Single Phase to Three Phase Power: Rotary Phase Converter vs Digital Phase Shifter

[@stumccabe]

A better analogy for three phase is to think of a single piston internal combustion engine compared with a three cylinder engine - the three cylinder is smoother running as the power is delivered more evenly through each revolution.

[@jrb_sland]

Agreed. Even better, the instantaneous power sum of the three phases is exactly the same at any time in the cycles - there can be ZERO ripple in the torque provided by a *well-designed* three-phase induction motor, i.e. no need for a flywheel other than the rotating mass of the rotor itself. Nicola Tesla invented & patented [in 1888] a two-phase early version of the modern three-phase induction motor [and ~simultaneously by Italy's Galileo Ferraris], but the final step to the beautiful result was left to Mikhail Dolivo-Dobrovolsky in 1889. Only three wires needed to transport mechanical [rotary] energy for hundreds of miles at high efficiency. The world would never be the same...

[@stumccabe]

@@jrb_sland Yes, excellent explanation.

[@CatNolara]

One other advantage of three phase is that you can run motors on it that don't need brushes like single-phase and dc motors do. Ok, there are motors with capacitors to create an auxillary phase, but those don't run as smooth and aren't as efficient as true three phase motors.

[@VintageMachinery]

That is a very good analogy!

[@nicholasstanziola]

​@CatNolara it's a minor point, but not all single phase AC motors require brushes. AC Induction motors do not.

[@jeffreykull4676]

when i got my bridgeport mill , i looked in to vfd and static phase converters . i was told not to use them on motors built before 1980 because the varnish that was used in the older motors melts at a lower temp and you will more then likely burn it out. Two you don't have any whare nere full power. good videos keith. can't wait to see your next one!!!

[@nilzlima3027]

its not the melting of the varnish that is the problem its the withstand. the output from a vfd is very noisy, those spikes can stress the winding insulation and induce lots of static charge on the rotor which can pit the bearings. I have seen these things in action so pick your poison.

[@johnyoungquist6540]

The technical details of AC power and especially 3 phase power are beyond what most electricians and many engineers understand. AC power is not the simple product of voltage and current like DC is because of phase differences. Three phase power is even more complex. To draw any real conclusions you need a true AC power meter. Fluke has them about $12K. Almost every AC motor uses a capacitor to shift the phase. The rotary phase convertor uses them too. The capacitor phase shifter produces a third phase shifted signal that is not perfect. But it doesn't need to be to get the motor to spin. The cap values are chosen for a typical motor which means performance will differ from one motor to the next using a shifter way outside it rating may work very poorly or not at all. A shifter will always delver less than full HP which in many cases is acceptable considering we never use it all anyway. There no reason to believe that the motor will suffer in any way by operation on a shifter. You can't just measure voltage and current in a AC circuit and jump to that conclusion. In your case the current on two legs was higher but the other lower so maybe the power was the same or even less. A better test would be to run the motor on the two power sources under identical loads and measure the temperature. No doubt the temperature would differ by a few degrees but who cares you're not going to run that tool all day long at max power. The capacitor phase shifter is a simple reliable and safe means of driving a 3 phase motor from single phase power. When properly done it will not harm your motor. While it is a compromise in many cases the value for money wins out over the rotary convertor especially for the hobbyist. it is more efficient than the rotary convertor which uses substantial power even when idling. Those that turn on their rotary convertor on and leave it on waste a lot of power. The VFD is a great way of driving a motor but doesn't share between machines but has many other advantages. The shifter and the VFD are perfectly valid low cost ways of driving a motor. In many applications the VFD us probably the best, American Rotary would like to demonize these and make them disappear.

[@ibiufos]

Best explanation, I was confused whether I use a VFD or a rotary converter and after reading your comment I'm going with the VFD as I didn't think of the constant running of the 3ph converter . In my case the extra saving is better in the long run. thanks from Australia 🇦🇺

[@a-k-jun-1]

I run my lathe off single phase with a homemade rotary converter. I used a potential relay and a pile of capacitors from the scrap yard. I set it up with a digital amp and voltage gauge for each leg from Amazon. It's a 10hp and has been in use for 10 years. The slave motor was also brought from the scrap yard just needing bearings, 25hp motor. With the digital gauges I can live data monitor each leg while using the lathe or any other machine plugged into that outlet. Study up on it and use common sense to get it done.

[@camatbattler2233]

G'day Keith, I run all my machines with VFD's. Easy to program with acceleration/deceleration, variable speed, braking etc. Got one of the newer generation units on my Victor Lathe, single phase direct to 415v, no need to rewire the motor to delta. They are cheap and for me with a small shop compared to a rotary which burns up power when the machines aren't running generates heat and noise, its the way to go. Cam

[@wilkbilt]

You think Rotary Phase Convertors being your sponsor had any influence on this test?

[@nilzlima3027]

NO. I was there to ensure that. american rotary supplied the 40hp unit keith is using and the two little boxes of caps and asked him to make this video and i live relatively close to them so no they exerted absolutely no external factors influenced the making of this video in any way.

[@howardosborne8647]

I am not surprised to see the big variations with the static digital phase shifter. I have heard a number of people having motor overheating problems with phase shifter devices. Of all the single phase to three phase converters these shifter devices are the least desirable option by a long way. VFD or Rotary converters are the only realistically dependable options.

