The Complete Guide to Motor Protection Circuit Breaker

01st Jun 2023

Motor Protection Circuit Breakers (MPCBs) are essential devices used to protect electric motors from overloads, short circuits, and other electrical faults. In this comprehensive guide, we will explore the definitions, types, functions, and applications and introduce TOSUNlux as a trusted manufacturer of MPCBs. Whether you are an electrician, engineer, or motor user, this guide will provide valuable insights into motor protection and the benefits of choosing TOSUNlux for your MPCB needs.

What is Motor Protection Circuit Breaker?

Motor Protection Circuit Breakers, also known as motor circuit protectors, are specialized electrical devices designed to protect electric motors from damage caused by excessive currents, voltage fluctuations, or other electrical faults. They combine the functions of a circuit breaker and a thermal overload relay, providing comprehensive protection for motor-driven systems.

Types of Motor Protection Circuit Breakers

  • Thermal MPCBs

These MPCBs use a bimetallic strip or an electronic thermal overload relay to sense and protect against motor overloads. They monitor the motor’s temperature and trip when the current exceeds a preset limit for a specific period.

  • Magnetic MPCBs

Magnetic MPCBs, also called magnetic contactors or magnetic motor starters, offer short circuit and motor overload protection. They rely on electromagnetic principles to detect short circuits and provide rapid disconnection of the motor circuit.

  • Electronic MPCBs

Electronic MPCBs utilize microprocessor-based technology to monitor motor currents, temperatures, and other parameters. They offer precise motor protection, diagnostic capabilities, and advanced features such as motor phase loss protection, phase imbalance detection, and communication interfaces.

Functions of Motor Protection Circuit Breakers

  • Overload Protection

The primary function of an MPCB is to protect electric motors from overloads. By monitoring the motor’s current, they can detect when the current exceeds a safe operating level for an extended period, and they trip to interrupt the circuit and prevent motor damage.

  • Short Circuit Protection

MPCBs provide protection against short circuits, which occur when there is a sudden, high-intensity current flow. They detect the short circuit and quickly interrupt the circuit, preventing damage to the motor and other connected equipment.

  • Phase Loss and Imbalance Protection

Some advanced MPCBs offer protection against phase loss or phase imbalance in three-phase motor systems. They monitor the phase voltages and currents and trip if any abnormalities are detected, safeguarding the motor from operating in unfavorable conditions.

Applications of Motor Protection Circuit Breakers

  • Industrial Machinery

MPCBs are widely used in various industrial applications such as manufacturing plants, conveyor systems, pumps, compressors, and HVAC systems. They protect motors driving heavy machinery from overloads and short circuits, ensuring efficient and safe operation.

  • Commercial Buildings

MPCBs find applications in commercial buildings for motor-driven equipment like elevators, escalators, air handling units, and water pumps. They provide reliable motor protection, reducing the risk of equipment failure and downtime.

  • Residential Sector

MPCBs are utilized in residential applications for protecting motors in appliances such as refrigerators, washing machines, and air conditioners. They ensure the motors operate within safe limits and prevent damage due to overloading.


When seeking high-quality Motor Protection Circuit Breakers, TOSUNlux is a reputable manufacturer to consider. With their expertise in electrical protection solutions, TOSUNlux offers a comprehensive range of reliable and innovative MPCBs that meet industry standards.

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