ABB MT Série Notice Technique page 8

These instructions do not cover all details or variations in equipment nor provide for every possible condition to be
met in connection with installation, operation or maintenance. Should additional information required, please contact
the nearest ABB Sales Office.
Motor trouble shooting chart
Your motor service and any trouble shooting must be handled by qualified persons with proper tools and equipment.
TROUBLE
Motor fails to start
Motor stalls
Motor runs and then
dies down
Motor does not come
up to speed
Motor takes too long to Excessive load
accelerate and/or draws Low voltage during start
high amp
Wrong rotation
Motor overheats while
running underloaded
8
CAUSE
Blown fuses
Overload trips
Improper power supply
Improper line connections
Open circuit in winding or control
switch
Mechanical failure
Short circuited stator
Poor stator coil connection
Rotor defective
Motor may be overloaded
One phase may be open
Wrong application
Overload
Low voltage
Open circuit
Power failure
Not applied properly
Voltage too low at motor terminals
because of line drop
Starting load too high
Broken rotor bars or loose rotor
Open primary circuit
Defective squirrel cage rotor
Applied voltage too low
Wrong sequence of phases
Overload
Frame or bracket vents may be
clogged with dirt and prevent proper
ventilation of motor
Motor may have one phase open
Grounded coil
Unbalanced terminal voltage
WHAT TO DO
Replace fuses with proper type and rating.
Check and reset overload in starter.
Check to see that power supplied agrees with motor
rating plate and load factor.
Check connections with diagram supplied with
motor.
Indicated by humming sound when switch is
closed. Check for loose wiring connections. Also,
ensure that all control contacts are closed.
Check to see if motor and drive turn freely. Check
bearings and lubrication.
Indicated by blown fuses. Motor must be rewound.
Remove end bells, locate with test lamp.
Look for broken bars or end rings.
Reduce load.
Check lines for open phase.
Change type or size. Consult manufacturer.
Reduce load.
Ensure the rating plate voltage is maintained.
Check connection.
Fuses blown, check overload relay, stator and push
buttons.
Check for loose connections to line, fuses and
control.
Consult supplier for proper type.
Use higher voltage or transformer terminals or
reduce load. Check connections. Check conductors
for proper size.
Check load motor is supposes to carry at start.
Look for cracks near the rings. A new rotor may be
required, as repairs are usually temporary.
Locate fault with testing device and repair.
Reduce load.
Check for high resistance. Adequate wire size.
Replace with new rotor.
Get power company to increase power tap.
Reverse connections at motor or at switchboard.
Reduce load.
Open vent holes and check for a continuous stream
of air from the motor.
Check to make sure that all leads are well
connected.
Locate and repair.
Check for faulty leads, connections and
transformers.
LV Motors/Machine Instructions 10-2000