Luckily, I was able to speed up the process of rewinding the motor by overheating it to the point the windings shorted. I thought it would be a good idea to drive down to Stanford and back (10 miles) on a hot day, and as I was about to pull into my place, the inverter shut down because it had detected a fault. I knew perfectly well what had happened. I had been meaning to install some sort of temperature instrumentation, as well as a blower for cooling air, but had been putting it off. I figured I would test my luck with my $150 ebay motor...
I've never rewound a motor before, so I am practicing with a smaller motor from my blower, which I also got on ebay, and which I will be installing in the car when I have the motor off. I bought the blower with a 575 volt motor, which I will rewind as a 220 volt motor and run off a smaller inverter. Here's the stator of the small motor:
It's a 2-pole, 1/2 hp motor, with 4 slots per pole, star wound. The windings are 25 AWG, which I am replacing with 20 AWG to do the voltage conversion. There's about 2.5 lbs of copper in this, which works out to about 1000 feet of 20 gauge.
Here's the rotor, along with the end bells and the impeller from the blower. Such elegant machinery.
6 comments:
hi, It might be that the constant power rating of the motor is below that of your constant speed requirement. Mal.
FYI 2 discussions you might like to take a look at before rewinding.
http://www.aeva.asn.au/forums/forum_posts.asp?TID=585
http://www.aeva.asn.au/forums/forum_posts.asp?TID=505
Regards, Mal.
Hi Kermit,
bummer about your motor.
I've been doing the sums for my own (future) conversion - rewinding for 80V with such a low power controller may be counter productive - I reckon you will need triple the current for the same torque/power. At low speed this may be outside your controller's capability. I'd do your sums carefully :-)
One way to flexibly use the motor is to shift from star wiring at low speed to delta wiring at high speed, using the lower current of star and the lower voltage of delta :-)
cheers,
Woody
Thanks for the links, Mal. The constant speed power rating (5HP) is most certainly too small for even 35 mph. I was getting by by making short trips in the cool part of the day. The longer trip during the hot afternoon was too much. That said, the power rating of the motor depends to some extent on how much heat I can remove. Having a forced air cooling system should make up for the small size of the motor. I was really looking for an excuse to rewind the motor operating it under those harsh conditions without additional cooling.
As far as current, my inverter should be fine with widings that draw 3x current, as the highest current I saw with this motor was 40A, and the inverter is rated at 150A for 1 minute.
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