In my younger days, a machine I worked on used Dynamic braking on a 50/100 HP 3600/7200 RPM (Used a rotary converter to make 120Hz for the 7200RPM) direct drive spindle. It would stop the spindle within seconds simply by applying a high DC current between two phase leads of the motor. A timer was used to turn off the DC shortly after the spindle had stopped. If set too long, the spindle could barely be turned by hand.

 

In my younger days, a machine I worked on used Dynamic braking on a 50/100 HP 3600/7200 RPM (Used a rotary converter to make 120Hz for the 7200RPM) direct drive spindle. It would stop the spindle within seconds simply by applying a high DC current between two phase leads of the motor. A timer was used to turn off the DC shortly after the spindle had stopped. If set too long, the spindle could barely be turned by hand.

The demo that I used was to spin up a 3-phase motor sitting on the shop floor and connected by an adequate power cord. After spinning it up, quickly unplugging it from the starter box and plugging it into a shorted outlet held in a bench vise would make the motor roll over on the floor. Yes, it was a crude non-instrumented demo, but it was adequate to prove a point. And of course, since I knew waht would happen, there were adequate safety provisions to keep everything safe.