Originally posted by RB211
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Need a new motor for South Bend
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If you are new to this kind of stuff.....
It is difficult to communicate to somebody
that a single phase motor is a motor that
USUALLY runs with a lot of noise and vibration.
The ones that do not, are the very small minority.
MOST single phase motors are noisy and vibrate.
You really have to see a single phase motor and
a 3 phase motor running side by side to appreciate
the difference. I have seen a single phase motor
running down on a concrete floor, and because of
the hummm and vibrations, it actually very slowly
moved sideways, ever so slowly. After a minute it
might have moved 6". A three phase motor is very
smooth. None of this hummmm and drum.
Even had a piece of machinery running, say like
a cheap single phase drill press or something?
Do this test.... Turn it on and listen to it rattle and
hummm. (Not the U2 record album). Then turn off
the power switch. Instantly and before the pulleys
coast to a stop, the noise goes away. The noise
is not a mechanical racket, it is electrically derived.
The evidence is that the machine gets measurably
quieter the instant that you switch it off.
(Most) single phase motors are horrible. Once you
have seen the light, it will be obvious when someone
turns of a single phase machine. Now wood working
tools are generally loud anyways, and you rarely notice
the extra noise and vibration from a single phase motor.
But a more refined machine, like a metal working lathe
or a precision grinder, sometimes a more violent mannered
single phase motor can make a precision machine almost
unusable. Ever use a single phase bench grinder that
just had that back and forth drone? That is why your
better engineered bench grinders, like Baldor, use capacitor
run induction single phase motors. There is no start winding
just a capacitor run main winding. These motors seem to
be devoid of this 60 cycle resonant harmonic drone.
They also have almost zero starting torque, but that's OK
for a bench grinder. Of course 3 phase grinders don't have
the drone. So get hip to the compromises that exist with
single phase induction motors and get hip to how great that
3 phase motors are, especially for machine tools.
Yes using a VFD is totally worth the price if you don't have
three phase. Some rotary phase converters are really
crappy, but that is a whole nother deep subject.
--Doozer
DZER
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I recently upgraded my Jet 1024 from a 1ø motor to 3ø + VFD and am very pleased.
I've always heard that used but usable 3ø motors are plentiful and cheap, but I haven't found that to be the case, at least for fractional HP motors. You may have to hunt if you want a bargain. Look for one locally on Craigslist. If you look on eBay, you'll find some with reasonable asking prices but unreasonable shipping costs, often greater than the price. But there's a merchant called Congruos eBay Stores that is reasonable on shipping. I bought a new 3/4 HP, 3ø motor for $55 and $30 shipping, which I thought was a bargain. Stocks vary of course, so you may have to watch for a while. (They have no suitable motors listed today, April 28, I just checked.)
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Originally posted by Tincamp01 View Post.................................................. ......... Would any 1725 rpm motor of 3/4 hp be able to run backward with the reversing switch? I was warned about that issue in the past by a guy who repaired electric motors.
usually they have a shaft at both ends .. The name plate should show rev confections !
Rich
Green Bay, WI
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Originally posted by RB211 View PostI've never seen a used 3 phase motor local to me, and if I did, I'd probably get a better deal on a new one.
RichGreen Bay, WI
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You can’t find cheap used 3 phase motors anymore because cheap VFDs that convert single phase to 3 phase made them much more valuable. At a previous job I designed small state of the art wastewater treatment plants and ran them on single phase with VFDs and 3 phase motors. We got one job because the competitors needed 3 phase and the power company wanted 500K to bring it to the site and nothing to get single phase!
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Originally posted by Rich Carlstedt View Post
The Junk yards that take in industrial scrap usually have a selection of 3 phase motors, all sizes... at least here in Wisconsin
Rich4357 2773 5150 9120 9135 8645 1007 1190 2133 9120 5942
Keep eye on ball.
Hashim Khan
Everything not impossible is compulsory
"There's no pleasing these serpents"......Lewis Carroll
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Originally posted by The Artful Bodger View PostIt is a known fact that one cannot get through life without a 3-phase workshop anymore than you could survive without an electric tooth brush.Last edited by Tundra Twin Track; 04-29-2022, 10:20 AM.
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Originally posted by J Tiers View Post
And you can't get in to them to buy anything.
Every time I go to the scrap yard,
the guy who unloads me, I give him
$10 gratuity. Then I ask if he has some
steel or whatever, such and such a size.
I am never refused the opportunity to
look around and buy something out of
their yard. Try it. It works.
-DoozerDZER
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Originally posted by chipmaker4130 View Post
Dang, Doozer. You musta swallowed a 'nice' pill this afternoon. Great writeup!
Just another opportunity for me to bitch about ignorant people and their
unwillingness to actually accept new information.(if you read between the lines)
--DDZER
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Originally posted by Doozer View Post
It is called making friends.
Every time I go to the scrap yard,
the guy who unloads me, I give him
$10 gratuity. Then I ask if he has some
steel or whatever, such and such a size.
I am never refused the opportunity to
look around and buy something out of
their yard. Try it. It works.
-Doozer
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