[@genej2185]

I'm a retired plant electrician and you are right on the money. These are a slow death to the motor and just because they work in the short term you will pay the piper when motor blows up and if you are real unlucky the fire will burn your shop down. You might comment if these have are UL listed. That in itself would speak volume's. I use a 10 HP American Rotary and on a 3 HP Acer 3VKH mill and the voltage and current is right on the spec. If money tight a properly installed VFD is a much better solution.

[@bencartee2113]

Speaking from my experience...rebuilt a Brideport Boss to modern controls/VFD, this is academic... If you run the numbers, factor in your hopes and dreams, and check your bank account, the choice is there. While a DPS may be bad choice, my VFD (set up for success) runs fine. Motor has never even gotten warm. Do your due diligence.

[@nilzlima3027]

so many things only have hopes and dreams...

[@elsdp-4560]

Thank you for sharing. 👍

[@georgejaros2781]

It would also be a good idea to have someone connect an oscilloscope to the 3 output phases to see what the waveforms look like. They will not be pure sine waves and they will not be equal in amplitude. Even the output of the rotary phase converter will not be a pure sine wave but it will be better than the phase shifter. Be careful so as to not burn out the oscilloscope, relatively high voltages phase to ground. Possibly use transformers.

[@grahamwright8440]

It would be interesting to see a speed check with both systems.

[@nilzlima3027]

the speed didnt change, just the start up times.

[@elmarqo_3448]

On the DPS you stated one phase passes through so its the other phase that is altered to create the 3rd phase. I wonder what the current was on each phase coming into the DPS.

[@carrollprice1213]

The input to the DPS is 240v single phase.

[@kevinwayne7546]

cool

[@kennyrmurray]

Im using a DPS on my Clausing Colchester 12X40 and mine goes out on reset after about 20 minutes of use because the motor is getting to hot. Can anybody tell me which VFD I should get for it? It’s a 3/4HP 3 phase. It’s against the wall right now and I forgot how many amps it draws. Thanks

[@kennyrmurray]

Actually my question is if I get like a 5HP model is that ok?

[@thisolesignguy2733]

Another thing to remember with digital phase convertors is that it's also changing the sine wave of the circuit. It converts standard wave to digital and back to standard. There's always a drop in efficiency when doing that, and when you do it with newer motors that are sensitive to that then there's even more problems with incorrect amperage, over-heating, and irregular spindle speeds/voltage draws. Think about it, your going from a variable wave that smoothly ramps up & down allowing for a more natural conversion of energy, to a digital wave that abruptly ramps up to full wave then sits there and drops rapidly. Then the phase converter has to change that back to a smooth wave which does not work very well. Motors are just not designed for that, but computers are because they use that for timing.

[@davidrush4908]

For the non-geeks out there a three phase motor is a brushless motor. In the stator or non moving windongs the coils generate a rotating magnetic field. This induces a current in the rotor coils. This current creates a magnetic field that opposes the stator field, causing the rotor to turn. The rotor current is minimized at full speed. Without three proper phases, the currents in both the stator and rotor will be way higher than they should be which will lead to failure. A rotary converter is basicly a single phase motor turning a three phase generator. There are also electronic converters which generate three phases, but they are much more sophisticated than the capacitor boxes being tested here.

[@iteerrex8166]

I’ve never even looked up these devices, but my guess is that there better ones out there, than this bottom of the line. That much variation from leg to leg is way too much to pass spec. This qualifies as “chineezium”.

[@nilzlima3027]

well they are made in korea so koreezium?

[@tpobrienjr]

Mr. Tesla would be proud.

[@johncloar1692]

Phase unbalance is not a good thing. It will shorten the life of a motor. VFD generate take AC voltage and turns it into DC voltage and then generates the 3 phases. Downside to VFD you need 1 for each motor. Just a though.

[@nilzlima3027]

one vfd can run more than one motor, many manufacturers have directions for this.

[@petemclinc]

I run 3 different machines with motors ranging from1 to 3 HP with the same VFD. Of coarse I don't run any of them at the same time and there aren't multiple motors on each machine. I do have to make sure the other machine motors are switched OFF or basically disconnected so as to not accidently start them up when using a machine on/off or forward/reverse control wired into the VFD.

[@williamharris1302]

Buy American and don't worry about it.

[@zumbazumba1]

You mean cardboard box proudly assembled in usa and product made in mexico?

[@oldschool1993]

WOW- this is a disappointing not so subtle commercial for American Rotary phase converters. Digital phase converters are different than VFD inverters. Digital converters only do one thing- convert single phase to 3 phase and are designed for high load applications, so the test with no load was deceptive- under load the voltage and amperage would even out. The Variable Frequency Drive ( VFD) inverter is a far more practical solution to a home or small shop because they are very inexpensive- 10HP units are available for under 200.00 from name brand manufacturers. The most popular function is the ability to control motor speed by varying the frequency and maintaining full voltage which gives a much broader range of speed without loss of power. Beyond that, they have hundreds of functions such as dynamic braking, timed pulsing for things like conveyors and can accept signals from a computer for control of speed and direction for any future CNC conversion. VFD drives are individually programmable to each motor based on the motor tag for voltage, amps, frequency, rpm and Hz, so if you have some older American made units with 60 Hz or some imports of 50Hz your VFD will output the exact power, amps and Hz for each individual machine. Cost wise they are far less expensive than rotary converters because you can add them one at a time as desired with no electrical panels or wiring- just plug them into either 120 or 220 existing supplies. Say you have a home shop with a mill and a lathe that you want to be able to adjust spindle speeds without all that belt changing. You can buy 2 VFD units for under 400.00, install them your self and plug them into the wall. A rotary phase converter with the same 10 HP capacity will cost 1500.00 plus the wiring into your panel and a new 3 phase panel etc.

