3-Phase motor upgrade

[DeanB]

I currently have a RF-30 with a single phase 2 Hp Marathon Electric motor. Frame 56HZ Looking to switch to a 3-phase so I can put a VFD on it. For anyone that's done this, did you get anything special for the motor or just match the frame and rpm but in 3-phase.

Thanks,
Dean

 

[DavidR8]

Following along as I'm also looking to upgrade to get variable speed and reverse.
I have a 1980 Taiwanese RF clone so frame size is a bit of a guess. My intent was to get close to the dimensions and go from there.

 

[Ulma Doctor]

matching a chinese frame motor with a NEMA frame will not be easy

i did a conversion on a lathe with a 3 hp motor & VFD control, it may be of interest...

Huanyang VFD Conversion, Shenwai SW900B 1236 Lathe

I did a VFD and 3 phase 3 hp motor upgrade to my Shenwai 900B lathe, because i had a problem with the anemic single phase 1 hp single phase motor the lathe came with. the issue was really evident when parting stainless. so much as to make me want to do the upgrade. i wanted to use the original...

www.hobby-machinist.com

and with a 2hp motor/VFD here...

VFD Retrofit - Shenwai SW900B 1236 Lathe

I finally got around to doing the retrofit on my Shenwai SW900B 1236 lathe it came with a 1.5 hp(ish) 115v/220v single phase motor, as the OEM powerplant. i had to change that :grin: i surfed the site that sounds a lot like E-PAY, and found an inverter rated 2 hp motor by Marathon, very...

www.hobby-machinist.com

of the 2, i like version 2 better- it was easier and less expensive, but the trade off was patience in finding components cheap.
it turned into a game to see how inexpensively i could do it and still retain my dignity
joking aside, project 2 was less than $150 and an investment of 2-3 hrs install/wire up/parameter set

 

[markba633csi]

If you already have an American-style frame motor then it should be an easy swap, the difficulty is when the original is a Chinese frame style and metric shaft size
-M

 

[DeanB]

I already have an American motor frame, Marathon from in Wisconsin. The real question is if I should be looking at something special as far as bearings with the belt drive on these mills.

 

[DavidR8]

I can't imagine there's anything particularly unique about the application that would require special bearings.

 

[DeanB]

In larger motors 50 Hp and up for belted applications you have to get roller bearings to handle the lateral load from belts. I just wasn't sure if in this size range there were different bearings to select for belt vs direct drive.

 

[Z2V]

Dean, I replaced the metric motor on my machine with a 145 frame and it works fine. If you already using 56 frame motor on the machine I would just match frame and speed and run with it.
The 50-75 hp belted motors I’ve worked with had 6-8 belts, I can understand the need for heavy duty bearings.

 

[DeanB]

Thanks Z2V. That's kind of what I was thinking but I didn't want to do all the other work to swap over and have a motor fail quickly due to lateral load on the bearings. I've done some really big belt drives in the 600 to 900 Hp range. Pretty amazing loads due to belt tension.

 

[DeanB]

I guess one other question while I'm at it, my machine currently has a 2 Hp motor on it. Is it worthwhile to go to 3 Hp while I'm at it or will the 2 pretty much cover anything normal for a smaller mill? I currently have a drive upgrade in progress on my 1940's Atlas lathe as well and for that one I decided not to increase with the gear train on the lathe and not wanting to get into possible damage. With the belt drive system on the mill I have less of a concern.