10.
MOTOR TESTS
The following tests will be helpful in pinpointing possible motor problems.
Before making any test,
remove the armature and field leads from the control.
a)
Shorts to the Frame – Using a Megger set for 400 volt test potential,
check leakage resistance between the A1, A2, motor field leads and
the motor frame. Readings of less than 10000 ohms indicate the
possible problems. A dead short indicates need for immediate repair.
Checks for dead shorts may be made with an ohmmeter or a continuity
tester if a Megger is not available. Retest while rotating armature by
hand.
b)
Open or Shorted Field – A resistance check between F1 and F2 ( also
F3 and F4) should indicate a resistance between 100 and 600 ohms.
c) Open
Armature – An ohmmeter between A1 and A2 should indicate a
resistance of less than 10 ohms. Rotate the motor shaft very slowly,
while observing the ohmmeter. Because of the residual magnetism on
shunt field motors or the field on permanent magnet motors, a CEMF
will be produced in rotating. This will cause the ohmmeter readings to
change during rotation. Therefore, after moving the shaft a small
amount, stop and check the resistance reading. A high resistance
reading at any position of the rotated motor shaft when it is stopped is
a trouble indication. Armature opens are usually the result of bad
brushes, burned commutator segments, or severed wires.
11.
CONTACTOR OPERATED SYSTEMS ( OPEN CHASSIS CONTROLS
ONLY)
In certain applications it may be necessary to start and stop the OC2-500 motor
control through the use of a magnetic contactor. The contactor may be used to
make and break the two AC lines, or it may break the two armature lines A1 and
A2.
11.1
CONTACTOR OPERTION ON THE DC LINES
If the contactor is connected to make and break the DC lines (A1 and A2),
A third set of normally open contactor contacts
must be provided
and
connected to 1TB terminals 10 and 11. This contact, which closes to run,
replace the factory-installed wire jumper that is normally supplied with the
control. This contact should be a signal level contact.
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