Phase converter.

J. Oeser

J. Oeser

Joined
May 13, 2009
Messages
4,182
I am hoping to get some good recommendations on a good phase converter to use for a 1 hp motor on a 6 x 12 Harig surface grinder I just had delivered. I have found a couple that seem very reputable on e-bay but wanted to check with the experts here for more enlightenment.

Before anybody recommends a VFD I must express that, although I am a huge proponent of variable speed on machine equipment ( everything I have is variable speed from my grinder to my band saw) I do not feel the expense of a KBAC 24D will provide me any benefit while grinding .002" of steel off the surface of a folder blade. Unless there is some other benefit that I am not aware of I would rather just use a phase converter.

Thank you all in advance for your help!
 
You don't need variable speed on a surface grinder really, and once you get one 3ph machine, you'll get more, so you're on track getting a rotary phase converter.

I built my first one, with a 5hp scrap yard motor and an ebay panel. It worked fine until I blew it up, but it wasn't the fault of the converter, it was mine.

The one I have now, is a 10hp digitally controlled cnc compatible unit from American Rotary Phase Converters. I did a lot of research, and got a very strong impression from people that handle these units for a living, that these are hands down the best. They have specially made shaftless "generator" motors built by Baldor specifically for these units. Aparantly the output is ultra stable, ideal for your machines, and the idle power consumption is miniscule. The unit I have is cnc compatible also, which most units aren't.

One thing to bear in mind is that while you can run a number of machines at once with the rotary, usually as much or more than the "generator" motor's hp rating, the max "starting" horsepower depends on the initial amperage load but is usually half or less of the generator motor's rating. What this translates to is the maximum single motor hp rating you can run. For instance, I can (roughly) only start and run a single 5hp or so motor with my 10hp unit, although I can run a total number of combined motors rating maybe 15hp, started seperately.

I got mine on sale, don't recall exactly, but I think it was $800-900 shipped, for the pimped out option, which was cheaper through their official ebay store than the website. I wish I had gotten a 20hp instead.

Bear in mind some few tools, that have very high starting amp requirements(like 3ph compressors) , or other oddities(like welders, induction forges) may have even higher requirements than the average double hp rating of most tools.
 
Another thing I wanted to mention, is to make sure you know the total hp requirement of your machines. Many industrial machines incorporate secondary motors. My SG has a 2hp spindle motor and a 1 or 2hp motor for the hydraulic system. A non hydraulic automatic feed unit may have a motor running the feed also.

Regardless, size up. 5hp minimum, if you can afford it, a 10hp will open up a *lot* of options for top quality used industrial machines that are too large for many hobbyists. My 36" vertical bandsaw actually has the smallest motor of all my gear at 1.5hp. My knee mill is 5hp for example, could wreck a bridgeport, and cost less than the crappiest new mill.
 
Thanks Javan, that definitely helps. I will take a look at American Rotary and make sure I upsize as much as possible. This SG is he last piece of the puzzle for me for a while. Space limitation dictate that unless I build a new shop I am done buying tools for a while. :)
 
Rotary phase converters are great, but if you buy one rather than DIY, they are not cheap. If you want 3 phase for 1 machine, a VFD may be the least expensive option, but if you want 3 phase for a whole shop, then the rotary converter becomes a good choice. Most cheap phase converters fall into the "you get what you pay for" category. With light use they, and the motor hooked to them, may hold up just fine. For heavy use you want good quality power going to your motor.
 
I purchased the 10hp rotary from American and I would do it again in a heartbeat. You should double the HP for the largest motor you intend on running. They can help you out in selecting the correct one for your application. The surface grinder (at least mine) is a hard start motor. I have a 3hp VFD that will not start it. And it is only a 1hp motor. I used a static converter and it worked ok. Once I got the Rotary it is even better.
 
Just because you might have a variable speed VFD does not mean you have to use the variable speed.
I use my VFD to run both my disk sander (utilizing both variable speed and reverse) and my surface grinder.
When I run the SG, I just keep it at 60 hz.\Plug and play and I already had the VFD.
No need to buy the PC.
 
Jared,

I have been running a static phase converter on my Harig for years now with good results. PM sent.
 
Thanks for all the input guys. My main concern is to set things up right. I have Vfd's that I use for my other machines already just not one that will run this particular machine. I don't plan to get a large phase converter for the whole shop because I don't have much of a need for it on anything other than the SG. And also because I would prefer to not spend that much on it right now.

Ken, PM replied. Thank you VERY much!
 
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