Question

describe how pressure switches are connected to start and stop a small motor and a large motors

Answer 1

A pressure switch is a mechanical device that relies on air pressure to control the operation of an electric air compressor . Terminals of the switch completes the circuit and allows power to the motor as long as system pressure is below a specified setting .

With the air compressor plugged in, the user moves the lever to the ‘auto’ position, forcing electrical contacts inside the switch together to complete the circuit. The motor starts and the air compressor begins to pressurize.

When the pressure above normal (normally set by the user) is reached, a diaphragm inside the pressure switch pushes against a mechanism which forces the electrical contacts apart, breaking the circuit and stopping the motor.

At the same time, the pressure relief valve opens and relieves back-pressure caught between the pump and check valve. As air is used and tank pressure drops to a specified ‘cut-in’ setting the contacts close and the motor starts again. The cycle continues as long is the air compressor is in use.