Which type of overload uses a coil to sense the level of motor current?

The type of overload that uses a coil to sense the level of motor current is the magnetic overload. In this system, the magnetic field generated by the current passing through the coil is utilized to detect overload conditions. When the motor current exceeds the preset limit, the magnetic field strengthens to a point where it can actuate a switch to disconnect the motor from the power supply, thus protecting the motor from damage due to excessive current.

This method is particularly effective because it responds quickly to current changes, making it suitable for applications where rapid disconnection is necessary to prevent overheating or equipment failure. Magnetic overloads are commonly used in applications with inductive loads where inrush currents can be high initially.

Other types like bimetallic and thermal overloads rely on temperature changes due to current flow, which may not be as immediate or sensitive as magnetic responses. Electronic overload devices utilize circuit components to monitor current levels and provide overload protection, but they do not operate based on magnetic fields.