ABB Molded Case Circuit Breakers
Molded case circuit breakers (MCCB) are electrical switches that are designed to trip during a short circuit or overload to protect against electrical faults and equipment failure. Overload protection is accomplished through a thermal operation with a slight time delay. When an overcurrent passes through an MCCB, a bimetallic strip is heated and bends. The bending causes a mechanical latch to release, opening the MCCB contacts, halting the flow of current. When the overcurrent is removed, the contacts close and the MCCB is reset. Short circuit protection is accomplished through an electromagnetic operation that is instantaneous. A current coil is tripped causing the mechanical release of the latch that opens the contacts that halt the flow of current. When the overcurrent is removed, the MCCB can be reset.
ABB SACE Tmax T series Molded Case Circuit Breakers are available with protection features up to 3200 A and in both 3-pole and 4-pole, fixed version; sizes T4 and T5 in the plug-in version. Thermal magnetic and electronic trip units are available for use in AC/DC or in AC only. It is possible to interchange trip units keeping the same breaking part, so that installation can be upgraded with fewer costs. A complete range of electronic trip units is suitable for different levels of protection, even enhancing selectivity values with Early Fault Detection and Prevention algorithm. SACE Tmax XT series is available in 7 different sizes and protection features of up to 1600A.
What is a Circuit Breaker?
There are two different types of technologies that are commonly used in circuit breakers.
Magnetic Breakers
Magnetic Breakers are designed to react to short circuits or sharp spikes in voltage and current. The more current that passes through the breaker’s electromagnet, the stronger the magnet becomes. When the current exceeds the rating for that particular breaker, the magnetic force becomes strong enough that it will pull the contact back and disconnect it from the other contact, disconnecting power from the device.
Thermal Protection Breakers
Thermal Protection Breakers protect against a sustained overcurrent, or a higher current, for a longer period of time. Thermal protection uses a Bimetal strip that will bend the contacts away from each other to disconnect power. Thermal Magnetic Breakers are the most common type of circuit breakers. They combine magnetic technology to protect against short circuits or sharp spikes and thermal technology that protects against sustained overcurrent for a long period of time.