Motor Protection Circuit Breaker (MPCB)

 

Overview

The term MPCB refers to Motor Protection Circuit Breaker. An MPCB is a circuit breaker designed specifically for protecting electric motors against overloads, short circuits, under voltage, and phase losses. The motor protection circuit breaker (MPCB) protects the motor from faults using a thermal-magnetic circuit breaker. For electric motors, the selection of the MPCB depends upon the motor’s full load current and the maximum short circuit current possible. MPCBs are available for different voltage levels, generally around 230 V to 660 V. They are unique in that they can withstand starting currents without interrupting the circuit.

Functions of MPCB:- 

Motor protection circuit breakers, or MPCBs, are specialized electromechanical devices that can be used with motor circuits at both 60Hz and 50Hz. Several functions allow it to provide a safe electrical supply for motors: 

1. A protection system against electrical faults, such as short circuits, line-to-ground faults, and line-to-line faults. Electrical faults that are below the MPCB’s breaking capacity can be interrupted by the board. 
2. Motor overload protection is used when a motor draws more current than its nameplate value for a prolonged period of time. MPCBs usually have overload protection that can be adjusted.
3.  Protection against phase imbalances and phase loss. In both cases, a three-phase motor can suffer severe damage, which is why the MPCB disconnects the motor as soon as the fault is detected. 
4. Thermal delay to prevent motors from being turned on immediately after overloads so that they can cool down. It is possible to permanently damage a motor if it is turned back on after it has overheated. 
5. Motor Circuit Switching – MPCBs are generally equipped with buttons or dials to switch motor circuits. 
6. Fault Signaling – Many motor protection circuit breakers have a display that turns on whenever a trip in the MPCB occurs. Until the fault is resolved, the electric motor must not be connected again. This visual signal alerts nearby personnel that a fault has occurred. 
7. Automatic Reconnection – Some MPCB models allow a cooling down period to be entered in case of overload. Once the cooling down period is entered, the motor will restart automatically. Due to the high cost of electric motors, motor protection circuit breakers are very important. Unless a motor is protected correctly, costly repair work or even equipment replacement may be necessary. MPCBs will extend the service life of an electric motor that is adequately protected.

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