[@MickHealey]

Interesting video - thank you. As someone with an electronics background, it would have been nice to see oscilloscope traces, comparing the rotary phase converter (RPC) with the digital phase shifter (DPS). It would also have shown your '3 guys hammering a tent peg' analogy very clearly. However, from the voltage and current readings you gave, the DPS is no substitute for the RPC.

[@lynnplestid2711]

Yes I like to geek out too on visual

[@ionstorm66]

They also didn't show a RPC worst feature, startup. They sag horribly on inrush on the third leg. That's the reason they have such large capacitor banks inside the RPC. The generated leg is limited to the locked rotor amps of the motor inside of it, but at that current voltage approaches zero. So you will see 10% or less of the inrush current on the generated leg vs the pass though legs, with a drop in voltage too. Due to the delta configuration of the 3 phase, this means your motors basically single phase on startup if there is a large load on the motor, as L1-L2 will have all the current, and L1-L3 and L2-L3 will have little current. The voltage sag will also effect the motors if you get close to the capacity of the RPC. The try to compensate for this with large banks of run caps wired in. A VFD/DFS will produce even voltage and current per phase up to the limit of the device. It will provide less peak inrush current to a motor, but all 3 phases will have the same inrush. Thus will have much much higher starting torque.

[@mhansl]

This is not to say it is impossible to have an entirely solid state three phase converter. It will have more to the electronics than half a dozen little caps.

[@captianm4766]

The guy failed to take into account power factor, THD, (total harmonic distortion), inrush current and many other factors. Bottom line, there is no great substitute for commercial three phase power other than an appropriately sized generator capable of three phase power. The old rotary phase converters were literally a single phase motor with a belt driven three phase generator next to it.

[@cda32]

weeeeeeeeeeeelllll also, at least assuming the current clamp was true RMS, you need to get the true reactive power. Obviously since the DPS can't create a good 120 degree phase shift you will have an imbalance but not sure it's the dire end of the world situation advertised here - but of course this channel will always give the edge to a RPC. I think an inverter with a nice big shunt reactor on it is the best option, but that's serious cash so I get it - RPS is probably the best balance of power, cost and reliability for a home shop.

[@donalddepew9605]

I've run two of them for about a year and a half now. Not a problem as of yet. A VFD will do the same thing but allow different parameters such as frequency control and soft starts on electrical motors, as well as many other things. For me it was a very inexpensive way for me to get 3 phase rather than buy a traditional phase converter. Great Video guys!!

[@lineshaftrestorations7903]

I have used a similar Tripp-Lite 5hp device for 25 years. They are effectively a starter. The motor is really running on just one leg. Power from the motor is reduced to less than 2/3 of nameplate rating. Never had any overheating problems. For low duty applications without frequent starts/stops/reversing, it can be cost effective over a rotary converter. Real 3phase is still the best followed by a rotary generated power.

[@markgeorge3960]

Thanks for the video, Keith. You can make a crude but workable rotary phase converter yourself using a spare three-phase motor (needs to be rated at higher HP than the motor you are starting) as an idler motor. Use a cap to start the idler motor, then tap off the three legs of the idler motor to the machine you want to start. Not as elegant as the American Rotary products, but much cheaper, and works fine.

[@nilzlima3027]

yea that is better than the box 'o' caps solution for sure. I have one and that is how every commercial rotary phase converter starts life, the question is how much further did the manufacturer take it.

[@motor2of7]

I’ve been running this configuration for years with zero problems

[@johncochran8497]

The idler motor trick is basically what rotary power does with some capacitors to even things out. Additionally, another trick that you can use for three phase power and assuming that you have multiple three phase machines is to simply turn on additional machines and let the idle. They won't really create much of a load if they're idle, and the back-emf they create simply because they're running will result in the three-phase power being smoother and capable of handling a larger motor under load.

[@edhoran1709]

Thread drift: I've used a spike maul and have participated in a triple spiking when spiking up rail. It starts off even, but after the second or third round, the hammer blows go from being even to one hammer following closely by the first followed by the fast incoming third hammer. Luckily, it doesn't take more than 3 rounds to drive a spike home, and the spikers will get used to the close together swings on the next spike to be driven. Instead of hit-pause- hit-pause-hit, the hammers sound like hit-hit-hit in rapid succession.. It makes no difference who is spiking, as they will fall into the same spiking pattern after the first round. It's pretty cool to listen and watch 3 spikers working together and hearing those hammers ring.

[@nilzlima3027]

dose it count of you are not singing?

[@edhoran1709]

Nice response! Thanks. "If the hammer isn't singing, you ain't a-swingin"

[@PatrickPoet]

I wonder why? Doing the same thing swinging hammers on iron out of a forge, blacksmiths get nice even timing as the usual thing. If someone speeds up or slows down they're a beginner that hasn't gotten it yet.

[@MyungYounElectronicsCoLtdDPS]

We are a DPS manufacturer and seller. Thank you for making DPS video. However, it seems like the video was made without much knowledge of the characteristics of DPS. It appears that there was no load on the motor when testing the DPS. However, the motor is never used without load. When the motor load is less than 50%, there may be an imbalance from the voltages and currents output from the DPS. Normally, when the motor load is 50% more, voltages and currents will be balanced. The current in the middle phase of the DPS output changes depending on the motor load. Most of our customers are using DPS very well on their 3 phase motors. We are concerned that customers may have misunderstandings about DPS due to this video. We think that if the person who made this video had read the DPS user manual carefully, he would not have made a video like this. Thank you.

