How to choose between a Relay, Solenoid, and Contactor.

Iversrud posted on Oct 22, 2020.

There are critical differences between relays, solenoids, and contactors that make them suitable for different applications.We will explain how each device works in this article.

The main job of a relay is to allow a low power signal to be used to control a higher power circuit.It can allow multiple circuits to be controlled by one signal, for example in a police car where one switch can turn on a sirens and warning lights at the same time.

Magnetic relays, which use magnets to physically open and close a switch, are one of the many designs of relays.Solid state relays have no moving parts and are more reliable.Solid state relays are not subject to electrical arcs that can cause internal wear and failure.

Solenoids are a type of relay that can remotely switch a heavier current.When electricity is passed through a coil, it creates a magnetic field, which opens or closes the circuit.

In the automotive market, the term "relay" is often referred to as a "metal can" type, whereas the "solenoid" refers to the standard "cube" style relay.

Vehicle starters, snowplows, and electrical motors are some of the common applications for solenoids.The ability to use a low input to generate a larger output via the coil is one of the main advantages of solenoids.

When a circuit needs to support a heavier current load, the contactor is the relay to use.contactors are a cost-effective, safe, lightweight solution for DC high-voltage power systems.

Common applications include industrial electric motors used in heavy trucks and equipment, buses, emergency vehicles, electric/ hybrid Vehicles, boats, light rail, mining, and other systems that simply require too much power for a standard relay or solenoid.

The power required to hold the contacts closed can be reduced with an integrated coil economizer.They are available with auxiliary contacts.

In terms of carrying capacity, relays are at the low end, followed by solenoids and contactors.contactors come with the highest price tag and require the most space, whereas relays can be purchased very cheaply.Many solenoids fall in the middle of these two, both in terms of carrying capacity and price.

The form factor should be considered when determining which product is right for your design.It's important to note the amount of space available to ensure the device you need will fit.If there is a conflict, you should either rethink your design layout or scale back the electrical system.

The environment in which the device will reside should be considered when selecting a device.

A sealed product is necessary if protection from elements such as humidity, submersion, dust, and vibration is needed.The specific protection offered can be determined by looking at the Ingress Protection rating.

The operating temperature is important.All neighboring devices must be rated according to the extreme temperatures generated by the engine and surrounding components.

solenoids and contactors are rated for either continuous or intermittent use.A starter switch is an intermittent application that has a brief activation period alternated with a longer rest time.It is possible to support applications requiring continuous run time with products with a continuous rating.

Is it possible to use a continuous duty solenoid in place of an intermittent duty one?We always recommend using the component designed for the job, but a continuous duty solenoid is in excess of what is needed.It is not possible to use an intermittent duty solenoid when a continuous duty one is required.

The decision to use a relay, solenoid, or contactor largely comes down to the current carrying capacity needed, while also considering how the form factor will fit into your design footprint.

Critical requirements like operating temperatures and environmental demands will help you narrow down your choices once you have identified which of the three types is right for you.We have a complete selection of relays, solenoids, and contactors.

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