14108242 Installation, operation and maintenance manual – Squirrel cage motor – WGM20 Line l 47
10
ABNORMALITIES, CAUSES AND SOLUTIONS
NOTE
The Table 10.1 present a basic list of abnormalities, causes and corrective actions. In case of questions, consult
WEG.
Table 10.1: Basic list of abnormalities, causes and corrective actions
ABNORMALITY
POSSIBLE CAUSES
CORRECTION
Neither coupled nor uncoupled
does the motor start
At least two power cables are interrupted,
without voltage
Check the control panel, the power cables
and the terminals
Rotor is locked
Unlock the rotor
Damaged bearing
Replace the bearing
Motor starts with no load, but fails
when load is applied. It starts very
slowly and does not reach the
rated speed
Load torque is too high during the start.
Do not apply load to the driven machine
during the start
Power supply voltage is too low
Measure the power supply voltage and set
it to the correct value.
Very high voltage drop in the power cables
Check the sizing of the installation
(transformer, cable section, relays, circuit
breakers, etc.)
Rotor with faulty or interrupted bars
Check and repair the rotor winding
A power cable was interrupted after the
start
Check the power cables
The stator current oscillates under
load with double the slip
frequency. The motor presents a
humming noise during starting
Rotor winding is interrupted
Check and repair the rotor winding
Very high no load current
Power supply voltage is too high
Measure the power supply voltage and set
it to the correct value
Hot spots in the stator winding.
Short-circuit between turns
Rewind the stator
Interruption of parallel wires or phases of
the stator winding
Redo the connection of the stator cables
Faulty connection
Redo the connection
Hot spots in the rotor.
Interruptions in the rotor bars
Repair the rotor or replace it
Abnormal noise during operation
with load.
Mechanical causes
The noise normally decreases when the
speed reduces; see also: “noisy operation
when uncoupled”
Electrical causes
The noise disappears when the motor is
switched off. Contact the manufacturer
When coupled, there is noise;
when uncoupled, the noise
disappears
Defect in the coupling parts or in the driven
machine
Check the power transmission, the
coupling and the alignment
Defect in the gear coupling
Align the driving set
Unaligned/unleveled base
Align/level the motor and the driven
machine
Faulty balancing of the components or of
the driven machine
Perform new balancing
Defective coupling
Repair the coupling
Wrong rotation direction of the motor
Invert the connection of two phases
