What Are The Differences Between Molded Case Circuit Breakers And Frame Circuit Breakers? How Do You Choose Between Them? Understanding These Points Will Help You.

What are molded case circuit breakers (MCCBs) and standard circuit breakers (SCBs)? Most electrical workers are likely very familiar with these terms. However, when it comes to the differences between SCCBs and MCCBs and how to choose between them, many electrical workers may only know one or the other, especially beginners. We all know that molded case circuit breakers are also called enclosure circuit breakers. They are terminals encased in a plastic shell, containing an internal connection network. They have very low discharge resistance and can prevent the equipment from being affected by moisture or dust in humid environments. These circuit breakers are characterized by their compact size, small footprint, and ability to release large amounts of current in a short time. In addition, MCCBs have advantages such as simple installation, low failure rate, and high reliability.

Simple circuit breakers, also known as universal circuit breakers, are mechanical switching devices capable of connecting, carrying, and disconnecting current under normal circuit conditions, as well as connecting, carrying, and disconnecting current for a specified time under specified abnormal circuit conditions. So, what are the specific differences between molded case circuit breakers and standard circuit breakers? And how should one be selected? This article will explain in detail the differences between molded case circuit breakers and standard circuit breakers, hoping to deepen the understanding of electrical personnel.

1) Differences in Appearance and Installation Dimensions
Firstly, in terms of appearance, the two differ in size. Standard circuit breakers are larger in size and volume, while molded case circuit breakers are relatively smaller.

2) The trip functions of the two types differ. The intelligent trip unit of a frame circuit breaker has protection, measurement, auxiliary, special, and communication functions. Protection functions include long-delay protection, short-delay protection, instantaneous protection, MCR protection, grounding protection, undervoltage protection/alarm, overvoltage protection/alarm, voltage imbalance phase loss protection/alarm, phase sequence protection, low-frequency protection, high-frequency protection, reverse power protection, voltage harmonic alarm, and current harmonic alarm.

Measurement functions include current measurement, voltage measurement, power measurement, frequency measurement, energy measurement, and harmonic measurement.

Auxiliary functions include pre-alarm, self-diagnostic function, fault history recording function, and testing function.

Special functions include load monitoring, regional control, and high/low temperature range monitoring.

Communication functions include communication protocol functions, etc.

Molded case circuit breakers mainly have long-delay protection, short-delay protection (i.e., overload protection), and instantaneous protection (i.e., short-circuit protection).

This demonstrates that the protective function of a frame circuit breaker is more robust than that of a molded case circuit breaker.

3) Their applicable ranges differ. Frame circuit breakers have a rated current from 400A to 6300A and are primarily used in power distribution networks to distribute electrical energy and protect lines and power equipment from overload, undervoltage, short circuit, single-phase grounding, and other faults. Molded case circuit breakers have a rated current from 10 to 800A and are used to protect lines and equipment from overload, short circuit, and undervoltage in power distribution lines. They can also provide overload, short circuit, and undervoltage protection for infrequent motor starts.