WEG WGM, Installation, Operation And Maintanance Manual

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Installation, operation and maintenance manual – Squirrel cage motor – W Line - Horizontal and vertical 11239449
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

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