Switching circuit

摘要

An electrical switching circuit comprising an electromagnetic relay and a bye directively controlled contactless switch. The electrical switching circuit being able to make and break a capacitive, inductive or pure resistive electrical loads without forming arcs and without substantial heat loss. A control voltage as applied through a phase detecting opticoel coupler to a bye directively controlled contactless switch, such as a triac. The same control voltage is also connected to a time delay circuit wherein the time delay circuit after being charged energizes an electromagnetic relay connecting the load circuit. Upon disconnecting the load the sequence of operation is reversed. The electromagnetic relay is deenergized while the time delay circuit retains the opticoel coupler connection which in turn retains the energization of the contactless switch until the phase of the load energy source to be precisely at the zero voltage crossing at which time the contactless switch is also deenergized. The delay built into the time delay circuit is at least one half of the period of the load energy source so that the disconnection will be made at the zero voltage crossover point to prevent any arc from occurring.