Hi Bruce - I've had this happen a couple times with my 17' 48V machine. I find that it breaks loose rather quickly if I just bypass the rectifiers, usually for about 30 seconds, although longer wouldn't hurt it I dont think. I think the idea arrangement would be a push button switch on each phase. One phase will usually melt it (since the current flows through 2/3 of the coils) loose, and while its doing that it's also providing some kind of torque on the rotor which also helps. Being able to do one phase for a bit, then another might help too, since you'd be putting torque in a couple directions on it.
I don't worry too much about hurting the windings - if there's ice on it (or even water) its going to stay fairly cool till it dries off I expect. The worst abuse mine ever had like this is when we got hit by lightning, and a couple of my rectifiers were blown to closed circuit. It was over 10 min before I'd realized what had happened (there was smoke coming from the tower top) and unplugged the machine. While it did get hot, and the stator was slightly warped, the damage was minimal and the machine still works fine. I dont think you're endangering your cold/iced up stator to bypass the rectifiers for a min or two.
