8.2
TROUBLESHOOTING PROCEDURE – IN CASE OF FUSE BLOWING
If fuses blow, a light bulb checkout procedure may be used without danger
of damaging the control and without excessive fuse blowing during
checkout. Proceed as follows:
a)
Turn power off at the source disconnect ahead of the control
b)
Connect two 120 volt, 100 watt bulbs in series with the ungrounded AC
input line ( L1 )
c)
Replace any blown control fuse(s) with a good fuse(s)
d)
Disconnect A1, A2, and field wires at the motor. Insulate wire ends.
e)
Turn power on at the service disconnect.
On controls without a DC loop contactor, make sure terminals 10 and 11
on 1TB are shorted together. On controls with a DC loop contactor make
sure that an auxiliary contact working in conjunction with the contactor is
closed when the DC contactor is energized. The bulb should not burn at
any setting of the speed control pot. If the bulb does not light, move on to
step (g). If the bulb does light, turn off the power and remove all
connections to 10TB. Reapply 230 volts to the control. If bulb does not
glow, trouble is probably a short in the external wiring. Rewire the
external wiring, one wire at a time until the wire(s) causing the problem
are located. Replace any defective wires. If the bulb still burns After all
external connections have been removed, move on to step (f). If the
problem has been corrected, move on to step (g).
f)
This step is to be done if step (e) shows that the light bulb still lights with
all external connections removed from 10TB including A1, A2, F1, and
F2. This probably indicates that the OC2 SCR’s, field diodes, and/or
power diodes are defective.
Only the power cubes and the free-wheeling diode (D50) are considered
field replaceable. The power cubes and D50 should be checked per
Section 9. Replace a power cube or D50 if found to be defective. After
replacement, the control should again be rechecked with all external
connections removed. If the light bulb still lights the field diodes, D1
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