Trouble shooting of electric motor. (part-C)

Many faults and its rectification are disclosed in Part-A & Part-B.Still some important faults are not disclosed.Here I will try to cover remaining all the faults

so maxmimum knoweledge you have,regarding trouble shooting of Electric Motor.It is also possible that you may find any other problem which is not

covered here,if this happens to you,you are requested to inform me,so I can add,hence other will also benifited.

This is the last post in this series,you are suggested to read Part-A & Part-B for total knowledge about rectification of faults in Electric motor which is used to

run Air Compressor.

Let's see some more faults,it's reason and rectification.

(I)FAULT:-UNBALNCED LINE CURRENT.

Reason:-(01) Unequal terminal voltage.

Rectification:-(01) Check lead and connection.

Reason:-(02) Single phase.

Rectification:-(02) Check for open circuit.

Reason:-(03) Poor rotor contacts in control wound rotor resistance.

Rectification:-(03) Check and rectify.

Reason:-(04) Brushes not in proper position in wound rotor.

Rectification:-(04) See the brushes are properly seated.

(J)FAULT:-SCRAPING NOISE.

Reason:-(01) Fan rubbing air shield.

Rectification:-(01) Remove interference.

Reason:-(02) Fan striking insulation.

Rectification:-(02) Clean fan.

Reason:-(03) Loose on base plate.

Rectification:-(03) Tighten holding bolts.

(K)FAULT:-MAGNETIC NOISE

Reason:-(01) Air gap not uniform.

Rectification:-(01) Check and correct bracket fits bearings.

Reason:-(02) Loose bearings.

Rectification:-(02) Correct or renew.

Reason:-(03) Rotor unbalance.

Rectification:-(03) Balance the rotor.

(L)FAULT:-MOTOR SPARKING AT SLIP-RING.

Reason:-(01) Motor may be overloaded.

Rectification:-(01) Reduce the load if overloaded.

Reason:-(02) Brushes may not be of correct quality and may be sticking in holders.

Rectification:-(02) Use brushes of recommended grade.(grade M-145E)

Reason:-(03) Brush pressure may be too light or too much.

Rectification:-(03) Adjust brush pressure correctly.The values are 0.15 to 0.20 kilogram per centimeter square of brush area.

Reason:-(04) Slip-ring may be rough,dirty or oily.

Rectification:-(04) Clean the slip-rings and maintain them smooth glossy and free from oil and dirt.

Reason:-(05) Slip-ring may be ridged or out of trueness.

Rectification:-(05) Turn and grind the slip-rings on lathe to smooth finish.

So,as per my knowledge these are the maximum faults may occure in Electric Motor.Read Part-A & Part-B to find out more problems and it's rectification.

For more details,please visit

http://www.pnengineering.blogspot.com/