How relays work

Update date:2018-04-29 Source:MAXGE

How relays work

There are several classifications of relays: such as electrical relays (its input can be current, voltage, frequency, power, etc.), non-electric relays (its input can be temperature, pressure, speed, etc.); protection relays, control relays; Contact relays, non-contact relays; open type (without protective measures for the main component), enclosed (plus protective enclosures), sealed (non-pneumatic power quality inside and outside the enclosure exchange) relays and so on.

Commonly used relays classified by working principle include electromagnetic relays, polarization relays, reed relays, thermal relays, and time relays.

Relay An automatic device whose electrical output circuit is switched on or off when the input physical quantity reaches a specified value.


Widely used in production process automation devices, power system protection devices, various types of remote control, remote control and communication devices, is one of the most basic electrical components in modern automatic control systems.

The input signal continues to increase and the output signal remains YMAX.

After the relay is actuated, if the input signal is reduced, the relay operates only when the input is reduced to XF, returns to the starting position, and the output signal jumps back to zero.

This feature is called relay characteristics.

Here, the input value (action value) for starting the relay operation, the maximum input value (return value) for returning the relay to its original state, the rated voltage and current of the contact (contact rating value), and the relay have a state The time (action time) to change to another state is the main technical parameter of the relay.


They both characterize the performance of the relay's working process and are the basis for selecting the relay.

After the 20th century, with regard to the use of time relays, relays have been greatly developed. There have been magnetic non-contact relays, semiconductor non-contact relays, application-specific integrated circuit electronic time relays, solid state relays, and printed circuit board mounted (double row) Plug-in) relays, with microprocessor protection relays and intelligent relays.


Relays generally consist of two parts: input sensing mechanism and output actuator.

The former is used to reflect the change in the amount of input. The latter completes the contact opening and closing action (for contact relays) or the switching of semiconductor elements (for contactless relays), and the relay has a skipped input-output characteristic.

When the relay accepts an input signal X, it only activates the action value XD. The relay then operates and the output jumps from zero to YMAX.

The time relay's electrical control system is a very important component.

It is generally divided into two types of power-on delay and power-off delay.

From the principle of action there are electronic, mechanical and so on.

Electronic is the use of capacitive charge and discharge with the principle of electronic components to achieve delay action.

There are many mechanical styles. There are airbags and airbags that use airbags and springs. The escapement of watches and clocks introduces some types and characteristics of time relays. There are also small shaded synchronous motors that drive cams. Now there are more new styles. The time relay appears.

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