Phase Converters: Anyone Have Experience With Them?

[K2PG]

I am preparing a vintage piece of heavy metal for its maiden voyage. In the event that my local electric utility wants too much to give me three phase service, my Plan B is to use a phase converter. Do any of you have experience with these devices, which, essentially, are three phase motors equipped with a starter to start them from single phase power and a bank of capacitors?

[W1RKW]

Phil,
I worked for a new FM station back in the early 90's, when it first went on the air the transmitter site only had single phase available. The 10kw transmitter required 3 phase so a phase converter was used to supply the power. The station owners didn't want to spend the money to have the power company run 3 phase to the transmitter site and do the job right.  We had trouble from day one.  I don't know if the converter was undersized or if the utility was inadequate because the site was located in an industrial park but we had power regulation problems.   After six months of running at 60% power we moved the transmitter site that had 3phase and dumped the converter.  Our problems went away and could run at 100%. 

The problems we saw at full power, mainly the transmitter would go into a protect mode and go to low power. My guess if I look back, it was probably due to the power to the transmitter site more so than the converter. And the problems were more related to the summer time than the cooler weather.   If converters aren't that good they wouldn't be used in the first place. So you'd probably be ok if you have clean and stable single phase power and a moderate load.

[kc2ifr]

Phil,
Years ago I had a drive-in theatre using the old carbon arc lamps. I wanted to convert to xeon lamps but the size lamps I needed required 3 phase power. The power company wanted about 8 grand to supply 3 phase to my drive-in because I was out in the boondocks. Anyway.....I purchased something called Ad-A-Phase. It was a static phase converter. The company said it would work just fine. Well it did not.......could not draw full power to the dc power supply that drove the xeon lamp. The lamp needed about 300 Amps at about 32 volts DC. All I could get was about 175 and the flicker was real bad.
Anyway....looks like the stuff your looking at is sort of the motor-generator type...not the static type. Good luck.

[W1RKW]

Phil,
Just to add to what Bill mentioned and that I didn't mention in my previous post is the phase converter was essentially a 3 phase generator driven by a single phase motor.

[flintstone mop]

LOOK OUT
Phil is going to dim the lights in his neighborhood with some 5kw flamethrower on 160M
Phil, I remember the transmissions from your home (the middle 90's?)and the RFI complaints you were getting.
Just pulling your chain!
It must be a rare Tx you are getting ready to fire up. I don't think your QTH can handle any more heavy metal transmitters.
I'll keep an ear out for you on 160M. I guess we have to start listening around 9PM .There's still some good nites left before Ma Nature get into it.
Fred

[wavebourn]

I used oil capacitors to shift phase of motors. To start them I used bipolar electrolytics.

[WA1GFZ]

Bill's Drive in.....featuring Gone with the Wind- bink and squee- pass the zig zags

second feature "kinkie ladies of burbon st."

[WBear2GCR]

You can build your own "rotary phase converter" without much difficulty.

There are numerous sites and plans on the web.
If you get stuck, post to USENET: rec.crafts.metalworking many folks there use them or have built them

I built one for my milling machine.

The trick is that you need a three phase motor that is rated *above* the load's rating. You'll have to convert from HP back to watts to figure it out. Then you need a starter circuit for a big-ass motor. I just plug mine in, since it is just a 3 hp motor. Bigger than that you'll need the starter circuit, imho.

Bunch of nice AC rated oil filleds...

Makes nice 3 ph.

I recommend a flywheel on the rotary converter's motor shaft, to help ride through sudden loads, doesn't take all that much...

[W3SLK]

I thought that Grainger sold these as 'Rotax' boxes. I know they are ok for starting 3Ø motors and such. But I think Phil's dilema lies in the fact that the HV supply relies on the 3rd Ø for efficiency.

[WBear2GCR]

It should work fine.

The cap generates the third phase with the rotation of the motor, the third phases amplitude can be fine tuned by adjusting the cap. It doesn't know if a motor is connected or a transformer. (Shhhh... don't tell it!    )

Of course you lose "efficiency" by just spinning the motor...

         _-_-WBear2GCR

[WBear2GCR]

Can't tell you about the stability of the third leg, beyond suggesting the websearch and rec.crafts.metalworking. There are some highly technical websites on this topic.

I'd definitely build my own, over buying anything.

Then a scope will tell you the whole story I would think.

          _-_-WBear2GCR

PS. even if you are drawing 5kW, at 240v that's 20 amps... not that big on the grand scale of running big machines. Seems do-able to me.

PPS. you could always build up a voltage monitor for the third leg that wacks out a contactor if it dropped below some predetermined level too...

[flintstone mop]

Hello All,
I did a serarch for a Collins 21E and it is indeed a BIG transmitter. And Phil it looks like there's another fellow Norman, WB2SYQ in New Jersey who is going through a refurbishing of the same monster Tx. Found it through Google. 
The poor Tx had been sitting neglected for many years.

Fred

[k4kyv]

I have thought about using a  motor-generator to protect my computer  from lightning.  We get it so bad out here that no matter what kind of surge protectors you have in line, a moderate lightning strike in the neighbourhood will wipe out computer, modem, answering machine, wireless phone, and anything else connected to the power lines, with the other leg of the dipole simulated by the phone line or TV/internet cable.

I have thought about setting the motor and generator up, mechanically coupled with about 3' of plastic rod, so that no way could the surge on the power line make it to the a.c. supplying the computer (which would still be protected with a UPS to "condition" the output from the generator, and keep the computer going in case of failure.  The cable modem would connect to the computer via a fibre optic convertor.

That should be a bullet-proof scheme to allow me to operate the computer and even surf the net during our very frequent (sometimes constant) thunderstorm activity during the summer months).
I'm getting tired of having my stuff wiped out by a blast from the sky.

[KB2WIG]

flyweel........   the rumor is that the USAF used them to keep their "stuff" secure... no feeding info back through the pwr lines, and other things
   klc

[WBear2GCR]

Just in case,

The typical "rotary phase converter" of this type is not a motor/generator. Nor a motor/alternator.

You could set up such a thing, of course.

This rotary phase converter uses standard 240 input to a three phase motor, where the third leg is supplied via a cap arrangement. The cap "creates" the third leg's phase in concert with the motors rotation thanks to phase shift. The cap is essentially a tuned circuit in this system.

           _-_-WBear2GCR

[N9NEO]

Phil,

I offer you Plans C & D.

If you are phasing back the power then just maybe you don't need three phase power.
So Plan B is to only slightly modify so that rig will run on single phase. 

Other option is to get away from the mechanical rotating solutions
Plan C would then be to use a static inverter to get the third phase. An old UPS or motor drive with a LC filter on the output should get you there.

My money would be on the slight mods required to get it to run single phase.

73
Bob