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Alex Middleton

Static Phase Converter

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I have a double spindle, 3hp, 440V, 3-phase motor that I picked up from work a while back.  Unfortunately I only have single phase power going to my shop.  Has anyone had any experience with using a static phase converter like this one: https://www.mscdirect.com/product/details/00099788#target4 ?  It would be a significantly cheaper option than installing a rotary phase converter, or having a 3 phase service put in.  Can a VFD be used in conjunction with it?

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I don't know about the converter, but a VFD will work fine.  They take single phase and make it three phase.  You'll need one with a 220v input for that 440 motor.

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What Alan said.  With VFDs so easily available now, the static 3-phase converters are obsolete.  One of the problems with a static converter is that you can't run the motor at it's full load rating.  Your 3hp motor would probably only develop 2hp with one.  However, with a VFD that will cost about the same amount, you not only get full power, but you get adjustable speed.

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I have used one to try and power my Kalamazoo 6x48 grinder. (An actual grinder not a sander.) It has a 3 hp motor direct drive and the grinder has too much load for the static phase converter. I even bought an oversized converter and it didnt help and the motor overheated severely. And now it sits in the corner awaiting the rotary phase converter to be finished. I would highly recommend the A2 series VFD found on flebay for around $100. I can help program the particular one. And your within driving distance. Hint hint.

Edited by Jeremy Blohm

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This is the one powering my power hammer. The brand name is Vevor and its the A2 series.

Honestly if you want to try the static phase converter you are welcome to have this one as I will never use it.

Edited by Jeremy Blohm

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Another thing to think about is using the 3 hp motor to build your own small rotary phase converter. 

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Thanks for the input guys.  When it comes to this type of electrical work I'm a little out of my element.  This particular motor is just begging to be converted into a 2x72 on one side with a disc grinder on the other.  I'm just trying to figure out an economical way to get power to it.

 

I'm looking forward to seeing your setup Jeremy.  Correct me if I'm wrong, but that particular VFD outputs 220v 3-phase, right?.  I've been all over the place online looking for a VFD that will take 220v single phase and output 440v 3 phase and am drawing a blank.  I'll probably end up having to get in contact with one of the drive manufacturers directly and see what they say.

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Many motors can be wired up for both 220v and 440v 3-phase.  Can you post a pic of the data plate on the motor?  Alternately, take off the cover int he connection box, and see if there is a label inside that show a low and high voltage connection diagram.

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20190813_101945.jpg

 

This is the best picture I have of the data plate.  Apparently it's only 2hp, I could have swore it was 3.  I'll dig it out this weekend and open up the electrical box and take a look inside.  Unfortunately at the moment its tucked in the back corner of the barn behind my boat and a bunch of other stuff that was put away for the winter.

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That's an oldie!

 

Unfortunately, based on the plate I suspect it is 440v only.

Edited by Brian Dougherty

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That it is.  Based on a serial number list that I found on another site, I'm guessing 30's-40's.  That's another reason that I want to put it to use, it's something that my grandpa would have had in his shop if he were still alive.  Here's a pic of what it looked like before I brought it home:

20190813_055739.jpg

Obviously it's been retrofitted some over the years.

After a little bit or web searching, apparently the company is still in business.  I just sent them an email looking for a little more information on this particular machine.  I also sent off an email to the company that @Geoff Keyes posted to see if they offer a VFD that will do what I need it to do.  Ill be curious to see what they come back with.

Edited by Alex Middleton

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Well, it would work...  :lol:  I gathered from the site that English is not their first, second, third, fourth, fifth, or even sixth language.  

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I kind of got that same impression from the emails.  After replying back to him he came back and said that a VFD wouldn't be able to do what I'm looking for.  Then he sent me a link to a $6,000 frequency converter and said that it would cover all of my needs. :rolleyes::blink:  I think I'll try a couple of other sites and see what they say.

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Thanks for the tip Jeff.  Automation Direct was already next on my contact list.  I just sent an email to their tech support for confirmation.

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That looks old. I would not try running it on a VFD unless a Sine-Wave filter was used in the circuit.

 

What follows is "as I understand things": somewhat oversimplified and perhaps not technically accurate, but close enough for me to get my head around. YMMV and it is worth researching things further if you are intending to go that way. 

 

Old motors often used a brittle Shellac-based impregnation material for the windings. I think some of the early synthetic impregnation materials were also rather brittle. Later polymeric resins are much "tougher". My rather limited experience is that post-1980-ish motors are no problem with VFDs. Pre-1960-ish motors are a problem and between 1960 and 1980, things are unclear.
 

On a true sine wave supply (mains), the voltage rise is quite slow. As the current rises, the magnetic fields around each of the coils rise and interact with the other coils in the winding. I think they cause the windings to move towards each other, compressing the insulation, with each peak (positive and negative), causing the characteristic transformer hum tone. 

 

VFDs use PWM to switch a DC Voltage on and off very fast (most modern VFDs switch at 4 kHz and up), giving an almost instantaneous Voltage (and current) rise time. The force exerted is dependent on the rate-of-change-of-Current, so the mechanical forces on the insulation are very much higher than when run from "real" mains power. On a motor with brittle insulation, the forces are higher than the insulation can withstand and tiny cracks form.

 

The upshot is that old motors tend to fail very quickly when run from VFDs. There are some other factors that come into play as well, but I can get my head around the one I've described and it has been sufficient to keep me from going down that particular rabbit-hole.

 

A Sine-Wave filter can be fitted between the VFD and the motor to smooth out the high-frequency stuff and leave a sinusoidal waveform very similar to "true" mains (though still with the Variable Frequency that we want for speed control). These will often let you run an old motor on a VFD. Sinusoidal filters typically seem to cost "about" as much as the VFD with which they are used, so they are not cheap. 

 

If an old motor has been rewound, it will have been done with the materials used at the time, so a 1935 motor rewound in 1995 can be treated as a 1995 motor (unless it was specifically rewound with 1935 materials as a museum piece, for example). 

Edited by timgunn

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I can find you just about any motor you would want. For instance I know of a 3 hp single phase and a few other 3 phase ranging from 1-5 hp. There is a 1 hp single phase also. If you wanted to build a rotary phase converter there is a 10 hp and a 15 hp that would make great 3 phase power. The 10 hp is brand new. Oh yeah there is a 30 hp motor with a fresh rebuild also all at auction not far from you. ;)

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Check this out!!!

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Thanks for the heads up on the issues with running older motors on a VFD @timgunn.  One of the things I love about this site is the incredible depth of the knowledge that's shared so freely.

Jeremy, that things a beast!  Theres just something about online auctions, I can never bring myself to pull the trigger.  Theres a couple of industrial supply houses around town that I've been poking around at that have a decent selection.  I'll probably end up picking one up from one of them at some point.

 

I did get an email back from tech support at Automation Direct.  They said that the only way I could do it with just a VFD is if the motor can be rewired to run on 230v.  It seems as though converting to 3-phase and stepping up the voltage at the same time just isnt going to happen.  I'll dig into the electrical panel and see if it has an alternate wiring diagram somewhere.  If not, maybe I'll find someone that will have 3-phase power in their shop someday that would be up for swapping it for a custom hammer...... :ph34r:

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