Running 380V 3-phase motor on 230V 1-phase

[jimalm]

On jimalm Said:

Hello Hans

Yes, please do send a copy of the wiring diagram. I know it’s hard to take a picture of the nameplate … on my lathe there is a hatch at the back that provided the best access, but it still took a few tries with my phone to get a photo I could use. I haven’t tried pulling the motor out of its cabinet, and would rather not, or at least not yet.

Thanks in advance

Jim

Hello Jim

here the page from my Leinen manual. Perhaps it is helpful. Unfortumately I can’t take a pictore of the motor. The access door is blocked by a heavy table.

 

Kind regards,
Hans

 

[Bazyle]

On Bazyle Said:

Vic, Thanks for the reassurance that this can be used with an omnimill. Does one use a 250v motor start cap or does it need to be 400v?

Sorry, only just seen your post. The capacitor voltage etc is mentioned in the picture I posted.

There always seem to be those that say things like this can’t be done, but I happily ran my Omnimill like this for about a year without any issues. The machine was only sold due to a house move. The machine cost me £550 at the time and the cost to move it was £1000.

Edit: I read many years ago that it was not at all uncommon for manufacturers to fit three phase motors into domestic appliances. Motors etc were bought on the open market and if a three phase motor was available at a good price then it would be used.

[Vic]

On Vic Said:

On Bazyle Said:

Vic, Thanks for the reassurance that this can be used with an omnimill. Does one use a 250v motor start cap or does it need to be 400v?

….

There always seem to be those that say things like this can’t be done,

Not in this thread so far as I can see!  On the other hand we have 3 members claiming that Steimetz connected motors are “perfect”.  This they cannot be!   More accurate to say “a Steinmetz connected motor might run well-enough to do the job”, but keep an open mind.   It’s a cheap compromise, great if works, but there is no guarantee that a Steinmetz connected motor will even start, especially if it’s heavily loaded at the get go.   Lathes and mills are not heavily loaded until cutting starts, so there’s a good chance they will spin up, but…

I suggest anyone thinking of trying Steimetz should check out the disadvantages before spending much money.  Briefly: reduced power, torque and efficiency, increased vibration and power factor, plus risk of overheating.

 

Edit: I read many years ago that it was not at all uncommon for manufacturers to fit three phase motors into domestic appliances. Motors etc were bought on the open market and if a three phase motor was available at a good price then it would be used.

Much less common today.  Robert lists the type of applications that used them – all light load starters like fans.  When efficiency and power matter, better to cough up for a single-phase motor, or – these days – to supply the motor with a built in  inverter.

Unfortunately banging the drum in favour of  Steinmetz doesn’t help jimalm!  His lathe has a multi-speed 415V motor with 3-windings.  Thus Vic’s Omnimill isn’t a good exemplar, no matter how pleased he is with it.

Easiest answer for jimalm, is to have utility 3-phase installed – if he can afford it.  Cost varies enormously, unlikely to be less than £2000, and could be 20 times more.   Think long cables, poles, trenches and transformers…  Only way to find out is to get a quote.

Single capacitor Steinmetz is a poor bet, not least because a step-up auto-transformer is needed too.  And I suspect a sophisticated commercial Static Converter – switching several capacitors and maybe an inductor – wouldn’t do do either.  So is a 240 single-phase to 415V VFD, because these do not like their outputs being switched under load.  (See the circuit diagrams supplied by  Hans!)  They also dislike single phase accessories hung off the 3-phase wiring – coolant pumps and machine lamps etc, if present.  Both bad answers to jimalm’s need.

My gut feel is a 415v rotary converter like this £1530 Transwave unit is a safe choice for him, because it will start the motor, run smoothly, have more power and torque, cope with pole changes, and supply other 415V tools, “plug an play” in the workshop.  Rotaries ameliorate most of the disadvantages of Steinmetz in naive form.  Almost as good as utility 3-phase apart from being big, noisy and rather inefficient! Or, even worse, plus fumes, a generator.

In engineering, I was taught the importance of identifying the actual problem and presenting a balanced view of the options.     Got marked down for jumping to conclusions, assumptions, over-simplifications, relying on previous experience, and above all for indulging ego and “not invented here” prejudices. So I owe no allegiance to any technical solution – it’s all about identifying which option best matches the requirement.  Plenty of examples where Steinmetz is valid, but jimalm’s lathe isn’t one of them!   No need to trust my opinion either – the pros and cons of the various ways of providing 3-phase are fairly well documented on the web, once the options are identified.

