DIY Static Phase Converter

In this video Iain shows how to build a simple static phase converter to run 3 phase motors on single phase power for under $100.

[@TorquinDSL]

Thanks for an excellent explanation and I appreciate you going through all of the components and what happens without them. This will help me troubleshoot a static converter that is having a problem.

[@bowlweevil4161]

GREAT VIDEO, now I fully understand how to do this, I have looked at several vids about these converters and they jump around the build and confuse me, but your's goes right down the line and explains place and function of parts THANX!

[@ScottAllen66]

Thanks, Iain! My saw is now up and running in large part due to this video. Learned a lot, saved money and had a lot more fun building one instead of going with an off the shelf solution.

[@iainportalupi]

Scott Allen I’m so happy to hear that! I think you’re really going to like that saw.

[@bobbyrochell5015]

Thank you for the great information. The motor in the drawing is Wye connected.

[@matsworld9386]

that was an unbelievably great explanation - thanks a lot!

[@iainportalupi]

Thanks!

[@OPHSTech]

Very nice explanation of the theory and diagram! I don't need one now, but if I did, I would give it a try! Thanks

[@iainportalupi]

OPHSTech thanks for watching!

[@cecilarnold6843]

Absolutely Awesome this guy is a wealth of knowledge

[@DeWaltRadialguy]

Iain, GREAT job! Thank you! You taught me sooooo much!

[@iainportalupi]

Leo Flannery my pleasure!

[@wangchun6784]

Very informative, nicely done, Thank you for posting and sharing.

[@johnh7500]

I like me the way you explain things. Just excellent!!!

[@bradylenamon8967]

Great job on the video. Thank you for sharing.

[@iainportalupi]

Thanks!

[@ajmoldmachine]

Thank you very much! Great explanation! Very clear!

[@ikifkif]

very refreshing.. someone who knows and.. can communicate. thanks.

[@iainportalupi]

Thanks!

[@thomassutrina7469]

You can tell when a 3 phase motor loses a phase, runs ruff. As a mechanical engineer that packaged power electronics drives an occasional the magnetic machine I expected this once. I do remember hearing about the rotary phase converter as you described, however; another video presented a 'E' core 3 phase transfer with a single phase input. In the title is Rotary Phase Converter. It is more accurately a Rotary Magnetic Phases Converter since no part actually rotates. The single phase coming into homes is 240AC with a center grounded tap thus creating two 120AC power with the average voltage about 72V, plus and minus. Each half is wound on one and a half legs as the primaries. The center secondaries if wound will with the same number of turns will not have the same RMS voltage. I can't remember exactly how to correct this presented. And 'E' or doubled core transform is significantly cheaper than using a motor idle. The only advantage of the idling motor is the moment of the rotor help with start up of the machine motor.

[@dwightcheck]

great job helping me understanding ,,,,,thanks !

[@justiceoscar]

Thanks Lain, I have a radial arm saw, and when I bought it it came with a lot of cables disconnected, I tried to reconnect and the motor ran "ok", but after some testing it smelled burnt. The engine is already repaired, the technician told me that the problem was that it had no phase, but I am afraid of making the same mistake. The point, how can I be sure that it is connected correctly?

[@AllooshO]

Man, such an informative video I have watched every bit of it, I have 3hp coffee grinder wired as 400v wye configuration, your video is exactly what I needed a standalone solution that doesn't require any modifications. Do you think that we need to add a 450v 40uf run capacitor to make it more stable? and where we can add it.

[@iainportalupi]

You’ll want to add the run cap in parallel with the relay coil. You will also want to downsize the start cap by 40uF to keep the overall starting capacitance the same.

[@charleskutrufis9612]

Good Job, Hoo-ray for you and me. Thanks

[@danieldumont9334]

If you are using a (DC relay) then you need to add a diode to the relay input, to turn the AC to DC or you could use a full bridge rectifier. As most relays are DC, 3 to 40 or so violts to activate, it might be easier to use a power brick of some kind. Say 12volts for instance just to power the relay. hope this makes sense.

