Electromechanical Relays and Contactors
Many applications and devices need to switch currents with high isolation, or require the ability to switch high voltages and high currents with a low power control signal. Sometimes, a solution based on semiconductors simply isn’t enough. Designers sometimes have to utilize electromechanical relays and contactors to provide the control they need.
Electromechanical relays can switch relatively high currents using a few volts of control signal, and they provide a decent amount of voltage isolation between the control signal and the switched power. Very high current loads and high switching voltages call for contactors, which are essentially enhanced relays.
Both relays and contactors are electromechanical devices that use an electromagnetic solenoid to actuate one or more pairs of contacts. A single pole relay or contactor has a single pair of contacts, but there are also double pole relays and contactors, and more. Contacts can be normally open, or normally closed. Some relays and contactors also have double-throw contacts that combine a normally open and a normally closed contact.
Relays are mainly used for switching low and medium current loads at relatively low voltages, and they are available in many form factors including plug-in and board mount versions designed to be soldered onto a PCB. Important relay specifications include coil voltage and AC or DC coil operation, contact current rating and configuration, the number of contacts, and the actuation/release times. It is important to avoid switching currents that are too small for a relay to operate reliably. A relay’s lower limit for the current that can be switched depends on several factors such as the contact material and geometry, and the mechanical sliding of the contact surfaces. Reed and mercury wetted reed relays are best suited for low level switch applications, for example.
A contactor is the heavy-duty equivalent of a relay, and is typically used in factory and industrial applications. They are more rugged than relays, and are often designed to mount on a standard DNI rail. Contactors are designed to switch high loads such as fractional and multiple horsepower, multiphase motors, large heating loads, and industrial/commercial lighting. Like relays, contactors are available in AC and DC configurations, and can be designed to be driven by a programmable logic controller with 24 volt DC solenoid coils, but coils rated for AC line voltages are also available.
At NSN Parts Now, owned and operated by ASAP Semiconductor, we can help you find all the electromechanical relays and contactors for the aerospace, civil aviation, and defense industries. 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, email us at sales@nsnpartsnow.com or call us at +1-714-705-4780.
