Nancy Quek Electrical

MCBs/RCDs
www.nancyquek.com

MINIATURE CIRCUIT BREAKERS (MCBs)

MCBs (Miniature Circuit Breakers) have replaced fuses in low voltage installations for buildings in many coubtries uo to a rate of 95%. The task of a MCB is to act as protection against overload and short-cirucit, thus providing protection against overheating, or in case of defective equipment, against indirect contact with live parts (in compliance with IEE 16th Edition, IEC 364; SS CP5). The MCB ensures this by separating the cirucit from the mains supply.

The S2 range of MCBs complies to international standards and regulations. ABB MCBs are designed to fulfil the reuqirements of safety in installations through stringent quality control; and they are easy to install and use.

All S2 MCBs (except the S230 range) are current-limiting types and utilise the state-of-the-art " hammer-trip" principle. Each pole is fitted with two different tripping devices operating on a trip-free switching mechanism:

the delayed thermal trip for protection against overload, and
the quick acting electromagnetic trip for protection against short-circuits

RESIDUAL CURRENT-OPERATED DEVICES (RCDs)

In electrical installations where neutral connections are commonly used, there are occasions for current to flow from the line conductor to earth and hence back to the current source. Such currents are usually caused by some kind of defects and are termed as earth fault currents.

Earth fault currents can be dangerous and even fatal, dependning on the magnitude and the surrounding environment. The consequences due to prolonged exposure of earth fault currents in installations are fire hazards and occurring. However, such faults can be quickly detected and isolated if Residual Current-operated Devices are installed.

ABB's range of RCDs (Residual Current-operated Devices) makes use of the well-proven principle of utilising core balance transformers with permanent magnet trip devices. These fault tripping devices are highly sensitive elements and are able to detect earth fault current and operate at lower than required levels. As such, the risks of fire hazards and electric shocks are greatly minimised.