View Full Version : Who makes the best rotary phase converter?

03-21-2009, 09:07 PM
I have a American Rotary for my cnc bridgeport and it is not very reliable. Anybody have a RPC that they have good luck with and would reccomend?



03-21-2009, 09:30 PM
Phase Perfect by American Rotary is still the best.

You might ask American Rotary to help pin down your problems.

03-22-2009, 05:26 PM
I was looking at a phase a matic with a voltage stabilizer?
Any comments?

03-22-2009, 05:58 PM
What's wrong with your American Rotary?

I have a 10HP and a 40HP. The 10HP is 2.5 years old and has been quite reliable. Voltage balance is good whenever I check it with a voltmeter and it makes no more noise than the day I installed it. The 40HP is less than a month old, but from the install and use so far, it seems just like the 10HP, only larger.

I have recommended them to a few people.

Chris Kirchen

03-23-2009, 07:34 AM
Well when I first bought it and installed it there was a large voltage imbalance between the three legs. My cnc Bridgeport would fault out. So I sent it back and they fixed it. Now my voltage is balanced nicely under no load but when I start my machine the voltage drops down to 130 volts between legs t-2 and t-3. and my machine faults out. After that I threw my hands in the air. I need to run parts not diognose voltage problems. Sorry just a little frustrated. I'm running a 5hp RPC by the way.


03-23-2009, 10:42 AM
Hmmm. Not exactly sure what could be causing the voltage to drop out like that. Assuming that the RPC is working, there are a few things to check:

How big is the machine? Could the RPC be undersized? My 40HP unit is running a 20HP lathe. The rule of thumb for CNC applications is 2 times the spindle HP.

Also, T3 is usually the manufactured (or wild) leg, it should not be used to power the computer side of the CNC. You might have to trace wires from the machine's input breaker to the computer power supply to be sure.

RPCs work be take single phase power and 'repurposing' (for lack of a better word, I am not an electrician) it into three phase. The RPC cannot create power; if the available single phase power is too low, it will not have enough power to make proper three phase. kVA_in = kVA_out (minus losses).

Attach a clamp ammeter onto one of the single phase input lines. Looking on American Rotary's website, that 5HP unit is rated for 8 amps at 5% voltage balance (that means is your CNC is drawing 8 amps in three phase power, the voltage balance will be within 5%). 8 amps three phase is approximately 14 amps single phase (current_three_phase = 1.73 * current_single_phase), so if you see more than 14 amps on the ammeter, the RPC is becoming unbalanced due to excessive load.

Chris Kirchen

03-23-2009, 07:30 PM
I checked voltage on the input lines (L1 & L2) and they were at 243V with no load and dropped to 227V at start up so thats not a big deal. I talked to american rotary today and they suggested running another 5hp RPC paralell with the one I have. I also could run 1 single 10 hp RPC to make sure I have plenty of power under anyload or of course theres Phase perfect but thats a little pricey. Its only a 2hp spindle motor but with a max RPm of 4200 which has a alot more voltage draw. On the mfg plate on the spindle motor shows 7 amps for the max. Anyways I want to get some more input from other manufactures before I dig into my wallet again.

Thanks alot for your input

03-28-2009, 12:12 AM
We got the phase converter for our pump at Temco. http://www.phaseconverter.com/ It helps that the phase converter is more HP than the equioment it is converting for. Our pump is 15HP but the phase converter is 20HP. Good Luck!

Farmers Machine
04-28-2009, 10:31 PM
You can hook up 100 5 horsepower units and still only run 3 horsepower. You have to have one unit larger than any motor you are making power for so that it has enough steel in the armeture to generate the electromagnetic force or energy to power the smaller motor. you can hook up all of the little motors you want, the more the better. if you are getting low amperage on the artificial leg add some motor run capicators from either of the single phase lines to the artifical leg. on the converters I build from scratch to use on remote jobsites the rule of thumb is 10 MFD per amp of under balance when loaded. Hook up a line reactor between the rotary and the CNC to protect the CNC control, and you should be off and running.
good luck
the Farmer.

04-28-2009, 10:58 PM
I have had phase a matic 10HP and now I use a 30HP unit with stabilizer purchased on ebay like new for 1,300.00 amps idle is 12 amps running cnc mill 3 hp fanuc pulls 16amps super quite I had a friends super loud & pulled way to many amps at start up popped 60amp break
I run phase a matic on same breaker no prob

04-28-2009, 11:46 PM
I have an Electram 5 Hp unit to run my lathe, bridgeport and surface grinder.

I have been very happy with it, I added a pilot light for a visual confirmation
that it is on 'cause the damn thing is too quiet....

04-30-2009, 09:27 PM
Hi guys. Thanks for all the imput. I did end up trading my 5hp American Rotary RPC in for a Remco heavy duty7.5 hp cnc RPC. Check them out at http://phaseconverterspecialist.com/
They actually design and build many different types and they can answer questions about installation and voltages, amps etc...Plus they are a local company in my area. I also installed a single phase buck boost transformer to step down my voltage from 242 to 230.
Now my spindle starts at any rpm with no errors.

11-23-2010, 03:14 PM
I'll bet if you worked with American Rotary, they could have made your 10hp work. Talk with Jay or Dave. I am a 3 time customer running a mitsubishi CNC (which is extremely voltage sensitive) It seems you bought a larger converter and fixed your single phase voltage to get the remco working, so not exactly a fair comparison. That said, rotary converters have to be balanced, they won't hardly ever be perfect right out of the box, but a good company will get it balanced. The thing I like about American Rotary is that they have used technology to balance their converters as close to a phase perfect as you can get with a rotary. The last one I bought had digital controls which supposedly solves all sorts of old rotary converter issues. So its been perfect.

... just looked at American Rotary's site American Rotary Phase Converters (http://www.americanrotary.com) and see that they have added some simpler cnc rated converters (that means their digital controls, voltage balancing etc.) with out starters which brings down the cost a bit. I remember their full blown cnc units being a better deal than the old phase-0-matic or phasemaster style converters.


12-01-2010, 01:22 AM
I have installed lots of Rotary phase converters to run CNC equipment and here is what I have learned.

1. Retrofits usually have single phase controls so wire them to the single phase line. Then the voltage balance does not matter so much on a motor spindle unless it is VFD controlled.

2. For a machning center such as a HAAS, where you don't want to rewire controls to isolate them, get a good voltage balanced converter. The best I have used has been American Rotary for probably the last 6 or 7 years. They are on top of their game when it comes to voltage balance and CNC, they even have a digitally controlled rotary which the HAAS dealer I work with often says it is the only Rotary Converter they will recommend and warranty to run a new machine. a link

Digitally Controlled Phase Converters >Digitally Controlled Phase Power Converters - Digitally Controlled Phase Converter (http://www.americanrotary.com/digitally-controlled-rotary-phase-converters.html)

3. Double the size of the converter for CNC equipment. Do this in amps because some converter companies disquise the HP rating of the converter for marketing reasons. If your machine needs 15 amps max (approx. 5 hp in three-phase and 240 volts) then get at least a rotary converter that is rated for 30 amps max output) this is slightly larger than a 10 hp so you may go to a 15 hp, but again, a company may not say its a 10hp... look at the amps. American Rotary is very upfront about this. They call a 10 a 10 which is capable of about 28 amps. No funny stuff. Good for simple electricians like myself.

4. You need a good voltage balanced converter for a CNC use. Phase-A-Matic and others don't balance the voltage or powerfactor correct which is important for phase shift which some CNC's are sensitive too. The only way to really balance a rotary converter is to have capacitance across two windings which means a separate start circuit on the converter.