Ray Behner
Diamond
- Joined
- Mar 27, 2009
- Location
- Brunswick Oh USA
Is there any advantage in using a VFD over a regular phase converter for a grinder? Speed control isn't needed, but what about the hp? Would it be the same?
Ray
Ray
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VFD for surface grinder?
- Thread starter Ray Behner
- Start date
- Replies 20
- Views 9,025
PixMan
Diamond
- Joined
- Jan 30, 2007
- Location
- Central MA USA
It depends what you mean by "regular phase converter". If you mean rotary phase converter, there's some variation in the quality of the output from different manufacturers by virtue of the electronics they may add downstream of the motor windings. There's also varying levels of power balance quality output from VFD's.
If you are referring to "regular" as a static phase converter, those have only 2/3rd's of the output of a RPC or VFD.
If you are referring to "regular" as a static phase converter, those have only 2/3rd's of the output of a RPC or VFD.
Ray Behner
Diamond
- Joined
- Mar 27, 2009
- Location
- Brunswick Oh USA
Pix,
Yup, I was referring to static. Will a VFD give a higher hp advantage to the unit than a static? What's a good name in VFDs?
Ray
Yup, I was referring to static. Will a VFD give a higher hp advantage to the unit than a static? What's a good name in VFDs?
Ray
928gene928
Cast Iron
- Joined
- Sep 13, 2005
- Location
- Joliet, Illinois
Vfd
Ray,
I'm installing a VFD on my Harig surface grinder as we speak. I have used the machine with a percision balanced single phase motor for some time with fairly good results. Since I still had the original three phase motor I decided to re-install it so I could get a better finish. I looked at several VFD's, but decided on a WEG unit from a local supplier, Joliet Technologies (815-725-2520). I talked to John Gierich there, and he was very helpful. They also are on the web, and have all the info about the units and prices listed. My unit cost $279 and has a lot of features, in addition to converting single phase 220V to three phase. It is small in size and easy to mount on the machine.
Ray,
I'm installing a VFD on my Harig surface grinder as we speak. I have used the machine with a percision balanced single phase motor for some time with fairly good results. Since I still had the original three phase motor I decided to re-install it so I could get a better finish. I looked at several VFD's, but decided on a WEG unit from a local supplier, Joliet Technologies (815-725-2520). I talked to John Gierich there, and he was very helpful. They also are on the web, and have all the info about the units and prices listed. My unit cost $279 and has a lot of features, in addition to converting single phase 220V to three phase. It is small in size and easy to mount on the machine.
Modelman
Titanium
- Joined
- Sep 12, 2007
- Location
- Northern Illinois
That's not entirely true. Speed control can be used judiciously to bring the surface feet up on a small diameter wheel.
I think the biggest advantage is "soft start", you can accelerate the wheel slowly enough that the startibg torque doesn't knock a form dressed wheel off center.
All that being said, I don't have a VFD on my grinder, since I have 3 ph. from the grid... but it's on my list of things to do.
Dennis
dgfoster
Diamond
- Joined
- Jun 14, 2008
- Location
- Bellingham, WA
Ray,
I have had good luck with Automation Direct.
Here is their link: Drives Products
I would at least consider them among the others likely to be recommended. They have excellent product support, prompt shipping, and quality materials.
Denis
Last edited:
Ray Behner
Diamond
- Joined
- Mar 27, 2009
- Location
- Brunswick Oh USA
Well, now I'm in more of a quandry. All three companies I called (Auto. Direct, Factorymation and Joliet) say if the motors on the grinder are not inverter capable and have class 2 insulation, you stand a chance of burning up the windings. Rats! I just don't want to go with an RPC, but looks like the only way.
Ray
Ray
Lakeside53
Stainless
- Joined
- Sep 28, 2007
- Location
- Woodinville, WA
I wouldn't be concerned... Sure, there is a remote chance of insulation breakdown, but try to find anyone where that's actually happened (OK, I'm sure there is someone! 
). As for "inverter rated" - try to find a non-vfd machine with a motor that is rated as such.. there are 10's of millions of motors on existing machines... I hate to think how few are inverter rated, but most will run just fine on a VFD.
I have installed dozens of VFDs on motors of every age and condition, and never a problem. My 1953 B&S Surface grinder motors are very happy..
