Author Topic: Single phase to three phase sinewave converter  (Read 10597 times)

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Offline T3sl4co1l

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Re: Single phase to three phase sinewave converter
« Reply #25 on: January 14, 2019, 12:13:17 am »
It's same frequency. :)

Shifting frequency is actually really hard to do, electrically!  If you needed, say, mains at 50Hz, you could use a synchronous machine with the stator driven at 60Hz, rotating it at 10Hz (600 RPM) via gearing from a normal (synchronous) motor, and taking 50Hz off the rotor.  Otherwise, a motor-generator set, or these days, using a VFD.

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Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #26 on: January 14, 2019, 12:45:45 am »
Doubt that rotary converters use synchronous motors (difficult to start), or that they use gearing to correct for the slightly under-synchronous speed of the induction motor. Because I think there is no need to correct for the slightly lower frequency in the first place.

The will very likely be a induction motor and synchronous generator on a single shaft. Hence the output frequency MUST be slightly lower, due to the slip of the induction motor.

Gearing is added cost, complexity, noise.
Synchronous motor is a problem to start up, not to mention I haven't seen a single phase synchronous motor bigger than a couple of watts.
 

Offline T3sl4co1l

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Re: Single phase to three phase sinewave converter
« Reply #27 on: January 14, 2019, 02:22:05 am »
No, rotary converter doesn't fall out of sync.  How could it?  Two of the three phases are supplied directly by the mains input!  The rotating mass is only there to supply the third phase.  Do you mean the third phase has a frequency shift?  But then its phase would be rotating relative to the mains, and a rotary phase converter it ain't. :)

The field in the rotor does slip, but it slips relative to the rotor itself.  That field, as seen by the stator, is rotating at mains frequency.  Slip manifests as a phase shift, not a frequency shift.  The phase shift won't be exactly 120 degrees, but a bit more because of the slip.  AFAIK, reactance dominates, so you need compensation capacitors anyway, and you probably can't measure this phase shift in operation, just under contrived circumstances (no load?).

Perhaps you're having a confusion similar to the "missing dollar paradox"?  In that one, the listener is misled to subtract quantities when the correct step is to add; in this case, the slip might be there, but it subtracts back out when you look at the field seen by the stator. :-+

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Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #28 on: January 14, 2019, 02:55:00 am »
 What if you would try to first state what kind of electric machine the converter is, instead of insisting that i am not right (i think i am pretty spot on with those induction motor driven generators in the isolated converters)? I haven't noticed once you specify, the usual non-isolating rotary converters use an induction motor directly as a generator for the third phase? No other machine is present on the shaft.
Without stating the basic concept, we could argue over and over and both be correct.

But thats no problem, I have already done a bit of research and informed myself.  :-+

So, cheap rubish uses specially wound* 3ph induction motors fed by a single phase using the remaining leg as the third phase.
*to acomodate for the higher current in the input phase and the output voltage assymetry.
Then it makes sense.

God bless those with (and without) 3ph available! :-/O

//EDIT: Typo.
« Last Edit: January 14, 2019, 01:08:07 pm by Yansi »
 

Offline T3sl4co1l

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Re: Single phase to three phase sinewave converter
« Reply #29 on: January 14, 2019, 04:52:32 am »
Ah hm, I thought this was the only kind but if there are others I'm not aware, that would be a problem!

http://www.phase-a-matic.com/images/Rotary-Converter-Connection.jpg

Where "rotary converter" is just an induction motor (no load) with capacitors as needed.

Or, better yet, this: https://electronics.stackexchange.com/questions/280486/diy-rotary-phase-converter-with-starter-motor-cutout-relay-in-parallel-with-loa

An "isolated" converter that is literally no more than a genset would indeed require a synchronous machine to produce synchronous output, and one made from induction motors would... hmm, I'm not sure offhand which way the field slips in generator mode actually, but that's rarely used anyway, so, a pair of sync machines it would be.

Cheers!

Tim
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Offline capt bullshot

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Re: Single phase to three phase sinewave converter
« Reply #30 on: January 14, 2019, 06:34:40 am »
Just a hint across the pond:

In Europe, a "rotary converter" in general refers to a Motor-Generator set on the same shaft. Could be anything including DC / single phase AC / induction / synchronous and even different frequencies.