[@samuraidriver4x4]

Would be interesting to see the output on a oscilloscope, the peak to peak voltage is probably all over the place. As long as people are not informed they keep buying this crap and as long as people are buying it the manufacturers are making them.

[@nilzlima3027]

that can be said of so many things. split lock washers for example, people still believe those things do something so they keep buying them. homeopathy, fuel line magnets, how many can you name?

[@petemclinc]

So, are all Digital Phase Shifter's or VFD's created equal? I don't think so, maybe that Korean unit is just plain crap. Not everyone can blow 5 to 10 grand on a Rotary Phase Converter. I've been running a WEG unit for several years without incident. These American Rotary Phase Converters can cost more than the used equipment they energize.

[@rgmoore]

Waste of time watching an advertisement for Rotary Phase Converters.

[@nilzlima3027]

there are a bunch more!

[@ve7cbh]

I am disapointed in the way this testing was carried out. One of the things one must take into account when doing testing on electrical machinery is the specifications in which it was designed to work. With this particular device the manual states that there will be I &V imballances under a no load condition which is how this testing was carried out. I am a big fan of this channel but I need to say that in this case there was no real test plan, no comparision of results at rated load conditions and contained obvious bias in the way it was presented.

[@nilzlima3027]

fair enough. you try it and get back to us.

[@TgWags69]

Single phase...1 guy pushing the merry-go-round. 3 phase...3 guys spinning it.

[@blitzkrueg07]

i have a American rotary 20ad rotary phase convertor L1 is 120 volts, L2 is 275 volts, L3 is 120 volts. I was told that was normal when I bought it in 2015 now I am not so sure. perhaps I should check amps also.

[@edwardmorgan4816]

As a degreed EE I find this to be "Halarious Stupidity" from start to finish. Anyone taking these two as competent to review anything electrical or electronic should think twice.

[@tomnorman5461]

More like a commercial for your sponsor Keith. Use a decent VFD for your 3-phase power requirements...no moving parts, stable outputs, motor overload protection, adjustable speed, braking, and very reliable. IMHO

[@nilzlima3027]

he has 20 motors all of various size so the rotophase was the best and most cost effective solution by far.

[@SteneWoodwork]

I think something that was missed was that in the DPS manual states that under 50% motor load the voltages will be irregular, but above that the voltages balance out. I think that should have been noted and tested before discrediting the device, especially since the channel is being sponsored by a company that would be threatened by this device. I have machines on VFD's and rotaries, and will be running my dust collector off of a DPS, which the motor will be under load all the time.

[@BLS2008]

I noticed that too! I want to see what this thing can/will do with load

[@CameronMcCreary]

I had a machine shop when I was younger and I paid PG&E $5000.00 to have 3 phase Delta power brought in from the switching yard about 5 miles away. It worked great and I never had any problems. It was 208 volts 60 cycles and ran my machines well.

[@carlthor91]

For me if I would want 3 ph now. I would have to pay $3k-$5k to go ~ 300 feet. I am just 300 feet from the transformer triplet up the pole.

[@DavidSellars-b8l]

@@carlthor91 It seems to me that within the last ten years a friend paid Pacific Graft and Extortion a whole bunch more than that. I believe that he had to "buy: three transformers, plus the poles and wire. The "engineering" was over $3-5k.

[@carlthor91]

@@DavidSellars-b8l I am in Northern Canada right dead between two hydro plants, three phase is only 300 feet North of me on a pole. My split phase pole is ~60 feet from my power mast. So no poles, just new wire, mast, and meter.

[@nilzlima3027]

oah how times have changed. there is 3ph not 150 yards from my house and xcell quoted me $11,000 for a connection to the garage only.

[@dannyl2598]

In my area, they just look at you and say No! If I owned a building that has three phase, it is my understanding that the monthly cost would be out of my budget.

[@matthewkantar5583]

A friend’s dad ran his three phase Bridgeport mill in a suburban basement on single phase and a couple of capacitors. He used it 5 days a week for 50 years. When an electrician saw the setup, he confidently told me it would burn the motor out in an hour.

[@nilzlima3027]

if the thing is well tuned and the motor is kept cool it can work, the question is how good are you and what are you willing to wager.

[@Comm0ut]

Mine had the simple converter but I prefer the power boost and speed control of the VFD I replaced it with. The primitive converter will now run a buffer.

[@mathewmolk2089]

We call that Appalachian Engineering. It's amazing how sophomoric 90% of the electricians can get (or those that do electrical work, anyway) . The first thing I'd consider is the actual load on the mill. Personally, as an industrial electrical/millwright contractor with over 50 years in the trade, I have never seen anybody continuously run a Bridgeport at 100% of the rated horsepower in my life, but I have seen dozens of guys cap starting lathes and mills in home shops with zero headaches. I have even done it myself when I was first starting out. Where you usually get into problems is with compressors. A sheave reduction of 15 or 20 % and converting it to continuous run (Unload to control cutin/ cutout) usually solves that problem and guys get to use their sandblaster with a 3 ph 5 horse industrial compressor in their home shop . An air conditioner starting cap and current relay makes a good starter if you are on a tight budget. (Just remember you cannot run the cap more then 2 or 3 seconds just to get the motor running.) Would I try it on a 96" tandem roll at the Steel Mill,,,,,,Hell no!!!! But if you got a little Clausing 5400 in the basement there is nothing to worry about. BTW, The thing nobody mentioned on that belt sander is the heaters in the Motor starter. - You have to change them with the cap box.....and Kieth, there is no way in hell you would barf that motor by grinding a radius in the end of a piece of 1/2x4 Hot rolled. Belt sanders are pretty crude machines and the effect of the imbalance is pretty much irrelevant. It takes a little screwing around with the values but you can easily make a phase converter out of a 3-pole disconnect, cheap starting cap and a common 15 Amp light switch. ---- I even saw a guy make one out of a disco a motor and a recoil starter off a model N Briggs gas motor. (Yep, you can pull start a 3ph motor).... It's not alchemy at all.

