I need some help to get this done!
I'm sad to say that I got a Bridgeport over a year ago and still cannot run it. I'm very mechanically inclined and pretty good with electricity. I troubleshoot commercial 3PH AC units often.
I gathered an enclosure, a 5HP 3 phase 230V motor, contactors, fuses, relays and other parts.
I've read through allot of posts and such but I feel like I'm overloaded because EVERYONE seems to do this differently. Which by the way, is the beauty and simplicity of the rotary converter.
I'd like to run my BP mill and someday a SB lathe (Heavy 10) but never both at the same time.
I need help with a good wiring diagram and also need to know what potential relay I need to run and what it is taking out of the circuit, it's function and why it needs to be in the converter.
I'll apologize in advance, I'm a member of numerous forums and Newbies always want their hand held instead of using the search feature. But, as I said, I seem to be getting overloaded by so many design differences.
I'm great with building one of these, I just need to understand them and get a wiring diagram within my head that makes complete sense to me. Merely copying someone else's stuff and treating it like the old Radio Shack kits which told us to connect a wire from A to B isn't what I want. I want to understand it, build it and enjoy it!!
It just seems to me that your taking the EMF from the 3rd leg of the idle motor to somehow create a phantom 3 phase?? But a potential relay has to remove something at 75% of run speed?
I just feel like such a hypocrite because I should have this done by now.
If you guys could help me out at all or simplify this a bit so I can better understand the complexity of it, I'd be very grateful.
I lost my job 9 weeks ago and I have the time to do this and want to get-r-done.
Thank you for reading!!
EDIT - It's been so long since I thought about this, that I forgot to mention the capacitors? I'm unsure how to size them correctly in terms of microfarad's and what there function is within the circuit. Maybe thats what the potential relay takes out after the idler gets up to run speed??
Sorry but I don't have a wiring diagram. I started drawing one but got my RPC running and dropped the schematic idea.
A couple of things I used that many don't but some do:
No PR on mine. I just use a momentary, spring loaded, N.O. push button to start mine.
This pulls in the 230vac coil on my start capacitor relay-just like a PR does but w/o the added circuitry. In doing this method one has to be quick to release the button or the start caps, which are generally the less expensive electrolytic type, don't fry. I used surplus oil filled for my 10hp start caps so the start current through these is much less of an issue. I used 850mfd 440vac rated start caps and it takes maybe 1/2 second to get the motor to full speed.
I used contactors-w-230vac coil that also have aux "dry" contacts that I use to pull in and hold the run contactor/capcitors. I like the idea of making/breaking both legs of a 230vac input although switching one leg works for energizing/de-energizing the coils. I used a 2-pole breaker where the feed comes into the cabinet but this could be considered overkill since the circuit is protected at my main panel.
i used it mainly as an on/off switch as I was tuning/balancing the legs which took me a very long time because as I was using the Fitch method I was assuming it would take a lot more run capacitor value than it did. I ended up-w-only two (maybe 3?) run caps after intitially trying a configuration similar to the one in the Fitch design. I got lucky I suppose and the RPC is balanced within 3-5 volts leg to leg and the current is way below the recommended safe limit. Maybe it has something to do-w-the quality or design of the motor used for the RPC?
On the front panel of mine (I posted pics here-you can look under my user name) all I have is a light for when it is plugged in, another for when it is running, a start button and a stop button. No gauges or meter but if I had them on hand I'd have used them.
I am sure you know-w- a 5hp you could easily run both the Bridgeport and the heavy 10 at the same time. Just use you feet for one and your hands for the other- the RPC will handle the 2 machines from a current standpoint.
PM me if this is not clear or if there is trouble-w-the pics.
Single Live RPC
Hello Gents, this is the 5HP single live RPC i built adapted from the Fitch design, to which it is identical save for a neutral replacing L2 & indicator light moved, so this is applicable to anyone in europe,aus or africa with single live & neutral..
The voltages with 3Hp load are 231,227,224 and could be better tuned but im tired of fannying about... Line current on L1 to neutral is 8.5amps without load and this seems to be the lowest i can achieve with the 5HP idler. Hope this is helpful to someone!
