Motor protection with MCB with thermal and magnetic trips
Operating mode: Same as for direct on line starting instead of fuses and thermal relay you can use a motor circuit breaker with thermal and magnetic trips, a simple but at least as effective component. By pressing Forward push button the Q2 coil contactor is energized the motor will be connected for clockwise run and maintains itself after the button Reverse by means of auxiliary switch Q2, the Stop button and the auxiliary contact of Q3, which serves as interlock, thus avoiding simultaneous connection of Q2 and Q3 contactors. In a similar manner things take place if we want to change the direction of rotation, thereby pressing Reverse button contactor Q3 is connected so the motor is rotating counterclockwise, this is possible only by activating previously the Stop button. When overload occur circuit breaker opens Q1 so the motor is stopped.
Calculation of MCB and contactors
The Q1, Q2, Q3 contactors must be chosen according with rated power of your motor.