I had read about the Uncle Sam style "rotary converter" before, there's no such thing here.
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Offline MrAl

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Re: Single phase to three phase sinewave converter
« Reply #31 on: January 14, 2019, 11:47:05 am »
Hi,

Back when i worked with a power converter company we used our own special designs to do single phase and three phase low distortion sine converters.  We were able to get high efficiency and very low distortion.
The main idea is to use a three phase bridge circuit with PWM.  The PWM comes from a controller board that generates the signals alone with driver boards that drive the main transistors of the 3 phase transistor bridge.  Power levels could go up to 30 kilowatts.

I see your power requirement looks low however.  Maybe you could look into 3 phase brushless motor drivers.
You can also type in "Three phase controller chip" and get some links to look at.

 

Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #32 on: January 14, 2019, 01:07:25 pm »
I have already suggested using a suitable microcontroller plus a 3phase power stage.

BLDC controllers would not very likely suit, because BLDC is typically (but not always, mind you) driven by square wave.  Any smarter controllers than that will likely have numerous feedback loops and it'll become quickly a mess, to make it produce a static voltage in open-loop mode.
 

Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #33 on: January 14, 2019, 01:14:37 pm »
An "isolated" converter that is literally no more than a genset would indeed require a synchronous machine to produce synchronous output, and one made from induction motors would... hmm, I'm not sure offhand which way the field slips in generator mode actually, but that's rarely used anyway, so, a pair of sync machines it would be.

In an asynchronous generator, you would need to up the speed above the synchronous speed, to obtain the synchronous frequency.

Induction generators are used too, not that often, but nothing that special.  You just connect a typical induction motor to the mains and then drive it above the synchronous speed, where you put it in a negative slip ratio, which is the generator mode. (Slip ratio above 1 is a braking mode).
 

Offline T3sl4co1l

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Re: Single phase to three phase sinewave converter
« Reply #34 on: January 14, 2019, 04:49:46 pm »
Negative slip, of course!  It would need gearing to account for two slip's worth.

Tim
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Offline soldar

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Re: Single phase to three phase sinewave converter
« Reply #35 on: January 14, 2019, 05:15:09 pm »
But I am not sure, how these are really made in the US, as we do not have to deal with this garbage in central EU. (3ph present in almost if not every household).
Really? Where is this? What city and country is it that "3ph present in almost if not every household"? I am curious.
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Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #36 on: January 14, 2019, 06:31:51 pm »
Germany, Poland, Austria, Czech Republic, Slovakia, (probably even others) all those very likely have 3ph present everywhere. haven't seen a single 1ph distribution transformer anywhere in my entire life. Always 3ph, always 3ph wiring, either cables in ground or hanging on the poles.

Small flats tend to be connected only single phase (due to small power requirements), but to get three, you just pay few bucks more to get the electricity meter change out to 3ph, three phase low voltage power is readily present in the incoming distribution cabling.
 

Offline soldar

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Re: Single phase to three phase sinewave converter
« Reply #37 on: January 14, 2019, 06:44:22 pm »
Nonsense.  I have traveled and lived in Europe, USA, Asia, etc. and there is no country in the world where there is "3 phase supply in almost every household".  I do not know where you live but there are people from many countries on this board who, I am sure, will confirm what I am saying.
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Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #38 on: January 14, 2019, 06:52:33 pm »
No, you do not know nothing, bro. Can you give example, where in Germany, or for example CZ is a place, where there is not 3ph available?

Having a 3ph available in household does not mean you have a 3ph outlets placed in your living room.

And as a plain tourist, you won't likely ever see how stuff is wired here.
 

Offline soldar

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Re: Single phase to three phase sinewave converter
« Reply #39 on: January 14, 2019, 07:15:41 pm »
The notion that anywhere in Europe, indeed anywhere in the world, there is "3 phase supply in almost every household" is ludicrous.  Saying it is "available in every household" means it is already wired and installed. That is nowhere true.  If by available you mean you can pay to have it wired and delivered then that is just as true in America as it is in Europe. I do not know what idea you have of America but I assure you they have 3 phase over there too. At least they did in the parts where I lived.

I travel in Europe regularly for business and pleasure and I know what domestic "household" installations are like in most European countries. In fact I was in Prague just some months ago (lovely city BTW) and stayed at an RB&B and exchanged some conversation with the apartment owner about some wiring problem he was having in the bathroom where he had installed a clothes washer in a less than perfect way.

