Make 3 Phase Power from Single Phase with a Rotary Phase Converter 

The older I get, the more I realize that many times I would have been better hiring someone and working a few extra hours at my day job to pay for it :)

Well what kept you scrolling past? Maybe we need to tweak our thumbnails. Glad you found us!

Tim the best I ever seen

Man I just ran across this trying to convert my shop to 3 phase so I can run my feed pellet mill with electric instead of pto tractor power to save money smh I thought i was doomed till I seen this.

Thanks Dave!

Glad to help Jeremiah!

You're welcome Anthony. Thanks for watching!

Tim Wilborne - Thank you for the video- I am with Anthony- I would also very much like to see a step by step guide to building a RPC. I like how yours was laid out in the box. I am trying to get ideas for how to lay mine out.

Wow that must been a beefy greenhouse. Thanks for watching!

Yes that would be a little steep unless they were all model machines. I think you'd end up with about 1.5 amps of capacity 😜

Thank you, I will!

Glad it was helpful!

Thanks Adam! Let me know if there are particular topics that would help your students.

Thank you, I will

Thank you David!

My previous one was the same setup. The only reason we switched to our current setup is our is some of our customers required the phases to be balanced when we tested their control panels. Also the idler heat sounds like you weren't dropping power to the motor one at speed. It should only be used while starting.

@@TimWilborne Thanks... I was dropping the power applied once the pony motor was running. Didn't you show in your other video that overheating is a problem when no capacitors are used?

That wasn't a capacitor problem. My idler motor should have been twice the size of my load. I used the same size motors which caused my overheating.

@@TimWilborne Just trying to determine the cause... so it was b/c your idler motor was not twice the size of the load motor...? That was probably the problem with my setup! My idler motor was quite a bit smaller than my lathe motor.

Thanks Fred. Let me know if you have any questions or clarifications you'd like to see in upcoming videos. I've made a desktop model of the rest phase converter to go into more detail.

Thanks a ton!

Yes I need to make a capacitor balancing video, I've got too many projects going on right now.

@@TimWilborne How much longer do we have to wait lol Good info & explained clearly! I'm ready to order parts but been holding out for this series for confirmation on how I should go about it. Thank you!

Parts are not easy to find in the whole state of va

Maybe should use a vfd but no fun in that huh!

@@TimWilborne Tim did you ever do the video on building the phase converter?

Thank you!

Interesting. I can't work this out in my head on a standard Wye Delta motor configuration. Can you send me a sketch? contactus@twcontrols.com.

@@TimWilborne did he ever send you info on how to do this?

Wont you lose the efficiency of the orginal 3 phase because it's not equally across all the windings?

The question is, is it equal across the windings? 🤓

@@TimWilborne It can be made equal with the proper run capacitors

You are welcome

You're welcome. I worked on a bench top rotary phase converter to use to show the details this weekend.

Thanks!

For the most part plus or minus 10% is acceptable. If I were in the 520 volt range I might start to worry. In this and most cases, there is no multitap transformer

Thanks Autry!

Thank you Dave.

You are welcome. Glad you like them!

Thanks. Occasionally I bog down my 5hp so I'm on the lookout for some parts to upgrade mine too.

Sorry to butt in but think that a 30HP unit would mean stepping up to 100 amp incoming power for a unit that size . Are you running up to 20 HP combined motors ? 5 HP is about the max motor size that can be run on a control panel with 30 amp 220 input that is shown here if I'm not mistaken. At that the idler would be 7.5 HP minimum as I understand these. Correct me if I'm off on that Tim.

That's been a popular request, I'm going to cover it more in an upcoming video.

Probably the biggest thing is you need at least a commercial or maybe even an industrial electricians. Many home electricians only know about 3 phase power from school. If it is just you then I wouldn't worry about having it so that only one machine can run at a time. You'll know, and if properly protected, it will simply trip the breaker.

Thanks Bryan!

Yes

@@TimWilborne Thanks man!

You are welcome, reach out to American Rotary if you need help selecting one. They are very helpful. www.americanrotary.com/

I would contact American Rotary, they will help you size your applicaiton.

Never seen that brand.

@@TimWilborne Smallish company out in South Dakota, but they make VFD's with barely any moving parts. And virtually 100% american made. They are pretty slick!

Glad to hear it!

No, I'm feeding 230 in on the secondary and getting 480 our on the primary. I am " back feeding" the transformer

Maybe one day I'll get another one done, I take it you watched the 2nd one.

Double the hp of your load. So if you have a 5hp load then you would need a 10hp idler. There is math behind it but that is a good rule of thumb.

