Building a Rotary Phase Converter: Part 2 Assembly, Balancing and Final Testing

The second of 2 parts covering the entire process of building a rotary phase converter. Components assembly, guided tour of components' interaction, capacitor
balancing, and final testing.
The plans referred to in the video can be found here:
www.homemadetools.net/forum/h...

[@michaelmurray3422]

Very nice presentation. You have been the only one I've seen run and test their work . Good job.

[@marcfournier823]

This series was the best rpc tutorial so far. Great job!

[@ederortega1901]

Hey that was just perfect what I’ve been looking for how do 3 phase current works since I’m fairly new at this topic, and trying to figure out my self since the “electrician” that I hired for installation, took the money and left me with a Phoenix rotary phase converter not running and can’t really afford paying anyone else, so thanks for this awesome explanation on how it works…👍

[@user-uk9ux5ku1r]

Very thorough pair of videos. Thank you for the detailed explanation. I would add that building one of these NOT a good idea as a DIY unless they have experience working with 240 VAC line voltage equipment. There are also compelling reasons to buy a commercial unit which I'll get to. A few key observations from an engineering safety point of view. 1) Where are your ground/earth connections? Grounding is the most important safety requirement of all yet you never discuss it. 1a) The earth ground from the 4 wire 220v plug should be bonded to the metal box holding the electronics, and also extended and bonded to the case of the motor. Be sure to scrape off any paint and use a star washer under a properly sized ring connector to bite into clean bare metal. Wiring to shop equipment should also carry a ground wire that is separately bonded to the control box, the metal chassis and parts of the tool, and the case of the motor separately. Every part of the equipment should be checked to be sure it's grounded. If an electrical fault develops, you don't want to be the path it takes to ground. 1b) Grounding should be checked for your single phase 220v and 110v equipment too. 1c) Modern AC powered portable equipment is likely double insulated. The External chassis of double insulated equipment is isolated and should not be grounded. 1d) f it's UL rated you needn't worry unless the equipment's electrical components have been modified. 2) Power fail shutoff that prevents restart is the ONLY safe way to operate this converter. This is true for every machine tool in your shop. This is really easily implemented by using a magnetic power switch, a common safety device on all Modern machines. That pull on Push off Red mushroom switch you used needs to get tossed. The magnetic power switch works by using a momentary On button that momentarily applies power to an internal electromagnet. The magnet in turn pulls closed a commentator which energizes the equipment. The electromagnet is powered from the equipment side of the commentator so stays energized until one of two things happen. If the stop switch is hit, it opens the connection to the electromagnet which in turn releases the commentator. 2nd, if power fails the electromagnet releases and the commentatorn opens. When power is restored the power stays off until the start button is pressed again. If you have machines that don't have this type of switch, i suggest you add one in a box ahead of the power connection to the machine. No, you don't want to depend on remembering to find and turn off the power switch to a lathe or any other equipment if the power fails. Last thing you want to do is be fumbling around in what will likely be in the dark while a mill or lathe chuck is spinning down. If the power goes out, stand still until all moving parts stop moving. 3) If ever there is a case to be for battery based emergency power fail lighting it's in a shop full of dangerous machines and sharp tools. That's an idea for another video. 4) Your wiring.. commentators, or any other piece with a screw down or pressure fit connection should only have a single wire within rated gauge and type for that device. With multiple wires going into those connectors it's a fire waiting to happen. You mentioned needing to upgrade to 4 guage wire. That's going to require a larger box and covered buss bars to make the multiple connections. Parallel connected Capacitors should each be connected to the appropriate buss bar and not daisy chained. Daisy chains have additive resistance and additive current flow. Not a good thing. Wires carrying high current should not be bent in sharp turns. 5) Layout - all connections are best coming out the bottom of the box to prevent moisture from entering. Use appropriate grommets and strain relief to prevents stress on connections or chaffed wires. 6) Since this is portable how are you planning on connecting shop machines? Last, you need to discuss up front the ramifications of building a DIY solution like this. IF anything bad were to happen at anytime in the future, having an unrated device like this in use will likely void any insurance policy you have. The burden of proof that this device and any equipment connected to it played not even a contributory role in what occurred is entirely on you. Is it a risk worth taking? That's the 1st question I ask myself. So, I hope the detailed analysis hits a few new notes not covered already. I truely mean them in a positive way. I appreciate very much your covering the subject. I'm not sure I'd need such a large RPC unless it was a shop that had 3 or 4 people working in it. 20 HP? 5 or more machines at the same time? The idle power usage is over 4A per leg.. about 1 Kw just for the RPC !! If you have that big a shop why not talk to the power company about providing a 3 phase drop? You'll need an isolation transformer. Probably about the size of your RPC and control box combined. Maybe you can find one where you found that huge motor. Where do you find such things for free? I've just aquired an antique Diamond M26 horizontal mill and a Craftsman 15 1/2 " Commercial drill press. Both in amazing shape. The drill press is 110v single phase. It's getting a new power cord and magnetic switch in a box. I want to preserve the original switch and function for restoration purposes. Easy. The mill is going to need retrofit too. Much more to think about there. Zero documentation and parts are made of unobtainium. First is getting it home. Disassembly required!!!!! Fortunately NO RUST. Also no manual and I'm not a machinist. Maybe we can trade advice! I restore antique clocks. I need to make parts.. so .. 😂😂😂 I'm used to no documentation. Lots of pictures. Keep the small parts sorted. Write stuff you see down before taking it apart. Penny for your thoughts on the M26. Start Disassembly tomorrow

