Vicor DC MegaPAC DC-DC Switcher - Manual (Page 8)

Pg. 8 Vicor 800-735-6200 Mission Power Solutions (760) 631-6846 (phone) or (760) 631-6972 (fax) Rev. 3/04
DC MegaPAC Operator’s Manual
Interface Connections
Chassis Input Power Terminals (J9)
Input DC power is applied to solderless lugs J9, using a wire size of 2 AWG. J9-1 is the +DC Voltage IN connection, and
J9-3 is the -DC Voltage IN connection. The Earth Ground is accessed via J9-2, a size 10-32 self-locking PEM nut.
Maximum torque recommended is 25 lb-in. A fault clearing device, such as a fuse or circuit breaker at the power supply
input is strongly recommended. For an output of 1600 watts with operation on 48 Vdc (and low line operation of 42 volts),
a fast-blow fuse of 50 amps is recommended. Start-up inrush current is limited by a thermistor, and in most cases, will be
less than nominal line current during operation. Start-up inrush current can be calculated by I = MaxVin/10 (where Max
Vin is the maximum operating voltage. See Table 2.). Example: for a nominal 48V input, the maximum operating voltage
is 68; therefore, I = 68V/10 = 6.8 amps.
Note: A fault clearing device, such as a fuse or circuit breaker at the power supply input is required per safety agency con-
ditions of acceptability.
Output Power Connections (+P, -P for Single Output, or J1A/J1B for Dual Outputs)
For single output ConverterPACs, these terminals are two 1/4-20 plated steel studs. The upper stud is positive with respect
to the lower stud. For dual output ConverterPACs, there is a 6-pin Molex connector for each output. J1A pins 1 and 4 are
the +Output, and J1A pins 2 and 5 are the -Output. Pins 3 and 6 are duplicates of the Remote Sense terminals present on
J2A and J2B. Use appropriate wire size rated to handle the full output current, including short circuit levels. Avoid large
current loops in output cables; run power and return cables next to one another to minimize inductive effects. All outputs
are isolated and can provide positive or negative outputs.
Output +/-Sense Connections (J2 for Single Output, or J2A/J2B for Dual Outputs)
Although all outputs are open-Sense protected, the +/-Sense terminals MUST be connected to their respective outputs
before the DC MegaPAC is powered up. Regardless of the output polarity configured, the +Sense should always connect to
the +Power output. The -Sense connects to the -Power output. Sense connections are not required on booster
ConverterPACs, BatPACs, or if the Local Sense option is specified. Sense pins can be accessed on J1A/J1B or J2A/J2B on
dual output units.
Signal Ground (J10-1, 2, 12, 15)
Signal Ground (Connector Pin Identification on page 14) is an isolated ground reference for all J10 interfacing signals, and
can be used for ConverterPAC output status signals such as Power Good. This is not the same as Earth Ground on input
power connector J9.
Enable/Disable (J10-8 to J10-11, and J10-21 through 24)
The Enable/Disable control pins allow ConverterPAC outputs to be sequenced either on or off. For the DC MegaPAC,
J10-8 through 11 and J10-21 through 24 are the control pins for output positions 1 through 8. For DualPACs, both outputs
are sequenced. In parallel arrays, only the driver ConverterPAC need be controlled. The Enable/Disable pins should be
pulled low to less than 0.7V with respect to Signal Ground to disable the outputs. They will sink 10 mA maximum. These
pins should be open circuited or allowed to exceed 4.5V when enabled. Do not apply more than 6V to these inputs at any
time. If driven from an electromechanical switch or relay, a capacitor should be connected to eliminate the effects of
switch bounce.
DC
+
DC
–
Figure 7. Input Panel Connectors