Automotive Relay Types

Q: What is the difference between a relay and a contactor?
A: In general, both terms designate an electromechanical switching device, working on the same physical principle, where a coil is used to generate a magnetic force that mechanically operates an electric contact. While the term relays is widely used in various industries for low and medium power devices, the term contactor is more common in the high power area. The magnetic “motor” is typically realized with a plunger in the center of the coil body for contactors, as opposed to a hinged armature design, which is normally used for relays.

Q: The new generation of contactors works without a gas-filling. What is the advantage of non gas-filled contactors? Can a gas filled contactor rupture?
A: In order to protect the switching contacts, and to support a quick extinguishing of switching arcs, many contactors are filled with pressurized inert gas. Nitrogen or Hydrogen is commonly used, SF6 (Sulfur-hexafluoride) is also applied, mainly in industrial applications. On the flip side, a pressurized gas filling requires a lot more effort in the design and the manufacturing process, to ensure a reliable holding of the gas throughout the lifetime of the contactor. As such contactors must be hermetically sealed by nature, it also bears the risk of rupture, when extremely strong arcing – in case of high over-currents or short-circuits – generates excess gas pressure inside the contact chamber.TE’s latest contactor designs therefore work with no inert gas, also eliminating the need for a hermetic seal. These designs are still environmentally protected against pollution and allow a gas exchange and an equalization of inside and outside pressure, which practically eliminates the risk of rupture in case of extreme arcing. Link to EVC 250 Video.

Read more FAQs about High-Voltage Automotive Relays and Contactors

A pulse width modulation (PWM) relay is essentially a relay that utilizes solid state control to operate. In addition, the use of a PWM is typically employed to regulate the power requirements of the relay coil hold current. This, in turn, helps in reducing heat dissipated by the relay coil. This method is generally employed for coil hold power efficiency and heat reduction of the relay coil and overall structure.

ISO mini relays are manufactured with a 1” cube body and feature four pins, or terminals, on the body. Also referred to as a make-and-break relay, it has only one high current circuit, and a contact that is either closed or open, depending on whether the relay is at rest or energized. When a contact is broken with the relay at rest, this is called Normally Open (NO), while if the contact is closed with the relay at rest the relay is Normally Closed (NC). NO relays are more common than NC relays. A standard relay with one circuit closed when the relay is closed and the other is closed with the relay is energized, is called a changeover relay and has 5 pins. Standard relays are commonly used in vehicle electrical systems.