The new Isomax SX range of current limiting moulded case circuit breakers (MCCBs) from ABB Control is designed to provide maximum protection for electrical installations and equipment against very high short circuit currents of up to 200kA at 380/415V, 180 kA at 440V and 75kA at 690V. Typical applications for the SX include marine installations.

The Isomax SX works by limiting both the current peak and specific let-through energy to a minimum in the event of a short circuit, extinguishing the arc in the shortest possible time to protect the circuits and equipment downstream. This is achieved by the use of a special breaking system, featuring two fixed contacts for each pole, which makes it possible to provide extremely fast breaking. At the same time, specially shaped breaking components limit the peak fault current to values significantly lower than those of the short circuit current.

The SX current limiting circuit breakers can be fitted in systems where back-up protection is required to allow the use of circuit breakers downstream which have a lower breaking capacity than that required to protect against the prospective short circuit current at the point of installation.

The SX range of current limiting breakers is an extension to ABB’s proven Isomax S series. SX breakers have the same modular construction, robust moulded case, corrosion proofed metal components and wide range of accessories such as auxiliary releases, electrical signaling, motor operating mechanisms, rotary handles and locks.