Magnetic circuit breaker RCBOs

overloadpowerresidual current

Rowe Hankins Ltd. Residual Circuit Breaker Overload products (RCBOs) have two main functions: Firstly, to help to measure AC residual current; Second, to trip whenever they detect a fault. The RCBOs are available in 2 and 4 pole configurations – specifically, the 2 pole series 373, and the 4 pole series 368. Additionally, these 2 and 4 pole versions are available at MCB ratings of up to 50 amps and different residual current trip levels. DETAILED LOOK AT RCBOs The circuit uses a current transformer to measure AC current imbalance. The signal is amplified, rectified and then passed to a time delay RCBO circuit. If the signal is present after the delay, then a solid-state switch energises the supply circuit breaker trip coil. Options for either a fixed time delay or an inverse time delay trip characteristic can be specified. Trip currents can be specified for factory setting at levels between 5 and 300mA (Trips levels up to 2A are possible on a 4 pole series). A unit with a trip level of 5mA is specifically suited for the American market to meet the requirements of the ‘National Electrical Code NFPA 70’. A wide range of time delay RCBOs can be specified and set during manufacture. The detector circuit power supply is derived from the AC supply. A test signal can be injected through the current transformer from a test button to confirm correct operation. Features: Our RCBO range uses AC residual current, the trip levels are typically between 30mA, 100mA and 300mA.