Three phase rotary converter.

[Joe Hillmann]

I have been looking at a couple 3 phase tools recently and before I go ahead and buy one I want to make sure I understand basics of how to get them running.

From what I have read it sounds like the most basic converter would be to take a 3 phase motor and hook up a 230 line to it it will run if given a pull start. Then to run a second motor I would take run lines of the three lugs on the first motor to the other machine I wanted to run. Is there any reason I need a separate motor to act as the converter? Can I just have two 3 phase machines and when ever I want to run one have both running? Wouldn't the one not under load act as a converter for the one under load?

[jack forsberg]

simple answer is yes but than all you need is a static convertor for that. Its goes with out saying that this only works on machine of 240 volt 3 phase motors. and the system is very dirty power with the wild generated leg way off on voltage and your motors will run hot with less than full HP. This is why run capacitors are added to rotary phase convertors wild leg to balance out the voltage in the generated leg

[Keith Hankins]

It's not quit that simple. You can do what you state, but the power will be uneven and what they call "dirty". you want those 3 legs running +- 3-5% or you will have issues. You also need to take into account HP drop on that generated leg. When I was in your position a few years ago, I did a lot of learning but in the end went with a commercial RPC. My 10hp American Rotary (in your neck of the woods) has a great reputation and is made in america. It will support up to a 7.5HP load. You also need to be careful on the voltage rating on the motor. My converter is designed for 220v 3 phase motors. You have motors that run at 400v+ 3 phase and thats a different bird. There are those out there that go for the static which if you have one or two tools might work. However I wanted to be set for the future so, I went the comercial route and got the baldor 10hp motor from them. Only thing I might do diff is to get a used 10hp motor and buy their panel and go that way. Mine's been runnin a few years now and is quiet as a mouse. The larger the motor the more noise you will live with. Not an issue in my case. Take care.

[Bradley Gray]

I have a homemade converter that has been in use for over 30 years. I use a 8 hp idler that I start with a push button that fires a pair of capacitors to get the idler going. With it i run an 8hp, two 5 hp and two 3 hp though usually only 2 machines at a time. You could also use a rope wrapped on the idler pulley or a small single phase motor with a slip clutch or even use your foot to spin the motor before turning on the power. I got the particulars from an early FWW magazine circa 1980.

[Rich Riddle]

Joe, one advantage to a rotary unit is that if one of the motors does go bad, it's usually the slave motor. I consider mine like a sacrificial motor more or less. If it goes bad, any 5 hp motor can take it's place. No need to find the exact motor that fits one of the tools. Good thing too; some of those 3 phase motors on the tools are quite unique. I am also not a fan of the pull start method.

[Dennis Nagle]

I run a 5hp phase converter and it works great. THere is a guy just north of me that builds them in his shed and sells them for the cost of parts plus a bit.

[Charles Lent]

Joe,

A rotary converter is best for your needs. A static converter can be used for smaller 3 phase needs on one machine, but it has limitations when trying to use it for more than one machine. You also can't get the full rated motor power when using them. You can build a rotary converter using a large 3 phase motor, but it's output won't be good enough to run any electronics and the machine that you connect to it won't behave as if it was connected to good 3 phase power. The motor on your tool will run slightly hotter and not at full HP output. For someone not well versed in electricity I suggest that you buy a rotary phase converter at least 30% larger in horsepower than the largest motor that you will be starting and at least equal to the total horsepower of all the motors that you will be running at the same time, but don't cut yourself short here if you think you may be buying additional 3 phase machines in the future. A purchased rotary converter will contain capacitors to boost and align the timing of the created phase to produce cleaner power. It will also contain the starting circuits to automatically start the converter and bring it up to speed when power is applied. In my opinion Kay Industries makes the most reliable rotary converters. Their customer service will help you size it correctly for your needs.

I was the sole North American electrical service rep for a printing press importer and I serviced presses in all 50 States and the Caribbean. I had many European 50 Hz 220 v 3 phase presses that I adapted to run from the US 60 Hz 3 phase 208, 240 volt 3 phase, or 240 volt single phase US power. When running from 240 volt single phase a rotary phase converter was always the choice.

Charley

[Scott Snyder]

What others have said. I wouldn't use the "slave one machine to another" method. Three phase motors are usually cheap, get one 1/3 larger than your largest motor and contact Jim at Phase Craft. Great guy, terrific service.

[Curtis Horswill]

+ 1 to Phase Craft panel suggestion. I found a nice Leeson 10 hp motor for $150 and purchased the 10 hp panel from Jim at Phase Craft through Ebay. Very easy connections and works great thus far. I check the voltages while running my 16" Knapp J/P combo and they were balanced within 2% of each leg. For the money I think the Phase Craft panels are the way to go.

[Andy Pratt]

Not an expert by any means on this but definitely look into phase converting VFDs. For the 1-5hp range they are very price competitive with rotary or static phase converters and offer many more features and protection for the motor, not to mention way smaller size.

I didn't know much about this before but I put one on a 1ph machine i converted to 3ph last year. I ordered from wolf automation and they were very helpful walking me through the process, even as a first-timer who had a lot of (probably) dumb questions.