There are many classification methods of relays, which can be classified according to operating principle, external size, protection characteristics, contact load, product use and so on.

One, according to the principle of action

1. Electromagnetic relay

A relay that produces a predetermined response to the relative motion of mechanical components under the action of current in an input circuit.

It includes DC electromagnetic relays, AC electromagnetic relays,  relays, polarization relays, tongue reed relays, energy-saving power relays.

(1) DC electromagnetic relay: an electromagnetic relay in which the control current in the input circuit is DC.

(2) AC electromagnetic relay: electromagnetic relay whose control current in the input circuit is AC.

(3)  relay: the magnetic steel is introduced into the magnetic circuit. After the relay coil is powered off, the armature of the relay can still maintain the state when the coil is energized, with two stable states.

(4) Polarization relay: a DC relay whose state changes depending on the polarity of the input excitation.

(5) Tongue reed relay: it is a relay that opens, closes or converts circuits by the action of the Tongue spring, which is sealed in the tube and has the dual action of the contact reed and the armature magnetic circuit.

(6) Energy-saving power relay: electromagnetic relay whose control current in the input circuit is AC, but it has large current (generally 30-100A), small size and power-saving function.

2. Solid state relay

A relay whose input and output functions are performed by electronic components without any mechanical moving parts.

3. Time relay

Relays in which the output part is delayed or limited to a specified time before closing or disconnecting the controlled circuit when the input signal is added or removed. 4. Temperature relay

A relay that operates when the external temperature reaches a specified value.

5. Wind speed relay

When the wind speed reaches a certain value, the controlled circuit will be connected or disconnected.

6. Acceleration relay

When the acceleration of the moving object reaches the specified value, the controlled circuit will be connected or disconnected.

7. Other types of relays

Such as optical relay, acoustic relay, thermal relay and so on.

Second, according to the external size

Names defined

Miniature relays Relays whose longest side size is not greater than 10mm

A relay whose longest side size is greater than 10mm but not greater than 25mm

Small relays whose longest side size is greater than 25mm but not greater than 50mm

Three, according to the contact load points

Names defined

Micropower relay Relays less than 0.2A.

Weak power relay 0.2 ~ 2A relay.

Medium power relays 2 ~ 10A relays.

High power relays over 10A.

Energy saving power relay 20A-100A relay

Four, according to the protection characteristics

Names defined

Sealed relay A relay with a low leakage rate by sealing contacts and coils in a metal cover by welding or other means

The plastic sealing relay adopts the method of sealing glue to seal contacts and coils in the plastic cover, and its leakage rate is high

Dust cover relay A relay that encloses contacts and coils, etc., for protection

Open Relay A relay that does not use a shield to protect contacts, coils, etc

Five, according to use

Names defined

Communication relays (including high frequency relays) This type of relay has contact loads ranging from low to medium current levels and is not required to operate under high environmental conditions.

Relays for machine tools Relays used in machine tools have high contact load power and long life.

Relay for Household Appliances A relay used in household appliances that is required to have good safety performance.

Automotive Relay A relay used in automobiles with high switching load power and high shock and vibration resistance.

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