What type of switch is designed to disconnect the starting winding from the circuit at 80% of full speed?

A centrifugal switch is specifically engineered to disconnect the starting winding of a motor from the power supply when the motor reaches approximately 80% of its full speed. The operation of this switch is based on centrifugal force; as the motor accelerates to its operating speed, the centrifugal force causes a mechanism within the switch to close, thus breaking the electrical connection to the starting winding. This action helps to prevent overheating and damage to the motor by ensuring that the starting winding is only engaged during the initial phase of starting, after which it is no longer needed.

This design is vital for the efficient operation of split-phase motors and similar types, ensuring they run smoothly without unnecessary energy loss or potential motor failure due to prolonged engagement of the starting winding. The other options do not fulfill this specific function; for instance, a relay switch is primarily used for controlling electrical circuits without the mechanical speed aspects tied to a motor's operation. Therefore, a centrifugal switch is the correct answer as it accurately represents the mechanism that operates at the designated speed threshold.