Well then I will put the stake in the heart and
post the photo of the flat-out ugliest rotary
converter ever assembled:
And I will also copy the text file about it
Here's a snapshot of my phase converter setup. It's made from a 5 hp
motor that I got for free, mounted on a wooden platform. There's a
1/4 hp repulsion-induction start motor mounted on another hinged platform
with the belt tension set by the motor. The idler motor is powered
thru a fused knife switch which is fed from a 240 volt, 15 amp breaker.
The converter runs my milling machine and lathe, each of which have
about 1 hp motors in them. There are no power factor correction capacitors,
no balancing capacitors, and no starting capacitors. It's manual
start, by powering the kicker motor which is plugged into a switched
outlet just ouside the view of the picture. Once the idler comes up
to speed the knife switch applies the excitation. Then the kicker is
switched off. Lifting up the hinged platform allows the belt to fly
This converter draws about 12 amps or so of reactive current when it
is just idling, but that does not spin the electric meter. This setup
is sort of stone-age because there are no bells or whistles at all, but
it was built for free and it has been running my machines for about 10
years now. The only fancy bit is that the wooden framework is resting
on some large rubber stoppers to provide vibration isolation. It's pretty
quiet while running.
This is just to show that any dope can make
a rotary conveter and run machines with it.
The bad part of it of course is there's no
drop-out contactor which means it cannot be left
running unattended, and it is quiet enough that
one can forget it's running.
It only draws about 250 watts of power when
idling as measured with my handy-dandy fluke
OK, now for somebody else to put some photos
of *real* converters here!
I have been soaking up all the knowledge that everyone here has so freely given.
Over the past 4/5 months I have been noting all the good, bad and ugly ways of doing an RPC. Here is my attempt at rolling all the good things into one design. I can not take credit for all the details and designs, just tried to put them all together.
While I am not done with it yet, here is a link to a quick and dirty webpage where I have posted what diagrams and notes that I have come up with.
It is a work in progress, both the website and the RPC. I have not built it yet, have most of the parts.
Am looking forward to what everyone thinks.....
Good or Bad
Here is my contribution to the cause. I'll just
move it up from a previous posting.
First is a picture of the finished RPC.
Motor and base actually came from an abandend
Commercial Air Conditioning unit, the motor
was new, so I took it. Recyclers only charged
me $20.00 bucks for it. For $5.00 more they let
me take all the caps and relays I could carry.
The case was a Junction box the recyclers sold
me for another $5.00. With a few odds and ends
the total cost was under $60 dollars.
These are the schematics that I used. They're
based upon an original set of schematics of a
friend of mine, with my modifications.
ie: letting the L3 Voltage rise, determine when
to cut-out the start capacitor.
That is a nice looking RPC.
I hope that when I get done with mine it looks as good.
Thanks. And it works great too. According to
Steve, it's been running great for the past
3 1/2 years. He bought it from me for his shop,
he's into custom Roll Cages. Mine has been
running for almost 5 years now, and has given
me great service.
do you wax all your stuff? It's always so neat, clean and proffesional looking,
good for you.
Dang it Jim,
I started the above post to ask why all those pulley flanges aren't filled with belts and just plain got dazzled with Jamies work.
Jim, like I've said before, your system appears to be simple, perfectly functional, devoid of ugliness and close to my definition of perfect.
I noticed the craftily placed, vertical pieces of plywood to restrain an errant belt, either way. [img]smile.gif[/img]
No, I don't polish, just like to keep things
clean. And just to show you the first one I made,
and it's quite the " eye sore ". But like I said,
it runs great and has served the purpose for
almost 5 years.
p.s. Thanks for the complements.
Sorry Don, been busy with day to day stuff. Aye carumba, here goes, lol.
Two DES rotary phase converters looking for a new home. They are both 220 Volts, the smaller has a 15 HP motor while the larger a 20 HP. They were used together to power our wire EDM for one year, but have not been needed since we moved a few months ago.
We are looking for $400 for the 15HP and $500 for the 20HP. Please keep in mind that the small one weighs 185-lbs and the large one maxed out the 250-lb scale. Glad to answer questions
Here are some construction examples - how things can fit together in surplus electrical cabinets.
These are all close variations of the r.c.m. / Hanrahan / Carlson / Fitch circuits. All 3 use 6X560 potential relays from Grainger, and are balanced RPC's using start capacitors sized to the idler at about 70uF/HP, and run capacitors sized at about 15uF/HP.
The first is a 5hp rotary converter I built in ~1996, started with a remote knife switch not in the photo. This used to hang outside the shop under a wide roof overhang. It is built in a 10x10x4 j-box which is bolted to the motor case in place of the original motor j-box.
Now it is a "portable", sits on the floor with a knife switch and 3 twist-lock receptacles bolted to the "wall" side of the frame.
