Specifications

12
1-800-927-9474
20-9
Autoranging MegaPAC/Mini MegaPAC Interface Connections (cont)
Vcc (J3-1)
The Vcc on J3-1 is an input that requires +5V either from the Auxiliary Vcc on J10-9, or from
another source. Input current to this pin is limited by an internal resistor to 3 mA. If the
Auxiliary Vcc on J10-9 is connected to Vcc on J3-1, then Signal Ground J10-10 must also be
connected to Signal Ground on J3-4.
Three Phase MegaPAC Technical Description
A Three Phase MegaPAC is configured by installing DC-DC ConverterPAC assemblies into a
three phase front-end chassis. The chassis takes three phase AC input power and performs
filtering and rectification functions. The ConverterPACs plug into a high-voltage backplane and
provide low-noise, independently regulated and fully isolated outputs.
Three Phase MegaPAC Chassis
Input AC mains voltage (L1, L2, L3 and GND) is applied to an agency-approved mating plug.
The input current is passed through an EMC 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-up storage capacitors and delivers unregulated 300Vdc 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 30A peak regardless of
hot or cold starts. The backplane supplies power to a variety of ConverterPAC assemblies that
provide the desired low-voltage, regulated outputs.
A housekeeping supply, isolated from the AC input, powers the brushless DC cooling fan and
other input monitoring circuits, 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 and provide a phase fail indication until input
power is recycled. This occurs when the peak input current reaches 30A. Analog and digital
temperature monitors are provided, as well as overtemperature 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.
Three Phase MegaPACs can be safely paralleled with accurate current sharing for high power
systems. All interface signals are safety-isolated using a common floating return.
Figure 12.
Three-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
J2
Remote Sense,
Trim Interface
J3
Power Good
Interface
3-Phase MegaPAC Chassis
ConverterPAC (Up to 10)
DC-DC
Converter
Start-up Control
Circuits
MegaPAC™ Family AC-DC, DC-DC Switchers