[@TheBuildist]

Excellent and thoughtful post. Thanks for sharing. You're right to point out the importance of grounding and bonding, from the panel all the way through to the equipment case. In the future I'd set it up not to auto restart as you suggest. I still disagree, but I'm apparently arguing against the entire planet, so I yield. But my single phase 110v auto restarts after power outage. And my single phase 240v auto restarts after power outage. Why shouldn't my 240v three phase auto restart after power outage? But, as I say, EVERYONE says I'm wrong about it, so I give up! 😁

[@user-uk9ux5ku1r]

@@TheBuildist The vintage machines will come back on. That doesn't mean that it's safe that they do. Some thing simply weren't considered or didn't have good, inexpensive solutions that are available today. Putting a single magnetic switch on your RPC will protect all the downstream three phase machines that it feeds. If you've got a sub panel providing power to your shop, you could add magnetic switchs near the sub panel to power fail protect all the single phase 220 and 110 outlets as well. Leverage the cost and effort to improve shop safety. That's a video worth making. Lighting should be on a different breaker. It's the one thing you WANT to come back on. For a shop full of vintage machines that's a huge safety gain at very little cost. Grounding safety. It's why you should also have GFI protection on all your shop power circuits. And yes, I know that older houses may not have GFI on their kitchen, bathroom and outside power outlets. It doesn't mean that it's not a VERY good idea to do this type of inexpensive code upgrade. Keep it safe !! Thanks again sharing your knowledge! It's a lot of effort to make videos

[@mikeanderson1139]

the sky is falling

[@andyfinck6652]

Very very informative

[@philliparm]

Nice work, well explained and demonstrated

[@GioProjects]

By far the best tutorial I ever seen..

[@978sdcox]

Really enjoy your videos. I hope to get a bridgeport this summer. Your video gave me a real understanding of rotary phase converters. I will probably go the VFD route. It is good to know the how and why of both.

[@okolioluchukwuchigozie1822]

This explanation is superb, thanks so so much

[@3cl1]

Great video and thank you.

[@francisofosuphilip2490]

Very interesting and comprehensive tutorials ever.. l now understand Rpc..

[@TheBuildist]

Great to hear!

