EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: Ed.Kloonk on July 30, 2017, 12:05:56 am
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Had a A/C installer at my place to discuss my air-con units that are reaching nearly the age of 40. He mentioned that 3 phase is, generally, more efficient than a similar spec'd A/C unit on connected to a single phase.
Existing system is 3 phase, 240v Sydney, Australia.
Can anyone explain if this if this is true?
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3 phase is 415V, not 240V. 240V is between phase and neutral. With 3 phase you can transfer more energy with less total cross section of wires.
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Also 3 phase has constant power transfer at all times. There are no dips to zero and peaks unlike with single phase.
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It can be more efficient at larger motor sizes, and the compressor in a central AC is one of the largest motors you will see in a residential application. This is from the additional parts and equipment required to start the single phase machine. But for an AC system the manufacturer has already calculated all of this away for you and you just need to look at the COP for the system which will already include all of those concerns.
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A lot of newer residential HVAC uses inverter drive, in which case there's no significant efficiency difference between single phase and three phase as it's always three phase internally.
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3 phase is 415V, not 240V.
Depends how you connect them - Star or Delta
(https://www.eevblog.com/forum/chat/3-phase-is-more-efficent-than-single-phase/?action=dlattach;attach=336464;image)
240V is between phase and neutral.
That's the Star configuration - and it is the standard household service around Australia. Properties are serviced by 1, 2 or 3 phases, plus a neutral (2, 3 or 4 wires, respectively).
If you have 4 wires to your home, you have full access to 3 phase (within the current limits of your service fuses) - and can use Star or Delta wired equipment as you wish. If you only have 2 or 3 wires, then you are out of luck - unless you want to pay for the extra phases to be run from the street to your house.
With 3 phase you can transfer more energy with less total cross section of wires.
That's when you are using 3 phase in the Delta configuration. Where the current carrying capacity of the conductors is the same with either Star or Delta, the voltage is higher with Delta - so more power can be transferred.
Also 3 phase has constant power transfer at all times. There are no dips to zero and peaks unlike with single phase.
This is where there is mathematical beauty in the flow of power - which translates into smoother mechanical forces on the armature of a motor that you won't get with single phase. This mathematical beauty exists with both the Star and Delta configurations - but you can get more powerful motors in the Delta configuration for a given current capacity of the location.
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A lot of newer residential HVAC uses inverter drive, in which case there's no significant efficiency difference between single phase and three phase as it's always three phase internally.
Then there's that. ;D
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A 3 phase install may cost a small fortune to install, leaving you not much choice but to stick to a single phase unit,
preferably branching from the incoming main with its own dedicated oversize/THICK cabling and isolation switch and RCOB etc
so it doesn't affect the rest of the house power too much
OTOH, if you know a qualified electrical contractor who is up for some extra weekend work to catch up on bills,
and you are prepared to provide FREE non qualified supervised basic labour duty, aka dig, route cables, climb ladders, move equipment, run around, pass tools, make coffee, and pay for materials, etc :phew:
you may save a lot of cash installing 3 phase, a good long term investment IMO :clap:
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In the US, some datacenters run 240V phase to phase, since it runs slightly lower amperage than the more common 208V phase to phase and is still within the operating range of common PSUs.
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3 phase is 415V, not 240V.
Depends how you connect them - Star or Delta
No it does not. The difference between star and delta is if you have neutral or not, voltage does not change.
240V is between phase and neutral.
That's the Star configuration - and it is the standard household service around Australia. Properties are serviced by 1, 2 or 3 phases, plus a neutral (2, 3 or 4 wires, respectively).
Three phases of 240V (live-neutral) is still 415V.
That's when you are using 3 phase in the Delta configuration. Where the current carrying capacity of the conductors is the same with either Star or Delta, the voltage is higher with Delta - so more power can be transferred.
EDIT, as there happens some stupid discussion below. I mean that either way power company supplies 3ph 415V regardless if their transformer is star (3ph+N) or delta. I'm not talking what will happen with motors if you wire them as star/delta or similar things.
(https://qph.ec.quoracdn.net/main-qimg-27907edf45eaee589b4490a8c251b74f-c)
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208/240/480, 120 split is standard in NA, which is using Delta.
