MCCB stands for Molded Case Circuit Breaker and helps protect electrical equipment from fault currents such as overcurrents, short circuits and other electrical faults. Molded case circuit breakers are suitable for switchboards, plug-ins, switchboards and motors. It also works like a fuse and doesn’t need to be replaced when a short circuit is detected.

MCCB circuit breakers are available in frame sizes ranging from 15 amps to 3200 amps. The trip unit is divided into thermal magnetic trip and electronic trip. Commonly used current ratings are 16, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 400 and 630A. It is widely used in military, industrial, commercial and mining fields.

Working principle:

Current limiting breaking capacity

When a short circuit occurs in the circuit breaker, the rapid opening of the contacts will produce an arc. The less time the circuit breaker is disconnected, the closer Ics is to lcu, the better the current limiting effect, which can also greatly reduce the electromagnetic, electric and thermal effects caused by short-circuit current on the circuit breaker and electrical equipment, and prolong the service life of the circuit breaker.

Short-circuit protection

Short-circuit protection is a short-circuit instantaneous tripping. Attention should be paid to the timely adjustment of the protection after the load change, to prevent the calibration value is too small frequent tripping affect the quality of power supply, or the calibration value is too ambassador lines and equipment can not be effectively protected.

Overload delay protection

Overload delay protection refers to the load current exceeds the limited range of equipment in danger of burning equipment, the protection device can cut off power within a certain period of time. Overload has a process of heat accumulation, the protection action does not need to be too fast. For short time overcurrent, the protection should not act.

Isolation function

Isolation function is to require the circuit breaker to break the leakage current does not cause harm to people and equipment. After multiple short-circuit tripping switch performance decreases, the leakage current will increase. For the human body below 30mA is a safe leakage current, and in a harsh environment, more than 300mA leakage current for more than 2 hours, it is possible to damage the insulation phase to phase short circuit and thus cause a fire.

In addition, molded case circuit breakers can also be installed with different functional modules to achieve leakage protection, under voltage protection and other functions.

Application:

* Provide secondary side protection for transformer.

* Short circuit protection for the motor.

* Maintain 2-6 times the continuous current of the generator.

* Personnel safety.

How to choose a suitable molded case circuit breaker?

More information on molded case circuit breaker and accessories.

The rotary handle is used to control the operation of MCCB through rotation control.

For molded case circuit breaker, the handle has three terminals: on, off and reset.

Before explaining the use of the rotating handle on molded case circuit breaker, let’s see why the molded case circuit breaker is used.

Molded case circuit breakers have three main functions:

Overload protection – the current exceeds the rated value and lasts longer than normal application.

Electrical fault protection – very high current must be interrupted immediately during faults such as short circuit or line fault.

Electrical Switch for disconnection – this is less common function of circuit breakers, which can be used as manual disconnection switches in case of emergency or maintenance operations.

In order to achieve these functions, conventional switches cannot be used because the interruption of high current during fault may lead to arc. It is safer to use the rotary handle.For example, when we turn on / off a conventional switch, you may see an arc, which occurs when the air around the switch contact is wet, the hand is wet or the voltage is low.

If you want to turn off a circuit with over-current, it is not safe to use a conventional switch. Therefore, people choose to use rotary switches.

There are two types of rotary handles:

1. Direct Rotary Handle (Mount the handle on MCCB & cut out the opening in the panel door).
2. Extended Rotary Handle (Mound base unit on MCCB & handle on panel door. This having a provision that the panel door cannot be opened in MCCB ON position).

Click here to see details on rotary handle, or contact us to get one!

The trip unit is a device mechanically connected to the circuit breaker to release the holding mechanism and automatically disconnect the circuit breaker. Its function is that the vector sum of the current passing through the zero-sequence current transformer is not equal to zero when there is leakage in the line or personal electric shock, and the voltage is generated on both sides of the secondary coil of the transformer, and is amplified by the integrated circuit. The trip unit cuts off the power supply within 0.1 seconds, thus playing the role of electric shock and leakage protection.

Release function

The trip unit has protection functions such as overload, open circuit, leakage, undervoltage, overvoltage, unbalance, underfrequency, overfrequency, reverse power, phase sequence, etc. It also has load monitoring, real-time value measurement, demand measurement, and harmonic measurement. , Measurement table setting, maintenance, communication, DI/DO, regional selective interlocking, test interlocking, LCD interface display and other functions.