The second is a 10hp I built in 2000 for a friend, also started w/ remote knife switch on the wall next to it. The idler sits on the floor under it. The large run capacitors are 92uF, surplus from some kind of discharge lighting gear. This is in an 8x12x16 type 12R cabinet. This one uses a split-primary transformer to derive a neutral reference for the potential relay, since he only ran an 8/2 from the panel, and I didn't want to use ground as neutral. There is no connection to the transformer secondary. The contactor is slaved to the potential relay.
The 3rd is a 7.5hp, helped a friend build, has front panel start/stop switches w/ internal contactor. This one uses a split-primary 240:24V transformer, with the split primary providing the neutral reference and the secondary powering the contactor coils. The large contactor is the start/stop controlling power to the whole RPC. The smaller contactor above the potential relay switches the start capacitors.
Nice work. I love seeing neat wiring.
What type of camera did you use to take
the pics? I can never get good pictures like
That last one was real sweet, I like the way
you provided the extra loop on the leads going
to the front panel.
However what happens when you close the cabinet
door, isn't it a bit rough on the incoming and
Seriously though that's some nice construction.
I found two pictures of the Inside Layout of the
RPC I first posted in this thread. I'm providing
them to show how I put it all together. I couldn't
Edit my original post, so I am placing them here.
I'm not very good, at taking pictures, these were
done using a film type camera.
I also wanted to mention that I keep the caps
inplace, by using Velcro tape on the bottom of
the panel, and the underside of the caps.
I see pics of rpc all together as one unit and neatly wired and wonder why mine looks so messy..
I put the start and L3-L2 run caps in the control box on the wall and the transformer and L1-L2 caps are in another box and the motor is floating around on a base of plasterzoate. This is the wall box, it was a fire alarm box I was given. It's a 420v 7.5 hp converter. with something like 200uf starting, 65uf L3-L2 and 35uf L1-L2. It's been in continous use since 2002 and I am very happy with it. I built it along the lines mentioned everywhere, except I have transformed the voltage to 420 volts before the converter. I couldn't find voltage relays so had to use resistor, capacitor and rectifier to do the job. The terminal block on the left side of the picture has the cap, resitor and rectifier in it, seems to work OK..
Folks thanks for the nice comments.
The camera was a Nikon Coolpix 900, "only" 1280x1024 but really good optics. Unfortunately it died, cost $250 to repair, died again. Then I bought a cheap Minolta with 3X more pixels but I hate it, the Nikon pics were better.
can't help with your film camera-to-digital degradation but in the thread "Building an RPC", all my digital photos are worse than yours, except the last shot of the guts of my panel. Magic solution? I used a clamp light to illuminate the box, reducing "shutter time" to freeze the photo, DUH! Have taken thousands of "good" daylight photos on my construction sites.
Obviously you are using a good light source as evidenced by sharp shadow contrast.
Digital cameras have gotten really cheap, my 3.1megapixle Fugi was less than $100, (on sale) a couple of years ago, but I've proven, AND demonstrated to all that the puny flash is worthless. :rolleyes: Old guy shake ain't helpin' either.
Just realized that your photos are probably scanned archival print's and that you probably know more about digital photogragphy than I. Doesn't everyone?
Slow study Bob, but I'm a whizz on abacus.
I am affiliated with this design.
If the hand-drawn details are a little fuzzy, go over to
and scroll down to files beginning with "phase". Right click, save the file to your hard drive, then open and "Insert Picture" into Microsoft Word or Powerpoint for a full-sized image that will fill an 8-1/2 x 11 printed page and hopefully be legible.
The designs aren't there to impress anyone, it's just a confidence builder that anyone with a little craftsman in them can do this...the principles aren't super hard or mysterious.
The info is a little dated, construction was in year 2002. The design uses a timing relay for auto-start whereas many others have used a potential relay for the same function. I have no balancing, the voltages are within 10% and has functioned with near daily use until (and hopefully beyond!) 2006 with zero problems.
I would also like to go back on the statement I made at the time of the article about the pony-motor-started RPCs. I've conversed with many people over the years, and any RPC 10hp or more electrically started is an ideal candidate for a pony motor, because it reduces the large ampacity one must account for with electrical "inrush" starting from a dead-stop. ALso this would remove the need for starting capacitors (a fair bank of them for a large RPC). I would simply direct-couple the large 3phase motor to a small single-phase motor of roughly 1/2hp. Run the small motor for a time period enough to attain full speed, then switch the 220v power to the 3phase motor, switch off the single phase motor if desired or simply let it run.
I may eventually undertake this direct-coupled design, for now it's just a recommendation.
You may wish to consider a belted design, which I first introduced Here, and the schematic of which is reproduced below.
This was built for my Deckel FP1, which has a 380V consequent pole two speed motor
I built it inside a spare Deckel/Seimens controll cabinet. Air flow for the motor is drawn through a filter on the lower left side and through a 4" hole in the floor, air exits an the upper right.
The 100uF start cap drops out on a timer set a 250 milliseconds.
Voltage across the lines is 380V/380V/381V when idle and I have added correction caps inside the main controll box for each of the two speeds and the motor for the high speed head.
The unit also provides neutrtal for the 220V controll curcuits for the main controll box