[@peterkimani3094]

I have built a rotay converter and you probably solved some issues i was3 facing especially chatterinh

[@andreasfarozirusli1066]

thanks Bro, very clear explanation, understood more on vfd, rotary and this method. …, will the motor get heat to much if run this in long hours ? because un-balanced (volt/amp between legs) … ? but anyway I WILL try with my 1,5 3 phase motor (coffee grinder)

[@rubarb0406]

. Lain, I have had a single to three-phase converter for motors up to 3 HP for a couple of years. It was commercially made in Az by a company that has not responded to an inquiry. Went to use the converter the other day and the motor just groaned. I plugged another three-phase tool into the converter and it too groaned. I shook the converter and could hear a rattle. I drilled out the rivets and could see a couple of white plastic strips in the bottom of the unit. It looked as if the power resistor had failed. I cut one leg off the resistor and tested it with a VOM. It had no resistance at all. There are no markings on the plastic strips or the remaining ceramic portion of the resistor. Does the motor groan sound as if it could have been caused by the defunct resistor or might I have other problems? The capacitor is a 324 micro farad 125 volt jobber. For the money would I be better to replace the converter with a VFD? Thanks in advance for your response.

[@MattC-nx1zw]

Thanks. I had a used static phase convertor. That started the 1 hp motor but the motor smoked after 45 sec. The capacitor was to large? It was 400mf. I changed it to 50-70mf and it worked fine so far. Is there something else I should be checking or looking for? It is on a bridgeport mill with a 3 phase 4 pole motor. Thanks Matt

[@meatball1974]

really well laid out video, thank you. I have a couple questions I was hoping you could help with - 1, could you explain what terminal numbers on the potential relay were used? my relay is in a box, more common with what would be found in a compressor or air conditioner I think. 2, can you tell me - if this is all sized to run a 3hp motor - in my case - on a lathe, the lathe has a second 1/8th hp coolant pump (3ph as well) - can I use this static converter to start that motor as well - after the 3hp motor is running?

[@iainportalupi]

I don’t know the terminal numbers without knowing the model number of the relay. However the 1/8th hp coolant pump motor will run just fine once the 3hp motor is running.

[@meatball1974]

The one I have is a “supr” potential relay by Supco - off Amazon. This form factor was quite common when shopping.

[@richardpayne352]

Hi Iain, great video! Do you happen to have a list of part numbers? Went to McMaster Carr website and the 7170K15 didnt come up, I may have missed it. Thanks!

[@richardpayne352]

I found the correct relay and capacitor. Do you have a wiring diagram on which wires go on which terminal for the relay holder? Thanks!

[@frankcadillac9151]

Lain, thank you best description I've heard. I have been using a rotary converter for 25 years to run my metal shop. Simple knife switch and momentary switch to the start capacitor. Next project is running a heavy duty Hobart three phase motor generator welder on single phase. I am hoping to do what your did with your radial arm saw as I don't run heavy rod . Would like to put a run capacitor on the motors third leg and use a start cap. to get it spinning. Any suggestions mate, thank you.

[@iainportalupi]

You’ll want 12-16uf per horse power for the run cap. You might have to estimate the welder’s hp from the unit’s amperage draw and see what size motor usually needs that much current.

[@frankcadillac9151]

Lain, thanks for your prompt reply, the motor gen. welder has a 15 hp three phase motor 38 amps. according to your reply I should need about 200 mfd. on the third leg.

[@danieldumont9334]

what kind of switch are you using to power the machine. and what power rated breaker/fuse are you using ? whta is you current draw?

[@markusmodaffari4437]

So does your 3 phase saw connect to your ghost motor windings?

[@williamchristensen2447]

Iain, the electrical schematic really helped understanding the static phase converter that I have for my Bridgeport mill. Mine has a run capacitor also in the circuit. The problem I’m having is a chattering relay. The cap was borderline at 88 uf. It also seemed to be leaking quite old, so I replaced it. The motor is 1/2 hp. This mill was a basket case and hasn’t run in years. The new cap measures 104uf. As I was putting it in together, I decided to check the motor to see if it would run. Hooked it up directly to a 2 pole breaker through the static phase converter. No problem, spun right up. I have 240 volts in the garage. I’m measuring 240volts between the 3 wires going to the drum switch. The spindle starts to turn but stops with the relay chattering. Any ideas would be greatly appreciated. I can send pictures of my converter and set up.

[@iainportalupi]

I would look at the drum switch. It sounds like a dirty/burnt contact in it.

[@williamchristensen2447]

@@iainportalupi thanks for your quick reply, I’ve been working on this mill/project for awhile. I rebuilt the drum switch and am inclined to agree because the idle/ detente arm pivot had enlarged so the contacts did not make good “contact.” Since the problem is persisting I’m going to replace it. If the contacts/ relay is bad what are the McMaster-Carr part numbers. I looked at the online cat. and your home built converter and noticed it plugs in. I appreciate your help. Sometimes I know just enough to be “dangerous.”

