60 | Flameproof motors
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TROUBLESHOOTING CHART
NOTE
This troubleshooting chart provides a basic list of unusual cases that may occur during motor
operation, possible causes and recommended corrective actions. For further information,
contact WEG Service Area.
Table 10-1 - Basic listing of abnormalities, causes and corrective actions
Abnormality
Possible causes
Correction actions
Motor does not start either
coupled or uncoupled to the
load.
At least two power supply cables are interrupted,
without voltage;
Check the command panel, the power
supply cables and the terminals;
Rotor is blocked;
Damaged bearing;
Replace the bearing;
Motor starts with no load, but
fails when load is applied.
Motor starts very slowly and
doesn’t reach rated speed.
Load torque very high during starting;
Don’t apply load on the driven machine on
starting;
Very low power supply voltage;
Measure the power supply voltage, set the
correct value;
Very high voltage drop on the power supply
cables;
Check the installation design (transformer,
cable section, check relays, circuit breakers,
etc.);
Rotor with interrupted bars;
Check and repair the rotor bars, test the
short-circuit device (rings);
The power supply cable was interrupted after
starting;
Check the power supply cables;
Excessive no load current.
Very high power supply voltage;
Measure the power supply voltage and set it
to the correct value;
Heating on the stator winding.
Short-circuit among turns;
Rewind;
Interruption of parallel wires or winding phases of
the stator;
Defective connection;
Provide reconnection;
Stator winding becomes very
hot under load
Insufficient cooling due to dirty air channels;
Open and clean the air channels;
Fans operating in the wrong direction;
Correct the rotation direction of the fans;
Overload;
Measure the stator current, decrease the
load and analyze the motor application;
High number of starts or very high moment of
inertia;
Reduce the number of starts;
Very high voltage, leading to iron losses are very
high;
Don’t exceed the rated voltage by 110%
except when specified on the nameplate;
Very low voltage, leading to current is very high;
Check the power supply voltage and the
motor voltage drop;
Interruption on a power supply cable or on
winding phase;
Measure the current in all phases and
correct it;
Rotor drags against the stator;
Check the air-gap, operation conditions
(vibration...), bearing conditions;
The operating
condition doesn’t correspond to
the nameplate data;
Maintain the operation condition according
to the nameplate or reduce the load;
Power supply unbalance (burnt fuse, wrong
control);
Check if there is voltage unbalance or
operation
with two phases and correct it;
Dirty windings;
Clean;
Interrupted air tubes;