VFD Who uses them?

Well Crap. :( So much for variable speed. Although , They do have some mechanical variable speed control units at the junkyard. But it would probably not be very efficient. Oh well. VFD here I come.
 
I use a 3 phase motor with a VFD on my disk grinder. I can forward, reverse, change RPM from full to nearly 0 at full torque. These things rock. I have another 2hp motor and VFD sitting in the garage when my Baldor DC motor craps out on the KMG. I probably should go ahead and switch it now as it is a much better way to go. The advantage to the frequency deal is full torque through out RPM changes. If you can get cheap 3 phase motors, start shopping ebay for cheap VFD's and you can have a great set up for cheap. I went new my first time around as I knew absolutely nothing about the whole business. I ended moving and tried to get two different electricians to wire up the VFD to my 230v outlets and they said it wouldn't work. I finally just did it myself to see if it would smoke test or not. Wiring it took 15 minutes. These are the only way to go.

The biggest problems are: understanding the controller is called a VFD, variable frequency drive and that such a small plastic looking deal will take in 1 phase and kick out 3 phase. Also pay attention to the horse power rating on the VFD's, it has to be at least as large as the motor is rated.
Rob Frink really has a handle on these things. He has talked about these here before. Also one of the guys here, and I can't recall who it is, really knows what to look for on ebay, we need to commission him to start watching. I need another motor and VFD for a second disk grinder.
 
I have one on my little bench mill

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You can even program the DRO to simulate a tachometer. :cool:

Works great! :)
 
It is an industrial electronic device and also by complexity expensive. If you are an electronics expert and have a good understanding of theory of operation you could design and build your own. Except for that Ebay, with caution, would be my suggestion.

RL
 
That dealer's electric site has Teco 1 hp VFDs for under $200.00. That's starting to sound like a great Christmas present for my 1HP 1954 step pulley Bridgeport. It would restore full power too as the Phase a Matic staric phase converter on it now only gives me 2/3 power. I know a guy who has one on a Rockwell mill and is real happy with it.

For another $250.00 they have a 2HP version that would run a great $25.00 motor to power the grinder I'm building. Hmmmm.....

John
 
Got my VFD from friesen.com for $250 - single to 3 phase converter, 220V + 1 yr. warranty.

Lots of programing options. One nice thing is that I can program it to quadruple the output frequency. 60Hz becomes 240Hz max. Which means, on a 1725 rpm motor (which is what I have) I can run in up to 6900 rpm. Realistically, I only ever get up to 5000 rpm, and go as low as 800 rpm. But those are two extremes I do use a lot.

go for it......its worth it.
 
I have to look at this as 2 seperate issues:

1: using inexpensive 3ph motors at home
2: variable speed.

For #2....variable speed with a 3ph motor you'll need a VFD. Either powered by single phase input or 3ph input. These little jewels are fantastic!

For using 3 ph motors at home.....STAY AWAY from the "static phase convertors" particularly phase-a-matic. For a single machine without thoughts of running anything else...I would use a VFD dedicated to the machine. VFD's make very clean 3ph power and have tremendous performance. Even if you don't need variable speed..they also provide motor protection and many other cool features such as reversing, ramped acceleration, dynamic braking..etc. Just use it as a 3ph convertor.

Now if you want to run several machines on 3 ph, then build a rotary ph convertor. I've built 2 of them....the first was 3hp, the outgrew it for a 10hp job. Place the idler motor outside under a cover so it doesn't drive you crazy with noise all day. They are not loud but after being in the same room with it for 8hrs, you'll appreciate the quite. They don't make perfect 3ph power...but plenty good enough and they get better with more motors running on-line. However, with the 3ph bus, you'll need to address starters/switches and overload protection for each machine. The most economical for me was to use a 3-pole fusible dissconnect box, (blade style) fused with dual element fuses for motors. This provided short circuit protection as well as thermal overload. These ran about $30 ea from the industrial electrical supplier.

I used this set-up for several years and was very happy. When I got my first CNC machine, I had to have a local motor shop come out to tune my rotary convertor to balance the 3 legs better. He played around with the capicitor sizes until the three legs were balanced enough for the CNC.


OK, with all of this in mind....if you set-up a common 3ph rotary convertor....then decide you want a variable speed machine.....you will still need to get a VFD. The VFD can run on your 3ph bus...or you can get one to plug in your std single phase outlet. So this is why it might make more sense to just use a VFD for each machine ...variable speed or not.


I'm not sure if this made any sense...?

Sincerely,
Rob
 
Thanks Rob. You had written something about your Rotary Converter somewhere else. I was looking at the site and they called you "Frugal Frink " :D The link to the article was dead but it was an interesting site anyway.......Why do you think they named you that? :D
 
I received plans from a fellow forumite for the rotary converter. I will make one after the beginning of the year.

All I can say is that it is cheap, simple and easy to do.


I'm into CHEAP!

Craig
 
VFD's not only give you speed control but also give forward/reverse capability. Which is darn nice on a disk grinder.

Ebay usually has quite a few VFD's listed.

When buying a VFD you will need to make sure it will run on single phase input. Some will not. Also make sure the operating voltage matches what you have available and that the horse power rating is equal to or greater than the motor you wish to run.


Mike
 
All this talk about VFD's apparantly killed my disk grinder VFD today. Not sure what happened other than it thinks it is getting 406volt input (there's an LED diagnostic built in) on my Delta VFD and it's only getting 230v. So I pulled that one off and slapped on my extra one. It took 15 minutes to remove the broken one and wire up the new one and it took right off. I have since purchased another VFD and 3/4hp 3 phase motor on eBay for a total of $110 plus shipping. I'll make a horizontal disk grinder out of that one.
 
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