Can someone tell me the differance between...on 3phase?

Brian Altop

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Tacoma, WA
Can someone tell me the difference between a rotary phase converter and a static phase converter? Is one better than the other?

I can not get 3phase to my house because "it's against our principle" according to the power company what ever that means.:huh:

I would be running an 8hp 3phase motor and possibly a 5hp motor (not at the same time). Also, would I need one for every piece of equipment (ie 2 3phase tools) or could I wire it into a branch off the electrical box?


Thanks!

Brian
 
a static phase converter does not make a true sign wave but uses transitors to replicate three phase power. A rotory phase converter is actually is a 1 phase motor that drives a 3 phase generator. the 3 phase produced from it is realy a true sinasoidle power. the static is cheaper and usually limited to smaller load while the rotory is used on larger loads. you would run either one off of your 1 phase panel and provide branch circuit protection to each load.
 
There are some new static phase converters out that are supported to be better than rotary phase converters. I will try to find the link if I can.

(edit)
Well no luck I thought I had it bookmarked but seem to have lost it.
 
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In my shop I have a 20 HP rotary converter which eeds a 3phase panel and then the 3 phase machines are wired to that panel. It works great.
 
I haven't personally built one, but had this conversation before. This is a general sense of what I learned talking with some guys that ran a little machine shop and made their own:

If you are making your own, there is an art to "balancing the load" I was just told get someone that knows what they're doing to do the initial setup for you off the taps. I think it's balancing the voltage from phase to phase based off the tap locations on the motor.
A lot of static types are rated on operating loads, not startup. Some requrie you to oversize the static converters by about 1/3 larger than the motor you are running.
Make sure you have enough power to run the thing. It takes a lot of amps to run 8hp motors from a 220 panel.
 
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Didn't Jeff build a converter a while back? I think he said it was easy, you just had to get a few simple things right. Or was that something else?

If you mean me, yes I built one a while back from plans a buddy of mine designed. His are Cadillac models. Took me a while to scrounge up the parts (EBay mainly) and lucked up on the motor.

Brian, basically 3 phase is 3 hot wires going to the motor as opposed to 2 for 110/220. You can run a 3 phase motor on 2 legs once you get it running. Static convertors typically just temporarily generate 3 legs long enough to start the motor and it runs on 2 legs and your getting about 2/3's it HP.

A rotary fires up 3 phase motor, then it runs that motor on 2 legs and uses the 3rd as a generator. That creates the 3rd electric leg for your machine while your 220 service provides the other 2 legs. So you get full rated HP of the motor.

Keep in mind there are a lot of cheap made Rotaries out there. That is why I built mine. It wasn't that hard but I find this kind of stuff fairly easy. But it did take me a while to wrap my head around the schematics and to understand how to assemble all the parts.

PS You would probably need at least a 10 hp motor on your rotary to start that big motor. A lot depends on how well the unit is built and how efficient it is. A cheap one might have to be 15 hp rotary motor. Running more than one at a time usually isn't a problem, it actually make then run better. It's just getting the biggest one started that could be an issue.
 
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In my shop I have a 20 HP rotary converter which eeds a 3phase panel and then the 3 phase machines are wired to that panel. It works great.
Wow, what feeds that 20 HP motor? Is it a single phase 230V supply? That would be at least 70 amps, maybe 80 at full load. And where do you find a single phase 20 HP motor? That must be about the biggest single phase motor they build.

Mike
 
Wow, what feeds that 20 HP motor? Is it a single phase 230V supply? That would be at least 70 amps, maybe 80 at full load. And where do you find a single phase 20 HP motor? That must be about the biggest single phase motor they build.

Mike

Don't you use a 3 phase motor to build these? But yeah I bet it pulls some serious power.
 
There seems to be confusion here'

A static phase converter is nothing but a few capacitors with maybe a relay that gives enough phase shift to get a three phase motor running on single phase.

Often basically included in a rotary converter to get the rotary running.

The rotary converters have to get spun up to speed to run on single phase and create the 3rd phase. Some have been as simple as wrapping a rope around the shaft and giving it a pull like an old lawnmower.

The ones with transistors and other complex circuity are inverters and the advantage they have is they can have the frequency adjusted to vary the speed of a 3 phase motor.

For static phase converters here is a pretty good article..
http://homemetalshopclub.org/projects/phconv/phconv.html


For rotary another article..
http://www.metalwebnews.com/howto/ph-conv/ph-conv.html

Inverter drives are fairly expensive and you can let the smoke out..

Garry
 
Jeb
As far as I know the motors hold up well enough but there are things you lose. I have a friend that bought one of the name brand static converters for his Bridgeport and he is real disappointed about the so called plug reversing. He can't instantly reverse his mill like he did when he had real 3 phase from the power company. I am not sure thats an issue with most woodworking tools.


Big 3 phase motors are cheap to build a rotary if you are in the right place at the right time...

I have a Mitsubishi inverter drive rated at 3 hp I believe it is and a 3 phase motor to put on my little Clausing mill when I get around to it....

Garry
 
Thanks for all the great information!

I think I will go with a rotary converter, I really don't have the time to build one.

I looked here:
http://www.cromanconverters.com/new_rotary_converter_pricing

And here:
http://www.phase-a-matic.com/RotaryModels&Prices.htm

and the price is double at the second. what is a proper price to expect to pay for one? I was looking at the 15hp since it would cover any startup loads from any machine 10hp and under(for table saws, planers, bandsaws etc). Also I could run two machines at once if I needed to, and last it would allow for future growth. (I hate buying something twice:D)

I have 100amps coming into the box in the shop.

Thanks again guys, your awesome!

Brian
 
In my shop I have a 20 HP rotary converter which eeds a 3phase panel and then the 3 phase machines are wired to that panel. It works great.

Al,
where is the converter in relation to the panel? do you have a feed from the 220 panel to the converter on the floor, then back into the bottom of the panel?

How have others wired theirs in?

Thanks!
 
Thanks for all the great information!

I think I will go with a rotary converter, I really don't have the time to build one.

...
Thanks again guys, your awesome!

Brian
I got tired of explaining it so I did a web page... see www.solowoodworker.com/tools/power.html

If I were buying one today, I would buy a Phase Perfect static converter.

Quick summary

Motor Generators are the old school way - a single phase motor runs a three phase generator. Two rotating devices connected by a shaft (and perhaps a clutch)

Rotary converters are one rotating machine with some extra wires that add and subtract components until you have nice clean three phase. However, they are noisy and take a lot of power when idling.

Cheap static converters just run one of the three phases of a 3 phase motor. Theoretically no problem (but I have concerns), and max of 70.7% of the full power (think 2/3 power).

Early full power static converters created full three phase, but the power was "dirty" (not good wave shapes) and were hard on motors, similar to portable generators wearing out electric power tools faster.

Current technology static 3 phase converters have gotten very good. Every wind turbine has one to convert the DC generated to proper AC. That is the technology used by Phase Perfect. Quiet and efficient. That is what I would buy.
 
Wow, what feeds that 20 HP motor? Is it a single phase 230V supply? That would be at least 70 amps, maybe 80 at full load. And where do you find a single phase 20 HP motor? That must be about the biggest single phase motor they build.

Mike

Mike, I am not sure how big they make single phase motors. Yes, It is run from a 200 amp panel. This panel is getting upgraded this winter. Yes,it pulls about 80 amps on startup.
 
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