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6
E) Parallel Wiring
The internal oring/isolation diode of the PM allows
parallel n+1 redundant wiring with no modification or
other external isolation de vices required. Figures 9-10
on the following page illustrate some typical parallel
wiring schemes.
IMPORTANT:
When wiring two or more units in parallel
d.c. wires for all units should be identical in gauge and
length and the output voltage of each module should be
adjusted (as outlined below) in order to facilitate droop
load sharing.
Parallel Load Sharing Adjustment Procedures
Method 1:
1) Shut off all but one of the Power Modules and apply
a load equivalent to 1/2 of the rating for that unit (e.g.,
for model PM-12-70 apply a 35 amp load).
2) Connect a digital voltmeter to the test points on the
front of the power module at the “V OUT” and (+) and (-)
positions.
3) Verify that the output voltage is at the correct factory
setting (see Specifications section) or at the desired
system voltage. If adjustment is neces sary, use a small
flat tip screwdriver to turn the “OUTPUT VOLTAGE
ADJUST” potentiometer on the front panel until the
voltmeter reads the desired system output voltage.
4) Shut off the PM, turn on the next unit in the system,
and repeat steps 2 through 4 until all PM’s in the system
have the identical “V OUT” output voltage.
Method 2:
1) With all Power Modules powered up, apply the
typical operational d.c. system load.
2) Using a clamp-on ammeter, measure the output
current of each PM in the system. If there is an out-
put current differential of greater than 5 % between
any two PM’s, attach the ammeter to the PM with
the highest output current and turn the “OUTPUT
VOLTAGE ADJUST” potentiometer on that unit slowly
counterclockwise, until the output current of that unit
reduces slightly.
3) Repeat step 2 until there is less than 5 % current
output differential between all PM’s in the system.
F) Chassis Grounding
If grounding of the PM chassis is required for the
installation, use the provided 1/4” grounding stud on the
rear panel for this purpose (see Figure 2 or 3).
PM # 3
PM # 2
PM # 1
(+) Positive to
Distribution Panel
or Battery
(fuse at battery per
N.E.C. or local codes)
(-) Negative to
Loads or Battery
Ground Bus Bar
FIGURE 9: Parallel (two to six Power Modules)
and N+1 redundancy, negative ground
PM # 3
PM # 2
PM # 1
(-) Negative to
Distribution Panel
or Battery
(fuse at battery per
N.E.C. or local codes)
Ground Bus Bar
(+) Positive to
Loads or Battery
FIGURE 10: Parallel (two to six Power Modules)
and N+1 redundancy, positive ground
Note: 1kW models illustrated here;
refer to Figure 2 for output terminal positions of 560 watt models