I don't think you can every say it is "as good" but it does work. We use ours to test all of our 3 phase panels including ones with sensative electronics with no trouble. Your idler motor must be twice the size of the load you want to run. So if you want 5 hp of usable power, you need a 10hp idler.

It is on the list, here is one were we go into the details of how it generates the 3rd leg. twcontrols.com/lessons/how-does-a-rotary-phase-converter-make-3-phase-from-single-phase

You are right. That's a sure way for elaborate explanation.

Thanks for the video. Can you provide a circuit diagram for this? Pls try. Thanks so much.

The capacitor sizing is the toughest thing, I would look at purchasing a kit from someone. It still saves you some money but removes a lot of the headaches.

As a general rule, your idler motor should be double the size of your load. So if you have a 25hp load, you need a 50hp idler. motor.

Either one will do the job. Mines an 1800 rpm

😁

American Rotary is a good start. They are very helpful with the sizing.

Not in the end. The 3rd leg is artificial so I still only have two legs coming from the breaker. But at the actual load you are correct, it does divide across them.

Those are great questions. I don't know how the VFD would handle the inrush of a motor starting across the line. It limits the current output through acceleration and deceleration so it doesn't have an unlimited amount of current available for starting. Even my Rotary phase converter will bog down enough to kick the starting capacitor back in if I start a super heavy load when testing a control system larger than it's designed for. also you won't have any protection with the VFD if it is oversized to run multiple motors. It's current production will be too large for any of your machines. As far as balancing there are arguments four or against weather balancing is necessary but I think it is a good practice. You balance through the run capacitors. There are no good rules of thumbs for balancing but I am making a video showing how to measure and maybe get some decent estimates on what size capacitors you should balance with. You peaked my interest about wheher a rotary phase converter or a VFD is more efficient. Not enough to go out and buy the parts but I may see if I can get some things donated to do a test for a video. Thanks for watching and the great comments and questions!

What kind of motor 110 v 1-2 hp how does it make the 3 rd leg that part I don’t understand. My motor is 15 hp 230-460 3 ph 36@230 v or 18amps at 460 v rpm is at 1750

Wye configuration or delta

It would depend on your load requirements

Here's one that goes into the details about how it works. Honestly I never did the one detailing out the capacitors because there's a lot more to it than the average viewer may understand and I didn't want people burning up their equipment. You can purchase premade panels to put on motors for almost the cost of the parts to build a panel that does it. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-eXS9ahNzds0.html

The reason I never have is the capacitors vary by horsepower. I'm planning on making a follow-up video about capacitor sizing, it just hasn't made it up the priority list.

Hi Rootboy, nice to hear from you! That is going to be a big one. If I was doing it for a customer then when they get that size I go to American Rotary. They are not the cheapest but they are beefy plus I have someone to blame if they quit working...not that I have every had one quit. Something like this one. amzn.to/3aOwIgW If it was for a friend, I'd find a 50hp motor and get this kit. Also he sells them with the motor also. www.ebay.com/itm/New-50hp-3-Phase-Cnc-Balanced-Rotary-Converter-Panel-10-Year-Warranty/233340188494?hash=item365428b74e:m:mVGSCTUTaWBhmPyEIeIYAyA Then you will need around a 30 KVA transformer. Something such as this. Also I might know where one is depending on where you are located. amzn.to/3dUWIt4

@@TimWilborne Hi Tim, We had already found a 50hp motor for $250 (cheap!!), and it's on its way here. We found a 45kva transformer locally, which was about $450 IIRC. So we've lucked out on finding affordable parts. I would have preferred a delta - delta transformer, but scroungers can't be choosers... The 45kva has taps so I can get the voltage close enough. The 50hp motor is a twelve lead job. I approve. :) We are still planning on using a pony motor to spin up the idler since a 50hp motor is going to put a bit of a load on the system were we to use a capacitor start. But I might add it in to see how well it performs. We just don't want it sagging the voltage to the other parts of the building during start up. As for balancing caps, I can get 60 mfd run caps all day long for about $10, but it would be nice to be able to figure out what I needed beforehand. And I have done converters without the balancing caps in the past and it was no problem. Rob already has a brand new American Rotary that he had purchased for a Bridge Saw, but it is about half the size of what the screw compressor needs. AR quoted us a second AI30 unit with the link for about $3800. I think that we will comfortably come in under that. :) If AR had taken the AI30 back and sold Rob a AI60 then we might have gone that direction, but no matter. That capacitor balancer looks nice, but doesn't anybody read the NEC? Green wire for controls? Really? I was toying with the idea of putting the balancing caps inside the transformer, but it might get a bit too warm in there for the caps.