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A 3 phase install may cost a small fortune to install, leaving you not much choice but to stick to a single phase unit,
preferably branching from the incoming main with its own dedicated oversize/THICK cabling and isolation switch and RCOB etc
so it doesn't affect the rest of the house power too much
OTOH, if you know a qualified electrical contractor who is up for some extra weekend work to catch up on bills,
and you are prepared to provide FREE non qualified supervised basic labour duty, aka dig, route cables, climb ladders, move equipment, run around, pass tools, make coffee, and pay for materials, etc :phew:
you may save a lot of cash installing 3 phase, a good long term investment IMO :clap:
In WA, 3ph is quite common.
Many electric water heaters are 3ph, & ovens are, strangely, 2 ph.
I have a honking great 3ph socket in the carport, so a previous owner must have had a fairly serious bit of
gear out there.
Not my "cup of tea", though, as the rain beats in there in the winter.
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208/240/480, 120 split is standard in NA, which is using Delta.
US is a whole different story, so many different variants/volatges it's sort of absurd.
(https://ctlsys.com/wp-content/uploads/2016/10/Single_phase_3_wire.png)
(https://ctlsys.com/wp-content/uploads/2016/10/3_phase_4_wire_wye.png)
(https://ctlsys.com/wp-content/uploads/2016/10/3_phase_3_wire_delta.png)
(https://ctlsys.com/wp-content/uploads/2016/10/3_phase_4_wire_delta_240.png)
(https://ctlsys.com/wp-content/uploads/2016/10/3_phase_2_wire_grounded_delta.png)
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3 phase is 415V, not 240V.
Depends how you connect them - Star or Delta
BTW this is a serious misconception. A while ago there was someone on this forum from Australia IIRC, who got a device (don't recall what, probably PSU) rated 3 ph 240V. Soo... he plugged it into the 3ph mains, thinking 3 phases of 240V, yeah :). And got some special effects and destroyed device because it was 3ph 240V device from US :palm:.
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208/240/480, 120 split is standard in NA, which is using Delta.
US is a whole different story, so many different variants/volatges it's sort of absurd.
(https://ctlsys.com/wp-content/uploads/2016/10/Single_phase_3_wire.png)
(https://ctlsys.com/wp-content/uploads/2016/10/3_phase_4_wire_wye.png)
(https://ctlsys.com/wp-content/uploads/2016/10/3_phase_3_wire_delta.png)
(https://ctlsys.com/wp-content/uploads/2016/10/3_phase_4_wire_delta_240.png)
(https://ctlsys.com/wp-content/uploads/2016/10/3_phase_2_wire_grounded_delta.png)
There are more different among STAR-TRIANGLE, the current. For this reason ,the star conection is used for starting the motors, because consume less current(1/root(3)) than the Delta conection . When the motors arrive to stationary regime , return to change("Manual" or Automatic by relays) to Delta conection
Now , i strange that on a Delta conection among phases there are 400V, when we consider that there are 230 V. It's more ,the technical plates it is marked than the Delta conection as 230 V
http://www.cifp-mantenimiento.es/e-learning/index.php?id=2&id_sec=7 (http://www.cifp-mantenimiento.es/e-learning/index.php?id=2&id_sec=7)
(http://www.cifp-mantenimiento.es/e-learning/contenidos/2/placa_motor.gif)
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Now , i strange that on a Delta conection among phases there are 400V, when we consider that there are 230 V.
Who we? There is 400V between phases, regardless supply transformer being with star or delta connection.
It's more ,the technical plates it is marked than the Delta conection as 230 V
That motor has windings rated for 230V so basically you cannot use it on standard 3 phase 400V supply with delta connection of motor windings.
There are more different among STAR-TRIANGLE, the current.
There is not. There is a difference in current if you connect the very same windings of a motor in star or delta connection. Because you know, you put different voltage on those windings. But as such it does not matter, transformers for star and delta connection are different. If we take 2 transformers of the same power, one for delta connection will have thinner wire and more turns, for star connection, thicker wire and less turns. Result will be the same. The same applies to the motors. In the end, with star connection you are not even required to use neutral wire at all.
BTW, if you look on that motor plate, you may notice that you don't use neutral wire in both star and delta connections.
On both connections of the given motor, power remains exactly the same.
(http://www.cifp-mantenimiento.es/e-learning/contenidos/2/comp_est_trian.gif)
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Now , i strange that on a Delta conection among phases there are 400V, when we consider that there are 230 V.