[@iainportalupi]

@@williamchristensen2447 I just looked and it appears that the particular relay I used in this converter is no longer sold by McMaster. The closest they have now is number 7170K15 they list the matching socket on the relay’s product page. I actually just finished assembling a 5hp version of this static phase converter last weekend to run my bandsaw.

[@jaycss]

Also, what happens if you are not really sure of the horsepower of the motor? Might be 2 HP or it might be 3 HP. Do you just figure it's 3 HP and go or will this cause a problem if the cap is too big?

[@williamchristensen2447]

I have an Bridgeport Mill that has a 1/2 HP motor. This is what it originally had, so not large. This machine has been inactive for years. I wired 220 to a panel in my garage. This machine came with a static phase converter. Awhile back, I checked to see if the motor worked with the converter. Hooked it up to a double pole breaker with the converter. No problems, motor spun up and worked fine. Now that I have 220 in the garage I have hooked everything up and I’m ready to make chips. Or so I thought. The spindle starts to turn. The relay chatters. At that point, I shut it down, not wanting to fry anything. Any ideas would be appreciated. I’ve watched the video and have some ideas. Great video by the way. Very informative.

[@Comm0ut]

Best method for a mill is using a VFD and its no contest. Statics are better for grinders, buffers etc where the considerable power loss isn't noticed. RPCs are better for high load use. Horses for courses.

[@TheTriangle4]

Do you think this would work well on a meat bandsaw or should I look for a VFD? Thanks

[@paddyharte4677]

Ian thanks for this video . I have a question what size starter did you use or did you use the original contactor builr in

[@iainportalupi]

I used the original starter that was already on the saw.

[@paddyharte4677]

@@iainportalupi Ian did you change the starter to run as single phase by looping 2 And 3 on the output. And more importantly where do I connect the contacts for the relay coil so that it kicks the capacitor out . I'm struggling to see where the connections goes. Thanks

[@paddyharte4677]

Ian you are a legend, I have my 3hp wadkin bursgreen radial saw up and running following your video and schematic drawing . Thank you for the information and for making your wonderful videos. Regards Pat.

[@iainportalupi]

@@paddyharte4677 that’s great! Glad I could help.

[@itanongmokayengineer]

nice lecture

[@cujbaion1]

you should use a running condenser for star(wye) connection In order to maintain 120° between the other two coils otherwise you have 180° in a wye 120° coils. Delta runs on a single coil and if you have 3 ends contactor at the condenser it's desired to set free those other two coils from one to another. But for American 120V coils delta connection doesn't fit.

[@joecoruzzi3494]

I want to build a converter for my 1/2 hp metal lathe. If I buy a 35-50mF capacitor what size resistor do I need? Thanks

[@jeromewelch7409]

It's a great video. all great information I'm just confused about one point , and I think you just misspoke because all your informations spot on! why do you call it Delta connected Motor ? The diagram shows the coils of the motor in a star or wye arrangement yes.

[@iainportalupi]

Yes I misspoke when I said Delta.

[@munkzwalm]

Hey Iain. Quick question. I'd like to run a 3kW saw table, 3 phase 400V. Is the rated voltage a problem if i start out with one phase 240V, or will I just loose some more power (on top of the 33 percent I already lost with this system). Thanks for your advice!

[@iainportalupi]

If the motor needs 400v you’ll need to give it 400v to get any usable power out of it. Some motors can be wired for different voltages. Does the name plate say anything about 240v operation? If it doesn’t you’ll have to get a big 240 to 400 transformer. If the saw is belt drive it would probably be cheaper and easier to find a used 240v motor for the it.

[@michaelstempek5530]

I want to make the exact phase converter in this video for a 3hp mill what is the part number for the relay?

[@lecky-arly7098]

Can we use this for forward and reverse ?

[@AllooshO]

I have a question Ian, can we use a run capacitor instead of the start capacitor and keep it connected without the relay? also since you are keeping the motor on Y , does this mean that it's voltage is still rated as 400v?

[@iainportalupi]

The issue with keeping the full capacitance value attached to the motor all the time is that because it still isn’t truly 3 phase power the current through the three motor windings won’t be equal and one winding is going to get more current than the other 2. This could burn out that winding.

