Automotive Electromagnetic Relays
(478)A relay is an electrical connector with contacts controlled by an electromagnet. Depending on the type, they can be normally open, normally closed or open/closed. The main difference between relays used in electronic devices and automotive relays is in the design. An automotive relay provides an increased guarantee of reliability in a difficult environment (pollution, high temperature, range of temperature changes, mechanical vibrations of different amplitude and frequency), and in case of damage it has to be easily replaced. Some contacts of automotive relays must conduct a significant current which is used to power lighting, window heating, ignition system and other circuits.
To meet such wide requirements, automotive relays are either inserted into a socket or are equipped with disconnectable terminals. They are also equipped with reinforced springs that ensure reliable contact of the contacts even in the presence of vibrations. They often feature an open housing to ensure easy ventilation of the contacts, and to remove the ionized gas between them, which prevents the formation of an electric arc.
Automotive relays – how they are controlled?
Automotive relays are controlled in a similar way as standard electromagnetic relays. Usually, the coil is powered by the voltage available in the vehicle (12V or 24V DC). Relay contacts, depending on their design and purpose, can conduct a current of significant value (even above 100A).
Types of automotive relays
In modern vehicles relays are often used, because not only they switch a significant current, they can also switch low-current circuits. Depending on the intended use, they can be screwed, placed in a socket, equipped with screw terminals or leads adapted to popular slide connectors.
What is more, solid state relays are now commonly used in vehicles, the use of which is easier because in most cases we deal with DC voltage, which is easily commutated with MOS transistors. The relay can have a ventilated or hermetic housing. Many relays used in cars, especially those that connect circuits that carry high current, have an open design.
Basic parameters of relays
The basic parameters of the relay include: contact configuration, maximum load current, coil control voltage, type of housing, relay mounting (socket, panel, soldered, screwed, etc.). Dimensions will also be important in some applications.
How to choose a relay for use in the vehicle?
When selecting an automotive relay for use in a vehicle, the general rules for the relays must be followed. The coil supply voltage will depend on the voltage available in the vehicle installation. The forward current of the contacts and the material from which they are made will be of great importance. Open relays should be used to switch the high-current load, but remember that they should be protected against environmental influences.
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