Overload relays are essential devices used in electrical systems, particularly for protecting motors from overheating due to excessive current. They serve as a safeguard that ensures motors operate within safe limits, preventing potential damage that could arise from operating under overload conditions. This article delves into the fundamental aspects of overload relays, including their working principles, types, applications, and importance in industrial environments.
Working Principle of Overload Relays At its core, an overload relay functions by monitoring the current flowing through an electric motor. When a motor starts or runs, it draws a significant amount of current. However, if the motor experiences an increase in load, the current will rise beyond its rated capacity, leading to overheating. The overload relay detects this rise in current, which is typically achieved through one of two primary methods： thermal or electronic sensing. Thermal Overload Relays： These relays utilize bimetallic strips that bend in response to heat generated by excessive current. As the current increases, the heat causes the strip to bend, eventually tripping the relay and breaking the circuit. Thermal overload relays are relatively simple and cost-effective but may be slower in response time.