What is a common feature of bimetallic overload relays?

Bimetallic overload relays are specifically designed to protect electric motors from overheating due to excessive current. A defining characteristic of these relays is their fixed trip points, which are determined by the physical properties of the materials used in their construction.

In a bimetallic overload relay, two different metals are bonded together. When the current flowing through the relay exceeds a predetermined level, the heat generated causes the bimetallic strip to bend due to the differing thermal expansion rates of the two metals. This bending activates the relay, interrupting the circuit to protect the motor from damage. The trip settings for these relays are usually set at the factory for specific motor ratings, ensuring that they will reliably interrupt the circuit at set current levels, thus offering consistent, effective protection against overcurrent conditions.

In contrast, features like adjustable trip settings or burst protection, which might be present in other types of overload relays, are not typical of bimetallic designs. Similarly, voltage sensing is more relevant to other components in motor control systems, such as contactors or circuit breakers, rather than being a fundamental feature of bimetallic overload relays.