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Old February 8th 04, 09:23 PM
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Default Potential Relay for phase converter

"gradstdnt" wrote in message
I am working on building a 7.5 hp rotary converter. I plan on using a
start circuit with start cap that drops out after a potential relay.

I used a double pole NO start push button. One pole to close the motor
contactor and the other to close a relay that connected the start caps.
After the convertor starts release the start button and the relay drops out
the start caps. No expensive potential relay needed.
Don Warner
Here is a shot of my 3 hp converter I built over three years ago. I
outgrew it and thus a 7.5 hp unit. Will be up for sale as soon as I
get my 7.5 hp unit together.

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Old February 9th 04, 06:22 AM
Ron Thompson
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Default Potential Relay for phase converter

On Fri, 06 Feb 2004 14:12:30 -0500, Artemia Salina

On Fri, 06 Feb 2004 19:03:52 +0000, Peter H. wrote:

Grainger is just as easy, if not easier, to do business with, as McM-C. YMMV,
of course.

Unless things have changed in the past two years Grainger will not sell to
anyone unless they have a tax number (i.e. must be buying for a registered
business). I know this from personal experience.

McMaster-Carr, Enco, MSC, etc. on the other hand make no such distinctions.

Maybe they just don't like you. Grainger in southern MS sells over the
counter to anyone.

Ron Thompson
Was On the Beautiful Mississippi Gulf Coast,
Now On the Beautiful Florida Space Coast, right beside the Kennedy Space Center, USA

'If you're standing in a puddle, don't touch anything that hums'
From the Red Green show
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Old April 26th 19, 02:18 PM posted to rec.crafts.metalworking
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Default Potential Relay for phase converter

replying to Peter H., Jim wrote:
The Steveco 90-66 is the one most folks have had the greatest success with.
G.E. potential relays are rated 3 HP.
Steveco potential relays are rated 5 HP.
You will have to use an auxiliary contactor to start your converter, because

your idler rating exceeds the potential relay rating. Select a contactor rated
at least 7.5 HP at 240 volts, assuming a 240 volt converter, of course.
Figure on about 900 microfarads for your start capacitor, also assuming a 240

volt converter.
Figure on about 90 microfarads for your A-B capacitor (across which would be

connected the 900 microfarad start capacitor, switched by the auxiliary
Figure on about 60 microfarads for your C-B capacitor, thereby giving you the

nearly ideal 60/40 percent balance (actually, an intentional imbalance).
Figure on about 30 microfarads for your A-C power factor correcting capacitor.

Hi Peter,

Would there be a wiring diagram to accompany the details above?

Have a good day,


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