[@timhoward5310]

I bought one and burned my 2hp Bridgeport mill motor in less than 3 minutes. Motor for mill is $1500.00 to $2500.00

[@Ratridez]

One of those Dps burnt out the 5 hp motor on my Modern 857 mill and the Dps also fried , I do believe it's the same motor on a Bridgeport and not very cheap to ship to Canada . I bought a generic new 5 hp motor same speed for $580 with a C face mount and modified the shaft from the original motor with the use of a bolt on bracket and a flex coupler that I machined in my lathe . Now I can run any motor that fits on my adapter plate . I'm in the process of building my own rotary phase converter right now .

[@duster8100]

A Variable Frequency Drive (VFD) sounds a whole lot better to me. It is way more versatile with variable ramp up times, motor braking, variable speed and about a hundred other things it can do. I have been running motors on VFD's for extended run times, unlimited starts per hour with no issues for over 10 years and with the latest vector drives there is very little loss of power at slow speeds.

[@katelights]

VFD are great, but their main disadvantage is cost. if you have a lot of machines they can add up real fast.

[@TgWags69]

Several examples I've seen on these videos always had a real high pitch whine that I find very uncomfortable to be around. I am very reluctant to try them for that reason.

[@GibClark]

@@katelights but also 1 vfd with a hanging hook with twistlock plugs can get you running in a one man shop if similar size motors. Did that til I got my rotary

[@carrollprice1213]

With internal components coming from the same place, you're wasting your money buying expensive VFDs that work no better or last any longer than Chinese imports.

[@rupertpowell]

I've converted many machines to run on single phase using HuanYang VFDs and they are very good and very reliable. At around $100 for a 3HP version I think they are excellent value too. As comparison SPCs suck. I have no experience of RPCs but the noise of the motor would drive me nuts.

[@apexmcboob5161]

Would have been interesting to have tested the leg voltages and currents at the rated load. I suspect they would have stabilized quite a bit.

[@nilzlima3027]

no the voltage would only shift a little and the current on the direct lines would increase proportionally to the current demand. remember its I 1ph X (square root)3= I 3phase.

[@chrisarmstrong8198]

The volume of a capacitor is an indicator of its energy storage capacity. At higher loads, when more energy needs to be stored, the fairly small energy storage capability of those capacitors may have led to worse unbalance. As you suggest, the best way to tell is to do a full-load test.

[@ron827]

Pure honesty backed with knowledge and reality.

[@bradcallaghan8099]

I have had an American Rotory phase converter in my shop for 10 years and it has worked flawlessly.

[@dannyl2598]

Thanks Keith. One dead giveaway is when you have a very heavy machine running on a little plastic box.

[@nilzlima3027]

just wait until the very heavy machine is "supported" by little plastic boxes!

[@gubr]

I've been running a three phase motor in delta configuration with a capacitor between two legs on 230 V single phase. This is called Steinmetz circuit over here and only recommended to a max 1 - 1.5 kw motor. I would never use that for a bigger or expensive motor since the phase shift is less than 90° instead of 120° and you get ripple curents and the different amperages. You also don't magically get the full power of real three phase. It's a simple solution for small tools, and should be treated as that. I am just running a small buffer this way and it's ok.

[@tacticalrabbit308]

When are you going to finish the steam stoker engine repair

[@robertmercersr3075]

Several years ago I had an industrial plant that had a 50 HP motor burn up the first night after it was rewound. The plant opened only two months before and everything was new. After checking everything I discovered that the heater block had a different colored reset button going over the paperwork there was a 25% differences depending on the color of the reset button. We went through every motor control room and had to drop two sizes in the heaters to get the right protection of the motors. The best part was my company had a 25 year working relationship. My son still does all their electrical and machinal work. Like a lot of things in life sometimes, you have to dig deep to find the problem. Cheep isn't always the best way to go.

[@craxd1]

Rotary converters are the best, will outlast electronics in my opinion, and the sine wave is clean. The old capacitor-type “converters” aren't really converters, as they're designed only for starting a 3 phase motor, where one leg kicks out after they start, and you lose 1/3 of the power. That is why rotary has always been the best, if a well-made motor is used. I used a 20 HP, 3 Phase, Lincoln Electric Co. motor on the converter I had, with a small 1/2 HP blower motor (also known as a pony motor) to start the larger turning at the push of a button. Really, they're easily made. When there's no 3 phase on the pole, it's your only hope, as I called the power company for an estimate to run 3 phase to my shop, and the price was staggering years ago.

[@shopdave7489]

There is another option, solid state phase conversion (Phase Technologies). I have two, one of which is in my machine shop powering CNC equipment. They are expensive but very precise 3 phase generation. If you hook an oscilloscope to the output you can not tell which phase is generated and which is original.

[@briangeiser5705]

That is the path I am headed down, more for the reasons of compact space and less noise that RPC.

