In any Air Compressor unit,Electric Motor is the most important accessory to drive thr air compressor.To start and run the electric motor starters are used.
These starters are mainly of two types one is Automatic type and another is Manual operated starter.

Automatic Starters are Contactor type and mostly used in all Air Compressor units now a days.The details about both Starters are already given in my
earlier posts,which you may refer.

Trouble shooting and rectification about Electric motor are given in previous posts in three parts.Here I will disclose some problems which may occure in
Contactor type Starter (Automatic Starter) in two parts.I hope these post will help you to rectify problems of your Starter of Air Compressor.

Lets see some problems,its reason and rectification of Automatic Starters (Contactor type).

(A)FAULT:-CONTACTOR FAILS TO CLOSE.

Reason:-(01) Coil open circuited.
Rectification:-(01) Change the coil.

Reason:-(02) Loose control circuit connections.
Rectification:-(02) Tighten all the screws.

Reason:-(03) Voltage too low.
Rectification:-(03) Improve voltage condations.

Reason:-(04) Coil rating wrong.
Rectification:-(04) Use correct rating coil.

Reason:-(05) Obstacles in moving contacts carriers movement.
Rectification:-(05) Remove the obstacles.

(B)FAULT:-FUSES BLOWS DURING STARTING.

Reason:-(01) Fuse rating is too low.
Rectification:-(01) Use correct rating of fuses.Fuse for DOL Starters should be 3 to 4 times of motor full load current and for Star-Delta 1.5 to 2.5 times.

Reason:-(02) Short circuit in the system.
Rectification:-(02) Check and rectify the faulty CCF.

(C)FAULT:-INADVERTENT TRIPPING OF STARTERS.

Reason:-(01) Overload Relay setting low or single phasing
Rectification:-(01) Check voltage and current drawn by the Electric Motor and adjust Overload Realy to motor full load current.

Reason:-(02) Motor takes very long time to accelerate due to very low incoming voltage.
Rectification:-(02) Improve the voltage condition and use proper size cables.

Reason:-(03) Motor overloaded.
Rectification:-(03) Unload the Air Compressor during the starting.

(D)FAULT:-SEVERE CONTACT BURNING OR WELDING.

Reason:-(01) Excessive voltage drop during starting preventing magnet from closing in one stroke.
Rectification:-(01) Check the cross section of the cables from supply source to motor.

Reason:-(02) Insufficient contact pressure.
Rectification:-(02) Check moving contact spring pressure,change if necessary.

Reason:-(03) Change over in Star-Delta is too early.
Rectification:-(03) Increase the timer setting.

Some more faults will be covered in next part-B.

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