Which device is primarily used for overcurrent protection in electrical circuits?

The device that is primarily used for overcurrent protection in electrical circuits is a fuse. Fuses are specifically designed to interrupt the flow of current when it exceeds a predetermined level, protecting the circuit from damage due to overheating or potential fires caused by excessive current. When an overcurrent condition occurs, the fuse element melts, breaking the circuit and preventing further current flow.

This is critical in protecting not only the wiring but also connected devices and equipment from the consequences of overcurrent situations. Fuses are simple, reliable, and cost-effective solutions for achieving overcurrent protection.

The other devices mentioned serve different purposes. Relays are used for switching circuits on and off and can serve various control functions, but they are not exclusively designed for overcurrent protection. Contactors are similar to relays but are specifically designed for controlling large loads in industrial applications, usually for starting and stopping motors. Transformers are electrical devices used to change voltage levels in an AC power supply and do not protect against overcurrent conditions.