Again, maybe posters here from other countries can confirm or deny.
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Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #40 on: January 14, 2019, 07:22:54 pm »
Do you have problems reading a text or what? I have written a CENTRAL EU.

The countries above mentioned (DE, AU, CZ, PL, SK) are pretty much what CENTRAL EU is about. And I am pretty sure I am correct with what I have stated.

But I am not sure, how these are really made in the US, as we do not have to deal with this garbage in central EU. (3ph present in almost if not every household).


And no bro, your interpretation of written text is again incorrect. All distribution is done in 3ph. No single phase transformer for distribution are being used.  Any point you can connect a house to, has a 3ph power available.   Having installed only a single phase meter is just cost optimization for low power demands, where 3ph would not justify.

But the cable into the house from the power company is always 3ph power, without an exception.  The meter is the last thing the power company owns, the rest is a problem of the house owner.

Please specify where exactly have you stayed, I will gladly check whether three phase distribution is available at the panel.

//EDIT: Maybe you just do not understand the difference: In the US and most Anglophonic countries, distribution is done in SINGLE phase ONLY, and there is NO way to get wired a three phase power in, even if you would like to. Unless you are willing to pay the power company to build those 5 miles of wiring to your house.

Changing a single ph to 3ph for a household in central EU means just having the power meter replaced!
« Last Edit: January 14, 2019, 07:26:36 pm by Yansi »
 

Offline CatalinaWOW

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Re: Single phase to three phase sinewave converter
« Reply #41 on: January 14, 2019, 07:37:29 pm »
Difference in detail.  Single phase distribution exists for local areas (like where I live currently), but unless you are really rural the distance to a 3 phase source is much less than 5 miles.  In my case it is about a half mile (one kilometer) to 3 phase power.  It still is not economical to bring that in.  Hence the market for VFD and other converter technologies.

I am sure that it is hard to generalize about this to entire regions or countries.  Lucky for you that you live where 3 phase is available.  Who knows whether the money spent on that has held back your economy in other ways?
 

Offline IanB

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Re: Single phase to three phase sinewave converter
« Reply #42 on: January 14, 2019, 07:40:49 pm »
The notion that anywhere in Europe, indeed anywhere in the world, there is "3 phase supply in almost every household" is ludicrous.  Saying it is "available in every household" means it is already wired and installed. That is nowhere true.  If by available you mean you can pay to have it wired and delivered then that is just as true in America as it is in Europe. I do not know what idea you have of America but I assure you they have 3 phase over there too. At least they did in the parts where I lived.

I travel in Europe regularly for business and pleasure and I know what domestic "household" installations are like in most European countries. In fact I was in Prague just some months ago (lovely city BTW) and stayed at an RB&B and exchanged some conversation with the apartment owner about some wiring problem he was having in the bathroom where he had installed a clothes washer in a less than perfect way.

Again, maybe posters here from other countries can confirm or deny.

In the UK, domestic low voltage power distribution is almost universally produced by utility transformers as three phase, 240 V / 415 V wye (three phases plus neutral). The normal arrangement is that each dwelling gets one phase plus the neutral at 240 V with typically 100 A or maybe 200 A service. Farms, commercial premises and small businesses may have all three phases inside the building, though still usually distributed and used as single phase supplies. Therefore the typical domestic household does not have access to a three phase supply, however light industrial users can have such access for heavy machinery.

In many parts of continental Europe I understand that domestic dwellings may have three phase service as standard, with perhaps 60 A per phase. Normal outlets get just one phase at the nominal 230 V, but power hungry devices such as water heaters, central heating or ovens may use all three phases. Since every country in Europe has different supply standards this may vary depending on which country is being considered.
 

Offline soldar

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Re: Single phase to three phase sinewave converter
« Reply #43 on: January 14, 2019, 08:03:02 pm »
Again, "3 phase supply in almost every household" is just not true anywhere. Installing it means paying for wiring, meter, etc. To cite that as a solution to someone who is asking about needing 3 phase, 100 mA supply is just ludicrous.

In Spain, new detached, single family homes, usually get 230volt and around 60 Amp service which is almost 14 KW and should be plenty enough for most homes. I suppose you could get more amps if you needed but that means a much more expensive installation and most homes simply do not need it. Now, I am sure that if you have special needs you can get three phase service but it is far from being "every household".

I participate in a Spanish forum for machinery and machinists and only people who have business shops with machinery would have three phase supply. The rest who have small shops in the homes or garages all use variable frequency drives for their three phase motors because getting three phases delivered is just too expensive and out of the question.

