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Home > Technology > Classification
Relays can be classified into many different categories according to their working principle, physical dimensions, protective features, contact loads and product applications.
I. According to working principle
1. Electromagnetic Relays : Relays in which the relative movements of their mechanical components produce preset responses under the effect of the current in the input circuit are called electromagnetic relays. Relays in this category include DC electromagnetic relays, AC electromagnetic relays, magnetic-latching relays, polarized relays, and reed relays.
(1) DC electromagnetic relays: relays whose control current in the input circuit is DC.
(2) AC electromagnetic relays: relays whose control current in the input circuit is AC.
(3) Magnetic-latching relays: relays, after the magnetic steel is introduced into the magnetic loop, even the relay coil is de-energized the armature iron steel still maintains its state as that when the coil is energized, with two steady states.
(4) Polarized relays: DC relays whose change of state depends on the polarity of the input exciting variable.
(5) Reed relays: Relays that rely on the movements of the reed which is built in the tube and has dual functions as contact reed and rmature iron magnetic circuit for connecting, breaking or switching circuits.
2. Solid-state Relays : Relays whose input and output functions are performed by electronic elements without mechanical movement components.
3. Time Relays : Relays whose controlled circuit connects or breaks when the output part is delayed or timed to a preset time after the input signal is added or erased.
4. Temperature Relays : Relays that get into motion when the outside temperature reaches a present point.
5. Wind-velocity Relays : When the wind velocity reaches a certain point, the controlled circuit will connect or break off.
6. Acceleration Relays : When the acceleration of the moving object reaches a preset point, the controlled circuit will connect or break off.
7. etc : Relays in Other Categories Including photo relays, sound relays, and heat relays.
II. According to Physical Dimensions
-Table 1. Classification of the Relays according to Physical Dimensions
Description |
Definition |
Mini Relays |
Relays whose maximum edge is no larger than 10mm |
Super Mini Relays |
Relays whose maximum edge is larger than 10mm but no larger than 25mm |
Compact Relays |
Relays whose maximum edge is larger than 25mm but no larger than 50mm |
III. According to Contact Load
- Table 2. Classification of the Relays according to Contact Load
Description |
Definition |
Micro-power Relay |
Relays whose current is smaller than 0.2A |
Low-power Relay |
Relays whose current is in the range of 0.2-2A |
Medium-power Relay |
Relays whose current is in the range of 2-10A |
High-power Relay |
Relays whose current is larger than 10A |
IV. According to Protective Features
- Table 3. Classification of the Relays according to Protective Features
Description |
Definition |
Sealed Relay |
Relays whose contact and coil are sealed in a metal case by welding or other methods and therefore enjoy low leakage rates . |
Plastic-cased Relay |
Relays whose contact and coil are sealed in a plastic case by gluing and have somewhat higher leakage rates.
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Dust-proof Relay |
Relays whose contact and coil are sealed in a case for protection purposes. |
Open Relay |
Relays whose contact and coil are not protected with a case. |
V. According to Applications
- Table 4. Classification of the Relays according to Applications
Description |
Definition |
Communication Relays (High-frequency Relays) |
Relays with contact load ranging from low level to medium current and therefore enjoying comparatively low ambient conditions for use. |
Machine Tool Relays |
Relays used on machine tools with high contact load power and long service life. |
Household Appliance Relays |
Relays used in household appliances must meet a high safety standard. |
Automobile Relays |
Relays used in automobiles with high switching load power and high impact and vibration resistance. |
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