Has anyone converted to a 3-phase motor with VFD?

[Pcmaker]

Sometime in the future, I want to convert my PM-835S mill from a step pulley to one with a 3-phase motor with a VFD and a tachometer. Just found out the motor is a 112M frame motor. What else do I need to find out? RPM, etc..

 

[Ken226]

I did.

It was a pain in the butt for me, because PM was long, long backordered on 3 phase motors.

If I remember right, the tag may say it's a 112m flange, but the actual flange definitely not.

I converted a Helmke motor, which required a bit of tig welding cast aluminum, and machining for the screw pattern.

Ill try and find my old thread on the conversion.

Here:

Adapted a standard 100l B5 flange motor to my PM935. It's was a PITA!

But, I got it done. Finally! Anyone else done something like this? If so, how did you do it? I picked up a Helmke Plus 3hp 3 phase motor on ebay. It was 200$ with free shipping from Germany. Kinda baffling that they could sell a 40lb motor, and ship it from Europe for that price. Oh, and...

www.hobby-machinist.com

The pics are gone from that thread, but I'll go snap a few.

 

[dbb-the-bruce]

It's relatively easy to do if you are comfortable reading the VFD controller setup/program guide and can handle basic electrical wiring. I've setup several over the years. Modern VFD controllers are relatively cheap and very sophisticated - you can ignore an awful lot of the programing unless you are trying to run an amusement ride or production line conveyor belt!

Most have a "quick start" section that will get you to a running motor quickly. Other people here will have a lot more info on setting one up to drive a mill but it shouldn't be that hard.

What I have found is that while you can use a VFD as a speed control for a motor, your low end speed will be somewhat limited in use, say down to 50% of the rated speed at 60hz, top end is not a much of a problem, but the motor may not like being driven at much more than 200% (double speed).

Controllers are rated for the load they are driving and the bigger the motor the more expensive the controller gets (quickly)

I use the site Automation Direct - lots of good info and selection of VFDs (and other stuff you might need). They are not the cheapest, you can get used stuff or cheap stuff from ebay or amazon. For me it was not worth the potential of bad or wrong stuff - But that's me.

 

[Ken226]

Here is the stock motor. The flange was most definitely not the flange indicated on the motor data plate.

Maybe you'll get lucky and PM will have some 3 phase motors available now.








I had to remove the Helmke flange from the new motor and build up some material with my Tig welder, then machine the welds flat and drill new holes.


Welding that cast aluminum sucked. It was like trying to weld styrofoam. It took a couple hours to get a passable result.





I used a teco l510 VFD and built my own control box/tach setup.

 

[JimDawson]

Sometime in the future, I want to convert my PM-835S mill from a step pulley to one with a 3-phase motor with a VFD and a tachometer. Just found out the motor is a 112M frame motor. What else do I need to find out? RPM, etc..

From the specs on the PM web site, it seems that it is a 1800 RPM motor. I would seriously consider a 2kW servo motor. Full torque at 0 to 3000 RPM. Maybe a bit more pricey than a good induction motor/VFD combo, but not excessively so. Were I to repower my machine, this is what I would do. You can run the servo motor with a pot and an on/off switch, just like a standard VFD/motor combo, no special controls required. I have started using servo motors in projects in place of standard induction motors/VFDs. More compact, high power density, and electrically more efficient. I found the electrical efficiency bonus when I repowered my lathe spindle with a servo, reduced my lathe power consumption by about 1/2.

What I have found is that while you can use a VFD as a speed control for a motor, your low end speed will be somewhat limited in use, say down to 50% of the rated speed at 60hz, top end is not a much of a problem, but the motor may not like being driven at much more than 200% (double speed).

I can reliably run mine down to about 2 Hz (60 RPM) at full torque, but do have the top limited to 120 Hz (3600 RPM). Any modern sensorless vector VFD will do this. Running direct drive with a 1:1.3 ratio geared up on the timing pulleys. The motor is a standard Baldor 3ph, 3 Hp, 1800 RPM, rated at 6000 RPM max. This is the standard for the small standard Baldor motors. I'm using an old Automation Direct GS3 VFD, no longer available. The GS line of VFDs has been replaced by more modern VFDs that are readily available.

 

[davidcarmichael]

Here is the stock motor. The flange was most definitely not the flange indicated on the motor data plate.

Maybe you'll get lucky and PM will have some 3 phase motors available now.








I had to remove the Helmke flange from the new motor and build up some material with my Tig welder, then machine the welds flat and drill new holes.


