# VFD and Motor Compatability?



## Uglydog (Apr 17, 2017)

When classes let out for summer I'll begin a 20" Clausing DP and gang table complete rebuild.
This DP came with a 3hp 3ph 1740rpm motor (see pic below). Yep, 3hp. More than my mills!
I'd like to slow her down with a VFD.
I've been gifted this VFD if it will work (see pic below).
I'll be driving her off of a 220v 20hp RPC and a 60amp breaker.

Will this work? The label on the VFD shows "max controlled current 135A" at 230v at 50hp. This is obviously much more than required for ta 3hp. 

Will it safely function with alot of unused capacity?

Thank you!!
Daryl
MN


----------



## mksj (Apr 17, 2017)

Hi Daryl,
Checking the specs for this VFD, the motor range is listed as 34A-135A which is way in excess of your motor specs. So you most likely not be able to dial it down sufficiently to protect the motor, I would also be concerned with the inrush current when turned on. Given that these list at around 6K new, and 1.5-2.5K as NOS, I think you would be better off selling it and buying a smaller VFD. A 2.2kW VFD, either single or 3 phase would be around $300. If you are running it off of 3 phase, I would up size to a 3.7kW (5Hp) VFD, the price difference is nominal. The newer VFDs with sensorless vector control  will give very tight motor control, you may also need an external braking resistor given the rotating mass in the system.
Mark


----------



## Uglydog (Apr 17, 2017)

mksj,
Huge help, and pretty much what I suspected. Albeit I had no idea of why.

Daryl
MN


----------



## Silverbullet (Apr 17, 2017)

Your VFD, is just to big for three hp . Don't ask me why but I've learned enough to know that ,if it was about five hp rated VFD  I think it would do what you want. I wonder if a reostat would work on the motor. I can understand the speed reduction, in my option most drill presses run to fast. I'd rather have torque then speed. Maybe a speed reducer on the motor. They use to have them to go on the motor shaft inline. When I was trying to figure things needed for my shop , I went back and forth till I came apon a slower speed motor. I have a big ole drill press 20" with power feed. I'm going nutts not being able to get at them , this back pain really is bad.


----------



## Uglydog (Apr 18, 2017)

Silverbullet said:


> ....They use to have them to go on the motor shaft inline. ... I came apon a slower speed motor. I have a big ole drill press 20" with power feed. I'm going nutts not being able to get at them , this back pain really is bad.



Yep, I'll be looking for a slower speed motor or an affordable VFD. See which one I score first. I've thought about a series of jackshafts with redution pulleys. Will need to learn how well this DP turns out. She needs a complete teardown as the gang table had been outside and the DP evidently saw many winter/summer cycles in a non-temperature controlled barn. 

I understand the whole back pain thing. I went through a couple years of meeting with Docs as they contemplated lumbar fusion. It worked out. But was a long and agonizing process. Now I just need to be very careful.

Daryl
MN


----------



## mksj (Apr 18, 2017)

You could get buy with an inexpensive VFD (around $200), Teco, Fuji, WEG, etc.  if you want something very basic.  You could either just use the VFD control panel directly, or make a very simple remote control box with and on/off and either speed pot or you can set several fixed speeds (controlled by the inputs) and use a rotary switch to set them.
http://dealerselectric.com/L510-203-H3-N.asp (three phase input)
http://dealerselectric.com/L510-203-H1-N.asp (single phase input)
http://dealerselectric.com/FRN003G11S-2UX.asp (three phase input)
http://dealerselectric.com/CFW100100SDPLZ.asp (single phase input)
OR
Look for a 2 speed motor. I have a friend that has a 3-2 Hp that was a takeoff from his lathe, I can see if he wants to sell it if it is something you are interested in. One note is that the two speed motors are significantly heavier and sometimes the next frame size larger (his is a 213T). Shipping can be expensive. I think the VFD option is the simplest
http://www.ebay.com/itm/LEESON-5-3H...66-00-3PH-1745-1465RPM-184T-NEW-/332024821528


----------



## Mad Monty (May 10, 2017)

There's another option that you might like for a couple of reasons:  treadmill motor.  I've replaced mill, drill, and lathe motors and have 2 bandsaws in the queue.  I have a couple of 3 HP, and have seen a couple advertised, new, for under $250.  If you're willing to look around and accept used, keep an eye out for out-of-shape people sauntering around in expensive jogging clothes.  They thought that if they bought the super-delux model and wore the high-tech duds they would enjoy exercising every day, but now its just a clothes rack and they'll sell it cheap so they won't have to confront it every day.  With the money they get, they can buy a new pair of cross-trainer shoes to keep up the image.

The DC motors will run both slower and faster than you need without changing a belt, have infinite speed control at the twist of a dial so you never run the wrong speed because you're lazy like me or in a hurry and don't want to take time to switch, and can tweak on the fly like when you're facing a large diameter and need to run slow on the outer but can speed up at you move in.  The low end torque is amazing - you can wind some pretty stiff springs with it. 

 They run on 120 VAC at up around 20 A, run through a rectifier and motor controller.  I got  up and running fast using just a HF router speed control $15-20 and a full-wave rectifier $5 or so.  That's the cheap and dirty way to get by until you decide how you want to do it in the long run.  You can't go as slow or use the full power, and it may hum a bit because the DC is unfiltered, but I still use it that way on my drill press after a couple of years.  Long term  options are buy a commercial DC motor controller (Amazon, Alibaba, etc.), make one from circuits on the web, or adapt the one that came with the treadmill.  Oh - and here's another plus:  you can set up a relay that removes the power when you step on (or step off, if you prefer, as I do) and puts a near short across the motor.  That acts like a hard brake.  I can stop my 12x31 lathe in about 1-2 seconds (yes, that's not an error, one to two seconds, depending on the mass of the work).  Mount a microswitch at either extreme of table travel and wire to the relay, and you'll never run the cross-slide into the chuck again.  It sounds more complicated than it really is, the hardest part is fitting up the pulley and customizing a bracket so it lines up with the spindle pulley.

[added afterward:  the dc motors are a lot smaller physically for the same HP - don't be alarmed.  Also:  they usually come with a heavy combo flywheel-fan-pulley that you will almost certainly remove and replace (trick - it's usually left-hand thread and comes off easily if you speed the motor up forward and then stop it fairly fast).  But - that means no more fan.  For light duty, you don't really need it, but for serious or prolonged work, attach an ordinary 12VDC 4" computer fan on the bottom of the motor and run it whenever you're at the lathe.  That's a much better solution than a fan on the motor shaft because you get full cooling regardless of the motor speed - an important thing because you'll often do the heaviest work at slow speeds.   Another trick:  you can monitor the load on the motor with an ammeter in series with the motor - use a DC ammeter at the motor, or AC model ahead of the rectifier-controller.  I use it when I want to max out the power just short of blowing the 20A fuse.]


----------



## strantor (May 10, 2017)

@Uglydog 
For future reference, what you have is not a VFD. It's a soft starter for pump motors
http://www.ab.com/en/epub/catalogs/12768/229240/229262/3073021/1179233/Introduction.html

Basically has all the same major components as a VFD, but none of the bells or whistles. I'm not even sure if you can set a speed with it. It's just to get you from 0 RPM to base speed without blowing fuses, popping breakers, or tearing anything up mechanically.


----------



## Uglydog (May 11, 2017)

Strantor,
Thanks for the heads up!!
Thanks to all of you!!!!! 

I've got some work to do on this project before I get close to thinking about wiring her. I've got this thread copied so I can refer back to it in a few months.

Daryl
MN


----------