Whatever you do, don't put a static converter on your grinder. Ignoring the issues of needing to keep your power down to about 50% (66% is theory.. but not in practice), you will see problems in surface finish due to the missing phase.
). As for "inverter rated" - try to find a non-vfd machine with a motor that is rated as such.. there are 10's of millions of motors on existing machines... I hate to think how few are inverter rated, but most will run just fine on a VFD.I have installed dozens of VFDs on motors of every age and condition, and never a problem. My 1953 B&S Surface grinder motors are very happy..
Whatever you do, don't put a static converter on your grinder. Ignoring the issues of needing to keep your power down to about 50% (66% is theory.. but not in practice), you will see problems in surface finish due to the missing phase.
Last edited:
Waterlogged
Hot Rolled
- Joined
- Feb 24, 2006
- Location
- Seattle, WA
I put a Teco VFD on my K.O. Lee. Works great. No regrets. Stop worrying and just do it.
Modelman
Titanium
- Joined
- Sep 12, 2007
- Location
- Northern Illinois
We are talking 240V, right?
Most the horror stories about non-inverter rated motors have been about 480V installations, because the motors are only insulated for 600V, and the inverters can put out spikes a lot higher than that. Plain old run-of-the-mill 240V motors are also insulated for 600V, but the spikes in the 240V inverter output are less than that.
I missed the part about a recommendation. This is a grinder, and that means a lot of conductive dust. It's worth going with a fully dust and moisture proof enclosure, NEMA 4X. Last time I looked, only AC Tech had a small VFD in a NEMA 4X enclosure, and I think it's well worth the extra hundred bucks. The heat sink for the big power transisters on these is external, and there is no fan to pull dust through the unit. I bought mylast one from Wolf Automation and was happy with their service.
Dennis
Ray Behner
Diamond
- Joined
- Mar 27, 2009
- Location
- Brunswick Oh USA
Sorry to keep bugging you guys, but this machine has a 3hp spindle motor, 2hp hyd and two small motors for coolant and elevation (Z). Will a VFD supply full hp to any or all motors? One or all could be running at the same time.
Finegrain
Diamond
- Joined
- Sep 6, 2007
- Location
- Seattle, Washington
Hi Ray,
I run a 3 HP mill (actually the motor's nameplate says 3.5 HP) with a VFD rated for 3 HP taking 1-phase input, and it works fine. The VFD only gives up when I overload the motor and exceed the VFD's rated output
.
Wouldn't you need 4 VFD's for the 4 motors, or at least 2 VFD's for the big ones? I'm told that that you can't run multiple motors offf of one VFD, and even if you could, you're going to need 5 HP's worth when you take a healthy cut, as the hydraulics will definitely be working. I wouldn't want to cut it that close and have the VFD shut down in the middle of a heavy grind.
BTW, did the truck show up for the G&L yet?
Regards.
Finegrain
I run a 3 HP mill (actually the motor's nameplate says 3.5 HP) with a VFD rated for 3 HP taking 1-phase input, and it works fine. The VFD only gives up when I overload the motor and exceed the VFD's rated output
.Wouldn't you need 4 VFD's for the 4 motors, or at least 2 VFD's for the big ones? I'm told that that you can't run multiple motors offf of one VFD, and even if you could, you're going to need 5 HP's worth when you take a healthy cut, as the hydraulics will definitely be working. I wouldn't want to cut it that close and have the VFD shut down in the middle of a heavy grind.
BTW, did the truck show up for the G&L yet?
Regards.
Finegrain
J.R. Williams
Hot Rolled
- Joined
- Mar 1, 2005
- Location
- Houston
Vfd
Ray
I installed an VFD on my grinder and it does a fine job. I find the motor runs much smoother when the frequency is reduced to 58 HZ. The grinder is a 6" x 18" Bridgeport.
JRW
Ray
I installed an VFD on my grinder and it does a fine job. I find the motor runs much smoother when the frequency is reduced to 58 HZ. The grinder is a 6" x 18" Bridgeport.
JRW
Mark Rand
Diamond
- Joined
- Jul 9, 2007
- Location
- UK Rugby Warwickshire
Jones & Shipman 1400 grinder here.
