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What is an MCCB?

A molded case circuit breaker (MCCB) protects electrical circuits from overcurrent caused by circuit overload, short courses, or bad wiring. They are nearly identical to the Miniature Circuit Breaker (MCB) in that they perform the same function. MCCB, on the other hand, is more advanced. It features a higher current rating of up to 2500 amps and changeable trip settings.

These characteristics allow them to use it for circuit protection on low, medium, and high voltage substations. The essential advantage of an MCCB is that you can customize it to meet your needs by adding additional features such as remote shutting and UV trip. It is the most cost-effective and functional replacement for an air circuit breaker. In the MCCB, you may also modify the current and time settings.


There are 5 Types of MCCB:

Professionals classify MCCBs into five categories based on their trip curve. They are as follows:

  • Type B: This breaker trips when the current rate is 3 to 5 times higher than the current rating. You can employ them in low-surge-current home appliances and light business applications.
  • Type C: This circuit breaker trips when the current exceeds its trip curve by 5 to 10 times. With mild surge currents, you can use this type of MCCB in commercial and industrial applications. Transformers, printers, fluorescent servers, and computers are just a few examples.
  • Type D: When the current is 10 to 20 times higher than the trip curve, these MCCBs trip. You can use this MCCB type in high-inrush-current industrial and commercial applications like X-ray equipment, pumps, massive winding motors, large transformers, and others.
  • Type K: When the current rate is 10 to 12 times greater than the current rating, experts recommend this MCCB trip. They’re suitable for inductive and motor loads with many inrushes current.
  • Type Z: When the current is 2 to 3 times higher than the trip curve, the MCCB trips. They are sensitive to short circuits and can protect sensitive items like semiconductors.


Components of MCCB:

  • Arc chute: It is a stack of mutually insulated parallel metal plates that divide the arc in an MCCB. The manufacturers use steel and glass fiber to construct the arc chute.
  • Moving contact: It uses an electrolyzed brass substance as a moving contact. The moving contact’s MOC (Material of Construction) should have strong arc resistance, corrosion resistance, and low resistivity. The MOC determines the MCCB’s lifespan.
  • Operating mechanism: It deals with the process of creating and ending contacts. The operating mechanism’s speed depends on how quickly it moves the handle. You can refer to it as a “fast make” and “quick break.”
  • Base cover: The base cover of the MCCB comprises a closed assembly of glass-fiber reinforced thermoset polymer material. It improves the mechanical strength of the product. You can house all of the MCCB’s components within these covers.

Other Components:

  • Terminal connector: A bolt assembly comprising steel material makes up the terminal connector. You can use it to connect the MCCB to the external circuit. Professionals commonly utilize Allen’s head (hexagonal) bolts with an 8.8 Ton torque range as a terminal connector. It ensures that the terminals are not in contact with each other.
  • Overload trip or Bimetallic contact: It is a temperature-sensitive component of steel and copper. In series with the line current, manufacturers build the bimetallic communication.
  • Handle knob: You can use it to close or open the contact manually. Furthermore, you cannot cause the breaker to cease tripping by holding the knob on the top side. It’s referred to as a “free trip.”
  • Manual trip button: A manual trip button is a red color button that manufacturers connect to the operational mechanism. Mostly, you can use them to trip the breaker for testing purposes manually.
  • CT – Current Transformer assembly: Manufacturers install a set of current transformers inside the breaker, and the relay tripping unit will connect to the CT’s output. It is the MCCB’s brain.


How does the MCCB work? 

Like miniature circuit breakers, the molded case switch detects and interrupts defective currents using a temperature-sensitive device (thermal element) and a current-sensitive electromagnetic device (the magnetic element). As a result, they can provide:

* Overload protection:

The MCCB protects against overload (the bimetallic contact). When subjected to high temperatures, this contact consists of two metals that expand at opposite rates. The connection shuts under operating conditions, allowing current to flow through it. The overload trip warms up and finally bends away when the current exceeds the adjusted trip value. Circuits themselves disrupt as a result of this.


* Short circuit protection:

This switchgear uses electromagnetic induction to protect against defective currents and overload protection. As the current travels through the solenoid coil, the MCCB generates a modest electromagnetic force. Higher currents go through the breaker when a short circuit occurs. As a result, the solenoid coil generates a powerful electromagnetic field, forcing the trip bar to open the course.


* Electrical switch for disconnection: 

It has a manual button ON and OFF the circuit for emergencies or maintenance and the breaker’s tripping mechanism.


Testing and maintenance of MCCB:

You can use the following test to verify the operational level of an MCCB according to the ANSI/NEMA AB 4 criteria for inspection and preventative maintenance of MCCBs.

  • Insulation resistance test – Assess the degree of insulation between phases and supply and load terminals.
  • The inverse time overcurrent trip test verifies the breaker’s inverse overcurrent tripping function.
  • Individual pole resistance test (millivolt drop test): Check the breaker’s internal connections and contacts for electrical integrity.
  • Instantaneous overcurrent trip test ensures that the immediate trip features are working correctly under field test conditions.
  • Mechanical operation test: Perform an automated operation test to see if the operating mechanism is in good working order.



Maintenance is rarely required because most manufacturers seal breaker casings, and no one can open them. Preventive care may include cleaning the breaker regularly and manually turning it on and off to ensure it is in good functioning, depending on the operating conditions.


Available Products

GYCM3-160S/H Molded Case Circuit Breaker (MCCB)


The insulation rate for this product is 1000v. You can install this product to protect your homes and offices from short-circuit, current overflow, and other faults. You can also use it if you face infrequent start or overload issues. This MCCB is small in size, and you can install it anywhere you want without facing any troubles.


GYCM3-315S/H Molded Case Circuit Breaker (MCCB)


This product is available worldwide and protects your homes from overcurrent flow and short circuits. 3 to 4 poles make the smooth passage of current flow within the course. Moreover, it has a rated voltage Ue(V) of AC400V with a rated insulation voltage Ui(V) of 800v. The weight of the MCCB is comparatively less when you compare it with any other product.