Double-rated ACB prevents overheating

Circuit-breaker specialist Terasaki claims to have developed the world`s first 6,300A ACB (air circuit breaker) with a double-rated neutral. The breaker is aimed at installations with large non-linear loads, such as variable speed drives, where high levels of harmonic distortion that can lead to neutral currents almost twice as large as the phase currents.

These large currents can result in over-heating. To tackle this, switchboards are increasingly being specified with double-rated neutral busbars but, according to Terasaki, the half-rated neutral poles supplied with most other ACBs are inadequate for such installations. Most offer fully rated neutrals up to 4,000A and a few stretch to 6,300A.

Terasaki`s new AH60DN breaker can switch and protect currents up to 12,000A in the neutral conductor, thus eliminating the risk of overheating, says the company. It has developed the breaker specifically for the UK market.

As well as VSDs, the ACB is also suitable for installations with other large non-linear loads such as uninterruptible and switched mode power supplies.