In a 3-wire push button start/stop circuit, which contacts are typically normally closed?

In a 3-wire push button start/stop circuit, the stop button is typically configured with normally closed contacts. This design is crucial for ensuring safety in electrical control systems. By utilizing normally closed contacts for the stop button, the circuit remains energized and operational until the stop button is intentionally pressed. When the stop button is engaged, it opens the circuit, interrupting the flow of electricity and stopping the motor or the machine that the circuit controls.

This configuration allows for immediate interruption of power during an emergency situation or when the machine needs to be stopped for any reason. In contrast, the start button typically uses normally open contacts that close when the button is pushed, allowing current to flow and start the machinery.

The common and auxiliary contacts serve different functions in the circuit but do not typically have the same role as the start and stop buttons. Understanding these configurations is essential for the safe and effective operation of control circuits in an industrial setting.