Determining the Types of Industrial Circuit Breakers

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage that is caused by an overload or short circuit. The fundamental purpose of the industrial circuit breakers is to detect a fault condition, interrupt continuity and immediately discontinue electrical flow. Conversely, a fuse is used one time and then needs to be replaced. An industrial circuit breaker can be reset in order to resume normal operation.

Many classifications of industrial circuit breakers exist with their differences being separated out by voltage class, construction type, interrupting type, and structural features. This article will discuss a few different types of industrial circuit breakers.

Low Voltage Industrial circuit breakers

Low voltage Circuit Breakers are common in domestic, commercial, and industrial applications. A few examples of these include: 1) Miniature circuit breaker (MCB) with a rated current not more than 100A and 2) Molded case circuit breaker (MCCB) with a rated current up to 2500A.

Magnetic Industrial Circuit Breakers

Magnetic industrial circuit breakers use a solenoid (electromagnetic) whose pulling force increases with the current. The circuit breaker contacts are held closed by a latch. As the current in the solenoid increases beyond the rating of the circuit breaker, the solenoid?s pull releases the latch which then allows the contacts to open by spring action.

Thermal Magnetic Industrial Circuit Breakers

Thermal magnetic industrial circuit breakers are mostly found in most distribution boards. The electromagnet responds instantly to large surges in current (i.e. short circuit) and the bimetallic strip responds to less extreme but long exposure over-current conditions. The thermal portion of the this type of industrial circuit breaker provides a unique response feature that is either faster or slower depending on the large or smaller currents it is exposed to.

Medium-Voltage Industrial Circuit Breakers

Medium-voltage circuit breakers rated between 1 and 72 kV may be assembled into metal-enclosed switchgear line ups for indoor use or may be individual components installed in outdoor substations. Medium-voltage circuit breakers are further classified by the method used to extinguish the arc (i.e. vacuum circuit breaker, air circuit breaker, SF6 circuit breaker).

High-Voltage Industrial Circuit Breakers

Generally, a high-voltage industrial circuit breaker is defined as 72.5 kV or higher. These types of industrial circuit breakers are found in electrical power transmission networks and they are almost always solenoid operated with current sensing protective relays operated through current transformers. In substations, the protective relay schematic is complex, protecting equipment and buses from various types of overload or ground/earth fault. Like the medium-voltage industrial circuit breaker, high-voltage industrial circuit breakers are classified by the method used to extinguish the arc (i.e. bulk oil, minimum oil, air blast, vacuum, SF6). However, due to environmental and cost containment concerns over insulating oil spills, most new industrial circuit breakers use SF6 gas to quench the arc.

Sulfur Hexafluoride (SF6) High-Voltage Industrial Circuit Breakers

A sulfur hexafluoride industrial circuit breaker uses contacts surrounded by sulfur hexafluoride gas to quench the arc. This type of industrial circuit breaker is most often used for transmission-level voltages and may be incorporated into compact gas insulated switchgear.