DC Injection Braking for a Slip-ring Motor?

Yes its possible, the Coal Board used this method for winding engines.Liquid resistance to vary the speed, reverse power or dc injection for stopping followed by a mechanical air brake to park.

Sure, but usually the motor is made for that kind of duty because of all that extra heat.

I have used it on an industrial DOL drop saw bench motor for emergency stopping. Works well, but you have to be careful with the duty cycle and ensure the braking contactor can handle the large inrush currents (properly oversized, series connected contacts and snubber networks).

I was thinking along the lines of switching maximum resistance back in to the rotor circuit and then applying the DC. Most heat should then be dissipated through the resistor bank. As the speed drops switch out the resistance to keep the rotor current about even.

I got involved with installing plug braking (capacitor discharge) on a 75HP skip hoist. It worked quite well until the motor shaft sheared, that one was a case of "back to the drawing board."

Basically, almost any AC/DC motor type can be stopped in a very short space of time by simply removing power and creating a short across the input wiring to the motor.....

To reduce the "instant" effect, resistances can be used instead of a 0 Ohm short if required.

It is often creatively used in hand power tools to stop them spinning when power is removed....for safety reasons. Cheap Crap tools often do not have it. Test before buying....

It is a simple method that does not require using any other power source, either DC or AC to work really well.....