Induction Motors – Fault Finding & Remedies

Induction Motors – Fault Findings and Remedies

Faults Symptons Possible
Fail to start without load Motionless & soundless Power-off Consult power company
Switch-off Switch-on
No-fuse Install fuse
Broken wiring Check wiring and repair
Broken lead Check wiring and repair
Broken windings Check windings and repair
Fuse blows
(Automatic switch trips off, slow start with electro-magnetic noise)
Short circuit of circuit switches Check circuit switches and replace
Incorrect wiring Check wiring according to nameplate
Poor contact at terminals Lock tightly
Windings grounded Factory repair
Broken windings Factory repair
Poor contact of circuit switches Check and repair
Broken wiring Check and repair
Poor contact of starting switches Check and repair
Short circuit of starting switches Check and repair
Incorrect connections of starting switches Connect according to nameplate
Loading after start Fuse blows
(Fail to restart due to trip-off of automatic switch)
Insufficient capacity of fuse Replace fuse if wiring permits
Overload Lighten load
High load at low voltage Check circuit capacity and reduce load
Motor overheats Overload or intermittent overload Lighten load
Under-voltage Check circuit capacity and power source
Over-voltage Check power source
Ventilation duct clogged Remove the foreign matter in the duct
Ambient temperature exceeds 40°C Correct insulation class to B or F, or lower ambient temperature.
Friction between rotor and stator Factory repair
Fuse blown (Single-phase rotating) Install the specified fuse
Poor contact of circuit switches Check and repair
Poor contact of circuit starting switches Check and repair
Unbalanced three-phase voltage Check circuit or consult power company
Speed falls sharply Voltage drops Check circuit and power source
Sudden overload Check machine
Single-phase rotating Check circuit and repair
Switch overheats Insufficient capacity of switch Replace switch
High load Lighten load
Bearing overheats High belt tension Adjust belt tension
Slack belt tension Adjust belt tension
Misalignment between motor and machine shafts Re-align
Over speed of bearing outer-ring Adjust bracket
High bearing noise Replace the damaged bearing
Noise Electro-magnetic noise induced by electricity Occurrence from its first operation Could be normal
Sudden sharp noise and smoky Short circuit of windings
Factory repair
Bearing noise Noise of low “Shi-Shi” or “Thru-Thru” Could be normal
“Kala-Kala” as result of poor lubrication Grease
“Kulo-Kulo” as a result of deteriorated grease Clean bearing and grease
“Sa-Sa” or larger noise Replace the damaged bearing
Mechanical noise caused by machinery Loose belt sheave Adjust key and lock the screw
Loose coupling Adjust the position of couplings, lock key and screw
Loose screw on fan cover Lock fan cover screw tightly
Fan rubbing Adjust fan position
Rubbing as a result of ingression of foreign materials Clean motor interior and ventilation ducts
Wind noise Noise induced by air flowing through ventilation ducts
Induced by conveyance machine Repair machine
Vibration Electro-magnetic vibration Short circuit of windings Factory repair
Open circuit of rotor Factory repair
Mechanical vibration Unbalanced rotor Factory repair
Unbalanced fan Factory repair
Broken fan blade Replace fan
Unsymmetrical centers between belt sheaves Align central points
Central points of couplings do not lie on the same level Adjust the central points of couplings to the same level
Improper mounting installation Lock the mounting screws
Motor mounting bed is not strong enough Reinforce mounting bed
Mounting bed vibration caused by machines near motor Eliminate the vibration source near
(1) Circuit switches: These include knife switches, electromagnetic switches, fuse and other connection switch etc.
(2) Starting switches: These include Delta-Star starters, compensate starters, reactance starters, resistor starters, starting controllers etc.