[@jasonsprouse2803]

@@iainportalupi ..... Not all 3 phase has equal voltage regardless. There are older systems that one phase is higher voltage (It's called the stinger leg). That's what we have here..... and we are outside of Cleveland.... not exactly rural America.

[@jonlauzon8555]

So I have bought all the parts and I’m not sure how to wire up this relay. I’ve bought the same one you have and it has 8 terminals on the base. Anyone have a drawing for which terminals to plug into?

[@paddyharte4677]

Ian can you answer me this. On static phase converter you used the original switch . Is the coil on the switch 380 volt or 220 volt . Also what voltage should I get between phases on the input to switch. . Just having issues getting the original switch to engage the coil which on mine is 380 v but I'm on 220 volt supply

[@iainportalupi]

The coil on mine is 220. If yours is 380 you’ll need to find one that will operate on 220. What voltage is your motor wired for?

[@lecky-arly7098]

Sir, do you have a video using your converter that shows forward and reverse ? Thanks

[@iainportalupi]

I don’t because I never have to reverse the saw.

[@jaycss]

Will this work on a delta wound motor?

[@roddiesmith8880]

Ian, Are run capacitors not needed to balance out the phases. What would be the advantage or disadvantage of using run capacitors and the start capacitor. By the way, you ought to go in to education. Amazing tutorial and thanks for the lesson.

[@iainportalupi]

Thanks! The advantage of adding run capacitors is that the motor will have more torque and can will develop more horse power. Without run caps it can output 70% of it’s rated hp and with run caps it can make 80-90% of it’s rated hp. However, there is a draw back with run caps. The current in the third winding will only balance out when the motor is loaded to the designed hp. For example if you have a 5hp motor and you use run caps to balance out the winding currents when it’s loaded down to 4hp the currents will only balance out at that load. If it’s something like a saw as soon as it stops cutting wood the winding currents will go way out of balance. If I were to put a smaller blade on it or cut softer wood with it and it wasn’t as taxing on the motor the currents would be out of balance. Any loading variation would upset the balance of currents. If the motor was on something that had a fixed load like a fan, water pump, or compressor then getting the run cap values dialed in would be easy because the load is constant and therefore the currents in the windings will be constant. My general rule is try is if it is a hand fed machine like a saw or a drill press try it without the run caps. If it the motor isn’t up to the task then it’s time to invest in run caps and a clamp on ammeter. There is one exception to this rule and that is any motor less than 1hp. Those I put run caps on out of the gate because those motors are so small you will be loading them to 80-90% of their hp every time you use them.

[@roddiesmith8880]

Iain Portalupi Thanks so much. I have a 3hp Bridgeport mill that I am running on my fathers old phase converter he had for a 3hp table saw. Your advise is fantastic. Thanks again.

[@jochoa72jv]

Can you give a part number for the relay

[@ikifkif]

i just thought.. wouldn't it be worth incorporating a run capacitor to the odd leg as well? wouldn't it at least give it something, and smooth out the running a bit?

[@iainportalupi]

If it’s on a constant load such as an air compressor or a pump it would help. However the run cap only truly helps at one point in the motor’s power curve so on a saw where the load constantly varies it doesn’t help as much as people think it would. If the motor is less than 1hp yes, add the run cap because those small motor’s are almost always loaded to their full rating.

[@propbuildervash]

What exactly do you mean when you say that the transformer need to be wired across leg 1 and leg 2?

[@mrsimpson2022]

he is saying to hook up the transformer to your same single phase wires from your extension cord (220v) . It turns 220 into 24v to pull in starter coil.. If your motor starter/contactor is 120 volts coil you would use 1 leg/wire and a neutral

[@MikeWilliams-nn9xh]

What are the specs on the voltage sensing relay I am connecting this to a 2hp 240v motor. Thanks, Mike

[@iainportalupi]

For a 2hp motor I’d go with a 10A relay with a 240VAC coil.

[@tg9507]

This was THE best educational video on building a static phase converter. I have a 3kW and a 4kW motor. I have 230VAC - 50Hz line power here. (Europe). I have ordered the parts as per yr. video. Hard to find 240VAC 30A NC relays. I have odered this one: Supco SUPR Universal Potential Relay, Single Phase, 110 - 270 Operating Voltage, 30 A Load Current. Can you pls. comment if this relay will fit my application?

[@iainportalupi]

I just looked into that potential relay and that should be perfect for what your converter.

[@tg9507]

Thank u so much for very quick reply. Can’t wait for the parts to arrive. Will post update then. tg.

