Selection Guide for Power Relays Over 2 A

Design Tools and Resources Product Selection Guide
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What is a power relay?

Power relays over 2 Amps are electromechanical devices that turn a large load on or off through the use of a smaller control signal. The category includes a variety of relays ranging from small PCB mount as well as DIN rail mounted products suitable for industrial control applications.

Image showing the variety of power relays offered by DigiKey.
Image showing the variety of power relays offered by DigiKey.2068×1185 424 KB

Introduction to DigiKey’s Product Selection Guide

This page is one of many in DigiKey’s Product Selection Guide (PSG). This particular page is focused on power relays, over 2 Amps. It provides a description of the individual parameters used to characterize the part. This information will allow you to better understand and navigate DigiKey’s parametric search engine. Click here for a case study showing how to use the search tools.

How are power relays categorized?

The DigiKey search tools include the following specification for power relays.

  • Mounting Type: Indicates how the device is physically attached.

  • Coil Voltage: The nominal voltage that must be applied to a relay’s control coil to actuate the device. Observe that the coil voltage is specified as either AC or DC. This distinction is paramount as a coil designed for DC operation will not activate when an AC signal is applied to the coil.

  • Contact Form: Describes the contact closures provided by a relay or relay-output device, in terms of the number of independent circuits that are actuated in parallel, the number of contact positions available for each, and their default states. For more information, please see this article introducing concepts of poles and throws.

  • Contact Rating (Current): The amount of current that a relay’s contacts are rated to interrupt when switching a resistive load. Ratings may differ for reactive loads and when switching AC or DC current.

  • Switching Voltage: The voltage that a relay’s output contacts are rated to interrupt.

  • Coil Current: The nominal current flow through a relay’s control coil when the indicated coil voltage is applied.

  • Coil Type: Whether the coil is latching or non-latching, single or dual coil.

  • Features: These are different capabilities or properties of the device such as a diode, lighted indicator, or test button.

  • Termination Style: Selection of termination style used to connect the device to a system, such as PC pins, socketable, or wire leads.

  • Seal Rating: Defines what type of sealing is on the relay.

  • Coil Insulation: The class of insulation the relay is built to meet. For more information, please see transformer insulation class.

  • Must Operate Voltage: The minimum voltage needed to energize the coil.

  • Must Release Voltage: The maximum applied voltage at which a relay must return to an inactive state.

  • Operate Time: Characterizes the time delay between the application of rated coil voltage and the closure (or opening) of all contacts that occurs as a result. Typically, does not include contact bounce time.

  • Release Time: Characterizes the time delay between the removal of power from the device coil and all contacts returning to their rest positions. Does not include bounce time, and may be affected by the choice of control circuitry.

  • Operating Temperature: Recommended operating temperature, typically given in a range or as a maximum. Exceeding these temperatures may affect performance or damage the device and other system components.

  • Contact Material: The material used for the electrical contacts on the relay.

  • Relay Type: Indicates a relay’s internal operating mechanism, typical usage, or other distinguishing feature.


Examples of power relays

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image640×640 39.6 KB


Image of the American Zettler brand AZ943-1CH-12DE relay.
Image of the American Zettler brand AZ943-1CH-12DE relay.640×640 66.9 KB


Image of a chassis mount Omron G2R-1A-T DC12 relay.
Image of a chassis mount Omron G2R-1A-T DC12 relay.640×640 47.8 KB


Schematic symbol

Schematic symbol for a SPST relay

Schematic symbols courtesy of Scheme-it.

Related media links

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Follow up

If you have any general questions on the specifications for power relays, please reply using the button below. If you have questions on a specific relay, please post your questions in the forum’s electromechanical category.

Return to DigiKey’s Product Selection Guide.