[@jamestregler1584]

Yep using your guidance; thanks 👍

[@hooter7003]

Thanks for the information ℹ️

[@MrWaalkman]

You might want to re-think the auto-start feature of your converter. If it's powering a machine when it comes back on, your converter will be trying to start the idler motor and the motor on the machine that it was running. There's a good chance that neither motor will start up, and things will start to get very hot, very quickly. Otherwise it's a very nice and clean build, and obviously it works just fine. :)

[@TheBuildist]

Close observation but not quite correct. The starting capacitor is only in circuit before the secondary output contactor has been closed. So on a power outage situation when power comes back on the power will immediately start the idler motor and as soon as the idler motor is spinning then the timer will pull the starting capacitor out of the circuit and activate the secondary output contactor which will make the machinery start back up. it may not be ideal to have your machinery start back up unattended. But that I leave to the common sense of the user. You should never walk away from a machine that is turned on even if the power has gone out. And though it could conceivably cause a machinery crash or some other undesired outcome, it will not lead to an overheat or damage to the rotary phase converter itself.

[@timmer9lives]

My only take is my experience with a city which has 100 year old infrastructure. On top of that, where I’m currently living is the only section in New Orleans with underground wiring. Just not maintained. FWIW, just last week our electricity would completely go out and almost immediately restart after about 3 seconds. This went on for over 6 hours and would happen about every one half hour. I’m sure this isn’t the norm in America. More like Iraq . Anyway, we still do get the electricity go off and restart just once or twice fairly often. But, this is New Orleans. All that said, this is still the best video on RPC’s. I’m going to do a build with a 5-hp…and your video is excellent. It won’t be hard to figure a way to prevent it from restarting in my opinion.

[@TheBuildist]

@@timmer9lives You make some good points. In the every 3 seconds scenario, assuming you are running something like a mill, when the power went out the mill and converter would both turn off. Three seconds later when the power came back on, the phase converter would immediately spin back up, and a second or so after that the mill would turn back on. I could see how that could be a little nerve-wracking. But I don't see how it would be dangerous. But the auto start feature is very simple to disable. Simply replace the 1 second timer with a momentary (push button) switch. Then to start the phase converter, turn on the master power and push the switch in for a second or two till you've heard it spin up, then release the switch. Then in case of a power outage, the two contactors will both turn off and will remain off until you've pushed the start switch again.

[@timmer9lives]

@@TheBuildist sounds good. FWIW, it’s probably less of a problem in the shop. But the poor electric issues do play havoc with HVAC Systems and refrigerators. It’s hard on the compressors. Every time the lights start to flicker I have to run to the house thermostat and turn off the A/C. Anyway, I agree that it’s probably not a dangerous issue for your set up. Thanks for the reply and thanks for the videos. Excellent rotary phase converter build description.

[@samrodian919]

Are there not no volt release starters on the machines? No machine should be able to start again after the power went out and then comes on again. That's mandatory here in the UK.

[@dannywilsher4165]

Thanks Mr. Buildist!!!

[@thegameguy5886]

I understood the content, thank you.

[@The52brandon]

Just a friendly headsup, that plug is 50A. The 30A version has the 90" middle prong rather than the straight blade

[@georgewages8539]

outstanding. I just got a freezer unit that requires 3 phase..also bought whats supposed to be a 3 phase converter. its needs connected. I will have to watch your videos over and over till I get it working...Whats confusing right off is coming out of the big motor are about 8 unmarked wires all the same color ! yikes...thank you for your time in making these videos

[@markminish]

You learnt me a lot hahaha. very good video I enjoyed.

[@carlojhonmatiga5998]

Thank you so much my friend 👍 I'm ahh 21yrs old pilipino technician.

[@stevedangerous1]

Ace. 😊 well done.

[@kingofl337]

You should consider adding a thermal overload to the contractor and breakers.

[@rodrigosanabria1907]

Very nice video, I want to install a phase converter in my garage to runs my 15 hp compressor, but a brand new converter is ridiculously expensive,

[@allamerican1248]

Very nice!

