moved, or changed as
necessary. The following ConverterPACs are used in the Mini MegaPAC.

ModuPAC

The ModuPAC output assembly consists of a VI-200 DC-DC converter that converts the
high voltage bus to the desired regulated output voltage. Each ModuPAC can provide
up to 200 Watts of power. Multiple ModuPACs can be paralleled in a Driver-Booster
configuration to provide more power. ModuPACs are fused with a PC-Tron, DC-rated,

+

fast-acting fuse. A passive LC filter is used to reduce output ripple/noise down to 1%

_

typical, and 2% maximum peak-to-peak from 10% to 100% of rated load. An optional
DC Power Good signal, or output voltage Trim potentiometer can be specified. The
ModuPAC contains overvoltage protection (OVP), overcurrent protection (OCP) and
overtemperature limiting (OTL). The OCP has automatic recovery when the overcurrent
condition is removed. The OVP and OTL are latching functions and require recycling of
the AC input power to restart.

JuniorPAC

The JuniorPAC consists of a VI-J00 DC-DC converter that converts the high voltage

+

bus to the desired regulated output voltage. JuniorPACs can provide up to 100 Watts of
output power and are fused with a single PC-Tron, DC-rated, fast-acting fuse. A passive

_

LC filter is used to reduce output ripple/noise down to 1% typical, and 2% maximum
peak-to-peak from 10% to 100% of rated load. An optional DC Power Good signal or
output voltage Trim potentiometer can be specified. The JuniorPAC contains output
overcurrent protection, which recovers automatically when the overcurrent condition is
removed. Overvoltage protection and overtemperature limiting are not available.

VI-J00 VI-J00

M2

VI-J00 RAM

M1

VI-200/BatMOD

DualPAC

RamPAC

BatPAC

DualPAC

M1

This output assembly consists of two VI-J00 DC-DC converters that convert the high
voltage bus to the desired regulated output voltages as noted above. The outputs

M2

are electrically isolated. Enabling and disabling the slot will control both outputs
simultaneously.

RamPAC

+

This output assembly consists of a VI-J00 DC-DC converter with a Ripple Attenuator
Module (RAM) and is designed for applications requiring low output ripple/noise.

_

The RamPAC can attenuate the ripple/noise down to 10 mV peak-to-peak or 0.15%
whichever is greater over a 20 MHz bandwidth from 10% to 100% of rated load of the
converter. RamPACs can only operate between 5–50 V and is limited to 100 W (20 A).

BatPAC

The BatPAC output assembly consists of a VI-200 BatMod current source that converts

+

the high voltage bus to the desired regulated output voltage. The converter is fused with
a PC-Tron, DC-rated, fast-acting fuse. The BatPAC is a 200 Watts programmable current

_

source that can be configured as a battery charger. Maximum current and voltage
settings are controlled using potentiometers that come as a standard feature, or through
Trim pin access as an option. BatPACs are available for 12 V, 24 V and 48 V battery
systems.

UG:110 vicorpower.com Applications Engineering: 800 927.9474 Page 6

M-1 STATUS

M-1 VOLTAGE ADJUSTMENT

M-4 STATUS

M-3 STATUS

M-2 VOLTAGE ADJUSTMENT

M-2 STATUS

M-4 VOLTAGE ADJUSTMENT

M-3 VOLTAGE ADJUSTMENT

CONNECTOR J1

FlexPAC

ConverterPAC Functional Description (Cont.)

FlexPAC

The FlexPAC output assembly consists of from two to four discrete outputs that
convert the high voltage bus to the desired output voltage. Each FlexPAC output can
be manually trimmed from 2 V to 25 V and supports up to 5 Amps with a maximum
output power of 50 W per output. All outputs maintain less than 50 mV noise over the
entire output range. All outputs support local sense only. For electrical trim options and
specific output sequencing contact the factory.

List of ConverterPACs used in the Autoranging MegaPAC and their features

ConverterPAC OVP OCP OTL RS/AS* LS/AS* PG TrimPot

ModuPAC Std Std Std AS* AS* Opt Opt

DualPAC N/A Std N/A AS* AS* N/A Opt

JuniorPAC N/A Std N/A AS* AS* Opt Opt

RamPAC N/A Std N/A AS* AS* Opt Opt

BatPAC N/A Std N/A N/A N/A N/A Opt

FlexPAC Std Std Std N/A LS N/A Std

* See Page 10 and 14 for more information on Autosense.

OVP Overvoltage Protection (latching) OCP Overcurrent Protection

OTL Overtemperature Limiting (latching) RS Remote Sense

PG Power Good (DC OK TTL Signal) LS Local Sense (replaced by Autosense)

AS Autosense

Note: All ConverterPACs mentioned above can be paralleled EXCEPT the DualPAC, JuniorPAC,
RamPAC and FlexPAC.

