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Multiple Motors on a Single VFD

AlxJ64

AlxJ64

Rust is Paint
Joined
Feb 3, 2021
Member Number
3436
Messages
735
Loc
Richmond / Cville - VA
So first I bugged ya'll with the question about wiring a 2 speed motor on a single VFD, and we figured that one out and it works pretty well! The big ol' lathe is up and running like a champ. I did have to buy a nicer VFD than the first one so that I could set the unit to ignore the motor RPM and just out put based on V and Hz parameters.

Lets say I used a similar VFD, would it be feasible to run multiple motors on the same VFD if it was set to only V and Hz similar to how the 2 speed single motor was wired.

The odd ball here though is that all 3 motors are of different HP rating as this is for my Universal Tool grinder... the fallback option is to build a small RPC, but I have a 3hp "pass around" VFD that is setup as an I/O output to run my big drill sharpener, slip roll, and a vertical bandsaw.

The grinder has a single power feed in and the main motor, the largest at 1-1/2 HP is on a mag starter. The other two motors are wired with their own switches that draw power from the mag starter. So they won't run without the main motor running. If I bypass the mag starter and turn the VFD into essentially the same function... would then switching on and off the other motors just make the VFD respond to the Amp draw and adjust as needed as if though it was running a single motor that was seeing more load? The speed ratings are all different but that shouldn't matter, right? Are there other factors here though that I am overlooking?

The machine in question is a Brown and Sharpe No 13 Universal Tool Grinder that was refurbed by a shop in Maryland, and then was never used by the company that owned it and had it refurbed. They made parts for Phillip Morris I have had it for quite some time and just haven't gotten around to even messing with it. I am cleaning up a hoard of Uni-punch frames and want to sharpen some of the punches and resurface some of the die faces, along with mess with sharpening some annular cutters too. I have a handful of fixtures with the machine and will have to learn as I go; never used one.

20230503_194113.jpg



Main table feed / Cam system motor.
20230503_194205.jpg


The overhead grinder head motor... its a Dayton 3N317A which is catalog as a 1.0 hp, which can be seen on the stamp but

20230503_194133.jpg


And the center grinder drive motor is only 1/4 Hp.

20230503_194149.jpg


Also, if anyone has any experience with this machine, I'd be open to pointers, tips, or warnings.
 
Generally, no. One VFD per motor.

You might get away with some of the cheap solid state phase converters since those motors are so small.


But really, just pick up a cheap rotary. A 3hp will run all of that and I've seen several on FB and CL lately for a few hundred bucks.
 
Depends. Some vfd’s have “motor groups” and will allow different settings for different motors. The ones I have here at work have three different groups. I can’t imagine this is cheaper than buying three cheap drives. We do it for space constraints in our equipment.
 
Rangerrod said:
Depends. Some vfd’s have “motor groups” and will allow different settings for different motors. The ones I have here at work have three different groups. I can’t imagine this is cheaper than buying three cheap drives. We do it for space constraints in our equipment.
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It isn't. They are so easy to come by nowdays, there is really no reason to try and save there.
 
I think you have cross over to running your shop over to a rotary phase converter territory. If you run similar motors on a single VFD each motor needs its own thermal over load. I also don’t thing the drive will like when one motor starts and stops and the over runs.
 
bgaidan said:
A 3hp will run all of that and I've seen several on FB and CL lately for a few hundred bucks.
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cj3a said:
I think you have cross over to running your shop over to a rotary phase converter territory.
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CarterKraft said:
I think you are squarely into needing a RPC now.
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UGGGH>> >BUT I DON'T WANT ONE>>>> Lol. Mainly because everyone on here has said this like 9 times and I have digressed to child mode of just being stubborn about it.

But for everyone's sake, who is about out of breath...
I have a friend giving me a 5 hp 3ph Leeson. I'll build a little RPC for this machine in the next few weeks. I just need to get the motor up here from Hampton Roads.

Everything else has its own VFDs already, except the big drill press and it is already sharing one with the Cincinnati mill and works pretty good. I even put a unit on the Kysor Johnson Model J bandsaw; dialing the exact blade speed is kinda satisfying.
 
Drive a idler with another motor off a VFD, have cake and eat it too!
:flipoff2:
 
AlxJ64 said:
UGGGH>> >BUT I DON'T WANT ONE>>>> Lol. Mainly because everyone on here has said this like 9 times and I have digressed to child mode of just being stubborn about it.

But for everyone's sake, who is about out of breath...
I have a friend giving me a 5 hp 3ph Leeson. I'll build a little RPC for this machine in the next few weeks. I just need to get the motor up here from Hampton Roads.

Everything else has its own VFDs already, except the big drill press and it is already sharing one with the Cincinnati mill and works pretty good. I even put a unit on the Kysor Johnson Model J bandsaw; dialing the exact blade speed is kinda satisfying.
Click to expand...
Really maybe three VFD's on that machine is fine?
Just seems like maybe not needed for the scope of work.
Onesy twosy machines here and there VFD all day, entire 3 ph shop might be better suited with RPC and VFD's where needed for speed, braking etc.

The VFD's don't have to be single phase to 3 phase, you can go 3ph to 3ph just as easily.
 
40hp RPC to a 100 amp three phase panel. Cry once type of deal.
 
It will be fine if its using v/hz control and your total motor loads especially startup are below the vfd's rating. I run a cheap teco vfd on a press brake. The main motor runs constantly, and I feed a switch from the same circuit to run the ram adjustment motor.

Here's some documentation from Rockwell.

Controlling Multiple Motors with One VFD | Rockwell Automation
 
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I’ve only wired multiple motors to a drive that were identical motors sharing the load.
 
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