[@3cl1]

Very nice work and video. I've assembled a few pony start rpc's but need to build a self starting 30hp unit. I have the motor and I've tested it in my old shop with a contactor, just don't know enough to source the rest of the build. Thank you!

[@branchandfoundry560]

Check out Sbirdranch's video series. He did a good job of showing components and sourcing. I just finished my build based on his and powered it up for the first time today. This is not my forte, so I was pleasantly surprised when it ran perfectly! Happy to help any way I can since I had to struggle through mine without help. You got this!

[@mrmatt2525able]

Wow nice work, I started to put my converter together last night. All going to plan until the start capacitor blew up in my face, I have the same brand as you but 1000uf, as I’m running a 15hp motor for the converter, lol

[@designandbuild3953]

I like your style and enjoyed your videos on building the phase converter. Both, liked and subscribed.

[@TheBuildist]

Thank you for the kind words!

[@leamrcs]

Great video. What about current on each phase with and without load ?

[@kevinwellington6978]

U could install a stop start switch to prevent it from coming back on after a power outage

[@TheBuildist]

Yes that suggestion has been made, but I really prefer the single switch with no extra momentary/push button switch necessary. From my point of view the phase converter is not a machine. It's part of the power supply infrastructure. If your single phase power goes out your three-phase power (RPC) goes out too. And when you're single phase power comes back on, then your three-phase power (RPC) will come back on as well, unless you have chosen to specifically turn it off during the outage. An operator of any single phase machinery knows that they need to turn it off in the event of a power outage. No one would just walk away from a running table saw or drill press just because the power went out. Three phase machinery needs to be turned off in the event of a power outage as well. In case of a power outage, simply turn off the mill or lathe or whatever that you are running.

[@fredflintstone8048]

I have to wonder if it's better to tune the rotary phase converter's capacitance under load as opposed to no load. As we know adding capacitors in parallel causes the capacitance to be additive, and the voltage rating to be the same (if they're all matched), or the value of the lowest voltage rating if they're not. If we wire capacitors in series the relationship cuts the capacitance as follows: (C1 x C2)/(C1 + C2) in the case of two caps. If you're placing more than two caps in series then use this formula: 1/ (1/C1 + 1/C2 + 1/C3 etc.) You can also use this for just two caps as well. As an example, wiring two 50ufd caps in series will give you 25ufd of capacitance, and the voltage rating is additive, in other words if the caps are rated for 370 volts the combination will give you a voltage rating of 740.

[@rodneykiemele4721]

Excellent series.......I think

[@TheBuildist]

Thank you! I guess? 😎

[@RocanMotor]

Excellent video series. A couple of notes, as someone who spent many years as an automation engineer- 1. I recognize your point regarding having the phase converter automatically re-start. While I do agree the operator must be mindful, there are some situations where an auto restart, even with no power connected, could prove very dangerous. In particular, it is not uncommon for power to come back online at a reduced capacity- lets say if a tree happened to take out one leg of your input. In this current configuration, it's possible that the RPC would fail to restart, the timed start relay drops out, and the RPC experiences catastrophic failure as it gets fed a ton of amperage in essentially a locked rotor position. This can lead to thermal overload and a fire. At the very least, some thermal overload protection is a good idea, or some other safety, if you insist on having your RPC auto start. A breaker won't always catch these in time- a fusable link or appropriately sized fuse will though. You can maintain your one button start using a magnetic contactor- if power is lost you will have to just press ON again- a mild nuisance, but the startup of a 20HP motor really should be monitored each time. 2. You have multiple leads in each terminal of the contactor. I would be extremely cautious of this- I have personally seen this have catastrophic results. It's directly mentioned in NFPA-70 as well, and is one of the first things I've had inspectors check for. The terminals cannot sufficiently clamp multiple leads at once. This can cause erratic behavior, and in really bad situations, shorts and fires. Using a 2 into 1 ferrule or soldering the leads into one is a bit better, but still frowned upon. Terminal blocks are cheap, provide a much more secure connection, and each lead can be inspected to be tight and to have good contact. 3. I am not sure if you mentioned it, but you will want a way to discharge the start capacitor after it has started. A small bleed resistor is usually used. Obviously, you exhibit a great deal of good sense and care in what you are doing. There are other things that an inspector would mention, such as having covers over exposed terminals and making everything "finger safe". I put this into the camp of having guards over all moving components- safer is always better, but some common sense will keep you alive. The above things I would strongly encourage though.

