The relay can generate the minimum current of the pull-in action. In normal use, the given current must be slightly greater than the suction current, so that the relay can work steadily. As for the working voltage of the coil, it should not exceed 1.5 times of the rated working voltage. Otherwise, the coil will be burnt down because of the large current.

As a control element, the relay has the following functions:

1) Expanding the scope of control. For example, when the control signal of multi-contact relay reaches a certain value, it can switch on, break and switch on multi-circuit according to different forms of contact group.

2) Enlargement. For example, sensitive relays, intermediate relays and so on, with a very small amount of control, can control a large power circuit.

3) Integrated signal. For example, when multiple control signals are input into multi-winding relays in a prescribed form, the desired control effect can be achieved by comparison and synthesis.

4) Automation, remote control and monitoring. For example, relays on automatic devices, together with other electrical appliances, can form programmable control circuits to achieve automatic operation.