Classification of relay
Relay can be found in everywhere in the modern. A relay is commonly used in many applications of our daily life. Basically, a relay is a device with contacts that opens and closes a switch as the result of an input signal (voltage or current) applied to a coil. Classification of relay can be mainly into two types: mechanical relays and solid state relays.
Classification of Mechanical relay
Mechanical relays have contacts and use electromagnetic force to mechanically open and close the contacts to turn ON/OFF signals, currents, or voltages.
Classification of SSR
SSRs do not have the mechanical moving parts that mechanical relays with contacts do. Instead they consist of semiconductors and electronic parts. SSRs turn ON/OFF signals, currents, or voltages electronically by the operation of these electronic circuits.
Other common classifications of relay can be made like the following:
Relays designed to operate with a DC input.
Relays designed to operate with an AC input.
DC relays that change status depending on the polarity of the control input current.
Note: There are single-side stable relays, double-sided stable relays, and centrally stable relays. Relays that are not affected by the polarity of the control input current are called nonpolarized relays (neutral relays).
Relays that are completely encased in a container and sealed.
Note: Generally, sealed relays are sealed in a metal and metal or metal and glass container by welding or similar method. Enclosed relays are sometimes called sealed relays even though they are simply closed without using welding or similar sealing methods.
Hinged relays are classified by the structure of the electromagnet. Hinged relays directly or indirectly switch contacts by the rotating movement of an armature around a fulcrum.
Note: Hinged relays with armatures that move at right angles to the core axis direction are called side armature type hinged. Those with armatures that move in the direction of the axis are called end-on armature type hinged relays.
Plunger relays are classified by the structure of the electromagnet. The armature in a plunger relay is at the center of the coil and it moves along the coil axis.
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