UG:110 vicorpower.com Applications Engineering: 800 927.9474 Page 7

Part Numbering

Mini MegaPAC MMxA-1xBxxxx

eg. MM4-143605

MM = Mini MegaPAC Prefix

xA = number of outputs

1 = Mini MegaPAC Chassis

xB = number of modules + FlexPACs

xxxx = assigned by Westcor

ConverterPAC XxDV/xEAx

F

eg. M15V/10A eg. M15V/10ADFI eg. D15V/6.7A-12V/8.3AT

X = ConverterPAC type (For RoHS, add G to current prefix)
M = ModuPAC D = DualPAC R = RamPAC J = JuniorPAC B = BatPAC
(RoHS = GM) (RoHS = GD) (RoHS = GR) (RoHS = GJ) (RoHS = GB)
xD = Voltage out

x

= Current out (rounded to 1 decimal point)

E

xF = Can be multiple options* (see below)

FlexPAC Fxxaaa-bbb-ccc-ddd

F = FlexPAC xx = pack chassis variations

aaa = voltage setting for output 1 with implicit factor of 10 (103 = 10.3 V)

bbb = output 2 ccc = output 3 ddd = output 4

* ConverterPAC options

Booster module

B

D DC OK or Power Good

F Full 50-110% output adjustment

50-107.5% output adjustment

F1

50-105% output adjustment

F2

50-102.5% output adjustment

F3

50-100% output adjustment

F4

60-110% output adjustment

F5

70-110% output adjustment

F6

80-110% output adjustment

F7

90-110% output adjustment

F8

100-110% output adjustment

F9

Industrial Grade module

I

Custom SRF module used

K

[1]

[2]

Military Grade module

M

Preload

P

R RAM external

Trimpot removed for external BatPAC adjustment

S

T 90-110% output adjustment

90-107.5% output adjustment

T1

90-105% output adjustment

T2

90-102.5% output adjustment

T3

90-100% output adjustment

T4

98-105% output adjustment

T5

100-110% output adjustment

T6

V1 "VXI" low noise (150 mV)15 V < V

"VXI" low noise (50 mV) V

V2

"VXI" low noise (1% ripple) for outputs >24 V

V3

[3]

[4]

< 24 V output

OUT

< 15 Vdc

OUT

5

[1]

D option: Optional for all ConverterPACs EXCEPT the DualPAC, BatPAC, and FlexPAC

[2]

F option: Optional for all ConverterPACs EXCEPT the BatPAC, DualPAC and FlexPAC.

Trim Range based on module type and voltage.

[3]

R option: When using an external RAM, components such as Autosense resistors and Local Sense
jumpers must be removed before turning on the supply. In addition, in order to insure proper operation,
sense pins must be connected either locally or remotely after the RAM's output. For further information,
contact Applications Engineering.

[4]

T option: Optional for all ConverterPACs EXCEPT the BatPAC, DualPAC and FlexPAC. Trim range
determined based on module type and voltage.

[5]

V option: Optional ONLY on the ModuPAC, DualPAC and JuniorPAC. N/A on all other
ConverterPACs.

UG:110 vicorpower.com Applications Engineering: 800 927.9474 Page 8

ConverterPAC Output and Connector Pin Identification for the Mini MegaPAC

DUALPAC

BATPAC

ModuPAC
JuniorPAC

RAMPAC

DualPAC

+ V0UT

J2-PIN1

0UTPUT ADJUST

- VOUT

J3-PIN1

J1-B-PIN1

J2-B-PIN1

OUTPUT ADJUST

J1-A-PIN1

J2-A-PIN1

OUTPUT ADJUST

(REMOTE SENSE)

J2

TRIM PIN ACCESS

1

2

+ SENSE

3

- SENSE

J3 DC OK (POWER GOOD)

Vcc IN

4

3

POWER GOOD

2

POWER GOOD INVERTED

1

SIGNAL GROUND

J1

(OUTPUT CONNECTORS)

1 AND 4 +V OUT

1

4

2 AND 5 -V OUT

2

5

6

3 +R/SENSE 6 -R/SENSE

3

J2

(REMOTE SENSE)

TRIM PIN ACCESS

1

2

+ SENSE

3

- SENSE

MATING HDWR:

HOUSING- MOLEX P/N: 50-57-9403

TERMINALS- MOLEX P/N: 16-02-0103

CRIMP TOOL MOLEX P/N: 11-01-0118

MATING HDWR:

HOUSING- MOLEX P/N: 39-01-0043

TERMINALS- MOLEX P/N: 30-00-0031

CRIMP TOOL MOLEX P/N: 57005-5000

MATING HDWR:

HOUSING- MOLEX P/N: 39-01-2060

TERMINALS- MOLEX P/N: 39-00-0039

CRIMP TOOL MOLEX P/N: 11-01-0197

MATING HDWR:

HOUSING- MOLEX P/N: 50-57-9403

TERMINALS- MOLEX P/N: 16-02-0103

CRIMP TOOL MOLEX P/N: 11-01-0118

BatPAC

FlexPAC

+ V0UT

CURRENT LIMIT ADJUST

VOLTAGE LIMIT ADJUST

- VOUT

J2-PIN1

M-1 STATUS

M-2 STATUS
M-1 VOLTAGE ADJUSTMENT
M-2 VOLTAGE ADJUSTMENT

CONNECTOR J1

M-3 VOLTAGE ADJUSTMENT
M-4 VOLTAGE ADJUSTMENT

M-3 STATUS

M-4 STATUS

J2 (BATPAC REMOTE INTERFACE)

CURRENT LIMIT ADJUST

4

3

VOLTAGE LIMIT ADJUST

2

CURRENT MONITOR

1

- VOUT

MATING HDWR:

HOUSING- MOLEX P/N: 39-01-0043

TERMINALS- MOLEX P/N: 30-00-0031

CRIMP TOOL MOLEX P/N: 57005-5000

MATING HDWR:

HOUSING MOLEX P/N 39-01-2120

TERMINALS MOLEX P/N 39-00-0039

CRIMP TOOL MOLEX P/N 11-01-0197

Note: New output studs have been installed on the ConverterPACs and are 1/8 inch longer.
Refer to Page 21 for more information.

UG:110 vicorpower.com Applications Engineering: 800 927.9474 Page 9