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Posted by on October 9, 2006, 8:36 am
> > Advice, comments?
>
> a 220v ac motor is designed to operate at 220v not 115 volts. Believe it or
> not, operating that motor at 115 will most likely draw too much current and
> make the motor overheat. The exhaust air going over it to cool it may help,
> but it is dead wrong to run it at 115volts.
> The motor will try to run at its normal RPM, a factor of 60Hz and the number
> of poles the motor is wound for. Lets say it is a 2 pole motor; at 60 Hz,
> even though this is not made to be a synchronous motor, it will try to run
> at 3600 RPM.
>
> It will more like run at and be rated at 3450 RPM or so due to normal "slip"
> at 230 volt operation. That will draw a certain current at 230 volts with
> the load. And, we are not even talking about the same load here.
>
> 1)When you try to run it at 115 volts, using the same load, it will try to
> achieve the same RPM, and at 115 volts, that RPM will require double the
> amps (sound strange, but true). If the windings heat up beyond the
> insulation class rating of the motor, it will burn up.
>
> 2) AC motors and transformers and other wound devices have inductive
> reactance which causes its impedance to the flow of AC current to be much,
> much lower than the DC resistance you would measure with an ohmmeter. The
> motors are designed to present this impedance to the flow of current at
> specific voltages that get the magnetic core at saturation design values.
> Operation at 115 volts will most likely not achieve this, and the motor may
> appear to be closer to the DC winding resistance value and draw lots of
> current converted into heat unless that saturation point is reached, but it
> will not be.
>
> Those items 1 and 2 will try to make your motor fail and possible cause a
> tragedy in your life. It is not worth the experiment. Buy a unit designed to
> do what you need and run on 115v. I can't say it would be OK to run your
> setup at 230 volts either. Would your insurance company??
>
> Using WD40 as a lubricant (WD20??) is not an ideal motor lubricant.
>
> I have oversimplified the technical aspects of the motor, but I believe it
> to be pretty accurate as far as I went with it. Don't leave it running!
> You have been warned by many already.
>
> Bob
Bob,
FYI
http://www.wd40.com/Brands/3in1_product_info.html
Blue can: "It is a special blend of high-grade oils, equivalent to SAE
20. Its formulation is ideal for lubricating moving parts of electrical
motors. "
( I meant to write SAE 20.)
I agree that running a 220 VAC motor with a run capacitor will draw
more current proportionally then halving the voltage.
In a fan situation, the moving air will help.
After running for 9 hours, this motor did not overheat.
However, I will take you advice, and increase the voltage to 220 VAC.
Thanks
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