The Basics of Molded Case Circuit Breaker (MCCB)

Molded Case Circuit Breakers (MCCB) is a required component of electrical systems, providing overload protection and short-circuit protection. In most cases, MCCBs are installed in the main power distribution board of a facility, allowing the system to be easily shut down when necessary. MCCBs are available in various sizes and ratings, depending on the size of the electrical system.

In this guide, we’ll cover the components and features of a typical MCCB, how they work, and which types are available. We’ll also discuss the benefits of using this type of breaker in your electrical system.

What is a Molded Case Circuit Breaker

A molded case circuit breaker, or MCCB, is a safety device used to protect an electrical circuit from overload or short circuits. It works by automatically cutting off the power supply when a fault or overcurrent situation arises, thus preventing any damage to the electrical system. MCCBs can be used in both low-voltage and high-voltage systems.

In addition to providing protection against faults, they also provide isolation of the circuit for maintenance. MCCBs are typically installed in the distribution panel and provide a visible indication to let users know when the power is off.

The main components of an MCCB are:

Molding Case

The molded case or frame is the cushion that keeps all parts of the circuit breaker in place. It is solidly built from ‘glass polyester’ or ‘thermoset composite resin that gives a great nonconducting strength despite its compressed size.

Terminals

The terminals serve as connectors between external conductors and molded cases. They should be connected properly to prevent unusual heat production.

Operating Apparatus

This is the switch that opens and closes the molded case. Its handle connects the pull of the device and manual push.

Trip 'Unit

The Trip System is composed of temperature and current-reactive electromagnetic sensors that trigger the Operating Apparatus in case of short-circuit or current overloads. Its button can be pressed to reset the circuit breaker.

Arc Chamber

The Arc Extinguisher’s primary role is to curb and split the arc that can damage your circuit breaker. The action results in exterminating the current flow in the circuit breaker. Inside the arc chamber are contacts. Their role is to conduct and disrupt functions. Arc ‘Runners, on the other hand, function as new electrodes for the arc. Arc chutes, on the other hand, compress the arc in the middle of sidewall insulators.

Molded Case Circuit Breaker Application

On application, MCCBs are designed to handle high currents, especially on expensive equipment. You will often find MCCB used commonly used in industrial-levels of machinery such as the following:

Motors

MCCBs protect motors by having their settings modify the inrush current and give the delay it may need. When done correctly, the motors are protected from overloads without triggering the tripping mechanism.

Welding Machinery

Welding machines utilize high currents, which normal circuit breakers cannot handle. An MCCB can be used to protect welding machines by connecting the machine to its own circuit breaker.

Generators

It is widely known that generators produce high levels of amps and need costly gen-sets. To shield the linked circuits and generator from faults that may happen in the system, having an MCCB is essential as it can handle its high current ratings and protects your generators as needed.

Capacitor Banks

MCCB lessens the currents, which in turn, corrects the ‘power factor’ in commercial and industrial-level systems.

Modifiable Trip Modes

These settings allow MCCBs to be utilized in low-current appliances in the household. This makes it an all-rounder use as it can be adjusted between low and high-current settings.

Electric Feeders

MCCB has adjustable settings that can be adjusted and allows it to handle high currents. If applied to electric feeders that produce hundreds of amps, MCCB can dissipate these energies easily. It also acts as its primary ‘incoming breaker.

The design of Temperature & humidity sensor

As shown in the figure below, Temperature & humidity sensor consists of 9 parts, namely Non-isolated DC/DC power supply、Motion detection、Temperature sensor、Ambient light sensor、Signal input/output protection、Digital processing、Self-diagnostics/monitoring、Non-isolated DC/DC power supply、Energy storage、Wireless interface.

Motion detection

A passive infrared (PIR) sensor can be used for room occupancy or motion detection. Motion detection includes General-purpose op amps、Precision op amps (Vos<1mV)、Comparators、Series voltage references、Shunt voltage references、Precision ADCs, the corresponding products are LM2904B、OP07C、TLV3691、REF35、LM4040-N、ADS1015

Temperature sensor

Temperature and humidity are closely monitored by wireless environmental sensors. A humidity sensor with integrated temperature sensor can be an option for designs requiring both sets of data. A standalone temperature sensor or a thermistor with a corresponding operational amplifier may be used in designs that only require temperature data. Temperature sensor includes Humidity sensors、General-purpose op amps、Precision op amps (Vos<1mV)、Comparators、Series voltage references、Shunt voltage references、Precision ADCs, the corresponding products are HDC3020、TLV9062、OP07C、TLV3691、REF35、LM4040-N、ADS1015

Ambient light sensor

A light-to-digital sensor with integrated amplifier, analog-to-digital converter, and digital interface can be used for faster time-to-market and ease-of-use. A light dependent resistor may also be used. Ambient light sensor includes Light sensors、General-purpose op amps、Precision op amps (Vos<1mV)、Comparators、Series voltage references、Shunt voltage references、Precision ADCs, the corresponding products are OPT3002、TLV9302、OP07C、TLV3691、REF35、LM4040-N、ADS1015

Signal input/output protection

An ESD protection device may be required for protection on user buttons. Signal input/output protection includes ESD protection diodes, the corresponding products are TPD4S012、TPD4S010、TPD1E10B06

Digital processing

The design can use a dedicated microcontroller or a single system-on-chip solution which combines the microcontroller and radio on a single device. Digital processing includes Arm Cortex-M0+ MCUs、MSP430 microcontrollers、Low-power 2.4-GHz products、Sub-1 GHz wireless MCUs、Sub-1 GHz transceivers、Wi-Fi products、Series voltage references、Supervisor & reset ICs、Shunt voltage references、Noninverting buffers & drivers, the corresponding products are MSPM0G1106、MSP430F1612、CC2674P10、CC1352P、CC110L、CC3220SF、REF35、TPS3839、LM4040-N、SN74LVC2G17

Self-diagnostics/monitoring

A voltage supervisor can be used to keep the microcontroller in reset until valid voltage levels are reached. Self-diagnostics/monitoring includes Supervisor & reset ICs, the corresponding products are TPS3839、TPS3840

Energy storage

Wireless environmental sensors may harvest energy from a window or light source. An ultra low power harvester power management IC can be used to charge a super capacitor or rechargeable battery using a solar cell. Energy storage includes Load switches、Battery charger ICs、Analog switches & muxes、Real-time clocks (RTCs) & timers, the corresponding products are BQ25505、TPS22916、TS5A3160、TPL5110

Wireless interface

A system-on-chip solution which integrates a microcontroller and radio allows designs to run the application layer and wireless protocol stack on one chip. A microcontroller with dedicated RF radio topology allows designs to separate the wireless protocol stack from the application layer. Wireless interface includes Low-power 2.4-GHz products、Sub-1 GHz wireless MCUs、Other wireless products、Sub-1 GHz transceivers、Wi-Fi products, the corresponding products are CC2674P10、CC1352R、CC2592、CC110L、CC3220S

Conclusion

MCCBs are a must-have in any industrial, commercial, or home wiring. They are designed to be adjustable and can handle low and high currents. Their trip settings enable them to be used in applications such as motors and welding machines, while their higher capacity allows them to handle large electrical feeders. In any case, it is important to consult with the manufacturers to get reliable and high-quality MCCBs.