My Rotary Phase Converter build

Jeff Horton

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The Heart of Dixie
WARNING - RPC's are dealing with high voltage and amperage. ENOUGH TO BE LETHAL! If you don't know what you doing this is not something to learn on!

With that out of the way I finally have started building my Rotary Phase Converter. It purpose is to generate 3 phase power for the Lab for a couple of restored old machines

First step is to get a plan or design for the RPC. I got mine from Bruce Norton and no doubt he will share his plans. His designs incorporate potential relay for safer start up. With his design you simple hit the start button and once it spins up and start generating power the potential relay kicks out the start circuit. Most designs depend on you to hold down and then release the button once the RPC starts. No expert but I am impressed with Bruce's design. It's not the simplest or the cheapest but I believe is a very safe design for you and the machines. I will ask Bruce about posting his design(s) in PDF format.

Next step, find the components. New components would be very expensive, so surplus and used are the way to go. If your seriously thinking about building one in the future and know what size you want. It's a good idea to start looking now and buying parts.

The hard parts to find are a suitable electronic enclosure. A motor overload relay and the motor starter. I got lucky on the enclosure. Someone I know gave me a large one. I just had to pay shipping on it. The rest of the components came off of EBay after a lot of digging around the site.

enclosure1.jpg enclosure2.jpg

I studied the plans and finally decided on a layout of the components and start mounting them in the box.

components.jpg

Just have to remember to allow space for the capacitors and there are several of those that will go in the box.

caps.jpg

Now I am ready to start wiring up the all the components. I have a couple of items I searched for and just now found. They should be in the mail but I can still start wiring.

Jeff
 
WARNING - RPC's are dealing with high voltage and amperage. ENOUGH TO BE LETHAL! If you don't know what you doing this is not something to learn on!
So...are you saying that it's not OK to lick the leads to see if they're hot? :huh:




:rofl:

Thanks for starting this thread. Ill be watching with interest. :lurk:
 
So...are you saying that it's not OK to lick the leads to see if they're hot? :huh:


Only for you Vaughn, not for anyone else. :rofl:

I forgot to add this little tidbit and I am sure it varies by area. I went to the local electrical supply house where the big boys deal. Bought from them when building the house. I wanted to buy a few feet of wire. To my surprise the smaller more common sizes, like 12 and 14 gage, they only sold in 500 foot rolls. Needless to say that would last me..... ummm, the rest of my life! I did get the short lengths of larger gage wire I needed however.

I can get it the hardware store, it just darned expensive. I remember I have a dead.. well dying washing machine in my garage. So I decided I will just pop the back off it and see whats inside. I was going to do that anyway so I will see if there is any wire in the that is suitable. Strip it out and save a few bucks.
 
Vaughn fro

Hey Vaughn, I want to watch! I can just imagine the large circumferance fro you'l git when you lick them leads. On the other hand, those large caps will probably cause a reaction not unlike a large bug zapper. Got to remember that even with the power disconnected those caps can be deadly unless they are discharged at shutdown.:thumb:
 
I spent a little time in the Lab working on the RPC. I thought I was going to have all day but lots of things came up and I didn't get to spend much more than hour on it today.

This morning I stripped the old washing machine and got a lot of good stuff for the rat hole. ;) Actually I grabbed the wiring harness. I was surprised at home much wire was in there. And a few pieces here and there. Just what I figured I would actually use. The wire came in very handy tonight.

I am waiting on the distribution blocks to get here. Just about everything connects to these so there is a lot I cannot do. But I could wire the start and stop circuits. Bruce's plans are pretty simple to follow. I had one difference from his plan. He shows a indicator light (to show it's running) and I had a lighted switch instead. No biggie, I would just wire it so the light was only on when it was running. Of course I got confused and had to do this :huh: for a bit.

Then I decided that Bruce had a mistake in his plans. He had changed them for my needs and just knew what I was looking at was mistake. It just wouldn't work. After finally just walking up stairs, getting something to drink and then sat down and traced through the schematic again and finally realize that Bruce was just cleaver! What he had looked wrong but was really just a slick answer to a problem. :doh:

Till I get the distribution blocks I can't do much more.

And I will organize the wires and bundle them once I get more done. It won't look like a rats nest when I am done!!


wiring1.jpg wiring2.jpg
 
Well almost finished with the wiring. Not much to talk about. Except now that I see it wired, I would have mounted the components to have routed the larger heavy wires in a straighter line. Wasn't hard to install them, just would have looked better.

I need to install the capacitors now and mount it to the wall and wire it in the panel.

more_wiring1.jpg more_wiring2.jpg
 
Jeff,

Do you have a schematic diagram and parts list for your project? Specs as to it's capacity and performance?

Yes. A friend of mine has been refining this design for many years now. This however is the first of his 10hp unit to be built. So he asked I not make it public till it is proven. But once we know there are not problems with the design I can pass it out.

