ROTARY PHASE CONVERTORS

[W2PFY]

What do any of you out there know about rotary phase convertors?
On eBay there are kits to make one. I have seen two types, one had a pony motor to bring the phase motor up to speed and the other type uses a three phase motor with a capacitor start. Then there are other caps for the run position that are in the circuit for the third phase. The one with the pony motor does not use any caps in the circuit, they just take the third phase off the motor winding.

I would like to find a small three phase motor to experiment with this technology. If anyone has any good tip or articles about this subject, I would like to hear what you have to say.

Thanks Terry

[K7LYF]

I have two of the pony motor types that I run my vertical mill and my surface grinder with. An important thing to remember is the 3 phase motor needs to be sized larger than the one you are going to run. Such as a 1 horse 3 phase motor on a mill say, needs at least a 2 or 3 horse drive motor driven by a 1/2 horse pony motor. This is not a very economical method but I have several hours of run time on both machines. There are several web sites that show the schematic etc.....mostly in the wood working area.

good luck   mike

[Opcom]

I wanted to do the same experiments! but there was a mishap with the 3HP motor when it was not in my care. If you do this, please post up all the details, capacitors, your schematic, etc.

[The Slab Bacon]

Terry,
        You really seem to have a fascination with 3-phase stuff  

A friend of mine used to have a very interesting machine shop on his farm. His shop took up several very large pole buildings. He specialized in rebuilding LARGE engines.
his specialty was gas line and oil field pumping engines, some with cylinders so large you could crawl through them. His name was George Miller, and he lived in Whiteford, Md. (unfortunately, we lost touch, and I haven't heard from him in years)

All of his machine tools were 3-phase, and he didnt have 3-phase power on his farm.
He had all of the single phase power you could possibly want, but no 3-phase. He told me that the power company wanted a fortune to run the lines to his farm, and the draw/demand charges would eat him alive. So he used all rotary converters.

He literally had a shed full of them. He used the single motor/capacitor for the smaller machines, and the large motor/pony motor for the big stuff. Both seemed to work well, except for the fact of the inefficiency and he had to remember to start the converter before the machine.

the reason for the pony motor is to spin the converter motor up before applying power to it. (the pony motor is a single phase motor) If you dont spin up the converter motor before you apply the single phase power to it is that it will act like it has lost it's 2nd and 3rd phases and has a locked rotor to boot. This will in tern burn up the one winding that has power applied to it. Basically all you have to do is spin it up just fast enough for the induction to take over.

Now...................... there are several companies out there making electronic phase converters specifically for motor applications, and they are relatively simple and inexpensive. You get a little less torque out of the motor, but you save a lot of wasted power. I installed one on a Bridgeport milling machine for another friend of mine. IIRC, it was a relatively small box and didn't have much inside of it. Took all of 15 or 20 minutes to install.

If you have need for one, I'll call him and see if he remembers what the brand-name was.

[WB3JOK]

Lots of good reading here: http://www.phaseconverterinfo.com/

The small boxes (with just a couple of capacitors and a relay) don't sound like a good long-term solution except for known, fixed loads, and even then they don't balance the three phases very well. A complete off-line switching inverter will probably be out of your price range...

[W2PFY]

Terry,
        You really seem to have a fascination with 3-phase stuff Huh  Huh

Yes, I love three phase but this as simple as it may be, it is a learning curve for me and I want to build one. I have no need for one just yet but if I move the Westinghouse to a place without three phase, I want to put to use what I may have learned here. As far as that guy that used to work on large engines, that is something I would love to do, at least until I got sick of it

A complete off-line switching inverter will probably be out of your price range...

I don't think they recommend inverters for radio transmitters?

I'm still holding out for someone on here who has built one!  

[W7TFO]

Those motor-cum-cap converters won't work into a single core polyphase transformer without frying something.

They are for motors only, and border on junk science IMO.

here are the real ones, get your pocketbook out:

http://kayind.com/pdf_files/product_data_sheets/t_brochure.pdf

73DG

[Ralph W3GL]

Hey Terry,

Just get your diesel gen-set running and if you move the "circle bar W"
rig, take the gen-set along as part of the load... 

[N4LTA]

I think you will not be successful trying to feed a 3 phase transformer with a rotary phase converter. As stated earlier they are not real effective. You would be better off buying a three phase generator and hooking it up to a single phase motor - or just using a engine run generator.

The three phase motor efficiency is good about .9 or so for a decent motor and the generator is likely that or a little less. Combined you might get 78 % or so efficiency.

