SINGLE PHASING PREVENTER FOR THE PROTECTION OF THREE PHASE FAULTS

This paper proposes a protection scheme for three phase
induction motors against single- phasing faults. Dynamic
model of the induction motor in the stationary reference frame was adopted and modified to reflect single-phasing fault. A simulation algorithm was proposed, which can help determine the impact of single-phasing on any three-phase induction motor. A case study simulation was carried-out with sudden single-phasing using MATLAB/SIMULINK software. A
single-phasing protection by means of contactors was
reviewed before an enhanced single-phasing protection was
designed. A prototype of the enhanced protection method was
implemented by the use of ac to dc converter, PIC16F877A
and DC relays. The latter, in additional to offering protection
against single- phasing, also protects the motor from undervoltage,
over-voltage and voltage unbalance. Index Term- --
Single-phasing, Three-phase induction motor, PIC16F877A,
ADC, contactor. It is 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. 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 supplies to the motor gets 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.