Circuit breakers: circuit breaker is to control the electrical circuit of the switch, if the air for the arc medium called air circuit breakers (switch). The circuit breaker is normally rated at the rated current (load) and is used as the main switch for the electrical circuit.
Residual current protector and residual current protection switch:
When an air switch with leakage protection function, called the residual current devices. If it is an electrical device used only for residual current protection, it is called a residual current protector, because it does not manually turn off and close the body.
The principle of determining whether or not to leak is based on the residual current devices, which detects "inflows" and "outflows" for the power supply, since the current on the line of fire is equivalent to the outflow point of the power supply and the current in the neutral line is In the power supply current "inflow" point, the line is normally no leakage, the incoming and outgoing power of the current value of the same size, the opposite direction, but when there is leakage in the circuit when the zero line back to the power supply current should be less than from the power into the electricity circuit current value, up to 30mA when the protector will action, while cutting zero line and fire line.
The current flowing into and out of the switch must be equal, otherwise it is judged to be leaking. When the leakage current reaches and exceeds a certain degree, the protection action - trip. Determine the threshold can be set, because the circuit is designed. Only when the application according to different occasions, the use of different sensitivity of the protector. The residual current is the vector sum of the instantaneous value of the current instantaneous value of the main circuit (zero sequence transformer) of the residual current action protection device. The residual current is the current leakage of the phase to the single phase line. Three-phase line, the residual current is the instantaneous value of each phase current vector sum, with its effective value.
The residual current devices are basically a molded case circuit breaker which is installed to detect the residual current element. It is mainly composed of plastic shell, operating mechanism, contact system, interrupter, release, zero sequence current transformer and test device.