[@nilzlima3027]

I have installed those things too. they are more or less a vfd that has a static out put at 60hz. a vfd is likely cheaper. depends on how many machines you are going to have hooked to it. they make the same whine that vfds do as well.

[@nevetslleksah]

Thanks for the video. Would like to see the same comparison using a VFD.

[@carrollprice1213]

Every VFD I have checked showed essentially equal voltages and currents on each phase, which is what you want to see on all 3 phase motors.

[@nevetslleksah]

@@carrollprice1213- thanks.

[@akfishoner4143]

Hey I built a RPC myself using a baldor 10hp for the third leg. It’sdouble thehp largest motor so works great. I went with Vfd for my 2x72 grinder though bc I need variable speed. The KBAC series Vfd does such a great job and is, I believe, a better build compared to all other Vfd I’ve tried. Anyone feel different?

[@alexanderkupke920]

I wonder what you mean by "for the third leg". At least what I know about RPCs, the generator part creates real 3 phase power, which the same as with a gnerator set, needs some smoothing and stabilization. If you would simply create a "third leg" using what is a 240 V or two phase supply in the us, your phases would be out of whack, as those 240 V are just the opposite end of one transformer, shifted by 180°. The 110/120V circuits are just a tab in the center of those windings creating the neutral. So I guess I got confused by how you expressed it, and the RPC did not just get you the two phases 180 from each other and a third one somewhere in between. My insight into such things as RPCs or DPS is quite limited anyways, as living in Germany I am blessed with real three phase out of the breaker panel. (Which, lets be honest, most houses would not even actually need as three phase. It is just how our grid and distribution to the houses is set up differently.)

[@llapmsp]

Great video Keith, well explained for those of us that don't use 3 phase. Thanks for sharing.

[@Dino_Buk]

0:45 🇰🇵 😂👍

[@BLS2008]

Hey Keith! I wanted to point out that the DPS manual states there are voltage imbalances up to 50% that will balance under load. Is there any way you can test this?

[@crazor01]

So after watching the video, my fist thought was: why don't you give the bigger DPS a go here? Maybe they're overpromising, like e.g. the car hifi guys do with their amplifiers. Then I went to the their website and looked at the MY-PS-10 specs. It says "It must be used for 7.5HP motor. Do not use with 5HP motor or 3HP motor. If the MY-PS-10 model is used with a 5HP motor or less, the motor will heat up or make noise due to overcurrent." So there is literally no power electronics going on inside these boxes except to switch from start to run, it seems? I wonder if you ran into the issue the manufacturer warns about, e.g. running your 3HP motor basically at idle, causing the mentioned overcurrent. Of course this dependence on minimum load makes those boxes entirely useless for most kinds of machines in the shop. Alright, time to brush up my 3phase knowledge, as I'm still not entirely sure how those boxes even work ;)

[@henningventer2917]

I would like to see the difference on a power analyzer. I don't think the phase shift is 120deg and that will cause the unbalance on the current. What worries me is that one phase was in an over current state. Power analyzer is basically a 6 channel oscilloscope, nice to compare voltage and current curves on one screen. We have compared the wave forms on a FVD before and after the line inductors. Even after the inductor the wave form was not a sinewave.

[@davidgleatham9966]

as a 'marine electrician' i got lots of stories.... amazing what can be done with old scrap... and salvage.... I was shown a jointer with 1' blades and 7' table w/ a7.5hp 3ph drive. powered from a 50amp 1ph breaker (??)....that fed 240vac into two legs of a 3ph switch to run a 240v 1ph 1.5hp motor and another switch tied to a 10hp 3ph motor paralleled with the jointer motor. These 2 motors were also joined with a lovejoy coupling ya, man! weird... so turn on the power, turn on the 1ph motor to spin up the 10hp... turn on the 3ph switch, then turn off the 1ph switch and the planer gets the 3rd phase to run well. I moved the 'converter' to in side the shop from it's dog house; and later an old planer (7.5?hp) was added that could be used if the jointer was off.

[@HappyHarryHardon]

I put a VFD on my 10hp screw compressor. Loaded it runs at 50hz and unloaded idles at 30hz. I enjoy the speed control for most of my machines.

[@PatrickPoet]

That didn't make any sense when he said, "remember electronic tolerance is 20%." Different electronic components are built to all sorts of tolerances. The same component, say a 5W 600 ohm resistor could be manufactured to be 1%, 5%, 10%, or 20%. There's no such a thing as "electronic tolerance is 20%."

[@byronlaw6724]

Last year I bought the diesel version of a large piece of equipment I wanted because the electric version required 3-phase power and when I called the electric company, I was informed there was no way to provide me 3-phase power without a significant investment ($100K+) since I am rural. Then I find something called a phase converter on FB Marketplace and after looking into it, realize that the electric company providing me the 3-phase power was not my only option and that I could have bought the more convenient 3-phase version of the equipment with a minor investment in a phase converter. You would think that someone working for an electric company would have known that and been able to suggest that possibility. Oh well...live and learn. At least now, I understand that I do not need to rent out facilities in town that already have 3-phase power.

[@itsallokay]

From watching your video I can tell that you went in pretty much with your minds made up. I have 2 hydraulic presses running and separate VFD's in a combined total of (1)3yrs and the other 4yrs and that VFD costed me $175dls each.

[@mkelleyp7]

Great Video!! Industrial Electrician and Machinist here. This is spot on. A static phase converter starts the motor by creating the third phase but runs the motor on single phase. For small HP motors, single phase VFDs work great. Set the VFD to 60HZ, and use the machine controls to control speed. Most older motors do not have the proper winding insulation to handle VFD speed control.