2hp motor and 1hp hydraulic pump both DOL started of the same VFD. completely reliable. To be fair, the VFD is 24kVA, downrated to 16kVA because I'm feeding it with single phase. Eventually, it'll feed 415V 3ph to the milling machine and HLV lathe as well.
If the VFD blows up, I'm out by £10, if the grinder blows up, I'm out by £83
2hp motor and 1hp hydraulic pump both DOL started of the same VFD. completely reliable. To be fair, the VFD is 24kVA, downrated to 16kVA because I'm feeding it with single phase. Eventually, it'll feed 415V 3ph to the milling machine and HLV lathe as well.
If the VFD blows up, I'm out by £10, if the grinder blows up, I'm out by £83
dgfoster
Diamond
- Joined
- Jun 14, 2008
- Location
- Bellingham, WA
Ray,
Automation Direct should be able to give you a clear and engineering-based answer to how many and what power VFD's you might need for the assorted motors you have. I would guess the others could as well.
"This is a grinder, and that means a lot of conductive dust. It's worth going with a fully dust and moisture proof enclosure, NEMA 4X. "
I made my own metal NEMA enclosure with filtered air for cooling. Has worked well for a couple of years now in a dusty environment.
" I called (Auto. Direct, Factorymation and Joliet) say if the motors on the grinder are not inverter capable and have class 2 insulation, you stand a chance of burning up the windings.'
I am running a 1950's Bridgeport on my VFD and I can assure you it works wonderfully and it is certainly not inverter rated. I like "Waterlogged's" comment. I wonder if the inverter rating might be more of an issue if the motor were to be run at low RPM and high load--not likely on a grinder. I am not qualified to comment on that aspect really, but I THINK that may be the case.
Denis
Automation Direct should be able to give you a clear and engineering-based answer to how many and what power VFD's you might need for the assorted motors you have. I would guess the others could as well.
"This is a grinder, and that means a lot of conductive dust. It's worth going with a fully dust and moisture proof enclosure, NEMA 4X. "
I made my own metal NEMA enclosure with filtered air for cooling. Has worked well for a couple of years now in a dusty environment.
" I called (Auto. Direct, Factorymation and Joliet) say if the motors on the grinder are not inverter capable and have class 2 insulation, you stand a chance of burning up the windings.'
I am running a 1950's Bridgeport on my VFD and I can assure you it works wonderfully and it is certainly not inverter rated. I like "Waterlogged's" comment. I wonder if the inverter rating might be more of an issue if the motor were to be run at low RPM and high load--not likely on a grinder. I am not qualified to comment on that aspect really, but I THINK that may be the case.
Denis
mark thomas
Titanium
- Joined
- Dec 15, 2004
- Location
- SF Bay Area
This subject is also discussed frequently on the "Transformers, Phase Converters and VFD" forum.
The Inverter rating for the windings has to do with the voltage waveforms going to the motor. The VFD may try to use Square waves, or partial Square Waves to the motor. The windings in the motor will see large voltage spikes because of that. The longer the distance (wiring) from the inverter to the motor the bigger the potential spikes.
The inverter rated motor has better insulation in it.
You might run a rotary converter for most of the machine, and a VFD just for the spindle. I've run VFD's from a Rotary converter. They think it is three phase power.
No way I'd try to run multiple motors from the same VFD, unless there was no way to turn them On or Off individually.
The inverter rated motor has better insulation in it.
You might run a rotary converter for most of the machine, and a VFD just for the spindle. I've run VFD's from a Rotary converter. They think it is three phase power.
No way I'd try to run multiple motors from the same VFD, unless there was no way to turn them On or Off individually.
Lakeside53
Stainless
- Joined
- Sep 28, 2007
- Location
- Woodinville, WA
You will need separate VFD for each..... Although it is technically possible to run multiple motors from one VFD, they should be matched (essentially identical) motors. Even then you loose the motor protection afforded by the vfd.
For a rotary converter, you'll likely get away with a 5hp model - but.. the hydraulic motor starting may affect the spindle motor momentarily... and surface finish. A 7.5hp may be better.
Ray Behner
Diamond
- Joined
- Mar 27, 2009
- Location
- Brunswick Oh USA
I went and bit the bullet. Bought a Kay Industries RPC. It's a fifteen horse, so I guess it'll do the job.
Thanks for all the suggestions.
Ray
Thanks for all the suggestions.
Ray
