If motor is switched on while one phase is cut off, motor will fail to start. It will make noise and draw considerable current. If proper protection (thermal overload relay / single phase preventer relay) is provided, it will trip supply to the motor. In absence of protection, motor will burn.
However if a phase is cut while motor is running, it will continue to run with more noise and vibrations, at least for some more time. What happens in long term depends upon the load.
If motor is operating at or less than 33% load, it will continue to operate without any harm.
If motor is operating at slightly higher than 33% load, motor will continue to operate, but it will draw current more than it's rated value. The motor temperature will start increasing. If thermal overload relay is provided in the motor starter, it will stop the motor before motor burns. But if thermal overload rely is not provided, motor may get burnt.
If motor is operating at higher load (near to the rated load), motor speed will drop gradually to zero.
It may take 1-30 seconds, depending upon amount of the overload and inertia of the load connected. For high inertia loads, it may take even more time to reduce the speed to zero. In this case thermal overload relay may stop the motor current or fuse may blow. If thermal overload relay / fuses are not provided, motor may get burnt.
Suzhou Smart Motor Equipment Manufacturing Co., Ltd. has two main business divisions. The first division is to provide different kinds of motor manufacturing machinery, including stand along machine, fully-auto complete line for armature ,stator production, and the motor assembly line, The second division is to provide technical support and consulting, project support and turn-key service for some motor manufacturing.
Contact Person: Mr. Larry