PROTECTION OF THREE PHASE INDUCTION MOTOR FROM SI

Abstract

The topic is introduced to protect an induction motor from single phasing and over temperature.
Providing a protection system is very important in industries, using lot of motors such that production is not hampered
owing to failure of any motor.
The basic idea for the development of this topic is to provide safety to the industrial motor/pump/lift Motor
etc. If any of the phases, out of the 3 phases is missing or if the temperature of the motor during operation exceeds the
threshold value, motor stops immediately. The system uses a 3-Phase power supply where three single phase
transformers are connected to it. If any of the phases is not available the corresponding transformer stops supplying
power to the circuit. This leads to one of the four relays getting switched OFF. The main relay which is powered through
a set of four relays gets disconnected because of one relay not being powered. Thus the main relay that delivers 3 phase
supply to the motor gets disconnected. A thermister is connected to the motor body to sense the temperature. If the
temperature increases then supply to the fourth relay is disconnected.
Three phase induction motor generally suffers from overheating, single phasing and phase reversal problems.
The rise in temperature level of a motor during its operation beyond a permissible limit is known as overheating. The
causes of motor overheating are motor overloading, distortion in the supply voltage, impaired cooling capability,
unbalanced supply voltages etc. Because of overheating, we can face the problems such as Electrical fire, Insulation
failure, Decrease in life time of motor due to earlier wear and tear of the motor windings etc.