What type of relay is used to protect against phase loss in motors?

Phase failure relays are specifically designed to detect conditions where one or more phases in a three-phase electrical system are lost or drop below a specified level. These devices monitor the voltage levels across the different phases and can quickly identify imbalances or a complete phase loss.

In the context of protecting motors, phase failure relays are crucial because they help prevent damage that can occur if a motor continues to operate under adverse conditions, such as running without one of its phases. The relay can disconnect the motor from the power supply to avoid overheating, excessive vibrations, and other potential issues that may arise from such conditions.

Others such as voltage relays focus on overvoltage or undervoltage situations rather than phase loss specifically, and current relays monitor the current flowing through the circuits, which may not specifically detect phase loss. Time delay relays, on the other hand, typically introduce delays before activating a circuit in response to certain conditions rather than detecting the presence or absence of phases themselves. Therefore, the phase failure relay is the most appropriate choice for protecting against phase loss in motors.