I use a solid state single phase in - 3 phase out inverter on my lathe and it workes very well. The motor is a 1HP and control is great and smooth and about twice the torque I had with a 3/4 HP single phase motor. Also - no belt changing to change speed. The inverter was cheap - $105 new.

Not sure how well it would work driving a transformer with respect to electrical noise.

Pat
N4LTA

[KA3EKH]

I moved a 5 kW Harris FM transmitter from a site that was 208v 3ph to a site next to a landfill that only had signal phase. The owners bought this thing that was like a motor generator that had some solid state junk on it and it developed the third or middle phase. The transmitter was installed with one leg each of the 240 volt line to two of the three phase terminals and the new synthetic phase was feed to the third. Had to allow ten seconds for the thing to spin up and synchronize but after it did you then had three phases at 240 volts per leg. Installed that mess five years ago and never been back so it's still working. Another three phase story, at one of the oldest sites I have, it’s a 5 kW AM site that was built back in 1949. It has the worlds stupidest three phase system, one leg is 120 to ground the middle leg is 250 volts to ground and the third 120 to ground with 1 to 3 being 240 volt but anything to center leg being some stupid high voltage. Ends up with every third barker in the panel being useless because of the high voltage on it. How far are you from Maryland? I have an old three phase 10 kW Onan you can have. It's got an almost useless diesel air cooled engine that never starts when you need it and has not been run in ten years but what do you want for nothing. Always make it interesting if you got to go out and start the generator before a QSO
Ray F

[Bill, KD0HG]

I have installed several rotary phase converters at radio tower sites where only single phase is available.

The smallest was one to run a Harris MW-5 AM transmitter.
The largest is powering a 35 KW FM transmitter that has an AC draw of about 50 KW. It runs from a 400 amp, 240 volt, single phase service on a mountain top. Probably weighs 500 pounds.

These rotary converters are made by Kay Industries and are called "Phasemasters".
These rotary phase converters are actually rotating transformers, they are not motor-generators.

http://www.kayind.com/basics/what.htm

They are ultra reliable, the oldest one I have operating has been in continuous 24x7 service since 1983. You only have to grease the bearings with a gun once a year. I have never had a problem powering any sort of 3-phase electronic gear with them.

Starting current is a *lot*., I measured 1,000 amps to start the 50 KW one I mentioned, but it drops within a few seconds. They also have a step-start modification for them to minimize the inrush.

Super simple hookup, see the drawing.

You can find used ones on Ebay for very reasonable prices.

[W7TFO]

Already been there, five posts previous.

73DG

[N0WEK]

Back in the 1970s a friend moved his woodworking shop to his house without 3 phase. We just bought one of those little boxes full of caps for about $35 and hooked it up.

It actually worked just fine, except that when it was cold out there in the morning it wouldn't start the air compressor with the oil cold. All we had to do was start up the radial arm saw, and when it came up to speed we just started the compressor and then turned off the  radial arm. After the first start and warm up the compressor worked fine.

The system improved when I added a spare 1 HP 3 phase motor to the line. All we had to do was turn on the 240 volt breaker in the morning, the spare motor just ran unloaded all day on the floor under the breaker box. 

[W7TFO]

It sounds like Terry PFY is interested in running a transmitter designed for polyphase power from single phase power.

3-phase transformer based power supplies are not motors.  They can't tolerate interphase differences.

73DG

[N4LTA]

A polyphase induction motor is nothing more than a rotary polyphase transformer. That is one of the first concepts introduced in rotary machinery courses in engineering school.

The Kay system is not what was first being proposed. The item being called a rotary phase converter is a crude rotary phase shifter that is not efficient.

The Kay system is single phase motor with a three phase induction winding on a common shaft. Nothing new.

A solid state inverter system would work fine and be very efficient but probably not cheap enough for a ham transmitter - nor would the Kay system.

Pat
N4LTA



Pat
N4LTA

[Ralph W3GL]

 
As far as I know, Terry might want to move his Westinghouse (what I call the
"Circle Bar W" from their branding iron trade mark) MW-2 transmitter.  He has
a 3 phase Diesel Generator that took a dump some time ago.  

Not sure if he has gotten it running yet as last time I worked him he was using the
little rig (BC 610)...  We all know that is a 115 volt, single phase peanut whistle
compared to the multiple KW 3 Phase MW-2 (a 5736 modded by 833's run at the
AM legal limit, of course).

[W7TFO]

[quote author=N4LTA link=topic=29077.msg224937#msg224937 date=1317692236
The Kay system is not what was first being proposed.

The item being called a rotary phase converter is a crude rotary phase shifter that is not efficient.

Indeed.  Caps and a relay in a box isn't going to do it for him.

