Rotary Phase Converters

      Some modern three-phase machinery requires high-quality power, which requires careful shopping when you're buying a phase converter. March 16, 2015

Question (WOODWEB Member) :
I'm purchasing a Kündig two-head, wide-belt sander with 25 HP and 15 HP motors. That plus I'm running a dust collector with a 7.5 HP motor. The recommendation I've gotten is that I need a 50-75 HP rotary converter and a 200-250 amp service. My question is, what are the best converters out there? With the money I'm putting out for the sander, and a new jointer, not getting the best converter doesn't make a whole lot of sense.

Forum Responses
(Solid Wood Machining Forum)
From contributor X:
I use Kah converters, they have served me well.

From contributor U:
Well that's a great question, I used a rotary inverter for years and they always produced a high leg of power which was never an issue. The most recent machine purchase I find the manufacturer has tightened up the parameters on the frequency control on the speed. When I tried to run saw, dust collection, and profile grinder at same time the grinder shut off. Manufacturers of equipment have tightened up the parameters of their electrical controls to protect the motors the control. I did a lot of research and found a company named Phase Perfect that make digital phase invertors . I purchased one last year - perfect phase power on every leg, no noise, no heat. Look into this, you won’t regret it.

From contributor X:
Contributor U is right about the Phase Perfect converters. They are supposed to be the best thing for modern machinery, especially machines that have CNC controls. I was fine with my Kah converters until I got a new Martin shaper that has computer controls. It doesn't like it - it throws errors telling me I don't have the correct voltage. As long as I am running my dust collector (which I do anyway) it seems to run fine. Once I upgrade my slider to a computerized slider I will definitely have to get a Phaze Perfect converter. If your sander is a basic sander with no computer on it you will probably be fine with a rotary, but if it has a lot of electronics on it I would get the Phase Perfect for sure.

From the original questioner:
I've received recommendations for Kay Industries and Phase Perfect from other sources as well - a good indication. It does seem that a digital converter is overkill for my application (I won't be running a CNC machine with it). More checking to do, but that's the direction I'm leaning.

From Contributor K:
I would suggest American Rotary.

From contributor F:
I had (JD's Electric in Joplin, MO) build my converters out of motors I had. I'm running a 20hp and 15hp in parallel. My sander has 2-20 hp motors on it and my dust collector is 5hp. You can't start it all at once but I wouldn't on true 3 phase anyway. I'm running it on a 200 amp service and haven't had any trouble. One advantage to having two smaller converters is you can run just one if I only want to run the dust collection.

From contributor H:
I have three from American Rotary - one small that I take on large jobs to run a table saw and three wheel feeder. One CNC rated for point to point and a 60 hp standard for two head widebelt. A 15 hp that runs the Striebig, DC, all 5 shapers, edge sander, Maggi borer and hinge borer.

From Contributor C:
I've used an American Rotary (four years) parallel with a Phase-a-matic (seven years) and both do great. The 7.5 hp Phase-a-matic actually has started my 7.5hp SCM jointer a couple times all on its own when I forgot to throw the last on switch. Started a tad slow, but still got it spinning. Once running the 7.5 on its own does just fine. Sad to have the other running just for the start up. The phase perfect seems like a great route but you would have to get all you need for HP up front. If you needed to add another 5hp later, a RPC would be easy just to add on to the same system. If I had to do it again, I would probably go with a phase perfect and get oversized.

From contributor H:
It’s not real hard to build one. Simply a three phase motor running on single phase and generating the third leg. The trick is getting it started - either a bank of capacitors, rope and pulley or a small motor to get it spinning. Look around and you should be able to come up with a 25hp three phase motor for a couple of hundred dollars.

From contributor B:
I have two 20 hp models from American Rotary. I have had one for eight years and the second is four years old. Both have been rock solid. They are available 24/7 for aftermarket support.

From Contributor C:
I have now been trying to get another machine running. Long story but have had to rethink my system a bit. American Rotary will recommend double HP for hard starting motor such as planers, sanders, etc. Phase-a-matic says to add 50%. I think the Phase-a-matic keeps a better voltage level during heavy loading than the American Rotary. So I would follow AR's recommendation of doubling. I am now wondering what Kay Industries does to offer 10hp for 10hp applications. All I can think is that they may have a built in torque booster. Like Phase-a-matic builds. Kays are pretty competitively priced as well. The Phase-a-matic is insulated so does not get as hot as the American Rotary. You wouldn't be able hold your hand on the motor, at least 150-160F. I think they all will get the job done but need to be sized accordingly.

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