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RE: Power for a lift.

To: "'Bob Kramer'" <>
Subject: RE: Power for a lift.
From: Randall Young <>
Date: Thu, 7 Nov 2002 11:12:42 -0800
Russ Moore wrote :
> Typically a 5-6 HP
> compresser would have just the item I believe.

Investigate the motor carefully though, as many "consumer grade" "5 hp"
compressors only have a 2hp motor or less.  A quick rule of thumb is to
multiply the nameplate voltage and current together, then divide by 1000.
The result is pretty close to the actual hp available.

Before that though, you might check out

Starting torque is the problem with most phase converters, they don't
deliver very much.  This is fine when the motor starts unloaded like most
machine tools, but wouldn't work very well on your screw-drive.  My
suggestion would be to add a 3-pole switch (or relay) between the converter
and the load, so the 'idler' motor can be started first.  Then when the load
motor is switched in, the 'idler' motor will actually act as a generator to
supply extra current to the third leg, improving starting torque.  Adding a
flywheel to the idler may help too.

Since you've got two lifts, you could experiment using the motor from one as
the idler.  That way, you can find out if it works for your application
without laying out a lot of money.  If it does, I'm told that suitable idler
motors can be had for $50-$100 with some creative scrounging.  My previous
employer had several of them hauled away for scrap, wish I'd had the sense
to haul them home instead !


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