Elcb Tripping

If it is running at full load, the two healthy phases will start carrying √3 x FLA, so the MCB will trip on overload in due course.

At the time of starting if motor is fully loaded, it might not be able to produce enough starting torque and consume 5 times current which will trip MCB.

At running also if it is full loaded at single phasing condition probably motor will stall.

Do you mean the situation if the supply is only 2 phases at starting? If so, there will not be any rotating field at all ! The MCB will trip sensing locked rotor current.

Yes, depending on the design, a fully loaded motor may stall on single-phasing, but i have not seen this often. Mostly it continues to run, and the severe negative sequence currents can damage the rotor unless protection is proper.

KVS! Are three pole ELCBs available in the market?

Not to my knowledge, 2 and 4 pole are what i have seen.

Generally in motor circuit ELCBs are not used. Fire protection is provided through earth fault relays with trip setting around 300mA. They are of three pole type.

Digital clamp type O/L relays with inbuilt earth fault protection are wided used. Example Siemens 3RB series.

If you want each phase of the three phase supply to the motor to be monitored sensitively. Then you install a "Phase Failure Device". The "phase failure device" will take out all three phases if one phase is low, over voltage, or a short occurrs on it.

As the purpose of the <...MCB...> is to protect the wiring, of which details have been withheld from this forum, it is not possible to say.

To protect the <...Motor...>, a motor overload device is needed in addition to the <...MCB...>.

Why anyone would <...remove one of the phases...> is a mystery that remains unsolved.

The <...ELCB...> serves no real purpose if there is no risk of a human being being downstream of it.

If in doubt, consult a qualified local Electrician.