Dave

 

[Robert Atkinson 2Participant @robertatkinson2]

I’m not so sure about the transwave converter. Apart from the cost of the converter it requires a dedicated supply of 25A.Although this is likely less of an issue in France where radial circuits are the norm unlike the UK. No variable speed though.
As I said earlier on in the thread wiring the motor as delta low speed (720RPM) 220V and using a VFD to give 3 phase output, variable speed and frequency increase to 100Hz  (1400 RPM) would appear to be the optimal solution. A voltage step-up VFD would improve torque at higher speeds.

Question for @jimalm When the machine was running in Holland and Germany did you see it running on all three speeds?

Robert.

[Bob WorsleyParticipant @bobworsley31976]

One of the requirements for being a moderator is knowing about things, and unfortunately SoD doesn’t know about the capacitor 3 phase motor converter and how it works, Why not say that you have read the paper I referenced and then described why the converter won’t work instead of pushing your own ideas?

Is it perfect? Have I said it is perfect? No and no. Why isn’t it perfect? Is it actaually important that it is perfect? No. So what level of perfection is needed? What deviation from the 120 degrees phase difference is the point at which it is important? A three phase motor, once started, will run with one phase completely missing, so where, on the curve of 0V to 400V on the third phase is it a problem? The easiest method of determining this perfection is to simply put a voltmeter across each of the three phases, line to line. When they all indicate the same voltage then you have, by definition, a perfect three phase supply, however it is generated. If the voltages are 5V different, how important is that? If the motor is being run at 100% then it is more important than if it is just idling. But then you find three more meters and measure the phase currents of the three phases, and then, amazingly, you discover that the phase currents actually vary by only 10% or so from idle to full load. Why is this? Now you need another three meters that measure phase angle between current annd voltage, and amazingly you discover that the phase angle varies from a power factor of around 10% to 90% as the load varies from idle to full load.

Congratulations, you have just sussed out why the capacitor converter actually works, it is the shifting of the power factor as the load changes that means that the single value capacitor will work very efficiently over a very wide load range, certainly the range of a motor driving a machine tool from not cutting to serious cutting. It is the shifting of the current drawn from reactive, low power factor, to real, high power factor, that is doing the work.

 

[Bob Worsley]

On Bob Worsley Said:

One of the requirements for being a moderator is knowing about things….

Not so; the moderators are there to moderate bad behaviour, breaking of forum rules and removing inappropriate commercial advertising. They are not there to moderate people talking technical twaddle.

Julie

[Robert Atkinson 2Participant @robertatkinson2]

@bobworsley31976
If you pay for access to the paper you linked to I’ll read it. But I doubt it will change my views.
Running a 3 phase motor on single phase greatly reduces the starting torque. This may not be an issue with a mill or lathe with a clutch but is for many applications. The available power is also reduced by around 50% of rating.  The required capacitors, step-up transformer and control gear are likely to cost as much as a VFD.
You have not provided full details of your converter and what it drives so I can’t comment on that.

I assume that if you knew Dave, his knowledge and current situation you would not have made such comments.

Robert.

[Robert Atkinson 2Participant @robertatkinson2]

Bob said: “The easiest method of determining this perfection is to simply put a voltmeter across each of the three phases, line to line. When they all indicate the same voltage then you have, by definition, a perfect three phase supply,”

I wish I’d known this before. Can you give me a reference for this definition?
Maybe I didn’t need to spend money on my three phase power analyser. How do your voltmeters measure the relative phase of the three phases? And the frequency? There are numerous combination of 3 voltages and phases, never mind frequency, that will read the same on 3 voltmeters connected across them. I won’t even start on distortion and harmonics.

Robert.

[jimalmParticipant @jimalm]

Hi Robert

Sorry for the delay in responding … yes, indeed, I saw it running with all 3 speeds at the seller’s shop in Holland, and then I ran it myself on all 3 speeds in my brother-in-law’s shop in Germany before crating it up to ship to France. That’s been the big mystery … why it runs on 380 when the nameplate says 220. I don`t think I have mentioned it in this forum yet, but I have some circumstantial “evidence” to share: I’ve got paperwork from the original sale to a technical school in Amsterdam in 1967 (which almost certainly had 380 3-phase which apparently was the industrial standard in that area at that time). The second owner (now deceased) worked at the school and bought it when the school was re-organized, in the 90s, I think. He was the uncle of the person who sold the lathe to me. Apparently the lathe sat unused for a couple of decades, collecting dust. A lot of dust! As I’ve been starting to clean it up, I have noticed a number of things (change wheel reversed, screws that don’t match, etc.) that suggest the lathe has been partially disassembled and then put back together not exactly right. I’m guessing the second owner removed things, including the motor, to reduce the weight and then had to get an electrician to hook the motor up again. Hence the hand printed diagrams on the motor housing, which definitely could not have been done with the motor in place. Anyway, I strongly doubt that the motor has been rewired, and of course I know for a fact that it runs on (actually, 400V), so I’m going to go with that if I can get a 400V supply one way or another. Otherwise I’ll have to get a new 230V motor and VFD.

