When using momentary contact start and stop pushbutton switches, where are holding (memory) contacts wired?

• A. In series with the start pushbutton switch
• B. In parallel with the stop pushbutton switch(es)
• C. In series with the stop pushbutton switch(es)
• D. In parallel with the start pushbutton switch(es)

Answer: (C)

The correct answer involves understanding the functional arrangement of momentary contact start and stop pushbutton switches in a control circuit. Holding (memory) contacts are typically wired in parallel with the start pushbutton switch.

The purpose of holding contacts is to maintain the coil of the motor or other controlled device in an energized state even after the momentary contact pushbutton has been released. When the start pushbutton is pressed, the control circuit is energized, closing the circuit path. The holding contacts provide a secondary path for current to flow to the coil of the motor after the pushbutton is released. This allows the circuit to remain closed, keeping the motor running.

If holding contacts were in series with the stop pushbutton switches, the circuit would not remain closed after the start pushbutton is released, thus not providing the intended function of holding the motor in operation. Therefore, this configuration is not correct. The parallel arrangement ensures that even when the momentary pushbutton is no longer engaged, the current can still flow through the holding contacts, energizing the coil and allowing the operation to continue. Thus, they are correctly placed in parallel with the start pushbutton switch.