# Variable speed control help



## tcleve4911 (Mar 26, 2006)

I am running a 1/3 hp motor on a woodworking lathe.










It currently just has a standard household on/off switch
I would like to replace the switch with a variable speed control.

As I go to the supply house, what should I be specifically hunting for?
Will a ceiling fan control switch work?
I would like to have something that will fit right into the existing outlet box.

Thanks for your help
T


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## BigReds (Feb 27, 2009)

How many speed is the motor? If it has more than 1 speed, you can have a switch installed that does hi med and lo.


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## mrmike (Dec 9, 2008)

You probably have a AC induction 1/3 hp motor there by the looks & you will not be able to vary the speed of it like you are thinking...........


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## John Valdes (Apr 14, 2010)

It's doubtful this motor is rated for more than one speed. Look on the nameplate. You could use a small VFD. But that motor looks very old and may not be able to withstand a VFD output. Here is a picture of a small VFD that can be used. It has a start/stop and a potentiometer for speed control. If you could post the motor nameplate specs, that would really help.

The VFD pictured is a wash down model and excellent for applications like yours.


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## tcleve4911 (Mar 26, 2006)

Here's the specs on the side of the motor 

WestingHouse
Handy-Craft Motor
Sleeve Bearing
1/2 hp
1725 RPM
115 volts...60 cycles
8 amp...1 phase

Thanks


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## Inner10 (Mar 12, 2009)

> 1725 RPM


Probably a split phase induction motor, if so you would have to change the power frequency.


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## mrmike (Dec 9, 2008)

John is right on here- I want to add the VFD will probably cost more than the motor is worth, & the motor probably will not last long........... You have the sheeves on it for changing the speeds--- if you need more control you would have to go to a whole new vfd with motor set-up......


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## tcleve4911 (Mar 26, 2006)

Thanks for the replies

I did a quick search and a variable frequency drive is as much as a new motor.
So for now, I will just have to be content with changing the belt location to change my speeds.

The good news is, a forum like this prevented me from just throwing a fan control switch in there and doing damage to the motor. 

What did we do before we had information like this so readily available:whistling

Thanks again, guys:thumbsup:


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## Leo G (May 12, 2005)

Can't you get the squirrels to just run slower in the wheel?


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## PrestigeR&D (Jan 6, 2010)

tclev,,,
an INDUCTION rated motor is what you need...induction motors are rated that way because the windings have a heavier class of insulation and can handle the heat that may be generated at variable rates of frequency changes (speed) .
3ph motors are the most common for induction class.... you can run a 3ph off of the vfd using single ph.. sometimes even 110v VFD will transform the voltage into 220 3ph but the hp rating for this is very limited- the options for vfd's are almost limitless..... forward.reverse.soft start.dynamic breaking.. ramping.. slow down cut offs (ramp down) ramp timed.. etc.etc.etc... for example.... I can run my 20C in 4th gear(low end) and run the frequency drive at 5hrtz and the spindle barley moves....and you can not stop it- literally... there is an incredible amount of torque on the spindle at low speed thanks to the VFD technology- so my point is they are an amazing piece of technology...:notworthy you can run it from your lap top if you like.. I wouldn't ,, but you can...


I have a 1-1/2hp rated induction motor in my rat hole if you need one...what is the lathe? 

B.


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## Leo G (May 12, 2005)

Inverter rated, Brian. Induction is a type of motor.


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## John Valdes (Apr 14, 2010)

tcleve4911 said:


> Here's the specs on the side of the motor
> 
> WestingHouse
> Handy-Craft Motor
> ...


I did not realize you had a single phase motor. VFD's will not operate single phase motors. They will operate 3 phase motors on single phase power. 
So, a VFD is not an option.



PrestigeR&D said:


> tclev,,,
> an INDUCTION rated motor is what you need...induction motors are rated that way because the windings have a heavier class of insulation and can handle the heat that may be generated at variable rates of frequency changes (speed) .
> 3ph motors are the most common for induction class.... you can run a 3ph off of the vfd using single ph.. sometimes even 110v VFD will transform the voltage into 220 3ph but the hp rating for this is very limited- the options for vfd's are almost limitless..... forward.reverse.soft start.dynamic breaking.. ramping.. slow down cut offs (ramp down) ramp timed.. etc.etc.etc... for example.... I can run my 20C in 4th gear(low end) and run the frequency drive at 5hrtz and the spindle barley moves....and you can not stop it- literally... there is an incredible amount of torque on the spindle at low speed thanks to the VFD technology- so my point is they are an amazing piece of technology...:notworthy you can run it from your lap top if you like.. I wouldn't ,, but you can...
> 
> ...


Never met a motor that was not an induction type motor. Never in 35 years. Where did you get this information?


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## PrestigeR&D (Jan 6, 2010)

John,,
not saying that I have either... ... I was referring to getting a 3ph motor with the proper class of insulation..."F". The older motors.. say something from the 1920's-1970's , the insulation on the windings were not designed to take the abuse of a variable frequency drives if being used at a variable frequency rate... that is what I meant to say...

I pulled this off an engineering forum regarding inverter duty vs induction ...


_Strictly speaking there is no difference. Any standard AC Induction Motor can be connected to VFD. But, it may so happen that during very low speeds, the shaft mounted fan may not provide sufficient ventilation to remove the heat from the motor. So, today we have got what is called Inverter Duty Motors, wherein there is an external fan with a separate power supply so that the fan speed is independent of the motor shaft speed. Also, inverter duty motors have better insulation._

.. it's the insulation that is important from what I have been told... I am no electrician and never claimed to be one... I have had to become some what educated on 3ph motors from having to deal with several vfd's for my machines... but never claimed to be an expert....:no: 


I had to buy a spike filter for my 1952 MOAK 32' special because the insulation class on the motor was not not rated F to avoid large spikes in voltage and avoiding over heating the windings....should I change the frequency on the VFD...

Lee,
Yes, I am aware,,,,,,thank you ...it's the way I worded this... my apologies gentleman...:notworthy

B.:thumbsup:


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## John Valdes (Apr 14, 2010)

PrestigeR&D said:


> John,,
> not saying that I have either... ... I was referring to getting a 3ph motor with the proper class of insulation..."F". The older motors.. say something from the 1920's-1970's , the insulation on the windings were not designed to take the abuse of a variable frequency drives if being used at a variable frequency rate... that is what I meant to say...
> 
> I pulled this off an engineering forum regarding inverter duty vs induction ...
> ...


No problem. Keep in mind class "F" magnet wire is the standard for most every motor manufacturer out there. Class "H" is the next step up and then inverter coated wire next.
Inverter duty wire is class "F" or "H" with coating. This coating changes the maximum voltage for the wire to 1600 volts.
This is to protect the windings from pin holes that will appear when using a VFD. All VFD's output a simulated sign wave. Some are better than others.

Older motors like you say are not wound for inverter use, and could fry the motor promptly, or run for another 20 years. No one knows.
Inverter motors not only have coated wire, they usually have special bearings to allow for higher speeds.


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