Fault, Causes and Remedies for: Induction Motor

Fault Heading

Fault

Causes

Remedies

Induction motor

1) Motor does not start on load.

a) No supply voltage

a) Check voltage at Motor Terminals.

b) Driven equipment jam

b) Ensure freeness of driven equipment.

c) Motor shaft jammed.

c) Check freeness of motor shaft.

2) Motor starts and gets trips (star delta starter)

a) Timer setting on lowest step

a) Set timer on proper setting.

b) Relay setting on lower reading than rated current.

b) Set overload relay at 110% of rated full load current punched on Nameplate.

c) Terminal voltage is low.

c) Ensure rated voltage OR increase realy setting slightly.

d) Backup fuse blowing.

d) Correct rating of back-up fuse to be used.

e) Starting current is high due to heavy inertia.

e) Start stop the relay continously till motor, pick up full speed. If problem persist, Contact Us and inform Gd2 of load.

f) Misalignment.

f) Ensure proper alignment.

3) Motor connected but does not picks up full speed.

a) No supply of voltage

a) Check voltage between each two phases.

b) Motor jam

b) Check freeness of motor without coupling it to load.

c) Motor may be overloaded

c) Reduce load.

d) Loose connection.

d)Tight connection properly.

4) Motors runs and then stops

a) Power failure

a) Check loose connection to the line of fuses and starter in the motor Terminals.

b) Unbalance incoming 3 Phase voltage to motor.

b)1) Check loose connection. 2)Check the unbalance voltage and inform to Electricity Board people. c)Check all 3 fuses are proper rating.

c) Overload

c) Examine overload relay and see that they are set correctly to approximately 110% full load current punched on nameplate.

5) Motor does not achieve full speed.

a) Wrong KW / HP Selection.

a) Consult supplier for proper type of motor.

b) Voltage too low at motor terminals because voltage drop.

b) Use higher voltage tap on transformer terminals or increase cable size.

c) Starting load too high.

c) Reduce load, check the load, motor is supposed to start.

d) Wrong connection.

d) Do the connection as per connection diagram provided inside the Terminal box.

6) Motor takes too long to accelerate

a) Excess loading

a) Reduce load if motor is driving a heavy load or select higher rating motor

b) Applied voltage too low

b) Contact Electric Board to increase voltage tap.

b) Centrifugal switch open.

b) Check contact of centrifugal switch.

7) Winding burnt due to single phasing

a) Faulty starter (All 3 contact strip may not contact properly.)

a) Replace the starter.

b) Discontinuity in cable/cable short.

b) 1)Replace the cable. 2)Use single phase preventor.

c) One fuse blown

c) Replace fuse of correct rating.

d) Loose connection in starter or motor.

d) Ensure proper tightness of connection.

8) Wrong rotation

a) Wrong sequence of phases.

a) Reverse any two leads (phase)connections of motor or at switch board.

9) Motor not running incase of duel speed motor.

a) Connection not as per diagram provided.

a) Do connection as per connection diagram given inside the Terminal Box.

10) Motor shaft not free

a) Fan not rotating due to touching with Fancover.

a) Replace Fan / Fancover.

b) Dust, dirt and foreign particle got stuck between the Oilseal / O ring seal and shaft.

b) Remove the dust, dirt and foreign particles.

c) Rotor endrings fins obstructing with bearing cover nuts due to bearing cover fitted wrongly.

c) Open the motor and refit. Open the motor and refit the bearing cover correctly.

11) Excess Full Load current.

a) Excess loading.

a) Consult equipment manufacturer to ensure correct HP.

b) Low voltage

b) Ensure voltage at motor terminal as per nameplate details.

c) Driven Equipment jammed.

c) Contact equipment manufacturer.

d) Contact strip of starter rusty.

d) Replace starter.

e) Misalignment

e) Ensure proper alignment.

12) Excess no load current

a) Load of mechanism coming on motor.

a) De-couple the motor from the mechanism verify the current with Test Certificates.

b) The range of instrument selected for Checking the current is not suitable.

b) Select instrument having range 2 to 3 times of value to be measured.

c) Voltage at motor Terminals may be more than rated voltage of motor.

c) Correct the supply voltage by auto transformer.

d) Supply frequency less than rated frequency of motor.

d) Check the supply frequency and correct the supply voltage at terminals by using following formula at 50hz-415v site frequency. Test volts = (415 x 50)/(Supply Frequency)

e) Unbalance supply voltage.

e) While run in full load, the current should be within the rated value.

f) Loose connection in supply cables.

f) Locate and tightened a screw.

g) Wrong connection in stator.

g) Correct the connection.

13) Abnormal unbalanced current in 3 phases.

a) Unbalanced voltage.

a) Please correct voltage balance in all 3 phases and connected load. 2)Loose connection at starter. 3)Ensure fuses are proper size in all 3 phases.

14) Motor overheates while running on load.

a) Overload

a) Reduce load / overload protection to be given.

b) Fan blades may clogged with dirt and improper ventilation to motor.

b) Ensure the Cleaning of fan and continuous circulation of air over the motor for proper cooling.

c) Motor may have one phase open

c) Ensure that all leads are well connected and 3 phases supply is available.

15) Noise

a) Foundation is not Rigid.

a) Ensure rigidity.

b) Belt pulley misalignment.

b) Correct the alignment.

c) Noise due to solidification of Grease.

c) Remove the grease and re-apply the new high temperature grease or replace the bearing.

d) Noise due to driven equipment.

d) Check noise level of Bare motor.

e) Noise due to water / oil ingress into the bearings.

e) Change Oilseal to avoid liquid ingress into the Bearing.

f) Bearing noise due to punchmarks in bearing housing by unauthorised person.

f) Replace Flange OR Endcover.

g) Humming noise in motor

g) Certain amount of magnetic noise is inherent in some low speed design motor.

16) Motor vibrates after connection have been made.

a) Motor misaligned

a) Re-align

b) Coupling between driven member and motor shaft is out of balance.

b) Balance the coupling.

c) Driven equipment un-balanced or balanced with full key.

c) Rebalance drivenequipment or balance with half key.

d) Defective ball bearing.

d) Replace bearings.

e) Vibration due to fancover touches Bottom.

e) Ensure that there is a gap of 1 mm between fancover and base.

17) Shaft broken ---

a) Misalignment of pulley.

a) Ensure proper alignment of motor and driven equipment.

b) Impact / sudden load or sudden reversal of direction or no. of start / stops are more than 6 per hour.

b) Please inform during procurement of motor to select suitable shaft material with proper heat treatment.

c) Foundation not rigid.

c) Make foundation rigid.

d) Fixed coupling.

d) Use flexible coupling if there is slight misalignmnet.

e) Rework like drilling, punching and hammering on shaft extension.

e) Replace Rotor Shaft.

18) Shaft runout.

a) Shaft bent / twisted.

a) If runout of shaft is more than 40 um, replace shaft.

19) Starting speed less or motor does not start in Single Phase motor.

a) Loose connection of capacitor in Terminal Box.

a) Ensure the tight connection of capacitor in circuit as per connection diagram.

20) Motor rotating in both direction in Single Phase Motor.

a) Capacitor failure.

a) Replace capacitor.

21)Problem related to Brake.

a) --------

a) Contact us.