​@@MrWaalkman Man you are scoring big time! Up until my current phase converter, I didn't have balancing capacitors. One of my customers required phases be balanced for testing their systems so I purchased the box I'm using now so I didn't have to do the trial and error. I wouldn't put the caps in the transformer. Not only heat but ease of testing when something is wrong.

@@TimWilborne Yeah, we got lucky. :) As for the caps, I think that you are right, more for the next guy who comes in to service this thing.

@@MrWaalkman Good luck, let me know how it turns out!

Hi Hector. Here is one where we use a VFD to run a motor with Single Phase. There is also a phase shift starter but I'm not a fan of them. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Z_juhqYt1Ks.html

The rotary phase converter creates the third lag to give you 240 3 phase, then that is a three phase 480 to 240 volt 3 phase transformer. Backfeeding it gives you 480V 3 phase on the primary side.

Not 3 times the amps. 1.732 times the amps. Remember, you are already pulling on "2 legs". I'm in Christmas mode so short on time but go to a KW to amp calculator such as below and enter 1kw, 220VAC, a power factor of 0.85 then observe the amp change between AC single phase and AC 3 phase. www.rapidtables.com/calc/electric/kW_to_Amp_Calculator.html

@@TimWilborne Many thanks

many thanks ,, happy xmas

@@tomthompson7400 You're welcome!

Let's make sure we are talking the same terms. Many set up use a "pony" motor to start the idler motor. This set up uses starting capacitors to start the idler motor. If that is what you are talking about, any motor can be a pony motor. As for as the idler, such as this video shows, you double the horsepower. So if you have 10hp with of 3 phase load, you would need a 20hp motor.

@@TimWilborne yes that's what I am talking about. I'd like to run a 10hp motor for a hydraulic forging press.

@@TimWilborne so the people telling me I can source 3ph off a 5hp for a 10hp motor are not correct then? Or is there a way to accomplish that?

If you have a 10hp press then you need a 20hp idler.

It will last a long as any other motor. Plenty of them run 24/7. As long as you service the bearings if required, you should get a long life.

You want your control power such as the transformer on your main two legs, after that yes it will work in most applications. I would reach out to the rotary phase converter manufacturer before you purchase.

No, there are some good ones on Practical Machinists forum

I start going through that in the following video ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-eXS9ahNzds0.html. You can't really spec out what size capacitors you'll need but an upcoming video I'm going to give some good general rules.

No, it got pushed to the back burner for other projects, it is still on the list.

@@TimWilborne awesome I'm looking forward to it. I've built one but can't figure out the relay to cut the start capacitors out after it's running

That is what your size the run capacitors for. Typically they will run a little high when not loaded and even out when loaded. Welders and Plasmas usually work fine.

Correct, I hope to get a hold of a 3 phase scope and show it on a video.

@@TimWilborne That would be very interesting to see

It is a 5hp set up. For the most part, you would double the horsepower of your idler for your load. So my set up is good for 2.5hp.

That probably is a question for the local power company. For the most part, we dream of having access to 3 phase power and don't. I'm a little surprised that it cost more but my wild guess is this isn't about your power consumption and is more about a peak rate charge issue. I would be curious what you find but Oncor would be the people to ask.

@@TimWilborne I understand your response. My problem isn't THAT I have 3 phase available... regognizing your DESIRE, but unavailablity of it... but 2/3 of my bill is ACCESS to it. My energy usage is relatively small (1/3). And we're talking $Thousands per month. Oncor is no help. Why would they intentionally reduce their FREE revenue? So that's where my original question comes from. I can build a 3 Phase Converter system for some amount of capital, and save the 2/3 bill... or there is something I'm missing. Again... thanks for your insight.

I know a lot of shops that run on phase converters. There's nothing that says you can't. It still would be a good idea to get someone local to look at it. It's hard to get the whole picture in a RU-vid comment. Also depending on the exact situation, changing a few motors to single phase or putting VFDs on them could be a better option.

Here are a few videos about transformers plus we're going to make one specifically on backfeeding them soon. How to wire the primary and secondary of a transformer. www.theautomationstore.com/control-wiring-transformer-wiring-primary-and-secondary/ Backfeeding a three phase transformer to make 480VAC. www.theautomationstore.com/how-to-make-3-phase-power-from-single-phase-power-using-a-rotary-phase-converter-including-480vac/ How to make a basic transformer. www.theautomationstore.com/how-do-transformers-work-using-two-contactor-coils-and-a-bolt-to-show-how-magnetic-flux-works/

Yes, correct

I would definitely contact American Rotary about this application. Here are some of their phase converter offerings. amzn.to/3rK0NZw

I'm not familiar with those standards, looks like they are for the UK. In the US you would be looking for UL 508A

Most conveyors are available in single phase so that would be my first choice unless you need to vary the speed of the conveyor. Event then, there are many single phase drives that will output 3 phase and allow you to vary the speed.

