Motor Star Delta Starter

Let's assume that post to contain the question word "why?". To answer such a question requires more questions to be asked.

• Is the star timer expiring correctly and closing the delta solenoid?
• Is there a loose wire in the control circuit? Or a blown fuse?
• Is the mechanical interlock between the star and the delta contactors working correctly?
• Is the cabling to the motor corrected correctly at both ends?
• Is the MCC cubicle slide-out chassis correctly connected to the backplane?

Sir

Actually We are maked interlocking Bent star-delta contactor so interlocking fail or u r timer /timer contact fail

which contactor, timer u r use ?

....Bent....interlocking fail....

Un-jamming the mechanical interlock will solve the problem. Do not remove it, as its purpose is to prevent, absolutely, the star and delta contactors making contact at the same time; were they to do so then the supply fuses will be presented with a short-circuit, and will rupture, protecting the cabling.

...timer contact fail...

Replace the timer like-for-like, with a spare. Make sure the delay time setting is identical to the faulty one.