[@Tishers]

It is not a true three-phase device where each leg is 120 degrees out of phase with the other. It is a two phase device that create a 'fake' third leg by playing with capacitance. So legs 1 and 2 are 180 degrees out of phase and the fake phase is 90 degrees out of phase with those other two. It is 0,180,90 instead of 0, 120, 240 (phase angles). The third leg is created by the magic of capacitive reactance. It is also why the device needs to be sized so the motor takes up at least 50% of the device's rated capacity but not more than 100%. I have used similar devices on ten horsepower motors on things like a Limitorque valve drive (to open and close a gate valve on a sixteen inch petroleum pipeline (remote operated line-isolation valves). Over time the capacitors age (all capacitors have a limited life expectancy that starts the moment it is manufactured, they can age and go bad sitting on a shelf in a warehouse). This aging on capacitors is accelerated in high temperatures or under use (The ESR value of the capacitor decreases). Eventually the motor just stops working; What is worse is when the motor just stalls and sits there humming and getting hot. In unattended operation it eventually burns out one of the two windings (but never the one with the fake phase because that is the one that never functions because of the bad capacitors). ------------------------ A rotary phase converter can deal better with the inductive 'kick' of a motor when it is starting up and is a true 0,120,240 degree phase output.

[@ianrobinson509]

There's an old (Northern) UK saying "You don't get owt for nowt" basically meaning everything has a cost. This device would appear to bear this out.

[@martineastburn3679]

ELI the ICE man. Voltage leads Current in inductive circuits and Current leads Voltage in a Capacitor circuits. One is direct, one is shifted by a capacitor and the other leg is shifted by the motor inductive. It would have been better if it were an electronic voltage/current. VFD circuit. Speed control on 3 phase from 220 single phase. Also have 120v.

[@chrisrhodes5464]

The old saying you get what you pay for rings true here I don't have a shop full of three phase equipment but I use to work in a place that has tons of conveyor belts and other three phase stuff and know how much it matters having good power over the three phases

[@stuarthardy4626]

Ok I am an electrical engineer , worked in heavy power motors etc , question for your guy did you check the power factor in both cases ? the larger caps were there to provide a lag PF while the motor ( inductor ) will give a lag PF , I would be very interested if how much watt less current is present which would skew the reading as taken with the amp clamp simply analogy for single phase v three phase single phase is like a single cylinder engine and three phase is a three cylinder engine , all will know which is the smoother of the two ,but if the circuit is unbalanced the three phase will cause the motor to run rough . as a last request can you show us the wave form for a rotary and a the Little box of tricks ( I very much doubt that the motor winding will suffer with such a crude device VFD re synesize the three phase from DC in the unit and before the smoothing cap it is a square wave due to the circuity

[@nilzlima3027]

sure, if we had those tools but as with any video there needs to be a limit on how much stuff you put into it. idealy the capacitive reactance should cancel the motors inductive reactance to give you a PF of 1.0. the point of the box 'o' caps is to generate enough phase shift to create a rotating magnetic field in the motor. the degree of that shift will dictate the amount of torque the motor puts out. rest assured the PF is very poor, if the thing works like its supposed to i would expect something like 0.6 - 0.7. the only one who cares abute that is the power company and we have limited tools to make those measurements so its not in the video.

[@commonsense5105]

Well in reality, since the PF is the phase shift between voltage and current and the motor ideally has a maximum efficiency to reach it horsepower is at unity or PF = 1, it's more than the utility that cares. To get to the required needed HP the motor needs to do its job when the PF is shifted to 0.6 to 0.7 requires much greater current since the voltage, under normal conditions, would be fixed. This greater current will generate more heat, which will affect the lifespan of the windings/motor. So it doesn't just affect the utility, it will affect the life of the motor too.

[@paulputnam2305]

Great information in this splendid video, thanks! Have you seen the phase inverted Leo, from Tally Ho, uses on his big ‘ol ship saw?

[@edpopelas2844]

Great video Keith! There is quite a lot of information out there about these but some of the finer details are missing. I’ve long wondered about the EMF. I haven’t confirmed this with my scope but as I understand it a VFD effectively turns AC into DC. The issues you experienced make sense as an AC signal rises and falls DC can overlap as you described. I also wonder if the higher amperage and voltages you are seeing is the motor fighting itself due to the EMF or overlapping voltages (lead?). Lots of good food for thought. Will definitely have to reconsider my setup.

[@MrSleepProductionsInc]

This isn’t a VFD, it’s a static phase converter.

[@edpopelas2844]

@@MrSleepProductionsIncAh. I misunderstood I thought he was referring to a VFD with just a different wording.

[@nilzlima3027]

yea that is how vfds work, all of them. convert to DC, filter caps, then high current high voltage transistors to create an output of the desired voltage and frequency.

[@richweiner6735]

Perhaps the clumsiest explanation of rotary phase conversion, phase shifting and use of a VFD. Nice gents, just not a great video to understand single bs three phase power usage. And, no, I doubt I could do a better job .,.

[@ssmt2]

I lucked out. I found a residential property that had three phase already set up in a 4500 sqft shop building that the previous owner was using for his business. It was the deciding factor for buying the property. Otherwise I would have gone with the rotary option to power my machines.

[@be007]

Let me guess, the Rotary Phase Converter is really good and the other one is totally shit. It's almost funny to see how a sponsored video works. Are there still people here who still fall for this sponsored bs? and, that RPC is always using power, even if no machines are working, what will it cost on an annual basis in terms of lost power? Or do you walk to that RPC every time to turn it off when you have (briefly) finished milling or turning?

