What is Full from of the MPCB ?
What is MPCB ?
Motor protection circuit breaker is a motor protection device, which is combination of MCB and over load relay. MPCB is specially designed to protect the motor against overload and variations in input current, Including line faults and phase loss or unbalanced in main circuit.
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| MCB + OLR = MPCB |
MPCB is the combination of MCB and OLR.
A motor protection circuit breaker (MPCB) take a less space instead MBC and overload relay.
MPCB provides fuseless circuit and switch OFF the motor instantly to prevent the motor from any in main circuit.
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| Siemens MPCB |
The working process of MPCB
There are three main function of motor protection circuit breaker. The MPCB is specially designed to protect the three phase electric motor.
1) Thermal protection guard - The motor protect against the overload. The contacts will be disconnected of the motor from power supply. When an excessive current passes through it during overload.
At starting time a time delaye response is built to allow high inrrush current. if the inrrush current is extend to long time and motor is not starting then the thermal contact will be tripped.
2) Magnetic protection guard - The electric,motor protect against short circuit and dangerous electric faults. The motor is intently disconnected by the tripinng action when it detects the fault.
3) phase protection guard - The motor protect against phase loss or unbalance phase voltage in three phase system. The three phase motor running properly with balance phase voltage. If the phase voltage unbalanced more than 2% it will reduce the motor life span and motor efficiency. But in three phase system if suddenly any one phase will be loss then the current exceed in any two phases from rated value, which will couse the motor winding burn out. Due to this the phase protection is more important for motor control circuit.
The MPCB is constantly measuring the fluctuation or variation in phase voltage and instantly disconnect the motor during loss or imbalance in three phase system.