[@TheBuildist]

Those are excellent observations, and I accept them without argument. You're not the first to make the case that it shouldn't be set up to auto-restart, and after a number of sensible people tell you it's a bad idea, then you just accept that it's a bad idea. Bob

[@RocanMotor]

@@TheBuildist heck, I'm prone to bad ideas myself! Nearly every comment on my bridgeport unloading video is someone telling me it was a bad idea, haha. No harm, no foul, we can always build it better! Thanks again for the videos, I'm about to put together a 40HP RPC and its great seeing what others have come up with.

[@billdoodson4232]

I cannot disagree with anything you have said. I was going to make similar comments, you have done it far better than I would.

[@RocanMotor]

@@billdoodson4232 I'm in the process of getting my own shop wiring complete and part of that is building a large 40hp rpc. If I can keep to my schedule, I should be posting the RPC build video in about a months time.

[@bradsmith1046]

Terrific video thanks. Is there a detailed components list somewhere that I missed that would help me source the contactors/relays and timer needed for a similar 20hp build?

[@TheBuildist]

No, sorry

[@howiemoth3847]

Hello and TY for the vid.. @12:20 Capacitor p vs capacitor s ?

[@waincarew2240]

Hi. Thanks for a great video. I have a 7.5ph 3 phase lathe. And i would like to make one of these converters. What size motor would i need to make on of these converters for my 7.5hp lathe. Many thanks.

[@TheBuildist]

In general terms, your phase converter should be 33% larger than your motor. So to get the very full 7.5HP out of your motor, you'll need at least a 12HP RPC.

[@glenfreeman5850]

question i have the same setup when i load it voltage drops from 255 to 230 is that ok

[@makefitdepartment8621]

I have an Anderson MFG (out of business) 7.5 hp phase converter with bad capacitors (unlabeled) The 2 run capacitors are 2.5 x 4.85 round aluminum wired in parallel between 1 leg of 220 and the converter motor / 3rd leg. Can you help me estimate what capacitance I need and what kind of capacitors?

[@markjohnson5619]

I am building with 15hp idler motor. What would you recommend for contractors and a good place to purchase. Also what type of relay did you use on the timer. Mark

[@mauriceamollo8538]

So for start capacitor it is 70uf per hors,how about run capacitors per horse?

[@trayharris81]

How much was that setup?

[@stevecallachor]

How much would it cost a household to have 3 phase power connected to the house. Here in Australia we have three phases at 240 volts passing every house. The customer can have 1, 2 or 3 phases connected depending on load required. Each phase can have 100 amperes drawn so the power available is almost limitless. The phases are balanced in their draw by the supplier connecting each house to a different phase. Most houses draw on one phase only but many use two for cooking and heating. But three are available if the need arises. Each capable of 100 amps at 240 volts , with 415 volts RMS available between phases. The system works well and we pay about 25 cents per KWh. Depending on time of day. Stavros

[@TheBuildist]

Here in the States, at least in my sleepy residential area, three phase is just not available to a residence. if you could get them to install it the cost in labor and equipment would surely run into tens of thousands of dollars.

[@fredgeitner713]

Curious, What type of solid state relay did you use? Most I've seen have been for resistive loads only, not for inductive or capacitive loads.

[@TheBuildist]

It's been too long ago, I don't recall. It's possible that I didn't know that and used the wrong thing? But it worked fine. Perhaps because its use is so brief, well less than 1 second, only a couple times a day at most.

