Conversion Question

[2windy]

I have a Baldor 3 phase 230/460 volt motor that I would like to convert. It is 1140 rpm, it has a 4" dia rotor and a 36 slot stator that is 3" wide. I assume it is 6 pole. It has a coil span of 6 slots. The wire gage is 22. I was thinking of making a alum magnet cage and placing 1/2" dia x 1/4" N50 neo disc. 10 per pole(two rows of 5 ea. looks like it would fill the area inside the coil pretty good. My question is after searching the board for 6 pole conversions like this failed, I was wondering if this motor had any potential or is the winding to thin to make any usable power. Does anyone have any idea on what kind of power I could expect from it?  If need more info let me know. Thanks

[Flux]

Obviously it will work but how well I can't tell you. You could presumably base something on Zubblys watts per volume of magnet formula.

I would expect a 6 pole machine to have better proportioned slots for conversion than a 2 pole so that may be in your favour.

Inherently the rating of these motor conversions is related to the operating speed in relation to the original design speed so starting with a low speed machine should give you a bit of advantage. You give no idea of the rated power out, that should give you a fair idea. Things under 2hp don't produce much and low speed machines are  big for their rating so you may be looking at a modest power machine for that size of core.

All motor conversions are pushed incredibly hard to get a decent power out, it comes at a price in terms of efficiency and you tend to end up with rather high prop speeds.

You do tend to get better prop performance from running well up on the speed curve and this somewhat offsets the low electrical efficiency that you get from squeezing lots of power from something rather small.

Unfortunately you will have to do the conversion before you get much idea of what you can expect from it unless someone here has experience of a machine of this type.

If you are looking at 48v you may do quite well.If you want 12v then without rewinding you will have a mess of parallel connected pole groups as the series groups will have too much resistance.

Flux

[2windy]

It is 1 hp . I have a 24 volt system. Would I go with a smaller rotor dia for thicker magnets or leave more iron behind them, and just use thinner stronger magnets? I was going to use N50 . I think they are the strongest. Thank you very much for your reply Flux.

[ghurd]

If Zubbly's files don't give a good idea, then pretty much have to make it and see how it comes out.

I recall Zubbly saying a 3/4 or 1HP was a good bet for not needing a rewind, but that was probably for a 12V system.

For a 24V system the motor could be wired for 480V star if delta (Jerry Rig) output voltage is too low.

A 3-ph motor with 12 leads gives more (easier) options for output choices than a 6 wire motor.

The 6 pole speed is on your side.

Might check ebay for curved neos.  They may get more magnet per pole in the space available.

G-

[Flux]

With a 1hp motor you may be able to get about 500W so possibly something like 8ft blades.

The snag with all these conversions is getting enough flux in the gap. Perfectly curved magnets about 1/4" thick would most likely be fine. With the gaps between round magnets and the inability to follow the curvature correctly I suspect that you would do better with at least 3/8" thick. you are unlikely to saturate the rotor core  even if you reduce diameter to use thicker magnets. You will hit saturation in the teeth first so I wouldn't worry too much about the rotor iron unless you are planning to use the original cage rotor and you get down into the part where you have more aluminium cage than steel core.

If you can get N50 cost effectively the go for it, but it isn't normally cost effective and using 3/8 thick N40/42 would be better than 1/4" N50.

I suspect that the 230v connection will be slow for a 24v machine so you may well have to dive inside to split the pole groups. If you can break the star point and use Jerry connection it may be better. I find all this infinitely more hassle than building a dual rotor but everyone to his own choice.

Flux

[2windy]

Thanks guys for the info, it really helps. I have 8 of the Andy Kruse arc-skewed neos but they look a bit too wide for the coil space. If they would work I would need 4 more so I could double each pole(for the width) Don't know where I could find 4 more anyway. I could fit 10 -  1/2" dia neos or 18 -  3/8" dia neos . What would be better?

[SparWeb]

I think 500W is a little optimistic, unless you manage to get lots of magnets on it and re-wind the wire in its stator "perfectly".  Without a re-wind, my motor conversion from a 3HP motor is giving me 500W max, and I have an 8 foot prop on it.  The prop is slightly too small for the alternator.

A 1HP 6-pole isn't a bad place to start, though.  Also, 200 or 300 Watts is actually quite a bit of potential to experiment with as you "cut your teeth".  I'm finding that with multiple wire combinations available, I can experiment with motor conversions at different system voltages, until finding one that works best.  With mine, I tried almost everything available while at 12V, and now that I'm running it at 24V, I have finally found a good balance between prop power in and alternator power out.

Again, searching this board for Zubbly's motor conversions will lead to lots of helpful pictures and explanations.  Good luck and let us know how it goes!