Plugging is a means of stopping a motor by putting it in reverse for a short amount of time. This can be done using a centrifugal switch known as a zero speed switch.
I always wondered how these work, good explanation. Presumably the energy that comes from a suddenly collapsing coil cannot be dissipated by a slowing motor, so there will be extra voltage spikes and heat to deal with in the wiring....
which is why the speed switch action engages a reversing contactor (from what I understand), which would likely reverse the power supply to cause a rotating magnetic field in the opposite circular direction and cause the motor to decelerate faster and stop.
