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Motor is started too frequently
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Supply voltage too low, too high, or unbalanced
= 1
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Motor misaligned to load.
7,
Load out of balance (Direct drive application)
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Uneven tension on multiple belts
Driven load operating at resonant point / natural
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frequency.
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VFD torque pulsations
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Motor miswired at terminal box
6,
Uneven, weak or loose mounting support.
&,
Motor bearings defective
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Motor out of balance
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4
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Load to motor may be excessive or unbalanced
7,
Bearings contaminated.
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Incorrect grease or bearings for ambient extremes.
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VFD bearing damage
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Contact between rotating and stationary components
(
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The motor acceleration time is too long
7,
Motor is being started too frequently
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Motor voltage low
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Defective start switch inside motor
$
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High ambient temperature
0
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11 4 4
0
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See section 3.4.5.3
(1) Ensure that steady state supply voltage at motor terminals is within limits (see
section 3.4.1.3) Correct as needed (2) Reconnect motor per input voltage (3)
Obtain correct motor to match power supply.
Realign load
(1) Ensure that load is dynamically balanced: (2) Remove motor from load and
inspect motor by itself. Verify that motor shaft is not bent. Rule of thumb is 0.002"
runout for shafts extension lengths up to 3.00". Add 0.0005" per every additional
inch of shaft length beyond 3.00".
Mixing new with used belts. Replace multiple belt applications with a complete set
of matched belts.
(1) De energize motor and record vibration as load coasts from 100% speed to 0
RPM. If vibration drops immediately, vibration source is electrical. If levels do not
drop immediately, source is mechanical (2) Redesign system to operate below the
resonant point (3) On VFD driven loads, program skip frequencies to bypass
resonant points (4) Increase carrier frequency to obtain <3% THD current (5) On
variable torque loads reduce volts/hertz below base speed.
(1) Adjust VFD to obtain <3% THD current @ rated motor current (2) Adjust VFD
stability for smooth operation. Vector drives may be unstable at light load.
Match motor lead wiring to nameplate connection diagram.
Shim, strengthen or tighten where required.
Test motor by itself. If bearings are bad, you will hear noise or feel roughness.
Roller bearings are normally noisy when operated without load. If sleeve bearing,
add oil per nameplate instructions. For motors with regreasing provisions, add
grease per relubricating instructions (see section 4.2.3). If noise persists contact
warranty service.
Disconnect from load. Set motor on rubber pads on solid floor. Secure a ½ height
key in shaft keyway and energize from balanced power supply @ rated voltage.
Record vibration levels and compare with appropriate standards. If excessive
vibration persists contact motor manufacturer.
(1) If belt drive check system per section 3.3.4. (2) Other than belting, check
loading on motor shaft. An unbalanced load will also cause the bearings to fail. (3)
Check runouts of mating components, such as a C face and pump flange.
Motor enclosure not suitable for environment. Replace with correct enclosure
construction
See section 4.2.1
Ground brush, common mode filter, or insulated bearings must be added. Contact
motor manufacturer.
4
:
Belt squeal during across the line starting is normal: (1) Verify that supply voltage
is within limits (see section 3.4.1.3). (2) Ensure that motor lead wiring matches
nameplate connection diagram: (3) Isolate motor from load. (4) To locate point of
contact turn motor shaft by hand. (5) If point of contact is not located contact
motor service shop.
Motor may be too small for load. Record acceleration time. Start capacitors may
fail if acceleration time exceeds 3 seconds.
Excessive starting will damage motor capacitors. Contact motor manufacturer if
motor is started more than 20 times/hour or if acceleration time exceeds 3
seconds.
Verify that voltage at the motor terminals is within limits (see section 3.4.1.3).
Motor internal switch failure overheats start capacitor. Contact service shop or
motor manufacturer.
Verify that the ambient does not exceed motor's nameplate value
4
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