Operator`s manual
Pg. 6 Vicor 800-735-6200 Westcor Division 408-522-5280 Applications Engineering 978-749-3524 or -3525
Rev. 1/99
3 Phase MegaPAC Owner’s Manual
Technical Description
A 3 Phase MegaPAC is configured by installing ConverterPAC assemblies into a 3-Phase-front-end chassis. The chassis
takes AC input power and performs filtering and rectification functions. The ConverterPACs plug into a high-voltage back-
plane and provide low-noise, independently regulated and fully isolated outputs.
Input AC mains voltage (L1, L2, L3 and GND) is applied to an agency-approved mating plug. The input current is passed
through an EMI filter designed to meet conducted noise limit "A" specifications of FCC Part 15 and VDE 0871, before it is
passed to a three-phase full-wave bridge rectifier. The rectifier charges storage capacitors and delivers unregulated 300 Vdc
to a backplane after passing through a large choke that improves input power factor. The power factor typically exceeds 0.9
depending upon load, line voltage, frequency and line balance. Inrush current is actively controlled with an IGBT and never
exceeds 25A peak regardless of hot or cold starts.
A housekeeping supply, isolated from the AC input, powers the brushless DC cooling fan and other input monitoring cir-
cuits, in addition to providing an auxiliary +5V power source for the user. Excessive input currents caused by loss of a
phase, or excessive output loading in single phase operation, will safely shut down the unit until input power is recycled.
This occurs when the peak input current reaches 25A. An analog temperature monitor is provided, as well as overtempera-
ture shutdown. An active-high TTL compatible, Enable control is included for each ConverterPAC assembly, as well as an
active-low General Shutdown control; the polarities, active-high or active-low, are factory set. 3 Phase MegaPACs can be
safely paralleled with accurate current sharing for high power systems. All interface signals are safety-isolated using a com-
mon floating return.
Upon power-up, all outputs are first disabled to limit the inrush current, and to allow the unregulated bus to reach correct
operating levels for ConverterPAC assemblies. The internal housekeeping supply comes up within 500 mS after input
power is applied, and the AC Power OK signal asserts to a TTL "1," indicating the input power is OK. The low voltage
power outputs come up within 10-20 mS after the AC Power OK asserts to a TTL "1." Output ramp-up time from Enable or
General Shutdown is 10-20 mS. Output fall time from Disable is dependent on load, but is typically a few hundred
microseconds.
Figure 1. 3 Phase MegaPAC Architecture
Fuse
Housekeeping
Power Supply
DC Brushless
Cooling Fan
FCC/VDE
"A" EMI
Filter
3 Phase
Full-Wave
Rectifier
PFC Choke
IGBT
Opto-isolated
Control/Status
J10
Customer
Interface
J1
Input
Power
+P, -P
Output
Power
Remote Sense,
Trim Interface
Power Good
Interface
ConverterPAC (Up to 10)
DC/DC
Converter
Start-up Control
Circuits