The Kay system is single phase motor with a three phase induction winding on a common shaft. Nothing new.

I never said it was anything new, just that it was a good answer to his problem.  I installed my first one of these over 35 years ago.

A solid state inverter system would work fine and be very efficient but probably not cheap enough for a ham transmitter - nor would the Kay system.

It's only $   73DG

Pat
N4LTA



Pat
N4LTA
[/quote]

[N4LTA]

Yep - Just money

You would probably be better off having a new single phase transformer wound or find one that would work. Transformers are very efficient - rotary machines are a lot less - especially two in series.

Just money  

Pat

[WBear2GCR]

Dunno what Terry wants to run.

I run my Index milling machine all the time on a single phase line that is hooked up to a three phase motor where an oil cap is across the third wire on the three phase making motor. The mill's motor is hooked across that. You have to dork with the cap size to get it to run right... works fine.

My neighbor has been running his mill for at least 40 years with JUST a start cap on the mill's motor that he pops in to get it running...

You loose power and eat power with this, but you get three phase.

SCREW THAT IF UR SERIOUS.

What you want is one of those commercial inverter controllers for 3 phase motors. They not only create the three phase in but they will vary the freq so that you can adjust the speed over a scary wide range with the push of a button. They're all over epay... that is THE WAY TO GO at least for motors. Dunno what it will do with transformers...

                          _-_-bear

[Detroit47]

This is what I run my Bridgeport with

http://www.pts-tools.com/cgi/CGPTSRIM?PMITEM=RD501300B&PARTPG=CGPTLMXI&PAMENU=&PMLFNO=10_02_001_010

73 N8QPC

[KA3EKH]

Why not just buy a signal phase motor? Three phase motors can't be all that efficient if you're not running them on three phase. Companies like Baldor produce all kind of motors and they are not that expensive. On a couple old transmitters I have run across three phase motors in the blowers and when they fail have replaced them with equal size and HP signal phase motors and never had to worry about rotation direction again. Can see why with a transmitters plate supply you want three phase because if you don’t have it you need new transformer, rectifier and filter circuits but other than not spending money what advantage is there to not just changing the motor on a milling machine or drill press or whatever then trying to rig up something for fake three phase? Don’t get me wrong, not trying to be ignorant or insulting but just don’t see why if you have a tool and are serious about using it why not do it right? After you spend all the money and time to buy something, transport it , do everything to get it set up in the shop and ready to go  how much more is it to spring for a new motor and dump the three phase  one? Of course I have always been a sucker for spending money on tools.

[KD6VXI]

Why not just buy a signal phase motor?

My Uncle's response to that question was (and he runs 2 RPCs)

"Because I can run many tools off that single converter (albeit one at a time)...  BUT, I can only use a replacement motor in one press."


Makes sense to me.  3 phase equipment can also be had on the cheap at times, because it's harder to get power to.


--Shane
KD6VXI

[WBear2GCR]

Also three phase motors have far more "oomph". Or so it seems...

And while he isn't saying, I think Terry may want to run his big iron farm off three phase without having to run a generator, or maybe off a cheaper generator, etc...

                    _-_-bear

[KA2QFX]

As I recall from my machines class (in another life) we digressed into this topic for a week.  Basically, there are several ways to build a rotary phase converter using a three phase motor as the rotary transformer.  The key is whether you use a delta or wye motor. 

The delta motors can be started using a start (phase shifting) capacitor applied to the third winding (call this Phase C). L1 and L2 being applied to A and B. This motor will continue running on it's own.  These three phase are now applied to the load but either L1 or L2 must be phase shifted -60 degrees to have the proper relationship.  This requires knowing the average load impedance of the load and selecting an appropriate cap for that shift.  The third (synthesised) phase gets it's power from the original two. So that the motor's rating need only handle the averaged power required of the third phase. But phase relationships are never quite right and losses must be accommodated.  I would suspect that variable loads like a plate supply going from xmit to standby would be intolerable.

The wye motors apply power between one phase and "neutral" and must be driven by an outboard single phase motor as one phase cannot sustain rotation alone.  The benefit of this is that the phase relationships are far more stable with variable loads (no phase shift caps). The drawback, aside from the added mechanical issues, are that the power for two phases must be delivered by the single excited phase, thus a far larger motor is required for a given load.  About 4:1 IIRC.


I'm sure there's a lot I'm forgetting, much of which involves the sq. root of 3, but I hope that helps.   

Mark

PS. I converted ball my machine tools to single phase motors. Much simpler and cheaper.  I'd do the same for 3 phase transformers if needed.