B-65285EN/03 MOTOR MAINTENANCE 1.SERVO MOTOR MAINTENANCE
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1.3 PERIODIC INSPECTION OF AC SERVO MOTORS
We recommend that you inspect the AC servo motors for the following
items at least once a year.
(1) Observation of torque command (TCMD) and speed command
Observe normal voltage waveforms with an oscilloscope, and
keep notes of them. During periodic inspection, check the current
waveforms with the records.
The waveforms vary according to the operating conditions such as
load and cutting speed. Note that you should make comparisons
under the same condition (for example, during fast traverse to the
reference position or low-speed cutting).
See descriptions on the check boards in FANUC AC Servo Motor
αis/αi series Parameter Manual (B-65270EN) for detailed inspection
(2) Diagnosis by waveforms
Check the measured waveforms to see whether:
<1> The peak current is within the limit to the current in the
amplifier during rapid traverse, acceleration, or
The limit to the amplifier current is listed below. A voltage
of 4.44 V is indicated when the current flowing through the
amplifier is equal to the current limit for the amplifier
(common to all models).
Limit to the amplifier
Þ The motor used to accelerate/decelerate with the amplifier
current within the limit (the acceleration/deceleration torque
used to be sufficient), but something is wrong now. If this is
the case, the probable causes are:
• The load conditions in the machine have changed because
of changed friction or reduced machine efficiency after
long period of use.
• Motor failure