# 3-phase motor on single phase supply

I want to use a 3-phase 400V AC motor an a 230V single phase supply. It says 230/400V and 73.6W on the motor and I know it's possible but that
you need a capacitor connected to the motor windings.
My question:
How to calculate the size of the capacitor, and where to put it ? (the motor has 3 windings, U, V and W)
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wrote:

I have heard the number 4mfd per HP tossed around but I don't know. Use a clamp on amp meter to tune it in with the normal load.
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No matter what you do with a capacitor - you will not get a true balanced 3 phase. You will get a capacitor run single phase motor for which the current/HP will be higher than for 3 phase operation. This may not be important depending on the load that you actually have. (by the way 73.6 watts is a very strange rating -particularly for a 3 phase motor. What is the full nameplate data?)
--

Don Kelly @shawcross.ca
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I just want it to run on single phase, if it draws a few amp's more isn't a problem.
The full spec's:
380V 50Hz 0.1 Hp 660rpm Y/D 380/220V 0.4/0.7A
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Thank you- try it.
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Don Kelly @shawcross.ca
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That's just a small motor. If you find you need real 3-phase, there are many companies that can be googled that provide converters.
Probably you will want the smallest one possible. Is there a special reason that a motor this small needs to run on 3-phase? Beachcomber
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On Tue, 22 Nov 2005 03:04:03 GMT, not snipped-for-privacy@xxx.yyy (Beachcomber) wrote:

My problem as well. I have a 2HP 3 phase motor in my table saw that I want to run from my home. It's 208-220/440 also. It's a question of whether to use a static or rotary phase converter. A static converter will allow the motor to run at @ 2/3 it's rating. A rotary converter is more efficient but you need a second 3 phase motor at the same or greater HP rating to act as the "generator" Here's a link for you to look at when you have the time. http://www.homemetalshopclub.org/projects/phconv/phconv.html
One thing to point out is that you might also wind up with a difference in rpm if you drop from 380 to 220. In the case of my motor I would go from 2850 to 3450 if I went from 220 to 440. This might affect what ever the thing is supposed to operate and may require you to do some mechanical modifications if the motor speed is important.
You can also check out Ebay. For \$2 this guy will email you plans for making a static or rotary converter. http://cgi.ebay.com/Three-3-Phase-Converter-Static-Rotary-Plans-Since1960s_W0QQitemZ7564026378QQcategoryZ633QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
BTW, you can also use a rope and simply pull start the motor.
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allen bradley makes an inverter that wil do just this but it will cost you the price of a replacement motor. why bother.
fearfakter
(Beachcomber)

http://cgi.ebay.com/Three-3-Phase-Converter-Static-Rotary-Plans-Since1960s_W0QQitemZ7564026378QQcategoryZ633QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
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