Classification of trip units

1. Thermal release
Thermal magnetic release provides magnetic protection and thermal protection, thermal protection is overload protection. Thermal protection: When the current passes through the release, the thermal element heats up (the direct heating current directly passes through the bimetallic sheet), and the bimetallic sheet is deformed by heat. When the deformation reaches a certain level, it hits the drawbar to drive the mechanism to cut off the circuit. Generally speaking, thermal magnetic trips are used in circuits to provide short-circuit and overload protection. Only in some special occasions, electromagnetic trips are used to provide short-circuit protection, while other components (such as thermal relays) provide overload protection.
2. Electromagnetic release
The electromagnetic release is connected in series with the protected circuit. When a normal current passes through the line, the electromagnetic force generated by the electromagnet is less than the pulling force of the reaction force spring, the armature cannot be attracted by the electromagnet, and the circuit breaker operates normally. When a short circuit fault occurs in the line, the current exceeds several times of the normal current, the electromagnetic force generated by the electromagnet is greater than the force of the reaction force spring, and the armature is attracted by the electromagnet and pushes the free tripping mechanism to release the main contact through the transmission mechanism. The main contacts separate and cut off the circuit under the action of the opening spring to protect the short circuit.
3. Loss of pressure release
The voltage-loss release is connected in parallel with the power supply side of the circuit breaker, which can play the role of under-voltage and zero-voltage protection. When the power supply voltage is normal, the operating handle is pulled, the normally open auxiliary contact of the circuit breaker is closed, the electromagnet is energized, the armature is attracted by the electromagnet, and the main contact can be locked in the closed position by the free trip mechanism, and the circuit breaker is put into operation. . When the power supply side is powered off or the power supply voltage is too low, the electromagnetic force generated by the electromagnet is not enough to overcome the pulling force of the reaction force spring, the armature is pulled up, and the free tripping mechanism is pushed by the transmission mechanism to make the circuit breaker trip, resulting in undervoltage. and zero voltage protection.
When the power supply voltage is 75% to 105% of the rated voltage, the loss-of-voltage release is guaranteed to pull in, so that the circuit breaker can be closed smoothly; when the supply voltage is lower than 40% of the rated voltage, the loss-of-voltage release is guaranteed to be disconnected Make the circuit breaker trip off. Generally, the normally closed button connected in series in the electromagnetic coil circuit of the loss-of-voltage release can also be used for the opening operation.
4. Shunt release
The shunt release is used for remote-operated low-voltage circuit breaker opening control. Its electromagnetic coil is connected in parallel with the power supply side of the low-voltage circuit breaker. When the opening operation is required, press the normally open button to make the electromagnet of the shunt release get electricity to attract the armature, and push the free release mechanism through the transmission mechanism to make the low-voltage circuit breaker trip.
5. Electronic release
The electronic release can have all the above functions and can be easily adjusted. Electronic trip unit is a circuit composed of electronic components, detects the current of the main circuit, amplifies and pushes the tripping mechanism.

Thermal release protection principle
The main purpose of overheating protection is to prevent the motor from overheating. Therefore, a model to simulate the motor heating is set up in the device, and the different heating effects of positive and negative sequence overload currents are considered comprehensively, and the heating and cooling process of the motor is simulated and calculated, mainly for the heating of the motor and long-term overload. Provide protection. And it has thermal memory, that is, after the protection acts on trip or signal, the motor is allowed to start again only when the heat accumulation value is reduced to below the fixed value through the process of heat dissipation.
Thermal tripping is the tripping of the overheat protection action, and the overheating protection is the overload protection with the characteristics of delayed tripping and delayed return. Setting of thermal release: larger than the rated current (1.1 to 1.2 times).

SSPD MCCB CNS series is suitable and popular in Russia market.

Cold resistance characteristics (lowest ambient temperature -50 °C)

 ● CNS molded case circuit breaker may be used between -25 °C and +70 °C. For temperatures higher than 40 °C, (+65 °C for circuit breaker used to protect motor feeders) devices must be derated.

 ● Circuit breaker should be put into service under normal ambient, operating-temperature conditions. Exceptionally, the circuit breaker may be put into service when the ambient temperature is between -35 °C and -25 °C.

 ● The permissible storage temperature range in the original packing is -50 °C and +85 °C.

We do test for MCCB：-50℃ for one hour, turn to℃ for one hour, and then turn to -50℃ for one hour, high and low temperature repeatedly, 72 hours in total. After 72 hours test, there is no any crack on the appearance of the MCCB and also spare parts. The breaker can be ON and OFF normally, and it can work normally. The test result indicates, our moulded case circuit breaker can work normally in the severe cold environment -50℃, like Russia and other countries.

 OEM Service

 ● Additional function, like two knobs of trip unit.

 ● Color customization, color of complete MCCB, include front cover, middle cover, bottom case, handle etc.

 ● Front cover design.

 ● Packing design with your company logo, labels,boxes,cartons.

Shendian Electrical, looking forward to our cooperation.

Sales manager: Helen

Email: [email protected]

Phone: 0086-13758416788(whatsapp, skype, wechat)

Shendian Electrical, надеемся на наше сотрудничество.

управляющий делами: Helen

Почта: [email protected]

Сотовый телефон: 0086-13758416788 (ватсап, скайп, вичат)