I am willing to be corrected if someone comes here and posts "I live in city X, country Y, and here all residential households have 3 phase supply as a matter of course". I would like to see that because it would be very, very, unusual.
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Offline IanB

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Re: Single phase to three phase sinewave converter
« Reply #44 on: January 14, 2019, 08:07:35 pm »
Again, "3 phase supply in almost every household" is just not true anywhere.
...
I am willing to be corrected if someone comes here and posts "I live in city X, country Y, and here all residential households have 3 phase supply as a matter of course". I would like to see that because it would be very, very, unusual.

Someone will come along and tell you that it is true where they live. It may not be true in Spain, or Britain, or France, but I have been told it is true in central and eastern parts of Europe. In such places every home has three phases at the switchboard and big appliances like heaters use a three phase supply as standard. You may not believe it, but that does not mean it is not true.
 

Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #45 on: January 14, 2019, 08:24:09 pm »
Why are you again putting in my mouth something I haven't said?  Are you troll or dumb or what? Could you please take the time and point me to the place, where I have offered as a solution to the OP, to get a 3ph power to his house?

And again and last time, I am clearly stating, that to obtain a 3ph here, you just need a meter change-out, You will NOT pay any extra wiring (except your own side to the 3ph appliance), 3ph power is already and always present at the place of the meter.

Detached houses in central EU do have indeed 3ph power available, and even more often used than just flats, as typical mountain cottages uses 3ph for heating, water pumps and even for cutting firewood. In flats, the 3ph is used sometimes also for heating and for example electric cooking stoves.

Okay, then leave your singlephase in Spain, nobody in central EU could care less.   14kW you say? That would be a nice 3x20A supply in here.  That means you (in Spain) have about 2x 16mm square wires. Impressive. We need just 3x 2.5mm square for the same 14kW. You are probably smart enough to figure out, if 3ph power into remote household makes sense, aren't you?

But you can still be an non-believer, as you wish.  No wonder that you are stuck with single phase, if people think like you.
 

Offline soldar

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Re: Single phase to three phase sinewave converter
« Reply #46 on: January 14, 2019, 08:40:20 pm »
Ok, I will wait for someone to come in and say "I have three phase supply in my residential home as do all the homes around me and I am located in such and such place". In the meanwhile I stand by what I said. It is not true that "in the countries above mentioned (DE, AU, CZ, PL, SK) 3ph present in almost if not every household". Not true at all.
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Offline Yansi

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Re: Single phase to three phase sinewave converter
« Reply #47 on: January 14, 2019, 08:45:49 pm »
Unfortunately for you, it is true.  Please continue living in Spain and leave this thread.

You have probably  not once put any useful information in this thread, you seem to be just trolling for whatever reason.  Continue doing so, you will probably get reported.
 

Offline soldar

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Re: Single phase to three phase sinewave converter
« Reply #48 on: January 14, 2019, 08:52:26 pm »
Someone will come along and tell you that it is true where they live. It may not be true in Spain, or Britain, or France, but I have been told it is true in central and eastern parts of Europe. In such places every home has three phases at the switchboard and big appliances like heaters use a three phase supply as standard. You may not believe it, but that does not mean it is not true.
Well, I am not saying it is somehow impossible, I am saying I have not seen it. And he said
But I am not sure, how these are really made in the US, as we do not have to deal with this garbage in central EU. (3ph present in almost if not every household).
which is hogwash. He is talking like the US is some backward water compared to Europe where we all have 3 phase supply at home. I am willing to bet that only a very small percentage of homes in Europe have 3 phase supply.
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Offline sanwal209Topic starter

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Re: Single phase to three phase sinewave converter
« Reply #49 on: January 14, 2019, 08:58:47 pm »
Sorry folks for late reply, I had fever.

Let me write down brief requirements. So We developed a device which does testing coils of diesel generator. While testing there is a point when generator have to be off due to certain requirements and to continue testing we need to feed 3 phase AC to the coils of generator. Attached is rough block diagram.

Problem is we dont have time to develop inverter which is controlled by micorcontroller. it will require alot of firmware development. Our best bet would be a SoC or IC which takes downgraded mains supply and generates 3 phase output which is synced with input mains.
« Last Edit: January 14, 2019, 09:06:16 pm by sanwal209 »
 


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