1800 vs 3600 RPM for phase converter

I recall from various discussions here that 1800 RPM motors were
preferred over the higher speed ones when making a phase converter. I
picked up a 3 HP Baldor at a factory closing today for $10 with the
intent of making a phase converter, and it's 3600 RPM. Why are the
lower RPM motors preferred?
Source for inexpensive run capacitors?
RWL
Reply to
GeoLane at PTD dot NET
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they are quieter. Otherwise a 3600 RPM motor will do just fine.
Try
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Reply to
Ignoramus28617
I think the size of the motor is the key. A three hp 3450 rpm motor is smaller than a three hp 1750 rpm motor.
For run caps try your electric company or whoever maintains the street lights.
Dan
Reply to
dcaster
Dan sez: "For run caps try your electric company or whoever maintains the street lights"
Also try any HVAC outlet. They usu. have a good selection of run caps and potential relays.
Bob Swinney
I think the size of the motor is the key. A three hp 3450 rpm motor is smaller than a three hp 1750 rpm motor.
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Dan
Reply to
Robert Swinney
I have been told that a 1750 rpm motor was 4 pole and 3600 rpm was 2 pole. Thus making the 1750 rpm a better candidate, because it had more copper in it to generate the third leg.
Richard W.
Reply to
Richard W.
True. But I'm wondering.....
The kinetic energy energy of a rotating body is a function of the square of the angular velocity. Thus a flywheel of n kilograms on a 3600 rpm motor will have 4x the energy of the 1800 RPM one.
That sounds relevant...
Reply to
David Lesher
From my experience it's down to the noise; the cooling fan in my 2 pole 3000RPM motor (50Hz over here) was so noisy that I pulled it out and fitted a 6" enclosure fan (Muffin fan) on the end case instead, it's now tolerably noisy although the motor itself is still noisier than a 4 pole would have been. Aside from that, the motor works well as an idler. Martin
Reply to
Martin Whybrow
It may be, but you have 2 legs running the motor to generate the third leg on both motors. It not just idling under load, it's generating the third leg. So it would seem that a 4 pole motor would be better under higher loads.
Richard W.
Reply to
Richard W.

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