[@BigMikeECV]

It would be interesting to see the power factor on the 240 side (e.g. the ratio of the input current to the input voltage). That might explain why different output legs have different voltages and current.

[@austen-morris]

Great video. I just bought a laguna 18-36 wood lathe that uses a dps to convert 110 to three phase and adds a vfd for speed control and reverse. Are they basically using this same setup?

[@charlieromeo7663]

Just curious if anyone watching uses or has seen a Phase Perfect DPC? They are pricey for the home shop guy, but are supposed to provide service-grade 3 phase power that can be used for machines with sensitive electronics.

[@carrollprice1213]

Single phase electrical phase power and three phase electrical power are identical in principle to one-cylinder and three-cylinder internal combustion engines, in that for single-cylinder IC engines, one power pulse occurs for each two revolutions of the crank shaft, whereas with three-cylinder IC engines, three power pulses occur over the same time period. As to the DPS converter shown here, I ordered and installed one on a 3 phase, 5 HP lathe and returned it to Amazon after testing and finding the same set of conditions seen in this video. Including the motor becoming too hot to touch after running for less than 10 minutes under light load. They are junk and should be taken off the market. As to my lathe, I installed a 4 KW Chinese import VFD, followed by minor modifications made to the start-stop control wiring.

[@bchrisl1491]

So does this box rectify the incoming AC to DC and then drive a three phase inverter creating three phases, each 120 degrees out of phase? I would have liked to see the waveforms of the three phases displayed on a scope.

[@andrewwolf4430]

15 years ago I needed a phase converter. Since I was using cnc press brakes I chose an American rotary phase converter as it had a real sine wave output and well balanced legs. I then tried a vfd on my mill. It worked great until I let the magic smoke out. And couldn’t put it back again

[@nilzlima3027]

stoopid magic smoke! i tried the liquid smoke, no dice.

[@raikbusse7697]

My house was built in 1964 in Germany and has 3 phases of power since then, why is that so hard to do in the US? Best regards

[@someguy2741]

I bought a couple of these from another company on Ali. It worked ok until i tried the "self learning". Then it blew its mosfets and everything went live and it melted the motor. It then blew all the magic out the side. 240v two phase on canada. It tripped the breaker on the garage panel AND the breaker at the subpanel that feeds the garage leaving me in the dark. It blew the tops off of all of the mosfets and they all failed closed. It is the most perfectly white sparks I have ever seen.

[@digital_harry]

I like Keith and his trajectory as a machinist, however this is a misleading video made by two guys that dont have the knowledge or expertise about what they are trying to convey. Let alone he states one of his sponsors is a company that sells rotary phase converters, seems there maybe a little bias and conflict of interest.

[@robroysyd]

I think these cheap devices have their place in the grand scheme of things e.g. a grinder or linisher that you're not going to have running for long, For sure running the motor for too long could cause a single winding to overheat but even with a VFD running a motor that has fan cooling at low RPM can cause overheating problems.

[@shamanking5195]

Why did the amps increased when the voltage increased ??? can someone explain that ??? it does not make sense , as voltage goes up amps should go down and vice versa.

[@davidvik1451]

I've heard these described as two phase with a starting circuit which your demo proved out. For an in depth, but easy to follow review of motors controllers and VFD's go to Pump Ed 101 by Dr. Joe Evans. I have had the pleasure of sitting in on his presentations at workshops in the past. His online material appears to be transcriptions of his presentations. really good stuff. Thanks again for providing another very informative video.

[@bryansmant870]

Great review. Curious to see the differences compared to an Automation Direct or similar VFD. As an engineer, I love the geekery!

[@nilzlima3027]

at some point i may have a 'scope, one or more of those and some time so we might do that.

[@williamwinsor7376]

You probably should have explained exactly what a phase is to us knuckleheads.

[@alarthofer4611]

I am really glad you are not using electronics from North Korea, doesn’t sound safe. 😉

[@howardvillanueva2354]

15KVA I USED Idler DC CAP.400VDC 2200uf

[@KitCullen-zn4id]

That God I live in Australia wire up my 3 phase machines and a way we go , if it goes the wrong way change a wire ! Kit from down under

[@dansvec5411]

You would never want to use a digital converter for an air compressor, they need maximum current on all 3 phases

[@MrAutodan]

This is not a digital converter AR makes this type of phase converter that are better matched for 3 phase motors,

[@timziegler9358]

Great advise and great demo! Thank you.

[@davidsomerville7868]

a good example for single phase vs three phase is a merry go round being spun by a single person or three people

[@chuckinwyoming8526]

3 phase motors can run on single phase at a reduced power BUT THEY CAN'T START on single phase. Starting requires a phase shifted 3rd leg. The capacitors can provide a phase shift that will give a direction to start the motor but it will most likely never be a balanced 120 degrees. The angle will depend on the capacitors, induction of the motor and it's load. I have built phase converters and 3 phase capacitor start/run circuits for specific motor and load. It is possible to come close to 120 phase shifts over a wide load range but you really need to know what you are doing and get the whole system balanced. This is what the professionally built rotary phase converters do!

[@lecky-arly7098]

Can we forward and reverse the motor using DPS?

[@babarkhan1217]

Apple to Oragne comparion - kill the purpose of comprison

[@jd3497]

Call a spade a spade in your title. It's a static phase converter.

[@adammontgomery7980]

People are so bad at explaining electrical stuff.

[@richardcurtis556]

A public service: thanks.