Who we? There is 400V between phases, regardless supply transformer being with star or delta connection.
dude read some theory around 3 phase systems.... if you wire the same generator to star, then you get higher voltage but lower current, and if you wire the same generator to triangle , then you get more current but lower voltage...
if you have a power outlet in star configuration it's 400(415) V between phases, and the only way to make it a delta power outlet is a 3phase transformer , and that will yield 230(240)V between phases but at higher current.
you seem to be confusing the wiring of the load with the wiring of the source/generator... of course if you have a star wired power outlet with 400V between phases and you connect a delta wired load to it the voltage will stay 400V between phases....
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if you have a power outlet in star configuration it's 400(415) V between phases, and the only way to make it a delta power outlet is a 3phase transformer , and that will yield 230(240)V between phases but at higher current.
Ask your power company to supply 3 phase 230V without neutral, would like to hear what they'll say to you.
if you wire the same generator to star, then you get higher voltage but lower current, and if you wire the same generator to triangle
I already said this about motor.
Again supply from power company can be as follows.
(https://qph.ec.quoracdn.net/main-qimg-27907edf45eaee589b4490a8c251b74f-c)
Of course if you take a motor designed for star connection at 3ph 400V, you cannot rewire it as delta and still use it @ 400V.
If the motor was designed for 400V with delta winding connection, you can still use it as star @400V but with reduced power.
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if you have a power outlet in star configuration it's 400(415) V between phases, and the only way to make it a delta power outlet is a 3phase transformer
Ask your power company to supply 3 phase 230V without neutral, would like to hear what they'll say to you.
that's why i freaking mention the only way to get a delta at home is a transformer....
if you wire the same generator to star, then you get higher voltage but lower current, and if you wire the same generator to triangle
I already said this about motor.
Again supply from power company can be as follows.
(https://qph.ec.quoracdn.net/main-qimg-27907edf45eaee589b4490a8c251b74f-c)
let me remind your own words... "ask your power company to provide you a delta without ground".... so stop talking bullshit... your power outlet will be star only... so stop stating you can have a delta outlet in your home.
Of course if you take a motor designed for star connection at 3ph 400V, you cannot rewire it as delta and still use it @ 400V.
If the motor was designed for 400V with delta winding connection, you can still use it as star @400V but with reduced power.
yes using a delta 400V motor in star configuration is pretty common to start the motors without insane inrush currents (star-delta starter).
but back yo your very statement... you stated that regardless of the wiring you always have 400V between phases.. that's not correct ! doesn't matter if we talking about the wiring of a generator or a 3 phase transformer (both a source in a 3 phase system).. the voltage does change ! star is 400V between phases and triangle is 230V between phases.
your very statement is here:
3 phase is 415V, not 240V.
Depends how you connect them - Star or Delta
No it does not. The difference between star and delta is if you have neutral or not, voltage does not change.
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let me remind your own words... "ask your power company to provide you a delta without ground".... so stop talking bullshit... your power outlet will be star only... so stop stating you can have a delta outlet in your home.
I did not say I have delta at my home. But it is possible get it, especially for industrial purposes. 400V delta...
but back yo your very statement... you stated that regardless of the wiring you always have 400V between phases.. that's not correct ! doesn't matter if we talking about the wiring of a generator or a 3 phase transformer (both a source in a 3 phase system).. the voltage does change ! star is 400V between phases and triangle is 230V between phases.
Who said that you will get 400V delta while keeping the same transformer or generator which you used for star connection?
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Who said that you will get 400V delta while keeping the same transformer or generator which you used for star connection?
YOU ! you said regardless of the wiring you have 400V between phases.... that very statement implies the wiring is the only variable here.
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Who said that you will get 400V delta while keeping the same transformer or generator which you used for star connection?
YOU ! you said regardless of the wiring you have 400V between phases.... that very statement implies the wiring is the only variable here.
I said what you will get 400V from your power company regardless if they supply 3ph + N (star transformer) or if they supply 3ph (delta) without N. The fact that you use your own transformers to reduce voltage is up to you.
Read the freaking post of mine (second post in the tread https://www.eevblog.com/forum/chat/3-phase-is-more-efficent-than-single-phase/msg1268485/#msg1268485 (https://www.eevblog.com/forum/chat/3-phase-is-more-efficent-than-single-phase/msg1268485/#msg1268485)) what it was all said about, LOL. Op said he has 3ph 240V AC system at his location which I doubt very much. Then Brumby wrote it depends on connection...
