Residual current operated circuit breakers are suitable for circuits with 50/60Hz AC while the rated operational voltage is 230V under dual-line monopole or dual-pole configuration and 400V under tri-pole, quad-line tri-pole and quadrupole configuration. In a circuit with the rated operational current up to 60A, when a human body gets an electric shock or the leakage current becomes higher than the specified value, the residual current operated circuit breaker can cut off the malfunctioning power source in a very short time, protecting the safety of human and the electric equipment. The residual current operated circuit breaker enjoys overload and short circuit protection functions and can be used to protect the circuit and the electric motor. It can also be used for less frequent conversion starting.