Yes, I know people who run welders off of them. Check with the rotary phase convertor company, sometimes there are special capacitor configurations just for that.

Thanks 🙏

No, it would be near impossible to sync it up

No I've never heard that one Howie. As a general rule your idler needs to be twice the horsepower that you want to start. So if you have a 7.5hp load, your would need a 15 hp idler.

@@TimWilborne Thanks Tim

Hi Joe, yes phase converters can be repaired. Most of the time bad capacitors are the only problem. I'm not sure what you mean by a large vs small box converter. They are all based off of horsepower. Typically you double the horsepower of your load and that is the size rotary phase converter you need.

Yes, it is on my list to make a follow up video on this, I've just been short on time.

Plus help the world with a wiring diagram

If it requires 3 phases and you don't have it then this would generate it

Yes, there are very few "480 volt" rotary phase converters out there, most of the demand is is for 240V rotary phase converters. I like having both. I need it for testing control systems but even if I didn't, I think I would want both.

Hi,Tim. i am also planning to build the same setup for VFDs and servos testing at home. i have few questions. can we use static phase convertor (or VFDs ) to feed step up transformer. or rotary is the best? second which transformer is the best ,a isolation or auto transformer? thanks

Most 380VAC 50 hz motors can run on 460VAC 60 hz. Check your motor and see. You may be able to source a 220VAC to 480VAC 3 phase transformer cheaper than a 220VAC to 380VAC 3 phase transformer.

Hi Blake. Yes, as long as you have the proper run capacitors to balance the three legs and your transformer allows for a neutral connection (mine does) then you will have 277 to ground on all three legs. I'll be sure to address this when we dig into the details of how it works. Great question!

@@TimWilborne Hey thanks, if you're doing a more technical video on this subject see if you can measure phase to ground on a vfd setup as well, i'm interested to see if pullsed dc from a vfd will still give you 277V.

Voltage on a VFD can't be measured with a volt meter. You'll have to wait for the video on that one, to much to explain in a RU-vid comment 😀

Haha, I had to Google it :)

You double the hp of your load. So if you have 5hp of load than you would need a 10hp idler.

@TimWilborne I friend has a small machine shop. He hand cranks the motor before applying power. It's a huge 3 phase motor. I'll have to look on the tag too just using a small electric washing cabinet.

That's the old school way of doing it. Still works great. Some people will couple a single phase motor to it and use it to spin it up. I like the capacitors because it's a clean setup and I can start it from inside

Yes, I'm not sure it is a good practice but when I bog mine down, usually by testing a control panel with a drive that has a lot of inrush when you power it up, mine will bog down and the starting capacitors can kick back in sometimes. I would say that if this is happening normally then you need a bigger phase converter.

@@TimWilborne I built a 15hp one for a friend with a timer relay instead of a potential relay and reading into it more people say to use the potential relay to keep the start caps in the loop. Now I'm building 2 more. A 20hp and a 30hp and I like the timer aspect of it cause I know the start caps will always fall out. I've read that the potential relay needs to be "SIZED" correctly but no information out there about how to do that. Edit: heres my RFC ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-hyjYdEL-80s.html

Yes I risk my life to bring you this great content... twcontrols.com/lessons/plc-training-44-questions-and-answers-about-plc-programming-part-1

Great as long as you don't overload it.

The potential relay? It drops out the starting capacitor.

@@TimWilborne I don't understand the verb "drop" or "pull down" in this context.

Hi Bryan, it is an general purpose 480/240 to 240/120 VAC 3 phase transformer. I can't remember the specific KVA.

That is a big mill. Are you sure it is 25 hp? You would need a 50 hp phase converter.

@@TimWilborne Thanks 4 the reply, am sure coz it used to run on a diesel engine rated 24HP.

I would check it, 2hp would be a large mill. I think mine is 1/2 hp.

Is it a sawmill ?

@@jaspermcconnell6417 No , its a flour mill, in Kenya its called a posho mill, for making maize flour.

Hi Alex. I can probably point you in the right direction, what horsepower is your machine?

@@TimWilborne voltage 400-460 VAC / 3 phase. Frequency 50/60 Hz. Power 25 AMP (MAX) that's all on the label. Mega appreciate any advice. Thank you!

@@alexperry7631 That's a big machine. I'd probably reach out to www.americanrotary.com/ for one of that size. That load is big enough that you want to make sure you get it right.