User Manual Owner's manual

AC Induction Motors 11
• The fuses and other protective devices are in proper condition.
• All connections and contacts are properly made in the circuits
between the control apparatus and motor.
Motor Troubleshooting Chart
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
be desired for the purchaser’s purposes, the matter should be referred
to the manufacturer.
Your motor service and any troubleshooting must be handled by
qualified persons who have proper tools and equipment.
Trouble Cause What To Do
Motor fails to start Blown fuses Replace fuses with proper type and rating
Overload trips Check and reset overload in starter.
Improper power supply Verify that power supplied agrees with motor nameplate and load factor.
Improper line connections Check connections with diagram supplied with motor.
Open circuit in winding or control switch Indicated by humming sound when switch is closed. Check for loose
wiring connections. Also verify that all control contacts are closing.
Mechanical failure Verify that motor turns freely. Check bearings and lubrication.
Short circuited stator Indicated by blown fuses. Motor must be rewound.
Poor stator coil connection Remove end bells, locate with test lamp.
Rotor defective Look for broken bars or end rings.
Motor may be overloaded Reduce load.
Motor stalls One phase may be open Check lines for open phase.
Wrong application Change type or size. Consult manufacturer.
Overload Reduce load.
Low voltage Verify that nameplate voltage is maintained. Check connection.
Open circuit Fuses blown, check overload relay, stator and pushbuttons.
Motor runs and then dies
down
Power failure Check for loose connections to line, to fuses and to control.
Motor does not come up to
speed
Not applied properly Consult supplier for proper type.
Voltage too low at motor terminals because of
line drop.
Use higher voltage on transformer terminals or reduce load. Check
connections. Check conductors for proper size.
Starting load too high Check load motor is supposed to carry at start.
Broken rotor bars or loose rotor Look for cracks near the rings. A new rotor may be required as repairs
are usually temporary.
Open primary circuit Locate fault with testing device and repair.
Motor takes too long to
accelerate and/or draws
high amp
Excessive load Reduce load.
Low voltage during start Check for high resistance. Adequate wire size.
Defective squirrel cage rotor Replace with new rotor.
Applied voltage too low Get power company to increase power tap.
Wrong rotation Wrong sequence of phases Reverse connections at motor or at switchboard.
Motor overheats while
running under load
Overload Reduce load.
Frame or bracket vents may be clogged with
dirt and prevent proper ventilation of motor.
Open vent holes and check for a continuous stream of air from the
motor.
Motor may have one phase open Check to make sure that all leads are well connected.
Grounded coil Locate and repair.
Unbalanced terminal voltage Check for faulty leads, connections and transformers.