 

[Robert Atkinson 2Participant @robertatkinson2]

I’m pretty sure the “delta dash dash” symbology on the first line of stamped data on the motor plate indicates that the six individual windings are in two 220V in series for each side of the Delta. This gives the 440V operation.
It should be possible to connect the windings in parallel fro each side of the delta allowing the use of a standard, no voltage step-up VFD. This allows frequency increase for the higher speeds.
If a get a quiet moment I’ll try and sort out the winding switching on the circuit diagram and see if connection is possible

I must admit I struggle with some of the industrial cam switch diagrams.

Robert.

[Bob WorsleyParticipant @bobworsley31976]

Not so JA, SoD is selling his ideas, wrong ideas, in his missive, to which I objected.

I don’t understand, every phasor diagram for three phase shows the vectors as a triangle with aan included angle of 120 degrees, so what complication is there to interpret this as three equal voltages, if equal then balanced.

What possible importance are frequency, harmonics etc when all three phases will be affected similarly?

As to size, weight etc that is your decision to make, buy an inverter, or a converter, and since it is the same motor then the power requred will be the same, so what if either takes 25A, your shower takes more.

I have dug out my Steinmetz books, all seven of them, I like Steinmetz and he is worth reading. Without reading every word there is a danger of terminology, these were written 100 or more years ago, and he says that capacitors are not very good, so he tends to go for inductors. Reading the paper I referenced you can see that phase angle can be changed using R, L or C, but C is significantly more efficient.

I have three identical wattmeters, each can do a maximum of 10A and 500V, with switch selection for V, I or W. If anyone want them for postage cost you can have them, but the deal is you use them to monitor the three phases on a motor and write up the results. Why have I got three wattmeters? Guess!

 

 

[Andrew TinsleyParticipant @andrewtinsley63637]

All this is quite interesting, I only speak from direct experience. I doubt very much if Robert or SoD have ever used a Steinmetz circuit in  anger, but my apologies if they have. It appears to me that they are both quoting other peoples comments and not from their own direct experience.

I have both genuine 3 Phase supplies and Steinmetz circuits. I can tell absolutely no difference between the two supplies. Robert is quite specific and states that Steinmetz can work but the results are not as good as genuine 3 phase, or words to that effect (can’t be bothered to look back for his direct quote) I did ask him at the time, what the obvious difference was, but he never replied.

I do run with a step up transformer to produce the higher voltage for motors in star, but you can run in delta with a small increase in motor losses. As to the statement that you only get 50% of the motor power with a Steinmetz circuit, this is somewhat misleading. Most analysis of the Steinmetz circuit suggest a figure of 80%. I have run the whole gamut of machine tools with Steinmetz, lathes, mills shapers linishers, saw bench etc and I have never been troubled with lack of power on start up. What are the machine tools, that the amateur uses, that require large amounts of power on start up? Come to that how many amateurs run their machines close to the full rated power of their motors? I have a couple of dual beam scopes that I have used to check the phase angles of the Steinmetz supply, not spot on 120 degrees but near enough to make little difference. VFDs certainly have their place, but the older the motor the less reliable it becomes with a VFD source. Basically the insulation resistance of older motor are nowhere near that of the TEFC modern motors. You only have to look at the waveform of the current from a VFD to realise it contains high frequency switching which is bad news for older motors

It seems to me that their are entrenched views, obtained without direct experience. For the average amateur it is a cheap  and effective way of running 3 phase motors from 240 volts especially if a delta configuration is acceptable.

I was fortunate enough to get 3 phase installed for free, when the distribution company converted the village from overhead power lines to buried cables. I am quite happy with my genuine 3 phase, but I was also very happy with the Steinmetz conversions that I have used.

To sum up, Steinmetz circuits work well, I cannot tell any difference  between it and genuine 3 phase. VFDs are certainly a viable solution, although they do have some small drawbacks Ironically most folk run VFD with their motors in delta  using 240 volt 3 phase., just as you can run Steinmetz on 3 phase in delta, without the need of a step up transformer.

Andrew.

P.S. For anyone interested in running 3 phase motors from a 240 volt supply then  they should read the following.

Three Phase Conversions  by Graham Astbury No 47 in the Workshop practice  series.

