Relays can be divided into several kinds according to the principle of action

1. Electromagnetic relay
A relay in which a predetermined response is generated by the relative movement of mechanical components under the action of current in the input circuit.
It includes DC electromagnetic relay, AC electromagnetic relay, magnetic holding relay, polarization relay, reed relay, energy saving power relay.
(1) DC electromagnetic relay: The control current in the input circuit is DC electromagnetic relay.
(2) AC electromagnetic relay: the control current in the input circuit is an AC electromagnetic relay.
(3) Magnetic holding relay: the magnetic steel is introduced into the magnetic circuit, and after the relay coil is powered off, the armature of the relay can still maintain the state when the coil is powered on, with two stable states.
(4) Polarized relay: a DC relay whose state changes depending on the polarity of the input excitation.
(5) Reed relay: Use the action of the reed sealed in the tube, with the dual role of the contact reed and the armature magnetic circuit to open, close or convert the line of the relay.
(6) Energy-saving power relay: the control current in the input circuit is an AC electromagnetic relay, but its current is large (generally 30-100A), small size, and power-saving function.
2. Solid state relay
A relay in which the input and output functions are performed by electronic components without mechanical moving parts.
3. Time relay
When the input signal is added or removed, the output part needs to delay or limit the time to close or disconnect the relay of its controlled line.
4. Temperature relay
A relay that operates when the external temperature reaches a specified value.
5. Wind speed relay
When the speed of the wind reaches a certain value, the controlled circuit will be switched on or off.
6. Acceleration relay
When the acceleration of the moving object reaches the specified value, the controlled circuit will be switched on or off.
7. Other types of relays
Such as optical relay, acoustic relay, thermal relay and so on.