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what is the motor protection circuit breaker(MPCB)?

Motor protection is also called a low-voltage motor comprehensive protector. Its main functions: starting overtime, overload, phase failure, grounding, locked rotor, current imbalance, short circuit, under load, temperature, under voltage, overvoltage, high and low frequency, etc. Protective function. Protection mode: During the startup process, only startup overtime protection, phase failure protection, current unbalance protection, ground leakage protection, short circuit protection are activated. After the startup is completed, the related input protections are all put into operation.

 

how to select the motor protection circuit breaker

1 Motor: first understand the motor’s model specifications, functional characteristics, protection form, rated voltage, rated current, rated power, power frequency, insulation class, and so on. These contents can provide users with a reference basis for the correct use and maintenance and selection of protectors. such as single phase motor protection circuit breaker,three phase motor protection circuit breaker.

2 Environmental conditions: Mainly refer to normal temperature, high temperature, high cold, corrosion, vibration, wind and sand, altitude, electromagnetic pollution, etc.

3 Motor use: Mainly refers to the required characteristics when driving mechanical equipment, such as fans, pumps, compressors, and other different load mechanical characteristics.

4 Control system: control modes include manual, automatic, local control, remote control, stand-alone independent operation, centralized control of production lines, etc. Start-up methods include direct, step-down, star-delta, frequency-sensitive rheostat, inverter, and soft start.

5 Other aspects: whether the user’s on-site production monitoring and management are more casual or rigorous, the severity of the impact of abnormal shutdowns on production, etc.

6 In addition to the above 5 aspects, there are many factors related to the selection of motor protectors, such as:

  1. Installation location, power supply, coordination with the power distribution system, etc.;
  2. Consider whether to configure the protection of the newly purchased motor, upgrade the motor protection, or improve the protection of the accident motor, etc.;
  3. Consider the difficulty of changing the motor protection mode and the degree of impact on production;
  4. Actual working conditions on-site.

 

how to size motor protection circuit breaker

Mpcb dimension diagram:

 

motor protection circuit breaker vs mould case circuit breaker (mccb)

The biggest difference is that mpcb is specifically used to protect the motor, while mccb is universal

mpcb will not cut off the circuit, while mccb may

mpcb can prevent motor overload and short circuit, while mccb can only prevent short circuit. So mccb needs an additional overload relay and contactor