What is the primary purpose of phase failure relays?

The primary purpose of phase failure relays is to detect the loss of one phase in a motor system. These devices play a crucial role in protecting three-phase motors by monitoring the phases of the electrical supply. When a relay detects that one of the phases has dropped out or is significantly lower in voltage than the others, it triggers actions to protect the motor. This is essential because a loss of phase can lead to severe damage due to overheating or unbalanced loads, which can cause the motor to run inefficiently or even fail altogether.

By focusing on the detection of phase loss, these relays help ensure that motors operate within safe parameters and enhance the longevity and reliability of the motor systems they are integrated into. Other options, while related to electrical systems, do not specifically address the function of phase failure relays. For example, increasing power supply reliability is a broader goal that involves various systems and components, while regulating voltage levels pertains more to devices like voltage regulators. Measuring motor rpm falls under motor speed monitoring rather than phase protection.