Molded Case Circuit Breaker Overview: Types, Functions, and More

Molded case circuit breakers are advanced circuit protection devices. They protect electrical circuits from overload current and short circuit damage. Molded case circuit breaker solutions are widely used in many industries. These include power distribution systems, industrial control panels, HVAC equipment, and other applications that require circuit protection.

Types of Molded Case Circuit Breaker: Overview

There are two main types of MCCBs. These include:


1.Thermal-Magnetic MCCB

The thermal-magnetic molded case circuit breaker type contains a bi-metallic thermal element that deflects proportionally to its temperature rise under prolonged overloads. This directly mechanically trips the circuit. This type also integrates an electromagnetic trip coil that swiftly responds to abrupt, high-fault currents associated with short circuits. While reasonably effective, the electromagnetic response of these MCCBs is not quite as expeditious as dedicated electronic models at clearing extremely large surge currents.


2.Electronic MCCB

Electronic MCCBs house advanced digital monitoring components instead of discrete thermal and magnetic units. This unified electronic MCCB design facilitates more precise and rapid fault detection. This type can accurately sense current, voltage, temperature, and additional inputs simultaneously in real-time. Some leading models offer supplementary protection functions such as ground fault monitoring. Advanced communication and interface capabilities in state-of-the-art electronic circuit breaker models also provide integration with facility automation and power management systems.

Functions of Molded Case Circuit Breaker

Molded case circuit breaker products perform critical protection functions for electrical circuits and equipment. These include:


1.Overload Protection

A molded case circuit breaker contains a bi-metallic thermal element that continuously monitors current flow through the circuit. If the current surpasses the rated capacity of the wires and equipment, the element will heat up. Upon reaching a certain temperature threshold, a mechanism within the MCCB is triggered to automatically open the circuit and prevent damage from prolonged overloads. This protects equipment from overheating due to excessive loads over time.


2.Short Circuit Protection

Short circuits cause a sudden, dramatic surge of current that can destroy circuitry in an instant if not cleared quickly. The MCCB contains an electromagnetic trip mechanism that senses fault currents and disconnects the circuit in milliseconds before serious harm can occur. This rapid response at levels above thousands of amperes minimizes equipment impact.


3.Overload Pre-Alarm

Some advanced models feature an early-warning overload pre-alarm function. As the thermal element begins to heat up under marginal overload conditions, the molded case circuit breaker will signal a warning before fully tripping. This allows maintenance personnel to investigate and address the cause proactively instead of a sudden shutoff.


4.Thermal Memory

When the MCCB trips during an overload event, its thermal trip unit retains memory of peak temperature levels. Before automatic reclosure, it ensures the unit fully cools down to prevent repetitive tripping from residual heat. This provides a reliable cooldown period for equipment and circuits. The thermal memory function is only available in certain advanced models.


Product Highlight: iSGM6E-800H by Maxge

Maxge is an ISO-9001-certified company and a leading manufacturer and supplier of power distribution and control equipment. We have 100+ patents and national certifications, and we boast high production capacity with our strong R&D team and modern manufacturing facilities. We offer a comprehensive range of molded case circuit breaker solutions that are widely used and trusted for their high performance and reliability.


Our iSGM6E-800H electronic MCCB is suitable for AC 50Hz/60Hz applications up to 415V voltage. This 630A and 800A MCCB is ideal for medium voltage systems requiring infrequent changeover of circuits or motor starting. Some of its key features include:

  • High ultimate short-circuit breaking capacity up to 100kA
  • Optional electrical accessories for additional protection and monitoring capabilities
  • Digitization and information management and remote monitoring using IoT connectivity
  • Liquid Crystal Display for circuit parameters and alarms
  • Anti-touch transparent cover and anti-flame insulated enclosure for safety
  • Ergonomic handle and tripping button for ease of use
  • Proven track record of protecting electrical systems worldwide


Overall, MCCBs are invaluable devices that protect electrical circuits and equipment from damage. The main types, i.e., thermal-magnetic and electronic, vary in their short-circuit response capabilities. Advanced MCCBs provide additional protection functions and monitoring features. As a leading manufacturer, Maxge offers high-quality and reliable MCCBs that boast maximum protection and advanced features. Contact us to browse all of our circuit protection solutions.

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