Alright! I scored a 10 hp 3 phase motor from the scrap yard today (bought it for $69). Brand new in the cling wrap. Spins nice and smooth, and it has the capacitor on it and everything. Since I see these motors frequently the junk yard I think making a rotary phase converter makes economic sense. Has anyone made a rotary phase converter before? Any advice on where to begin? These are the specs.
If I got one of these panels to run the entire thing that might work nicely. But it seems a tad pricey st 500 bucks wtf... I know there are other ways to set up a rotary 3 phase system with my own wiring but is it worth it? Any benefit to rotary 3 phase compared to vfds?
About 12 years or so ago I made my own RPC from a 7.5 HP motor and a couple switches and caps. There are plenty of plans online. It probably took a couple days of fiddling with an enclosure for the switches and caps plus making a decent plywood cabinet to hold the motor and enclosure. Sure did not cost 500 bucks for parts. This guy sounds like he knows his stuff: One advantage of an RPC is it can run several motors simultaneously. But it’s frequency is fixed at line frequency. Mine has functioned fine for my Harig surface grinder and Monarch EE tool room lathe ever since and is used nearly daily. Denis
I was reading that unless the three legs are balanced electronically as the load changes there can be over heating issues. Not sure how true that is or if I even need to worry about it. I like the idea of multiple tools running though not sure that I'm that skilled to use 3 tools at the same time... haha
It’s been quite a while since I did mine, but the balancing I think is important in theory but difficult to achieve in practice as it is load dependent. I spent some time fiddling around with large caps to try to get balance. But then I read it was really not a practical issue. So, I forgot about it. No problems and I know I am not balanced and we are talking maybe 20% IIRC. You should double check this as it’s been many years. But that what I think I remember. Denis This was rattling around in my head, so, I did a quick search: http://chaski.org/homemachinist/viewtopic.php?t=89204
Hmm. Controversial indeed. That thread brings up interesting points. I imagine for sensitive machines/computer parts it probably makes a big difference. Maybe not for running motors. Still might be worth buying one premade. I basically have nearly everything I need. I want to put up a bigger sub breaker in the garage and wire in more 50 and 60 amp power outlets. That way I don't have to share plugs between machines. My current sub breaker is full. Do I need to run my cable inside that grey plastic tubing and attach it to the wall with brackets to be considered code? I want to run a thick cable up near where the wall meets the roof inside my garage and run it to the other side of the garage. I could probably set it up so that I have a 50 or 60 amp plug near the sub breaker then run the cable I found at the scrap yard to the lathe area and attach my rotary phase converter on that side next to the machinery. That way I can always unplug the long cable from the 60 amp wall plug if I ever want to. So the cable isn't permanently inside the wall. Anyway here is a pic of the motor in the wrapping. A little scuffed up from sitting next to the muddy scrap metal pile for a few days outside but nothing a little scrubbing won't fix.
Kick ass even better. They replied to my question. $328 for the phase converter. Thats even more affordable! 15 amps is nothing to scoff at! I could run a big ass machine off that kind of power. Or several smaller ones. Only using 30 amps two phase to boot. Now, can I wire up several 3 phase sockets to the line coming out of the 3 phase converter? Like a power strip kind of setup. That way I wouldn't need to unplug and plug each machine into the bank when I want to use it.
Does the pre-made one promise to balance your legs? I don’t see how. So convenience is the factor probably not quality. Do follow code You can run several machines simultaneously. It is not unusual for me to have my lathe running while also running my surface grinder both connected to the same circuit. No plugging and unplugging. Denis
This is the link https://www.northamericaphaseconverters.com/product/rotary-phase-converter-control-panel-cp-10/ These are the things it does. Is it missing something?
Seems to balance voltage within 2 to 5% by switching between a bank of caps digitally as load changes.
zap, Code says that any wiring mounted outside of a wall needs to be in a conduit (or armored) It can be the grey flexible "liquid tight" style or NMC (non metallic conduit) or metal conduit. The point it to protect you from accidently cutting into the cables and causing a fire or electrocution. Be careful pulling romex (multiple wires in a shared external jacket) is a no no in conduit in some places. others require it be in a much larger conduit (has to do with cooling ) pulling thhn through conduit is much much easier and the way I would recommend using it with conduit.
I would think you would want and need some protection down stream of the RPC like a sub panel with breaker(s). Here's my set up. My wire is run in the wall with wall receptacles at various locations because I did it 8 years ago when I built my shop, but could be run in conduit just the same. Best, Kelly
Damn thats nice work. So neat. Alright thats not a problem to run the cable inside some conduit. I'll buy some plastic electrical conduit from lowes and mount it. In terms of placing the motor and panel. I see you have yours right next to the breakers. If I were to place a 50 or 60 amp plug right under the incoming power panel then plug the cable into it and run it all the way 40 feet to the lathe and mill area then connect the rotary phase converter at that point. That should work too right? I see you have yours mounted up on the wall next to the panels. I doubt I can lift the motor up that high due to the weight.
WIth respect to where the RPC motor is located, it does not matter. Mine is halfway between my power panel and the lathe and grinder. It can be next to the lathe or next to the power panel. What does matter is that you protect the wires by using conduit or placing it in the wall behind drywall and size the wiring correctly for the amperage and distance you are running. Make certain you connections are absolutely secure---screws torqued down properly and ground wiring done without compromise. Screw connections that are sloppy can result in arcing and heating. There are many tables on this. An electrician should be able to advise you easily and accurately. I think there are folks on this board who likely can give credible answers as well. Denis
