We use reverse plugging to stop a rubber mill (200 hp, inward rolling rolls, 1/2" gap, rolls are about 7' long and 3'o.d.). It slams to a stop and reverses a little by design. It's not very repeatable, and when the plugging switch wears, it can be a pain to replace and adjust correctly. I have seen a slo-mo video of what it does to an ac motor rotor when it's suddenly reversed, and it's very brutal. We test our mill safety stop at least twice a week, but haven't had any major failures caused by the plugging stop. The operators actually measure the stopping distance and the reversal distance and it must fall within certain specs or maintenance is performed. Like I said, the repeatability is not great. It may stop within 45 degrees once, (final driven roll rotation) and the next time may travel only 10 degrees. Sometimes the reverse distance is nearly zero, other times it can be as much as 90 degrees. I would not recommend it for stopping a sharp blade, unless an additional brake could be used to hold the blade once stopped. Unless you can set it up for a known, constant load, repeatability is impossible.
I have tried DC injection braking on 1hp motors, and did not like the performance due to the frequency of stopping in my application. I could not use enough current to obtain the stopping power I needed without overheating the motors. (That application used DC braking at the end of index motions that occured every ten seconds). An infrequently used DC injection type braking method should provide a very quick stop, though.
In a safety application, what happens if the drive faults when you ask it to perform DC injection braking? Is it still safe? I think a mechanical fail-safe brake is the only way to go for personnel safety. For a quick stop for machine protection or other production related reasons, dynamic braking resistors or dc injection would probably do the best job if mechanical braking can't be installed. JMHO