[@fredgeitner713]

​@TheBuildist Thank you for the reply. Yes I can see that what you used worked really well. Maybe I'm over thinking it. I was thinking of using a solid state relay instead of a contactor to eliminate the possibility of it sticking on. I've already built a phase converter years ago and it's always been super reliable, however I recently found a larger delta wound motor in a scrap dumpster, and it runs and decided to build a bigger, better one.

[@dripschoetmer]

I have a 30 HP donor motor ( Brand New ). I would like to use it for a RPC. I contacted a capacitor company looking for a 2100 MFD ( 70 / HP ) capacitor. His input was that that was awfully high for a motor starter. Any advice???? TIA

[@TheBuildist]

I'm no expert, I went by what I read on the web. I will say that for my 20hp motor, the 1200mf I bought was smaller than the rule of thumb I was following ("70 to 100mfd per HP"). And it worked just fine. So I'd guess you don't have to have a full 2100mfd? Having said that, this is not a typical starting capacitor. "normal" starting capacitors are for single phase motors, and single phase motors, being "in sync" with their current supply, only need a "gentle" nudge to initiate enough rotation to come online. In our case, we have a 33% mismatch between our supply and our motor, So our motor needs a much more substantial kick to get enough rpm to come online. So if your capacitor supplier is thinking "typical" start capacitor, then this one seems too big. If it were me, and again, I am by no means an expert, If I could easily/cheaply get ahold of anything bigger than about 1600mfd, I'd be inclined to give it a try. It'll either spin up or not. As long as it's only hooked up for a few seconds, it's not going to hurt anything to try.

[@noelnogal3462]

can i run a big cnc router with this RPC?

[@TheBuildist]

If the router were 3 phase, then yes, you'd need something like this.

[@kevinlewis9151]

My question is why waste the energy by cutting off the shaft why not put a pulley on it hook both your rotary phase converter together and then link them to 1/3

[@alfredokoh8341]

Could you be kind enough to post the wiring diagram

[@TheBuildist]

Let me see if I can track it down. Bob

[@birdsCroatia]

I don't understand, how do you have 2 live in, I have only one live 230 v, one ground, and one neutral?

[@TheBuildist]

Here in the states, due to the design of the transformer outside my house, there are three "live" leads: 1 ground/neutral, and 2 that are "hot": Each hot wire is 120V with respect to neutral, and since they are perfectly out of phase with each other, they are 240V with respect to each other. This guy explains it very well: kzbin.info/www/bejne/oH7QhqKQnZh7p5Y

[@marianodiaz461]

@@TheBuildist so it means that here in Australia we can't use? because we only have a live , neutral and earth cables coming in?

[@wilber123ful]

Can I get this work on a 60hp Idler motor?

[@TheBuildist]

In theory, yes. Practically speaking, probably not. The principles are valid up to any size, but I suspect the current needs of a 60hp motor may be beyond what a standard residential electrical service can supply. And the high capacity devices (contactors, capacitors, etc) will be extremely expensive. So realistically, I doubt it.

[@wilber123ful]

@@TheBuildist the 60hp motor uses 148A at 208V. And is not for a residential use. But I get the expenses of it

[@thisisayoutubechannel4752]

Is there a specific reason you used the 200A contactors?

[@TheBuildist]

Not really. I had them in stock and they were plenty adequate for the application. So it didn't make sense to buy something smaller.

[@thisisayoutubechannel4752]

@@TheBuildist Okay. Thanks for the reply! I was wondering because those 200A contactors are very pricey. I am going to have to buy them. Do you suggest a contactor amperage that matches your breaker amperage?

[@TheBuildist]

@@thisisayoutubechannel4752 yes, at least the breaker size. Remember, it's three combined loads of all your motors simultaneously. The rpc pony motor plus whatever motor(s) downstream of it.

[@thisisayoutubechannel4752]

@@TheBuildist Just out curiosity what is the model # of the contactors you used?

[@TheBuildist]

@@thisisayoutubechannel4752 I don't know, and I no longer have that equipment. Sorry.

