Trouble shooting and rectification of Electric Motor.(Part-A)

In Air Compressor Technology Electric Motors are mostly used to drive the Air Compressor.Electric Motors are mainly two types one is "Alternet Current" (AC)
and other is "Direct Current" (DC) Motors.AC Motors are used in Air Compressor unit.Sometimes this Electric Motors are also give trouble and total
Compressor unit stops,resulting in plant shutdown.To avoid this,we have to take due care of our total Air Compressor unit alongwith Electric Motor.

I will describe some faults,it's reasons and rectification in three part.(Part A,Part B,Part C).You are suggested to read all the parts for total knowledge.

(A)FAULT:- MOTOR CONNECTED BUT DOES NOT START.

Reason:-(01) No supply voltage,one phase open,incoming voltage is too low.
Rectification:-(01) Check voltage on each phase.

Reason:-(02) Motor may be overloaded or control gear (Starter) defective.
Rectification:-(02) Reduce load,start uncoupled from load.Examine each step of the control gear (Starter) for bad contact or open circuit.Make sure that
brushes are making good contact with the slip-rings.

Reason:-(03) Rotor defective,Mechanical locking in bearings or at air gap.
Rectification:-(03) Look for broken rings or clean air gap,if choked.

(B)FAULT:-MOTOR RUNS AND THEN STOPS.

Reason:-(01)Power failure.
Rectification:-(01)Check for loose connections to line,to fuse and to control.

Reason:-(02) Overload on motor.
Rectification:-(02) Examine Overload trips.See that they are set correctly.See that Dash-pot are filled with correct grade and quantity of oil.

(C)FAULT:-MOTOR STALLS

Reason:-(01) Motor Overload.
Rectification:-(01) Reduce load.

Reason:-(02) Low Incoming Voltage.
Rectification:-(02) Insure that the incoming voltage required as per name plate is maintained.

Reason:-(03) Open Circuit.
Rectification:-(03) Fuse may be blownout,check Overload Relay,Starter & push out

Reason:-(04) Incorrect control resistance of Wound Motor.
Rectification:-(04) Check,control sequence,replace broken resistors.Repair open circuit.

(D)FAULT:-MOTOR DOES NOT COME UPTO SPEED.

Reason:-(01) Voltage too low at motor terminals because of line drop.
Rectification:-(01) Apply correct voltage as per name plate.Use correct size of cable.

Reason:-(02) If wound rotor,improper control operation of secondary resistance.
Rectification:-(02) Correct rotor control and connections.

Some more faults will be disclose in Part-B & part-C.

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