When the voltage amplitudes on both sides are not equal, the relay acts to open the closed circuit.
When the voltage phases on both sides are different, the relay acts to open and close the circuit.
When the frequencies of the two sides are not equal (the amplitude is equal), this relay is only released at the moment when the vector returns, and it acts at other times.
Only when the voltage amplitude, frequency and phase meet the requirements, and the voltage vectors on both sides almost return, can the relay remain in the released state and connect the closing circuit. At this time, synchronization can be completed as long as it is manually or automatically closed and a closing pulse is issued.
2. relay (English name: relay) is an electrical control device, which makes the controlled variable change in a predetermined step in the electrical output circuit when the input (excitation) changes to the specified requirements. It has the interactive relationship between the control system (also called input loop) and the controlled system (also called output loop). Usually used in automatic control circuits, it is actually an "automatic switch" that uses small current to control large current. Therefore, it plays the role of automatic adjustment, safety protection and conversion circuit in the circuit.