Hybrid relay offers the best of both worlds

Crouzet has developed a relay that combines solid-state and electromechanical switching elements to produce a hybrid device that it claims offers the advantages of both technologies, without their drawbacks.

A mechanical switching element operates in parallel with an electronic relay under the control of a microprocessor. When the device is switched on, the solid-state element "closes" to energise the load. A few milliseconds later, this element is short-circuited by the electromechanical relay contact which then maintains the load. When the load is disconnected, the cycle is reversed.

Crouzet claims that this approach means that the solid-state element does not dissipate heat, thus avoiding the need for a heatsink and allowing the relay to fit into a 17.5mm-wide DIN-rail-mounting package. And because the electromechanical relay is not switching current, there is no contact arcing and a life of 5 million operations - 50 times longer than as conventional electromechanical relay - is possible.

The hybrid relay is said to be almost silent and switches loads at zero volts, placing less stress on the switched components.

Although the relay has a switching capacity of 20A, it is only intended to handle resistive loads, not inductive loads such as motors.