NE1 help re dual phase motor please?

snipped-for-privacy@all.com wrote:


It should work ok, this is a small motor and the starting load is pretty low on a T&C grinder.
I'd suggest as a starting point say 15-20uF motor run cap. Get it running and measure the voltage between Neutral and your dummy 3rd phase. This should be as close to your line voltage as possible.
Wayne...
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snipped-for-privacy@all.com wrote:

There is a small paperback book called "Electric Motors in the Home Workshop" by Jim Cox. This covers a lot of these issues, especially the capacitor sizes to use to fool a 3 phase motor into running on a single phase. It might be worth investing in a copy, its still current (!) as far as I know.
Steve
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snipped-for-privacy@all.com wrote:

Why not get a single-3ph VFD to drive the motor? You can get them at reasonable prices from eBay, and you get the advantage of an infinitely variable motor speed too.
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Regards, Gary Wooding
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The tailpiece to this saga . . . . Got into e-conversation with helpful guy at Brook Compton Motors about this ancient Gryphon motor. It isn't a dual voltage motor or indeed one that'll run on 3 or 1ph by changing the wiring. The wiring instructions for "low voltage" operation refer only to delta or star 3ph operation. So, we're either into trying the Peter Forbes approach or buying a new 2 pole, 1ph motor. Thanks to all for contributions.
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snipped-for-privacy@all.com wrote:

Which implies that its a 3ph motor that can run on either 240v (delta format) or 415v (star). So you can use a single to 3ph VFD inverter to drive it from the standard single phase supply. You don't mention the power of the motor, but a 1hp VFD will cost around 40 to 50 on eBay.
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A "last final" note on this . . . This morning I put Peter Forbes' suggestion to the test and to my surprise the motor accelerated, slowly at first, then ran perfectly. I may now try a 20mfd capacitor to maybe improve initial acceleration. Renewed thanks, this has saved us much time and aggravation <IanC>
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