ABB DCS880 - DC-Motor Neutral Zone Adjustment; Types Concerned; Summary; General

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Service
3ADW000488R0101 DCS880 Service manual e a
DC-Motor neutral zone adjustment
Types concerned
DC-Motors.
Summary
Procedure to adjust the neutral zone of a DC-motor.
General
− Loosen the bolts holding the brush bridge.
− Connect a scope or a voltmeter between two adjacent brush-holder assemblies (holders with different
polarity).
− Set the scaling on the scope or voltmeter to mV AC.
− Disconnect the excitation cables and connect 110 … 240 V
AC
between F+ and F- (a normal extension cord
is sufficient).
− Start moving the brush bridge slowly in one direction and watch the scope or voltmeter. If the voltage is
increasing move the brush bridge in the other direction.
− Try to get the voltage down to less than 50 mV AC. The smaller the better.
− When this is achieved, start tightening the brush bridge bolts and watch the voltage. Sometimes you have to
do a little offset to compensate for movements during tightening.
− Finally, mark the correct neutral zone position in case the motor will be taken apart in the future.