# VFD for a 2 HP, 230 volt, single phase motor?



## PatMiles (Jun 18, 2021)

New guy here who is trying to accomplish something I've wanted to do for a while which is to power my lathe with a VFD. Needless to say, the VFD realm is way above my head so I am looking for info and direction.
Any and all help is greatly appreciated.
Pat


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## benmychree (Jun 18, 2021)

I think you will have to replace the single phase motor with a three phase to use a VFD.


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## PatMiles (Jun 18, 2021)

benmychree said:


> I think you will have to replace the single phase motor with a three phase to use a VFD.


Just what I was hoping not to hear, but if that's the reality of the situation...


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## Papa Charlie (Jun 18, 2021)

I had asked this same question, the answer from @benmychree is correct. you need a three phase motor to do this. The single phase motors work differently than a three phase.


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## rabler (Jun 18, 2021)

In addition to working well with a VFD, a three phase motor has the added benefit of providing consistent torque through 360 degrees of rotation where a single phase motor torque pulses as it goes around.  The uniform torque can reduce vibration and give a bit better finish.


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## Papa Charlie (Jun 18, 2021)

Would you replace a single phase 2hp motor with a 2 hp three phase motor.

Probably a dumb question.


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## matthewsx (Jun 18, 2021)

Papa Charlie said:


> Would you replace a single phase 2hp motor with a 2 hp three phase motor.
> 
> Probably a dumb question.


Yes, if you're planning on powering with a VFD. When using a static phase converter you will loose some power so uprating the motor might be desirable. However, this is an unlikely situation since the most common situation would be a three phase machine that needed to be powered from a single phase power source.

For the OP, is this a situation where you have a shop that only has 110v power and you have a 220v machine?

John


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## PatMiles (Jun 18, 2021)

matthewsx said:


> For the OP, is this a situation where you have a shop that only has 110v power and you have a 220v machine?
> 
> John


The "shop" is my garage, single phase to the house so I bought the lathe with the 220 volt single phase motor. I do have a static phase converter for my mill and surface grinder. The VFD will provide me with a few other benefits on the lathe.

I do appreciate all the input from you gents!


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## RJSakowski (Jun 18, 2021)

There are numerous examples of running a single phase motor with a VFD and there are VFD's specifically designed for running single phase motors. The biggest issue come with the start winding on capacitor start motors.  As the motor slows down, the centrifugal switch engages, causing large current draw,  Start windings are designed for very light duty cycles and this would cause premature failure.

One work-around is to disable the switch and remove the capacitor.  The start winding is then treated as the second leg of a three phase motor. The VFD can tuned to correct for the fact that the winding is not 120º out of phase with the run winding and to run a sustainable current through the winding.  A single phase tor generates its power in run mode entirely with the run winding.  It is my guess that using the start would in effect increase the available power of the motor although I haven't seen anything to verify that supposition.

Of the commercial single phase VFD's, it appears that they are commonly used for ventilation fans.  Such a use will not have a high torque requirement at low speeds which may be a problem for use on a mill or lathe.  I have not seen anything to refute of verify this though.

The idea of a single phase VFD appealed to me but most of those that I have seen require 240 volt input and I really wanted to use the existing 120 volt service for my 1 hp lathe motor rather than rewiring which is why I elected to go a different route. 

Here are some examples.









						2 hp (1.5 kW) Single Phase Output VFD
					

2hp 220v-240v single phase input & output VFD, running your single phase motor in variable speed with GoHz affordable price VFDs now.




					www.gohz.com
				





			Amazon.com
		









						2 hp (1.5 kW) VFD, Single Phase Input & Output
					

Discounted 2 hp VFD, 1 phase for single phase AC motor, 220V - 240V 9.6 amps, brand new direct sale by manufacturer.




					www.ato.com


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## PatMiles (Jun 18, 2021)

RJ,
Thanks for the info and education.
At this point it looks as though a new 3 phase motor is in my future. As I keep telling myself, I don't drink, do drugs or chase women so I need something to spend my meager wealth on.


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