[@jimm2311]

You seem to have made a substantial investment in time, relays, switches, and capacitors to make it work. Wouldn't it be more cost-effective to just drive the 3-phase motor with another motor, such as a DC motor, and thus use the 3-phase motor as a 3-phase generator?

[@TheBuildist]

Good question. The rotary phase converter was invented long before I came along. This is just my attempt to demystify it for anyone else who finds themselves in my situation: I have a plentiful supply of AC electricity that is the correct voltage, but the wrong phase type for my motors. So I simply need to convert my single phase AC to three phase AC. You could very well turn this three-phase motor into a generator. You could drive it from a DC motor, a single phase AC motor, or even from gasoline. But any of those would have cost me more time and expense, and would have been larger and heavier and noisier than the RPC that I ended up with. But I like the way you think! 🤔

[@leamrcs]

@@TheBuildist 3 phase motor don't have magnets guys, no chance to generate 3 phase. Read about deferent between 3 phase alternators and 3 phase motors. Good video btw. :P

[@alfredokoh8341]

kindly share your reference with us or email the link on such reference !! thanks in advance !!

[@TheBuildist]

Please see the link to the plans in the description

[@alfredokoh8341]

@@TheBuildist got it Sir !! Thank you , I really mean thank you !!

[@electromechanicalstuff2602]

If you bought A contactor with a 240 volt coil and you used the breaker as the switch or an external disconnect you don't need the solid state relay, 24 volt relay, or 5 volt power supply or the other contactor. You basically just need one contactor and the timer for the start cap. That's how I built all 3 of mine. The biggest concern I had when balancing the voltages was not to exceed nameplate current on the generated leg going to the poney at idle my wall current was at 3ish amps but the generated leg was over 20 amps. FYI. Good build kzbin.info/www/bejne/nqrNipd7gZJrZtU

[@TheBuildist]

You're right, of course. But I wanted the nice fancy looking red mushroom button, and the timer relay was only rated for 5 amps, so I needed to drive some kind of contactor with it. I figured the instantaneous nature of the solid state relay would work great with the sub- single second timing, and I wasn't disappointed. But you're exactly correct to point out that a fully working RPC can be built that's simpler and even cheaper than this one. Thanks for the info and your thoughtful reply.

[@shawnshannon984]

Definately a safety hazard by not setting your contactors on in the case of a power outage. It's a code violation as well. Good luck, and play at your own risk.

[@TheBuildist]

I'm not sure I follow. With single phase power active, the unit produces 3 phase power. When single phase power goes out, so does the 3 phase power. When single phase power comes back online, after a few seconds, so does the 3 phase power. What's the safety risk?

[@shawnshannon984]

@@TheBuildist it's outlined in the electrical code to have your contactors wired so they pull in power with a momentary switch and a stop switch wired in series so that when the power goes out without supervision the system does not re energize thus causing a potential hazard. If you are diligent about making sure things are turned off then you should be safe however to get an electrician to wire it by code he would be asked by the inspector to fix it or it does not get certified.

[@TheBuildist]

@@shawnshannon984 I don't doubt that you're accurate about the code. But an RPC isn't equipment, it's supply. I don't turn off any other parts of my electric supply during an outage: I leave my main breaker and all my branch circuits turned on, and when the power comes back on, all of my outlets automatically come back on as well, and anything I have plugged into them. I don't know anyone who has any concerns about that. Why should 3 phase power outlets be any different?

