Different Types of Relays

A relay is an electrically operated switch consisting of a set of input terminals for one or more control signals and a set of operating contact terminals. The switch can have any variety of contacts in multiple contact forms, such as make contacts, break contacts, or combinations of the two. There are many types of relays classified based on their function, applications, configuration, structure, and more. This blog will look at the most popular types of relays.

Latching Relays

Latching relays maintain their state after being actuated. Because of this, they are also known as keep or stay relays. Latching relays are best suited to applications where power consumption and dissipation needs to be limited. Latching relays consist of internal magnets that, when the current is supplied to the coil, hold the contact position without the need of power to maintain its position. Even after being actuated, removal of drive current to the coil cannot move the contact position. As such, latching relays conserve more energy.

Reed Relays

Like an electromechanical relay, reed relays produce the mechanical actuation of physical contacts to open or close a circuit. However, they do so while being much smaller. Reed relays are designed with coils wound around a reed switch that acts as an armature within a glass tube or capsule filled with inert gas and hermetically sealed by two overlapping reeds. Due to their small size, reed relays switch up to ten times faster than an electromechanical relay.

Polarized Relays

Polarized relays are highly sensitive to the direction of current by which it is energized. They are a type of direct current electromagnetic relay provided with an additional source of magnetic field to move the armature of the relay. In polarized relays, the circuit is built with permanent magnets, electromagnets, and an armature. The two most popular types of these relays include differential and bridge type relays.

Solid-state Relays

A solid-state relay is a solid state electronic component that provides a function similar to that of an electromechanical relay without the need for moving components, increasing its service life. Relays of this type use a thyristor, TRIAC, or other solid-state switching devices to switch the controlled load. This differs from other relays that use a solenoid to carry out this operation. An optocoupler is an example of a solid-state relay that can be used to isolate control and controlled circuits.

Inverse Definite Minimum Time (IDMT) Relays

These relays provide a definite-time current characteristic at higher values of the fault current and an inverse time current characteristic at the lower values of the fault current. IDMT relays are widely used for protection of distribution lines and to set the limits for current and time settings. In these relays, the operating time is inversely proportional to the fault current near the pickup value (the point where the actuating quantity initiates the relay to operate). This can be done by using the magnet’s core which gets saturated for slightly more than the pickup current.

Regardless of type, relays are needed wherever it is necessary to control a high power or high voltage circuit with a low power circuit. For all types of relays and much more, look no further than RFQ Experts, a trusted supplier of parts for a wide range of industries. We are an online distributor of aircraft parts as well as parts pertaining to the aerospace, civil aviation, defense, electronics, and IT hardware markets. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, call us at 1-780-851-3631 or email us at sales@rfqexperts.com.


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