[How do I?] My 2017 Rotary Phase Converter Build

Keith, thank you for taking the time to share the details. I appreciate the explanation. As a teen, I got pretty good at following the plans, but missed learning how the stuff actually worked. Now I'm trying to improve upon that.

Hi Dave H. (the other one), I'm Jason No. 3 (or was it No. 4). Thank you too. It's always nice to have more than one way to look at a solution.

Two items I still wanted to clarify, there are; 1) no issues mixing start and run capacitors in the start circuit, and 2) no issues allowing a RPC to run without a load for an extended period of time. That is my understanding at this point.

I have noticed a couple plans which include two start circuits. Paul actually designed for two potential relays but only used one. At first I thought maybe this would allow the system to be calibrated to different pieces of equipment but that doesn't make sense unless you have more than one idler motor which these do not. What is the reason for the second circuit?
 
Start caps and run caps. Can they be mixed yes, and no. Bigger question, is there any point?

Short answer is yes run caps will work as start caps but not the other way around.
Feasibility.
Start capacitance is typically 50 to 100uF per horsepower, so it would take a TON of run caps which are typically 30uF max, to produce enough capacitance to replace a single 350uF Start cap.

As far as mixing them, it's real easy to get things backwards and confuse yourself if you try to do that.
Running black plastic start caps, and metal cap run caps will get things wired easier. Less what hooks to what.

As far as running an RPC for a long time.
I fire mine up in the morning when I go into the shop. I have a lathe, mill and large MIG welder that all run off it. I do my thing, go in the house for breaks, phone calls and what have you. I don't turn it off unless I am done for a while in the garage. It has run 10 hours straight and never given me any issues. This was both with and without loads as I would cut or turn something, then work on layout or other things then go back to cutting.
I don't get hot or make a lot of noise so in reality I don't even notice it running unless the other machines are turned off. They are all louder than the RPC motor and are all a good bit smaller. I believe the lathe is 7.5 HP and the lathe is 3 HP. I have run the lathe and mill at the same time and it just sits there and powers it all without complaint. I do need once every other week to grease the bearings. But other than that, it's pain free.
 
LASTLY
As far as asking question and overstepping some boundary. The only way that will happen is if you ask me to build one for free and supply the parts myself as well. Anything else is fair game. I do build and repair these for funding the hobby, but it's just a hobby and I would rather see a guy enjoy it than fight it because I didn't share what I knew. I will litterally give you my number and talk you through it wire by wire if I need to and not be put out at all by doing so.
What I ask in return is pay it forward with knowledge. We are not here as union labor millrites. This is not a competition to see who is better. We are ALL on here to share what we know, what we have done and to share knowledge. And I enjoy being on here for that reason. That math we talked about before. I have not actually discussed that piece of knowledge in 20 years. I just knew it form college and high school electronics classes and have used it ever since.
In other words, ask whatever you don't know and I will do my level best to help. Don't worry about boundaries, there aren't any.

I want to express my appreciation for this site, and particularly for the example Keith is setting in being helpful and responsive. I too am building a RPC, and had read recommendations that another machinist site had a good deal of information on RPC's. When I went there and asked what I thought was a legitimate question I was lucky to get a single short answer, and then people simply went off on their own tangents, at much higher levels and essentially ignoring me and my original question. I've been cut-and-pasting Keith's valuable advice to a file for my own use, and feel much more welcome here. Thank you all.
 
This is a most excellent thread on the topic of RPCs. I was a HS physics teacher for 32 years, and we included the math of resistors and capacitors (each) both in series and parallel, so that is the easy part for me. But I sure appreciate the full discussion of how a RPC should be built and tuned. I had no idea that RPCs could be run in addition to each other, this might be very useful in my growing shop. Thanks to all participants for very good questions and excellent replies!

Paul in MN
 
As is too often the case (for me at least), after much reading I came up with a plan, gathered the components, made some progress, and then moved on to other projects. Such as replacing 16 windows in my house. But completing the RPC will be my winter project. I did get the rough installation completed . . . smaller box on the left is for the capacitors with homemade "bus bars" to connect them across the phase legs as needed, and the larger box will house the controllers and other components. I've installed V & A meters in the box cover to monitor the phases.

Will get there . . . eventually!


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I'm so confused iuf vfd high start run stop can't I just plug and go. Nope hopefully I'll be building mine by spring . Geezs I hate being down , I know it'll take months getting back too. Spine operations take recovery time xs 2 + longer. Hey 7T welcome to the site.
 
I don't get it. Why go to the expense and effort building and installing a rotary phase converter when a Variable Frequency Drive can be bought off the shelf that provides speed control, forward reverse control, and typically motor protection? Even the foreign ones with bad instructions work great after reading the instructions 30 or more times.
 
Because it gives you flexibility to buy more 3-phase tools (we all need more tools...), and it's more economical when (like me) you have machines with multiple 3-phase motors - in my case a mill with a 3HP spindle motor, 1HP feeds/rapids motor and 1/4HP coolant pump, plus electromagnetic clutch and brake that would need a new (large) transformer to operate them?

I'd need three VFDs (one variable, the other two fixed frequency), would have to go through converting all the switchgear (there's a lot of it!) converting it to operate the VFDs - more or less a complete rewire, and I know just how long converting my lathe (415v-only, 3-speed motor plus suds pump) took me...

Dave H. (the other one)
 
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Now I understand. Next, when building a RPC, do you have to build it for the maximum HP used? So if the caps are selected for the 3HP, it will still run a 1/4 HP?
 
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