I've searched thru all the posts I can find, but still didn't come across an answer. How do you size an idler motor to run a 3ph welder? It's a Lincoln R3R-400 DC. It draws a max of 75 amps at full load, but I can likley get away with less. (I don't weld much at 400 amps!)
I also have a 5hp tablesaw, 1 hp horizontal mill and 1-1/2 hp verticle mill. Can I start these as well as the idler to allow a smaller idler?
What happens when the idler is overloaded? If it's heat, would a cooling system help? If it bogs down on arc strike, could a flywheel help?
I have a quick question for Jim Rozen. I have a similar setup but use a drill to bring the idler up to speed before bringing in power. Do you leave the 1/4 hp motor running after you start the idler?
First off, that's a 1/8 hp motor that spins things up. That's how little power
After the idler is up and running, the platform holding the pony motor is lifted
up, and the belt flips off the pulleys. I tuck the belt under the hinged platform
to keep down the rattle, and the power for the pony motor is disconnected.
I built a RPC to run my 16" South Bend and Bridgeport with a borrowed 3 horse 3 phase motor. Lots of power to run both at the same time but I don't like to use borrowed stuff since if it goes south I feel responsible for it and I can't replace it right now. Searching around at the local scrap yard I found several 10 HP 3 phase motors for 15$ each. I bought 3 and brought them home to find all work fine but probably need bearings in 2,still a great deal.
I replaced the3 HP with one of the 10's and found the 270/325 cap was too small to fire it fast enough . I decided to add another cap of the same size to get the mf up to the 50/100 per HP recommended here so it wouldn't drag on the electrical system. The problem I had with this was, I didn't know how to connect the caps, series or paralell. I looked all over this site and couldn't find any advice or just overlooked it but finally found it somewhere and hooked them paralell and was tickled at how fast the motor started. I am now in business with a 10HP RPC of my own.
I think if anyone posts how to build a RPC which takes more than one cap they would be well served to explain how this is done so that electrical amatures like me don't have to search everywhere for the info. I know every item is not listed every time because of redundancy but, something like this would be a big help.
The next thing is I have a 25HP motor and if I want to start it how many 270/325 mf caps do I need to start it? I figure it would take 4 in paralell to start it without a pony motor. We got it running but it took the 2 caps in my system and a pony to get it running.
I really appreciate all the info here and the helpful people that frequent it and thank everyone who replies .
Two 100uf caps in series = 50uf
Two 100uf cap in parallel = 200uf
Exact opposite of resistors.
Hope that helps.....
My 5HP RPC specs:
Low voltage magnetic start and stop with indicator lamps mounted on hinged door.
7.5 HP Furnas contactor with inductive pickup overload block with phase loss detection.
Front panel contactor reset switch.
Wall mounted enclosure (12"wide x 15"high x 6"deep).
Phase voltage balanced to within 1volt of each other with lathe at 1000rpm
Example measurement - 247v-248v-247v.
i suppose you speak many languages congratulations or are you making fun of this man?
Originally Posted by sleek
Will RPC run on single live and neutral supply?
I'm planning to build a 2-HP RPC (already got all the parts). The only problem I'm having is that I only have single live and neutral supply from the mains (meaning the three wires from the mains are ground, neutral and live - basic single phase supply).
Question: Will the my RPC run if I use the neutral as the second hot leg, L2, and the live as the first hot leg, L1? Or should I make any changes to the designs given on this website?
Any input will be appreciated. Thanks in advance.
I think I understand how to build a simple rotary converter but I do have a problem which I hope one of the experts from the UK might be able to advise on.
Living in Australia our single phase supply is 50 hertz 240v whilst 3 phase is normally 50 hertz 415 v similar to the UK.
Sould I use a transformer before the idler motor to up the voltage and if so to what voltage or should I rewire both the idler motor and the 3 phase driven tool motor to accept 220v.
Am I right that most 3 phase motors can be wired up for 220 or 440 or is it different with motors designed for the UK/Australian 415 3 phase supply.
