An electromechanical or solid-state relay that waits for a predetermined amount of time before opening or closing its contacts after receiving a control signal. These are essential in motor starting sequences, alarm circuits, and protection schemes to allow temporary overloads to clear themselves before tripping the system.
Heard on the job
Set the time-delay relay to five seconds so the inrush current drops before the secondary contactor pulls in.
Related terms
Protection relay
Device that watches currents and voltages and orders a circuit breaker to trip when it detects a fault.
Inrush current
Large transient current drawn when a transformer, motor or capacitive load is first switched on.
Contactor
An electrically controlled switch used for switching an electrical power circuit.