A positive voltage on the Gate terminal switches the MOSFET “ON” and a negative voltage on the Gate make it “OFF”. This makes it ideal for MOSFET relay switch. A1 and A2 are the coil terminals on a relay. When voltage is applied to A1 and A2, the relay's. There are two types of mechanical relays: reed relays and electromechanical relays (EMRs). The reed relay blade bends rather than being moved on a pivot point, and the contact is. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. : 4 The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as. Current transformers step down the monitored current to a secondary (output) range of 0 to 5 amps AC to power the protective relay. An electromechanical relay is an electrical switch actuated by an electromagnet coil. It functions as a watchdog by constantly surveying multiple system components including voltage, current, frequency, and phase angle.