[@sclarksclark]

The fundamental video is very good and instructive, but I agree with others that having a start/stop/emergency switch wired in concert with a 'latching' relay would be advisable and I don't see how that is any more difficult than a push/pull. Push start to start, push stop to stop vs. pull to start/push to stop on a single button. If the power outage whether due to utility supply failure or breaker trip due to faulted condition in the unit, it is best not to allow reenergizing the unit without human intervention. As for the code...if it is considered part of the supply system then regardless of what you do for switching, safety, etc it is not legal---all electrical supply equipment must be listed by an approved listing agency such as UL, CSA etc or it cannot be installed. As shop equipment, the NEC does not require listing, though most device/appliance manufacturers get listed to be able to get insurance, but the NEC listing requirement is not applicable so I would consider it shop equipment. I think your video and the application is well done and clearly you, for your own use will be just fine----in my world we have way too many that shouldn't even be near anything electric but the responsibility doesn't seem to fall on the users anymore, it's always someone else's fault. Operator stupidity is automatically excused in lawsuits.

[@TheBuildist]

@@sclarksclark Well thought out comment. I suppose if I had to do over again I would do it as you describe. I'm still confident that I haven't produced an unsafe product. But if the whole world disagrees with you, then there's a chance that you might just be wrong! 🙂

[@seancollins9745]

I need to build a 100hp phase converter, don't ask, I have a 100hp motor, where can I find the maths for this ?

[@TheBuildist]

A 100 horsepower pony motor can support about a 65 horsepower RPC. If you need 100 horsepower output, then you'll need about 135/140 horsepower pony motor. Beyond that the schematics are no different than what's in the video. I have been convinced that it would be better for it to start with a single momentary push button and stop with a separate momentary push button. So that is a slight change to the schematic but not dramatic. And I don't recall it this second, but I think I spoke the math ratio out loud in the video of what is the appropriate capacitance to begin the balancing process with. Once you have installed the appropriate amount of capacitance to begin the balancing process, the rest of the balancing process proceeds as in the video but with proportionally higher values. I think the biggest challenge will be the starting capacitor. The one that is only online for a second that causes a phase/timing shift to get the motor to spin in the first place. You may struggle to find a big enough capacitor to perform that function. Again I set out loud the proper proportion but I don't recall it off the top of my head. I'll try tomorrow too track down my old notes and update this post accordingly.

[@TheBuildist]

www.homemadetools.net/forum/how-build-rotary-phase-converter-76547#post147353 has the plans that I found on the web and followed. These plans are for 10 hp, so your capacitance and amps will all be basically 10x these plans. Of course your wiring and contactors and such will need to be sized to handle that amperage. And I'm guessing your motor voltage is 400? If so, your capacitors will all need to be rated for... I don't know for sure. But at least 600 volts. Best of luck.

[@seancollins9745]

@@TheBuildist actually I need 60hp

[@davesalzer3220]

I just bought a 10 horse control box for $200. That’s gotta beca bargain doesn’t it?

[@TheBuildist]

That's certainly not too bad. The bill of materials for the components in the box would have to be in the $200 vicinity. Nicely done.

[@rok1475]

Dave Salzer You got deal of the century. Googled 10HP static phase converter and got Larson Electronics unit for $1054 (plus shipping and tax). Phase-A-Matic makes smaller static phase converters that allow running 3-phase motors off a single phase but you get 2/3 of the motor rated power at light to moderate loads. Those are in $200-300 range. For heavy load Phase-A-Matic says “ you must use rotary phase converter”. There is a long list of equipment that will not run off static converter. The good news is you can use static converter as a ready to use controller for a rotary phase converter. Just add properly sized 3-phase motor to act as generator. If you only have lathe and a mill with 1-3HP 3-phase 220v motor, an import VFD is a good option. For less than half price of static converter you get full rated power of the motor and as a bonus you get variable speed control of the motor. RPC is more robust, can handle overload, heavy continuous load, can power multiple devices at the same time (up to total capacity of the RPC) and each can be switched on/off independently. VFD or static converter is dedicated to a single motor.

[@evansyorke2284]

Good evening I like to ask can I have you build me a box for a single phase 240 volts coming in from the wall and 3phase coming out I install the motor when you ship the built box if you're capable of such requests my email address will be provided and we can take it from there

[@chauvinemmons]

One minor note please do not ever penetrate the top of a box come through the bottom or the side if necessary just never the top really for any reason