f Excessive pitting
A) Excessive pitting and welding of contacts chattering is caused by following reason 1) Reasons: Coil not picking due to low voltage Remedy: Ensure correct voltage conditions In case of persistent low voltage change coil to lower voltage or change control transformer tapping 2) Reason: Broken Short circuit ring (Shading ring) Remedy: The mechanical life of contactor is over. Replace the contactor 3) Chattering in switching device Remedy: Check & correct the condition in the control circuit 4)Reason: Small cross section/long length Remedy: Select sizes as per guideline in sect on of control cable control wiring 5)Reason: Improper termination of control cable Remedy: Use proper lugs for termination 6) Inadequate capacity of control transformer Remedy: Use correct control transformer 7)Reason: Capacitor switching Remedy: Use correct contactor & follow guidelines 8)Reason: Short circuit during star delta changeover Remedy: – Use 7PU 60 20 timer 9)Reason: Reversing a...