This covers Steinmetz connections, Phase converters, Motor generator supplies and Electronic variable speed drives (These are chapter headings taken from the book’s index). I found it to be a very even handed survey of all methods to run 3phase motors from single phase supplies. In fact a breath of fresh air compared to the entrenched positions sometimes found on the forum

 

[Robert Atkinson 2Participant @robertatkinson2]

Bob said:

1/ “I don’t understand” That is very clear.

2/ “every phasor diagram for three phase shows the vectors as a triangle with aan [sic] included angle of 120 degrees, so what complication is there to interpret this as three equal voltages, if equal then balanced.”  Yes the voltages are balanced in those diagrams because they are showing a proper 3 phase supply not a bodged arrangement with a single phase supply, motor and capacitor.

3/ “What possible importance are frequency, harmonics etc when all three phases will be affected similarly?” See 1/ above.

4/ “As to size, weight etc that is your decision to make, buy an inverter, or a converter, and since it is the same motor then the power requred [sic] will be the same, so what if either takes 25A, your shower takes more” Not true. First I never mentioned size, weight or 25A in respect of your converter. I did mention cost. You also seem to be avoiding the fact that you can typically only use Steinmetz type circuits up to 50% of the rated power of the motor. So to get the same power you need a motor twice as large as is required for a proper 3 phase supply.

5/ “I have three identical wattmeters, each can do a maximum of 10A and 500V, with switch selection for V, I or W.” Interesting, What make and model are these instruments? Do they measure Watts or Volt amperes? Have you measured your own converter(s) with them? Doy you have pictures and results?

Robert.

[Bob WorsleyParticipant @bobworsley31976]

What I don’t understand is why you find it so hard to believe that a three phase phasor diagram with equal vectors and 120 degree included angle is a three phase supply, however it is generated.

With a mains supply 240V then if one phase has a certain frequency then surely the other wires do to? Likewise with distortion, noise etc, what one wire has the other does to.

So why does the capacitor generating the third phase only give 50% power, which implies that both the voltage and current are down by 71%.

So what importance is the make and model of the wattmeters? They are wattmeters, so they measure watts, what has voltamperes got to do with it? As I said, I now have three phase but recently made a converter to run 6kW motor for a saw mill, started and ran fine, but now no longer have the transformers.

I rather suspect that AT has the right of it, people who have never designed and made and used a converter, so have to actually understand how it works, and more important, why it works. I note that no comment has been made about the chaange in power factor as to the magic ingredient, why?

 

[Robert Atkinson 2Participant @robertatkinson2]

Hi Bob,

“What I don’t understand is why you find it so hard to believe that a three phase phasor diagram with equal vectors and 120 degree included angle is a three phase supply, however it is generated.”

That is correct IF the generator IS making a true and correct 3 phase supply. A Steinmetz connection is NOT generating a true and correct 3 phase supply.

My comment about frequency was in relation to your assertion that if 3 AC voltmeters across the 3 “phases” of an AC supply all read the same voltage it was a perfect supply. I can build you a black box the provides 3 connects that read the same voltage as you describe but are not all the “phases” will be the same frequency.

I asked abut the power meters so I can assess their capabilities.

I’ve not built a “converter” as you describe them (I assume you mean a Steinmetz type) but I have designed and built several 3 phase power supplies using both analogue and digital techniques over the years. I’ve also been involved in the specification and testing of converters and control systems up to tens of kilowatts for use on aircraft. A lot has happened since Steinmetz.

Robert.

[jimalmParticipant @jimalm]

Hello to all, and yet again thank you for the lively and interesting discussion.

While I’m waiting for my first appointment with Enedis to see about getting 3-phase 400V installed (July 10), I’m still wondering about all this. Mostly I’m impressed with how little I know. Anyway, I’ve just been comparing the wiring diagram from Hans with my own. His diagram says it is for 380V, while mine says it is 220V. Otherwise, they are pretty much the same, except his has a transformer (to provide, I think, 220V for the plug in and light) and mine doesn’t. I don’t know if this is significant. Copy of my wiring diagram follows.

Jim

[Andrew KettParticipant @andrewkett50664]

Jim, If the drawing you have is correct, the outlet socket would have 400V across it on a 400V 3ph supply. That presents a serious danger.

Hans’ drawing shows it (poorly) as a phase to neutral connection giving 220V.

The Transformer in the drawing Hans has supplies the coil voltage to C1 and C2. (probably 220v but maybe 110v or 24v)

If the motor really is 220v 3ph it will need a 220v 3 phase supply,

Be careful

 

Andrew

 

 

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