# Using a VFD for 2hp 3PH motor on single phase

#### RogueRose

Joined Oct 10, 2014
374
I've been trying to find a 2HP motor comparable to the one I have (which is 208/230v 3PH) and they are all pretty expensive. The motor is for a bandsaw or tablesaw. I have single phase 120/240v at my house so I looked into a VFD and am having a hard time figuring out what would work as I've never used a VFD. Most are listed at 220v (I'm guessing input?) but the KW:HP rating is what I am really confused about as the numbers vary vastly. The FLA of the motor is 5.8-6.8

The prices vary by about $10 each with the 3HP being about$77 including shipping. I'm wondering if this VFD will be adequate.

2.2KW 3HP 220V VFD
https://www.ebay.com/itm/2-2KW-3HP-220V-Variable-Frequency-Drive-Inverter-CNC-VFD-VSD-Single-To-3-Phase/401691712487?epid=5028331895&hash=item5d86b11be7:g:tRAAAOSwJp1cRk8Q

220V 2HP 0.75KW
https://www.ebay.com/itm/220V-2HP-0-75KW-Single-Phase-To-3-Three-Phase-Output-Frequency-Converter-VFD-VSD/264126456397?hash=item3d7f29e24d:g:zDoAAOSwaPNcNhqi

220V 2HP 1.5KW

#### shteii01

Joined Feb 19, 2010
4,647
Can you get pic of the metal tag that is riveted to the motor?

#### shortbus

Joined Sep 30, 2009
7,237
If your motor is 2HP definitely go with the first one. It is or at least was always a good idea to go up one size on a VFD when running on single phase. But you will have to use 220V single phase. And you need to keep the VFD in a place away from any saw dust.

Don't knowwhere your at but these are a pretty good motor -
https://www.harborfreight.com/2-hp-compressor-duty-motor-67842.html

Joined Jul 18, 2013
19,437
One issue with the Chinese VFD as shown is the documentation and support.
If you think you can handle it, then they are priced about the lowest.
Max.

#### oz93666

Joined Sep 7, 2010
700
Interesting , so the VDU turns single phase 240V into variable frequency 3 phase output ....up to 400Hz !

So I guess you could run the motor at 8 times it's design speed at 50Hz ... would the rotor tear itself apart??? Centrifugal 'tear apart forces' increase with square of rotational speed , they'd be 64 times greater.

#### oz93666

Joined Sep 7, 2010
700
Don't knowwhere your at but these are a pretty good motor -
That links to a Single Phase motor .... all the VFD s above are three phase output ... surely a 3Ph motor is needed?

#### shteii01

Joined Feb 19, 2010
4,647
Interesting , so the VDU turns single phase 240V into variable frequency 3 phase output ....up to 400Hz !
Yes. Single phase goes in. 3 phases come out and go to the motor.

A small practical note about the units you linked. Do you see all the little openings on top, bottom and sides? They are for cooling. However, they also allow particles to get inside and metallic particles can short something inside and destroy the running VFD. The units you show are designed to be mounted inside an enclosure. They can be mounted in the open, but you need to be careful where you put them.

#### be80be

Joined Jul 5, 2008
1,961
You want a 3 ph motor the VFD we use are rated 2 times the motor amp rating you can set the VFD 0-400 hz
the ones we use are set at 60 hz but we have some that can do 400hz but are made for that.

Joined Jul 18, 2013
19,437
For a standard non-vector rated motor I would recommend not going above 120Hz for a 4 pole motor.
You can get the High rpm 24krpm 2 pole spindle motor, usually water cooled that will take 400Hz, but minimum rpm is restricted to around 6krpm.
Max.

#### shortbus

Joined Sep 30, 2009
7,237
That links to a Single Phase motor .... all the VFD s above are three phase output ... surely a 3Ph motor is needed?
He said he can't find a single phase motor that is inexpensive, I showed one that is. He is going to use a 3PH motor and VFD because that is what is on the saw now. Or at least that's how I read the first post

#### shortbus

Joined Sep 30, 2009
7,237
So I guess you could run the motor at 8 times it's design speed at 50Hz
No, the variance on Hz is usually kept between one half and double line frequency. The 1/2 because of cooling from the motors fan, and the double due to centrifugal forces in the motor.

Joined Jul 18, 2013
19,437
Although I am sure the standard motor and the vector rated use the same quality/type of enameled wire, it is possible the balancing process is less stringent on the Standard 50hz/60hz versions, also bearings maybe higher quality on vector rated versions.
This is the reason I limit them to ~120Hz.
Max.

#### MrSoftware

Joined Oct 29, 2013
1,613
Not sure if you're familiar with the AvE channel on YouTube, or if this would have any use beyond entertainment for your case, but he adapted a VFD to a home shop air compressor:

Joined Jul 18, 2013
19,437
Not sure if you're familiar with the AvE channel on YouTube, or if this would have any use beyond entertainment for your case, but he adapted a VFD to a home shop air compressor:
Entertainment is right, bit of a cowboy IMO.
Max.

#### RogueRose

Joined Oct 10, 2014
374
Thanks a lot to everyone who has contributed. I have a couple questions, and another option for a VFD ( a Allen-Bradley Powerflex40 which I have access to but they might be "bad" - I have little faith in the Techs diagnosing this). I'm taking a few to look at them and I have some that are 8, 10, 12, 15 and 20A from 120v or 240v so they should be able to handle some large drives.

Now what I'm a little confused about is when I hear about motors they say that they operate at a voltage of +/- 10% but the video was about 3 phase motors and a little about single phase - so IDK if this 10% thing is only for 3 phase.

The problem is all I have is 120v & 240 but I guess I might be able to create some step up transformer with a few more or less winding to increase or decrease the V by 10% from 240 or from 120 down to 110 or so.

Powerflex40 manufacturers - Allen-Bradley - page
https://ab.rockwellautomation.com/Drives/PowerFlex-40

Documentation of the Powerflex 40's
https://ab.rockwellautomation.com/Drives/PowerFlex-40#documentation

Example of 480v 2HP model on Ebay -

480v 15HpP - $1200! https://www.amazon.com/Allen-Bradley-Powerflex-480VAC-15HP/dp/B00E6GV3BE 480v 7.5HP -$400 - Ebay

the place I was working at have about 200 of these that were "broken" and were getting scrapped. I wanted to buy them as scrap (5x what they would have gotten for scrap value but was declined for some reason and now they all seem to have disappeared.... Makes me really mad, especially b/c they were all free (donated) to the company)....

So I'm hoping that one of the ones I can find left over might be fixable. I'm guessing these are better than Chinese ones.

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i just talked to a local electric motor shop who sells new, old and rewinds them, and they had some 1PH, 2HP that is basically identical to mine, but at $350, that is more than I want to pay. Then he had another 5HP single phase 240V that was called a compressor motor and it was almost identical (if not identical frame size - 56J or something). So it's 3HP more and same size and only$50 more. It is a Marathon motor with same service factor . I plan to run the motor for 15-30 mins normally w/ same amont of time off, maybe up to 45-60 mins on rare occasions (at end of day finishing a job). IDK if this motor would work or not. I'm not worried about speed of motor as I'm planning on using lots of various pulley sizes.