MPCB Uses, Advantages, Connection | Motor Protection Circuit Breaker

Hey, we are going to learn about a very important electrical protective device which is MPCB. The full form of MPCB is Motor Protection Circuit Breaker. Here we will discuss the main function of MPCB, MPCB applications and uses, MPCB Circuit and Connection Diagram, MPCB Advantages, etc.
MPCB is a specially designed protective device used for the protection and operating purposes of Electrical motors. Generally, MPCBs are used for low-power motors.

MPCB is called as a specially designed protective device because it has an inbuilt contactor and relay mechanism. MPCB can be called, it is a substitute for Thermal Overload Relay with many extra advanced features. 

MPCB Functions and Features

MPCB is used with electrical motors. The main function of MPCB is, it will trip when the motor draws current exceeding the set limit. MCB or MCCB also tripped when overcurrent flow but they do not have adjustable current set limit features. In MPCB, we can set the current limit manually.

MPCB also has an important function that, it can reconnect the motor automatically to the power supply after the elimination of fault.

MPCB can give protection against Phase unbalance also. If phase unbalances occur, the motor will not work properly, it will take unbalance current and will be overheated. So, when MPCB is used, it will automatically disconnect the motor if phase unbalances occur.

MPCB also gives protection against Line to Line fault and Line to Ground Fault. When line-to-line and line-to-ground faults occur, the MPCB disconnects the motor automatically.

MPCB gives protection against Overload and Short Circuit faults. Like an MCB, MPCB also has two mechanisms, one is bi-metallic strips for thermal overload protection and another is a magnetic coil for short circuit protection.

MPCB Connection and Circuit

Here you can see the connection diagram of MPCB with a three-phase motor. Two Indication lamps are also connected for indication purposes.

Here you can see the MPCB has a total of ten terminals. Three for the main input, three for output, two NC(Normally Closed), and two NO(Normally Open) terminals.

The upper three terminals are connected to the main power supply. The lower three terminals are connected to the motor.
The R phase is connected to the one NO and one NC terminal. Neutral is taken to provide a 230V supply to the indication lamps.

When the MPCB is ON condition, its contactor will close, so the motor gets a power supply. When the MPCB is tripped or in off condition, its contactor will open, so the motor not get any power supply.

As the green indication lamp is connected through NC terminals, it will glow when the MPCB is in OFF condition. The red indication lamp is connected through NO terminals, so it will glow when the MPCB is in ON condition.

MPCB Applications and Uses

1. As its name suggests, the main use of MPCB is, it used for protection purposes of electrical motors.

2. MPCB is used in AHU(Air Handling Unit) panels, to operate and give protection to the AHU Motors.

3. MPCB is used with Air Compressors, Lift Motors, Elevators, etc.

4. MPCB is used with those motors that drive the variable loads such as cranes, escalators, etc.

5. MPCB is also used for the control and protection purposes of Exhaust Motors.

Motor Protection Circuit Breaker or MPCB Advantages

1. MPCB has an adjustable current limit feature.
2. It has an inbuilt contactor and relay, so there is no need for additional contactor and relay.
3. It has an automatic reconnect feature.
4. MPCB is compact in size and can be placed in a small place also.



Read Also:

• Proper RCCB connection Diagram with MCB.
• Why RCCB cannot give protection against Overload and Short Circuit Faults?
• MCCB Full Form | MCB and MCCB Difference

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