Motor Controling CCT

Either a suitably rated contactor fitted with a thermal overload (to protect the motor) or a variable speed drive (VSD). Protect with a suitably rated 3 phase circuit breaker or MCCB, say 32A (next size up is 40A and that is a bit high to protect a motor running at about 28-29A at 400V, but it will depend on the type of load you are running).

Use of and sensitivity rating of the MCCB will depend on the application and the local standards. Common sensitivities are 30, 100 and 300mA. If it is in an industrial environment it will probably be either 100 or 300mA. If you want to use it with a variable speed drive you will need the type that is rated to handle the inrush current of the drive without tripping.

Dear Sir,

Thank You very much for valuable comments.

In your second para do mean RCCB (residual current circuit breaker).

Is it recommended to use RCCB with all the motor feeders in TT system?

Thanks

Yes (typo error). Use of an RCCB for earth leakage protection of the motor will depend on local electrical regulations standards. If it is required you may be able to protect multiple feeders using a single MCCB (with the separate feeder fitted with their own circuit breaker or linked-fuse bank), but again you will have to refer back to local electrical regulations.