Repulsion Start Electric Motor video

waynefromnscanada

Was some discussion a while back on Repulsion Start electric motors, now long gone from production. Here's a very interesting video for those who might be inclined to watch. They had very low start surge compared to "modern" induction motors, thus would have been great for many off grid applications.
Witness it's relatively slow gain in speed till the brushes kick off the commutator and the motor comes up to full speed. Then when the power is cut, it slowly spools down and finally the brushes snap back to the start position. Would be interesting to know what RPM this 10 HP beast is rated for. Sounds like it's really wound out.
https://www.youtube.com/watch?feature=player_embedded&v=gmk53FxtlVo#t=1s

RandomJoe

Re: Repulsion Start Electric Motor video

The specs listed below the video say it's 1750 RPM, which is fairly typical even now. The poster said it is running on only 90VAC from a Variac, so I suppose it's not at full speed in the video.

Interesting sound! Wonder how many start/stop cycles those brushes and the linkage they're attached to are rated for? Must do pretty well, since it was in use as an air compressor motor for (at least) 30 years. Unless their setup had it running continuously, an air compressor sees quite a few starts over time...

waynefromnscanada

Re: Repulsion Start Electric Motor video

Thanks for that info "Joe", I hadn't seen that. The 90 volts explains the slow rev-up. Also interesting that with the low start surge by design, it had no problem getting it's former compressor up and running. My grandfather had a piston type water pump powered by a 1/4 HP repulsion start motor. Unfortunately the armature finally burned up and that was the end of that motor

RandomJoe

Re: Repulsion Start Electric Motor video

I like to see old motors like this. Not that I knew about "repulsion type" motors before now. I just like the way they were made "back when" - dangerous-looking! :cool:

I did some HVAC work in an old (1909) hotel that had a large water-cooled chiller and coal-fired boiler (converted to natural gas at some point) in the basement. Neither were used anymore, but hadn't been removed, just disconnected and left to sit. The boiler was fascinating just from its immense size, but my favorite was the chiller - the motor was externally mounted, which is rare on modern units, and was (what I call) an "open frame" design. Huge wide openings, you could easily see the inner workings - and reach right in to touch if you were crazy enough to do so! This part of town was only wired for 208V, so the current ratings - and wire sizes - were insane too. All the control panels for running the old system were still there too, fun to see all that old stuff.

Of course all the asbestos warning signs were a bit of a turn-off...!