No-Load and Over Load Protection for Single Phase Induction Motors

Electric motors are the commonly used energy converter in various machines. The electrical energy is converted to mechanical energy with the help of electric motors. To protect the electric motors & connected machines from overload or short circuit conditions and save electrical energy when a no-load condition persists, there are different types of motor protectors used. There are different load conditions which may spoil the motor or even leads to a fire hazard. These abnormal load conditions of the motor must be monitored and initiate the shutdown action after a suitable confirmation time delay. This article describes the working of a no-load and overload/ short circuit protection for single phase induction motors using a microcontroller Atmega16, firmware development, and PCB design. The no-load protection feature is a new concept that is normally not available in commercially marketed motor protection devices. The microcontroller is used for fast computing and to take appropriate control action quickly. By using a microcontroller, the Variable Site Parameters (VSP) like upper and lower current limits can be configured by field engineers and an interfaced LCD display is used to monitor the values of VSPs and the operational events including real time load current.