USER GUIDE | UG:110
Mini MegaPAC™
AC-DC Switcher
Contents
Overview
Standard Features
Optional Features
Mechanical Considerations
MegaPAC Dos and Don’ts
Technical Description
Page
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2
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3
3
5
6
8
Configuring and
Reconfiguring MegaPACs
ConverterPAC Functional
Description
Part Numbering
Overview
The Mini MegaPAC AC-DC switcher allows users to instantly configure high-efficiency, off-line power
supplies that operate on either 115 or 230V
AC
(47 – 500Hz) or 260 – 380V
DC
. Although small in size
(3.4 x 6.0 x 9.5in [85,8 x 153,4 x 241,3mm]), the Mini MegaPAC provides up to 1,000W 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 offers 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 VE-2xx and VE-Jxx modules.
Manufactured at Vicor, the entire family of MegaPAC power supplies is completely user-configurable.
If output requirements change, i.e., more power or a different 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 400V). The driver is to the left of the boosters
when looking at the output end of the supply. A user-friendly 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.
ConverterPAC Output and
Connector Pin Identification
for the Mini MegaPAC
9
Mini MegaPAC
Quick Install Instructions
PFC MegaPAC
Mechanical Drawing
Interface Connections
Specifications
New Output Studs
MegaPAC Family Connector Kit
(43075) Listing
Current Share Boards -
Optional Feature
Current Share Boards -
Optional Feature Diagram
Low-Leakage Version
10
13
14
20
21
21
22
24
25
Note:
This user guide contains references to parts and products that are no longer available for new designs.
They remain included for reference only.
UG:110
Page 1
Standard Features
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Input voltage: 90 – 132V
AC
or 180 – 264V
AC
, 47 – 500Hz, or 260 – 380V
DC
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Output power: 1,000W @ 115V
AC
or 230V
AC
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Outputs: five slots (up to ten outputs)
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Full-power output to 45°C; half power to 65°C
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cooled
Fan
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Conducted EMI meets EN55022 Class A and B
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Power OK status signal
AC
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RoHS compliant available
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Output Sequencing and General Shut Down (Consult Applications Engineering
for automatic sequencing circuitry)
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Autosense (refer to pages 11 and 14 for more information on Autosense)
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Overcurrent protection standard on all outputs
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Output overvoltage protection on all ConverterPAC™ outputs with VI-200™ module
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Output overtemperature limiting on all ConverterPAC outputs with VI-200 module
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Size: 3.4 x 6.0 x 9.5in [85,8 x 153,4 x 241,3mm]
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Safety Agency Approvals: CE Mark, cTÜVus
Optional Features
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OK status signal
DC
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Reversed fan air-flow direction
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Extended temperature range DC-DC converters
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Current share boards (see pages 22 – 24)
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Low-leakage version (see page 25)
Mechanical Considerations
The Mini MegaPAC™ can be mounted on any of four surfaces using standard 8-32 or 4mm screws. The
chassis comes with four mounting points on each surface; maximum allowable torque is 20lb.in. The
maximum penetration is 0.15in [3,8mm].
When selecting a mounting location and orientation, the unit should be positioned so air flow is not
restricted. Maintain a 2in [5,1cm] minimum clearance at both ends of the Mini MegaPAC and route
all cables so air flow is not obstructed. The standard unit draws air in at the fan side and exhausts air
out the load side. If air-flow ducting is used, avoid sharp turns that could create back pressure. The fan
moves approximately 30CFM of air.
Avoid excessive bending of output power cables after 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 45lb.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.
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Page 2
MegaPAC Dos and Don’ts
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units without Autosense,
do not leave ConverterPAC™ sense lines open.
Always terminate
For
them to their respective output locally or at the load. Use twisted pair 22 – 24AWG wire. If
ConverterPAC has Autosense, no local sense connection is required. See pages 11 and 14 for more
information on Autosense.
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needed, use Connector Kit #19-130040 for the Mini MegaPAC™.
If
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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 air flow escape from an empty slot significantly degrades thermal performance
and
can result in overheating and damage to the power supply.
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not unplug ConverterPACs while input power is applied. They are not designed for
Do
hot-plug applications.
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not restrict air flow to the unit. The fan draws air into the unit and forces it out at the output
Do
power terminals.
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Single-output ConverterPACs should NOT be paralleled directly together.
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power expansion, use booster ConverterPACs. Viewing the unit from the output terminal side,
For
always insert boosters to the right side of the driver. For booster arrays,
do not power up with bus
bars removed.
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Always ensure that output hex-nuts are properly torqued before applying power to supply.
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not use boosters as independent outputs. Disconnecting bus bars will damage
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booster ConverterPACs.
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the output (+/–) power cables next to each other to minimize inductance.
Run
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Wait five minutes after shutting off power before inserting or removing ConverterPACs.
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MegaPACs do not have user-serviceable components. They must be returned to the factory for
The
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.
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Insert proper fault protection at power supply input terminals (i.e., a fuse).
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proper-size wires to avoid overheating and excessive voltage drop.
Use
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Never loosen the inner nut on a ConverterPAC. Verify output nuts are tight before powering up.
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Output voltages over 60V
DC
, 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.
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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.
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Page 3
Technical Description
The Mini MegaPAC™ chassis consists of an off-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 rectifier / voltage-doubler configuration. This operates as a full-wave bridge rectifier on 230V
AC
or can be manually strapped for operation as a voltage doubler on 115V
AC
, delivering unregulated
300V
DC
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 the Vicor 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 efficiencies.
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 low-power 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 115V
AC
,
the internal housekeeping V
CC
comes up within two seconds after the application of input power.
On 230V
AC
, it comes up within 500ms. 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 <50ms later. An auxiliary V
CC
output of 5V
DC
sourcing up to 0.3A 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 – 10ms. The General Shut Down
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 after the loss of input power. Detecting the loss of input power takes a finite time period
after which the AC Power OK signal goes from a TTL “1” to “0.” This signal is available for use within
1.2s after initial power-up and can be used to indicate an impending loss of power. A minimum of 3ms
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
Power
Input
EMI Filter
AC/DC Power Rectification,
Input Voltage Strapping,
Inrush Current Limiting
High Voltage
Unregulated Bus
DC/DC Output
ConverterPAC #1
Power Output
DC/DC Output
ConverterPAC #2
Power Output
DC
Fan
Logic Power
Supply
DC/DC Output
ConverterPAC #3
Power Output
Housekeeping
Circuits
DC Bus Sense
Control
DC/DC Output
ConverterPAC #4
Power Output
Customer Interface
(Optoisolators)
DC/DC Output
ConverterPAC #5
Power Output
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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 4kW
MegaPAC). They are driver ConverterPACs and can be inserted into any available slot. For outputs
greater than 200W, 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 left
empty, it will provide an air flow 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. Torque the retaining screw to 0.23N.m [2lb.in]; do not overtighten. Power and
interface connections can be made after 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 – 4. After 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 400V. For a detailed guideline on how outputs should be
placed in series, please refer to:
AN:204 Creating High-Voltge Outputs.
Figure 2
Paralleling ConverterPACs
Bus Bars for Paralleling
Loosen screw to
remove ConverterPAC
1
Driver
2
3
Boosters
4
5
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Page 5
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