So you are going to mount the panel to the wall?

Cord from there down to the idler motor?

Basically yes. Got to find something for a distribution for the 3 phase power. Still looking for something but I think I am going to fuses. you know, those round things before breakers came out. :D in a box and then pull wire from there around the shop. Wire up two circuits since I have three machines that will use 3 phase power.
 
No electrician here, although I did see an actor play one on TV...

With fuses, is there a greater danger because unlike a ganged breaker, one leg can open while the others remain hot?
 

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Yup, sure is. But "I THINK" the RPC won't run or run properly so you will know it.
Being an inspector you certainly understand that it is always best to have qualified folks do that type of work, which folks like galoots don't want to pay...I'm not siding with either side, and chose to seek some help from a friend that does understand electrical well to feel the comfort to knowing and not having to *think*.

I think it's worth considering to put a disconnect on the breaker, which uses slo-blo fuses. That way you have the protection of the disconnect slo-blos, and the breaker for the circuit. That's how I did mine. panel breaker -> slo-blo disconnect -> rpc -> 3-phase. I used the lever type disconnect (tougher to find, but I like it better than the pull-out), and got mine at Lowes I think. HD had only the style I don't care for. HD does sell the slo-blo fuses I need though, not that I have needed any...I know they're there. I have an extra pair already. The ones I am using are the small shotgun shell type.

Again, I had a friend help me, I plea ignorance to electricity, and want to know everything is wired correctly when I do flip the switch. Consider all aspect and seek advice from folks that do know electronics.
 
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Jeff. Your plan is to breaker the convertor, then fuse the machines?

60 amp breaker in my existing panel in the shop that will provide the 220v to the RPC and idler motor.

Then a distribution panel for the 3 phase power that has yet to be determined of what style. I am leaning toward fuses on the 3 phase side because I have a source for a some reasonable 3 fuse blocks that I can mount in a box.

Now if I happen to find a 3 phase breaker panel with breakers at a good price sure. But those things are pricey!! Besides fuses typically react faster than breakers.

The draw back, as Gary asked about, is that you could blow one fuse and still have two hot legs. Of course, if I am going to work on it I will just throw the breaker and kill the whole system. As for the "I think" that the phase converter won't run correctly if you loose one leg. I haven't studied the drawing yet to see. That's not a priority at this point, will do that once I actually get closer.

Regardless, once shut down I know the motors won't start on only 2 legs.
 
If the converter is going to run a piece of equipment at about its max capacity, then Steve's route is the way to go. If you're running say, 3 machines at 3 hp each with a 10 hp converter, then it might be a good idea to fuse the machines so you can't roast one before the converter's breaker trips. I don't think the converter itself will be bothered by losing a leg on the downstream side, but you'll sure notice at the 3 phase machine you're using. If its already running, it'll keep running, very badly. Some machines with low startup loads like a jointer will kinda start on two legs, but even then it'll be obvious somethings wrong. Bandsaws, compressors, etc probably won't start at all without all three legs.
 
There is another consideration about fusing the down stream/3 phase side. Most people don't understand/realize this. But breakers function is not to protect what ever is plugged in it, it's function is to prevent the wire from overloading, overheating, catching fire and burning down the house or shop. (OK, there are exceptions but normally that is the case) You size the breaker to wire your running, not the motor capacity.

In my case I am going to have a 60amp breaker feeding the converter. The only way a motor in my shop it going to draw that is a dead short! If I pull 12 gage wire to the bandsaw, the wire is only rated for 20 amps so that 60 amp breaker is not going to protect that wire from overheating. So that is why the fuses on the 3 phase legs.

Then on the motors I will (most likely) install magnetic starters with heaters sized to match the motor load. That will protect the motor in case it overloads.

Clear as mud? :D
 
There is another consideration about fusing the down stream/3 phase side. Most people don't understand/realize this. But breakers function is not to protect what ever is plugged in it, it's function is to prevent the wire from overloading, overheating, catching fire and burning down the house or shop. (OK, there are exceptions but normally that is the case) You size the breaker to wire your running, not the motor capacity.

This is true enough, IF you provide other means of protecting the motor, like the magnetic starter and heaters. Though the intent of overcurrent protection is to protect the wiring, in most hobby shop situations it ends up protecting the entire circuit - including the load, if everything is sized to do it - because most hobby shop owners don't want to spend the extra money on machine specific disconnecting means and overload protection. This is not an ideal situation by any means, but its the reality that leads to the confusion. Obviously, a 1.5 hp bandsaw's motor is not protected by the breaker on a 30 amp dryer outlet :D The other part that leads to confusion is that most induction motors can take a lot of current before being damaged, so a lot of hobbyists run them without protection and never have a problem.
 
Very true!

One thing people miss is that once you let the smoke escape from the a motor it will never run right again! I still wonder how they get the smoke inside it thought. Must me an industry secret? :dunno:
;)
 
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