ARR Series Three Phase, Six Pulse SCR Charger
Corrective Maintenance
RS-420, Rev. 7
5-1
5.
CORRECTIVE MAINTENANCE
5.1
VOLTAGE CHECKPOINTS
When there is no DC output on the charger, check the following list for possible failure points in the charger.
(The schematic given on page 10 indicates points where a voltage reading should be taken. The chart on the
schematic lists the proper voltages to be found at each point.)
5.2
BALANCING PROCEDURE
5.2.1
2010 Series (Refer to Cabinet Dimension section)
1.
Remove two 18 point B control boards. Energize the charger according to instructions in the manual
and load the charger to 1/3 of rated output.
2.
Connect the probe of the oscilloscope to the AC inputs of the active SCR bridge. The voltage
waveform should look like Fig. 1. If the horizontal spacings in the waveform are unequal, adjust the
reactor balance pot located on the 18 point “B” control board for that phase so that the pattern is
symmetrical. Repeat this step for the remaining SCR bridges, operating unit on one phase only for each
balancing process. Mark each board with the phase it was tested in.
3.
Replace all boards in their respective phases. Connect the probe of the scope to the DC output
terminals and examine the ripple pattern. The waveform should look like Fig. 2. To balance the
pattern, readjust the reactor balance pots in Step 1.
5.2.2
1329 Series (Refer to Cabinet Dimension section)
1.
Repeat Steps 1 & 2 of the above procedure.
2.
Replace all boards in their respective phases. Connect an amprobe (clip-on ammeter) to one of the AC
input leads to an SCR bridge and note the current. Repeat this for the remaining SCR bridges. The
readings should be close.
3. If a phase is out of balance, adjust the phase balance pot for that phase, which is located on the control
panel, until the current is about equal to the other phases. Recheck the current balance in the other two
phases. There should be no more than a 5 amp difference between phases.
