52 l
Installation, operation and maintenance manual – Squirrel cage motor – M line – Vertical 11371757
10
ABNORMALITIES, CAUSES AND SOLUTIONS
NOTE
The instructions of Table 10.1 present only 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
Bearing damaged
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 bar
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. 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
Interruption of the parallel wires or phases of
the stator winding
Faulty connection
Redo the connection
hot spots in the rotor
Interruptions in the rotor winding
Repair the rotor winding 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. Consult WEG
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 drive 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 or replace the coupling
Wrong rotation direction of the motor
Invert the connection of two phases