Welding that cast aluminum sucked. It was like trying to weld styrofoam. It took a couple hours to get a passable result.





I used a teco l510 VFD and built my own control box/tach setup.

I swapped out the single phase for a 3-phase on my PM-835S few years ago. The motor was available from PM themselves and I used a Fujitsu VFD for which I was lucky enough to find a braking resistor. It works great, I almost never have to swap belt position and it stops very quickly.
By the way is anyone is looking for a little used 3HP single phase motor then...

 

[Dabbler]

PM-835S

I have one of these in 3 phase (sourced from Modern Tool). and it is a great machine.

To answer your question, I have both converted a 7X42 mill from 3 phase to single phase, and converted a 9X49 mill to 3 phase+VFD. I still own those mills also (I have to stop being a hoarder)

If it is a step pulley it could not be easier.

you can use a 2KW servo motor, or a 2 HP 3 phase motor. It won't make any difference to the use.

If you go 2 HP 3 phase, get a flange mount motor - that is the kind with a face plate with 4 bolt holes on the motor drive shaft end. You will have to make an adapter plate that you can steal the pattern from you existing motor. 1/8" will work, but you are far better off with 3/16".

To save a lot of BS, try to get the same motor shaft diameter so your pulley will just slide on. You don't want to have to bore out your pulley or make a split bushing for your pulley either. That just adds more steps to the job.

Programming your VFD is covered in a lot of threads here, but you can always ask when you're ready.

 

[B2]

I converted my 3Phase ,3HP, PM1440GT ( https://www.precisionmatthews.com/shop/pm-1440gt/ ) with stock induction motor to VFD (Hitachi WJ200 series... and then posted it. In this write up you will find ALL OF the details, electrical and physical schematics, programing setup plus lots of description, photos and parts lists in Part 2 (5th attachment item of the link below). (Part 1 is a write up of the lathe operation and circuits as supplied by the factory.)

VFD conversion using solid state electronic components.

The only reason I mention this is that some folks have found the the motor stutters during startup acceleration and then usually even outs as it comes up to speed... and so many of these folks later changed to a different motor. I have not had this problem so I continue to use the stock motor, but I am not for sure what the difference is. Maybe it was just the luck of the draw that I got a motor that works better for this. In general, some induction motors, and this stock motor is not one of them, is designed to run at variable frequency. However, these tend to be more expensive. Anyway, one of the features in the VFD conversion and VFD controller is to jog the motor at slow speeds. In this VFD the Jog command causes the output frequency to be 6 Hz rather than 60 (or what ever you have it set to). The motor runs fine even at this low frequency and in fact I have found it to run fine even at 2Hz or so. With the lathe gearing that means that the spindle can turn at incredibly slow RPM. I find this to be useful if you want to do things like hand winding coils etc. Also, I have it set up so that the maximum frequency is ~100 HZ and I do not seem to have any difficulty at running the motor at any speed.

Good Luck

Dave L.

PS. Don't sweat the breaking resistor. I built my own from smaller 50watt power resistors and saved space. Since you are not starting and stopping large loads very often, you really do not need one of the huge things that folks on HM seem to use. As a test, I started my lathe up to a high RPM with the 3 jaw chuck and a 15# piece of metal in it and then stopped it quickly via the e-brake. I did this 10 or more times in a row as fast as I could and the breaking resistor only barely got warm. There is a picture of it in the posting above.

 

[hman]

I converted my PM835S to use a "random"3 phase motor (that I had on hand) back in 2020 ... had to fabricate a mount, as the 3 phase motor was not a face mount (see last photo in my post ...

Converting a knee mill to 3phase/VFD

I've recently bought a Precision Matthews PM-835S. Advertised as a "small" knee mill, it's still amazingly massive - and TALL. I've had to build a platform to stand on (re-using some of the the 2x4s and OSB the mill was crated with), just to be able to reach some of the controls and levers...

www.hobby-machinist.com

In addition, I mounted a 4" 110AC fan atop the motor, to help keep the motor cool at low PMs. The fan runs whenever the motor is on. Scroll down to post#6 on the same page.

 

[Dabbler]

I've had to build a platform to stand on

My version needs to be raised about 10" just to use it. It is an earlier model.

the lowest available speed on the 835 is a bit faster than I'd feel safe with when tapping.

One "feature" of these Bridgeport-type mills is that the head includes a back gear,

You don't like tapping in back gear?

a flat 1/2" thick plate on the shaft end,

All the motor adapters I've made were 3/16", even up to 4HP mills.