The classification of relays

Relays can be classified into the following categories based on their working principles, application scenarios and structural features:

Electromagnetic relay:

Principle: The mechanical contacts are driven to move through electromagnetic induction.

Features: Simple structure and low cost, but it requires continuous power supply to maintain its condition, and the contacts are prone to wear.

Solid State Relay (SSR):

Principle: Contactless switching is achieved by using semiconductor devices such as thyristors and MOSFETs.

Features: Long service life, anti-vibration, suitable for high-frequency operation, but there are issues of conduction pressure drop and heat dissipation.

Thermal relay:

Principle: The protection mechanism is triggered by the bending of the bimetallic strip when heated, which is used for overload protection.

Features: Slow response speed, specifically designed for overheat protection of motors or circuits.

Time relay:

Principle: Integrated delay circuit (mechanical or electronic) to control the action time.

Features: It is used for timed on/off or sequential control, such as delayed lighting off.

Magnetic latching relay (magnetic latching relay):

Principle: The state is maintained by using permanent magnets or magnetic circuit design, and only pulse switching is required.

Features: Extremely low power consumption, suitable for battery-powered scenarios, such as smart meters.

Polarization relay:

Principle: Sensitive to the direction of current, it switches contacts through the polarity of the magnetic field.

Features: It is used for precise control, such as signal routing in communication equipment.

High-frequency relay:

Principle: Optimize the structure to reduce distributed parameters for high-frequency signal switching.

Features: Suitable for RF and microwave circuits, such as antenna switching.

Among them, electromagnetic relays are the general term for all relays that drive mechanical contacts through electromagnetic coils, and Dc Relays are one type of them, whose coils are designed to be driven by DC power supplies (such as 12V DC, 24V DC, etc.).

AC relays (with coils driven by AC power sources, such as 220V AC) also fall under another subcategory of electromagnetic relays.