[@jimkimbrell4878]

Brute force and ignorance I love it

[@joshsundiwa]

well said thx

[@georgiojansen7758]

it's in star, does it have to be in delta?

[@SHARABSERVICES]

What if my input is 240 volts can u tell me what i need.

[@johnfowles4177]

when you say circuit in delta is it delta or star it looks star to me please comment

[@iainportalupi]

john fowles I misspoke, it is star, not delta. The drawing is correct. I had delta on the brain when filming this because the radial arm saw I have with the 3 phase motor is a Rockwell/Delta.

[@hectorcastellanos9793]

what values for 7.5 hp 3ph ????

[@charlescochran9803]

Iain I have ordered the parts to build the static phase converter. I am willing to pay you if would send to me the wiring schematic. I have several schematics but just not sure. Please consider my offer. Thanks and you do a good job without a doubt.

[@faranahmed848]

V informativ,

[@kevinmartin2597]

Hey Ian, I have an old Phase O Matic static phase converter which basically is the same as the converter you built. I think it is not working so I replaced the capacitors and it still won’t run my motor. Any ideas?

[@iainportalupi]

Kevin Martin are the relay contacts any good?

[@kevinmartin2597]

Not sure about the relay contacts. I blew the capacitors but don’t know if that damaged anything else. I replaced the capacitors but still can not get the motor to run. Just slow rotation like 60 rpm and zero torque. There is a relay in the box plus another component that everything plugs into. Looks like a small transformer but can’t tell since everything is riveted to the box.

[@kevinmartin2597]

I have some pics if there is a way to share with you.

[@iainportalupi]

Kevin Martin sounds like the relay isn’t connecting the start cap.

[@kevinmartin2597]

What relay spec did you use? I have 220V on a 30 amp circuit running a 3HP 3PH

[@lecky-arly7098]

Can we forward and reverse this kind of circuit?

[@iainportalupi]

Yes, you would put the drum switch between this phase converter and the motor. The motor will have to come to a complete stop before changing directions with this setup.

[@MAINTMAN73]

But if you have a piece of machinery that has a wye Delta start

[@michaeljennings5170]

what voltage capacitor?and the motor is y connected

[@iainportalupi]

Michael Jennings 240Vac. Yes it is Y, I miss spoke in the video.

[@brian2196]

You say delta windings but the schematic shows a wye or star winding config

[@revolution51]

9:55-Learning alot. Isn't the symbol there a 'WYE'.? Delta is represented by a triangle.?

[@iainportalupi]

Yes it is Wye. I miss-spoke in the video calling it Delta the diagram is right, what I said is wrong. Every time I say Delta just think Wye.

[@revolution51]

Thank you for the vid. I intend to make one to run at least a 10hp 3 phase motor. Also, regarding the rota-phase, what internal motor connection is required to make the rota-phase, or does it not matter.?@@iainportalupi

[@tonycarter3496]

Nicely explained, except your drawing shows Star not Delta wiring: 👍

[@iainportalupi]

Yes, I misspoke in the video, it is star wound. I had Delta on the mind because it’s a Delta brand saw.

[@larryjohnson5163]

Hard-wire RPC or electronic VFD, I'll go with hard-wire...

[@eduardodaquiljr1621]

do you have actual work?

[@iainportalupi]

Yes I do have actual work.

[@ericsnowman8]

I guess I’m an idiot… I cannot find a 30a nc 240v relay anywhere.

[@iainportalupi]

Try McMaster-Carr number 7384k56

[@talltimberswoodshop7552]

Iain, thanks for explaining a static phase converter to us electrically illiterate meatheads. I won't shy away from a 3 phase RAS now.

[@iainportalupi]

Airborne Ranger no problem! 3 phase RASs are great because they are designed for industrial use and they sell cheaply since most people don’t want to deal with a 3 phase saw which means you get a lot of RAS for the money!

[@jaycss]

ANYBODY?

[@jesscast5122]

Ian, the motor in your Diagram has a WYE configuration Not Delta. and also, Single phase power will provide you ONE POLE even if going thru 2 windings in a Real WYE motor. (single phase on a DELTA, obviously will result in ONE POLE, 1 Winding) in any case your knowledge is far better than that guy Tim W. who happens to be in SALES but doesn't really know what the heck he's talking about....Tries to put on a SHOW.......

[@iainportalupi]

Yes, like most of the comments before you point out, I miss spoke and said it was Delta wound I had Delta on my mind because that’s the brand of the saw.