If a centrifugal switch has two sets of contacts, what is the purpose of the second set?

The purpose of the second set of contacts in a centrifugal switch is to provide a safety circuit for other components in the machine. Centrifugal switches are typically used in motors to disconnect the starting circuit from the running circuit once the motor reaches a predetermined speed. The primary contacts engage and disengage the start winding, while the secondary contacts can serve various safety functions.

In many applications, these secondary set contacts can be connected to critical components such as overload relays or other safety devices. This means that when the motor reaches operational speed and the centrifugal switch opens, it can simultaneously disengage the start winding and also provide a mechanism to ensure that other safety-related features are activated. This can help to prevent equipment damage or ensure safe operation of the machinery, thus fulfilling a vital role in protecting both the equipment and the operator.

The other options refer to functions that don't align with the primary role of a centrifugal switch or its contacts. Engaging a capacitor bank, controlling a motor's cooling system, or directly increasing the motor's speed are not typical functions related to the secondary contacts in a centrifugal switch setup.