Hello everybody. This thread will serve as a "build log" I suppose. I'm working toward having a 3ph 480V 25A service in my shop. My progress up to now is that I have 3ph 480V with enough current to satisfy a single 3hp VFD and motor that I'm currently working with.
A bit of background... I'm an industrial Automation/Controls guy. I design & build control panels for industrial machinery, and I like to play around with CNC machines in my spare time. I'm newly self-employed and scrambling to obtain all the resources that I am accustomed to having at previous employers. I'm accustomed to working with 3ph motors exclusively, in facilities with 3ph service. Single phase motors rarely come up in my line of work, so start caps, run caps, split phase, all these terms are a bit nebulous to me, but I'm learning (quickly). The inner workings of the Rotary Phase Converter were/are a total enigma to me, so rather than trying to build one, under the time crunch that I find myself in right now, I decided to buy one. I'm currently designing a large panel for a conveyor line that will have (12) 3HP VFDs in it. The first application for this 480V setup will be to power up and perform FAT on that panel once it is built. Thereafter, it will serve whatever purpose I find for it, most likely refurbishing CNCs and more panel builds.
Anyways, on to the good stuff... I found a used
American Rotary ADX30 ($2,738 as configured, new) for sale on Craigslist. The asking price was $1,200. I went to look at it, and it was a strange setting. An Italian cougar driving new Mercedes Benz was selling it out of a storage building in a swanky area of Midtown Houston. She said she used to own an artisan pasta shop, and she had it installed to power a pasta dryer. I looked at the pasta dryer (which she was also selling) and the RPC was total overkill for the application, so I assume it's never been anywhere near its FLA. I offered $800 and after negotiations I took it for $950. It only saw 1yr of service and is in pristine condition. I aggravated my hernia loading the 382lb beast by myself, so any savings on the used unit are probably negated by what I'll have to pay to go down to Mexico for surgery (no medical insurance).
The 30kVA 3ph transformer I'm using was also a Craigslist find (
GE 9T23B3872, $3,272 new). The guy was only asking $270 so I didn't even try to haggle. This is actually a 480>208Y120 transformer, not a 480>240 transformer, but some quick math on-site led me to believe that it would work regardless (because of a wide selection of primary taps), and that proved to be true in practice.
I plan to set this up on a portable skid with a control panel of my own design, including failsafe controls and volt/amp displays. I will post the details of all that once I've built it and have documented it. For now it's just sitting on a cart in my garage office, haphazardly wired together with a bunch of undersized SO-cord.
Below is a video of the beast in action. The purpose of the video, is I was trying to come up with a ratio of single phase input amps to 3-phase output amps, so that I will know what size my breakers and wires need to be. American Rotary provides this information in several places, but the information is inconsistent and/or unclear. Here's what I mean:
- The dataplate on my ADX30 control box says 76A FLA @ 230V, and then further down it says "rated single phase amps = 3ph FLA * 1.6" which works out to 122A
- This video by American Rotary states "single phase amps = 3ph amps * 1.6 * 1.2" which works out to 146A
- The last page of the datasheet says "3ph load amps * 1.5" which works out to 114A
- The 4th page of the datasheet says "Max Total HP(Amps) for optimal performace: 30(84)" and does not specify whether they mean single phase or 3 phase, but which matches neither the 3ph nor the single phase rating on my dataplate. The same chart recommends 1AWG for single phase supply, which per NEC is good for 110A, 130A, or 150A, depending on wire type, which they don't specify.
- None of the values they provide adhere to my understanding of the conversion factor between single phase and 3 phase power, which is 1.73 (sqrt 3). If I use my own math it looks like this:
- rated 3ph FLA: 76A*240V*1.73= 31.56kW (42HP!, not 30HP!)......31.56kW/240V = 131A single phase amps
- or this:
- rated HP: 30 (22kW) / 240V = 91A single phase.... but on the 3ph side... 22kW / 1.73 / 240V = 53A
So I'm left wondering, have they de-rated the idler motor? Is this actually a 42HP motor that they're calling a 30HP motor, because 30HP more accurately describes what power you can get out of it as a generator? Or is this an honest-to-goodness 30HP motor that they're making all kind of wild claims about it's capabilities? Or am I under-estimating the extent to which power factor skews these numbers? I've selected a 125A breaker but maybe I need to shoot for worst case (2nd bullet above) and go with a 150A breaker.
Anyway, here's my video:
Feel free to chime in with any suggestions or clarification on the ratings.
P.S. Just turning this beast on causes brown-outs at all my neighbors which are on the same pole transformer. I'm going to move this to my new shop on the lot next door which is on a different transformer.
