What is an on-off switch with overload relays called?

The on-off switch with overload relays is referred to as a manual starter. This term is used to describe a device that not only turns the motor on and off but also includes overload protection via relays. The overload relays are crucial because they prevent the motor from overheating by disconnecting the power supply when the current exceeds a safe level. Manual starters are commonly used in various applications to ensure safe and reliable operation of electric motors.

In contrast, the other terms provided do not accurately encompass the full functionality of the device described. A relay switch typically refers to a different function involving control circuits rather than direct motor control. A power switch is a more generic term that does not imply any overload protection mechanism. An electromagnetic switch generally denotes components that operate through magnetic fields rather than specifically addressing the manual operation and overload protection characteristic of manual starters.