Need some information on building a 10hp RPC.
When you are building the RPC and you are using a contactor do you size the contactor for the 110 volt single phase amp or do you size it with 220 volt 3 phase amp?
What is the best part to use for the N.O contact for the starting caps? I was thinking of adding a extra set of N.O contacts on my start button and the wire thru it, but I not sure if there it would be to many amps and it will burn out the contacts.
Last question what is the best size wire to use for the starting caps # 8 the same as you use to feed the contactor with or do you use the same size you feed the ilder motor with?
Notice that underneath the contactor is the overload block. It has inductive pickups
Originally Posted by rons
which actually provide power to a integrated circuit that monitors the phase lines
and detects when a phase loss occurs.
Last edited by rons; 11-20-2009 at 07:21 PM.
Hi guys.... long time lurker first time poster love the site. I am now officialy 3 PHASED. My machines run 575v so first I had to find a transformer, wire it backwards ( step up 230v to 575v ) some switches some wire ( just the easy jim rozen method) 7.5 horse switcher motor, 1/2 115v kicker motor, bought it all at a Mennonite auction. Sawdust today, chips tomorrow, swarf on Sun. Thanx Trevor
Just Finished RPC
Just got done with my RPC. Wiring is still sloppy from testing but I can clean that up later. The idler motor is 12 lead 15hp wired in Wye configuration producing 4 wire 3 phase (3 hot+neutral). What do ya think? Am I lucky to still be alive, or should this work out well for me. I do plan on securing my bus bars as well as putting the half PVC under the neutral bus.
Other note when I start my air compressor (AVSRSB Gardner Denver 10hp) I have to hit the start button on the RPC to get it up to speed. Any suggested fixes to this halfassery.
looking for good rpc overview
Please forgive me if I am posting this in the wrong thread, I am very new here.
I'm a woodworker looking to build an RPC to power a dust collector (5hp) and boring machine (1hp). I recently picked up, for free, a number of 3ph motors rated at 12, 10, 7.5 and 1 hp. I also have a number of 1/4-3/4 1ph motors lying around. So I am thinking that this project shouldn't cost me much money...
I have some limited basic electrical experience, but will be relying mostly on my brother who is an EE.
Anyway, I'm looking for a good discussion of how these things work. I've looked at some of the available plans, but I'm not really getting the big picture, and I'd like to understand that before I start making decisions and buying things.
Any advice appreciated.
Jim Rozen gets full credit for this pony start RPC. The 1 hp pony was a take off from my Burr King, while the 10 hp idler was purchased for $50 from Joe's Junk Jungle. The pony sits on a pair of strap hinges that allow tilting it back to tension the belt to the idler. Even though I have a number of VFD's in the shop, this RPC was built to power a gear head lathe without a clutch. The lathe motor is 3 hp, so the 10 hp idler is probably larger than necessary, but I won't have to build it twice
There are no power factor correction capacitors,
no balancing capacitors, and no starting capacitors.
The pony drives an adjustable pitch sheave, so I was able to fine tune the idler rpm. The "ideal" (no load) idler rpm is 1793, and I ended up at 1812 rpm (according to my strobe tach). The frame is 1" square tube and 1.5" angle, butt welded.
Help me understand
The "ideal RPM". .... The 10 hp RPC pulls it's self up to speed once it gets a kick, what is the significance of "ideal or "non-ideal"?
04-09-2010, 05:41 AM
You're correct, the idler will come up to speed even if it gets nothing more than a pull from a rope wound around the shaft. The problem with that is the large inrush surge needed to bring the heavy rotor up to no load speed. My guess is that the surge would be over 200 amps for a second or two.
RPC pulls it's self up to speed once it gets a kick, what is the significance of "ideal or "non-ideal"?
By bringing the idler to full no load speed ("ideal rpm") there's almost no inrush. My Amprobe analog clamp meter shows a very brief bump up to 30 amps when power is applied to the idler, and the the current immediately drops down to about 10 amps. Even with all the shop lights on, there is no dimming when the idler comes on line.
Added a few photos.