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Op said he has 3ph 240V AC system at his location which I doubt very much. Then Brumby wrote it depends on connection...
Read what I wrote - not what you think I said.
Let me re-phrase then....
* In Australia - we have 3 phase mains available in the street.
* Normal connection to a household can be 2, 3 or 4 wires
* In the case of a two wire service, the household has one phase and a neutral - giving 240V (Actually, technically it's officially been 230V since 2000 - by a fudge - but we'll stay with 240 for this discussion)
* When you have 3 wires, you have 2 phases and a neutral - giving two 240V connections - with a phase difference (which, by the way, the average consumer wouldn't know or care about.)
* When you have 4 wires, you now have 3 phases and a neutral - giving three 240V connections - with phase differences.
This is what is described as 3 phase 240V - as it is measured with respect to the neutral. Anybody in Australia that has any idea of 3 phase will completely understand what is being described by this.
There is not confusion about this. There is no argument about this. It is correct.
Quite obviously, this is based on the STAR configuration.
BUT.... now that there are 3 phases to the premises, we can ignore the neutral and look at the service in the DELTA configuration. It is when we measure this way that we have 415V.
TELL ME I'M WRONG.
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This is what is described as 3 phase 240V - as it is measured with respect to the neutral.
Dunno if Australia is somewhat special in this regard but everywhere I know it's not described like this. All I can google about Australia says 415V. If there is mentioning of 240V, it's written like 240V single ph / 415V 3ph
And if it is, then it might be why this happened:
BTW this is a serious misconception. A while ago there was someone on this forum from Australia IIRC, who got a device (don't recall what, probably PSU) rated 3 ph 240V. Soo... he plugged it into the 3ph mains, thinking 3 phases of 240V, yeah :). And got some special effects and destroyed device because it was 3ph 240V device from US :palm:.
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Rectifying AC to DC also produces less ripple with 3 phase compared to single phase. 3 phase creates a better power factor as well.
Something to consider with 3 phase input to an inverter driven motor.
I suspect a 3 phase motor is more efficient as there is always one set of coils energised at a time, so the motor spins smoother.
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I suspect a 3 phase motor is more efficient as there is always one set of coils energised at a time, so the motor spins smoother.
At any time, at least two coils are energized.
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Instead of answering many posts.
1:
Never assume that what you have is similar to what the other guy will have when it comes to mains wiring.
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Repeat #1.
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You can find both 400/230V TN-systems as well as 400V IT-systems and / or 230V IT-systems in the same country. There is usually a reason why one system is used in one specific installation. None of them are equal. In addition we have a lot of other systems, for instance all the different American systems.
It does not make any sense to describe how to connect a motor to one system if you use the knowledge based on a different system. It will only add confusion.
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This is what is described as 3 phase 240V - as it is measured with respect to the neutral. Anybody in Australia that has any idea of 3 phase will completely understand what is being described by this.
There is not confusion about this. There is no argument about this. It is correct.
I seriously doubt that. In the UK, that system would be described as 3 phase 415 V. Since Australia broadly follows the UK pattern I think it will be the same there.
As to why, it is because anyone working with the system needs to know the highest voltage they can encounter in that system. This is a convention that I think is followed world wide, for fairly logical reasons.
If you doubt me, do an image search for "danger 415 volts" and see all of the red and black signs that show up following Australian standards.
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As to why, it is because anyone working with the system needs to know the highest voltage they can encounter in that system. This is a convention that I think is followed world wide, for fairly logical reasons.
If you have a three-phase system based on TN-wiring, the voltages are related by math. In domestic wiring, the most usual will be 400V/230V (actually 398.3V/230V) because we get normal mains between one phase and neutral. The voltage between two phases is the voltage between one phase and neutral multipled with the square root of 3 (1.73).
The britons believe they have 415/240V, but that is because the EU cheated them :) The nominal EU voltage is 230V with some percent allowed up and down. The British upper and lower voltage limits basically equals the EU limits, but they don't know it. :)
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As to why, it is because anyone working with the system needs to know the highest voltage they can encounter in that system. This is a convention that I think is followed world wide, for fairly logical reasons.
If you have a three-phase system based on TN-wiring, the voltages are related by math.
I imagine someone doing maths before opening electric box :). How do you know for sure that you must calculate, BTW? What if there is true 3 phase 240V like in US? or 3ph 230V like is still common in some mainly 3rd world countries. Or there is step down transformer used.
The britons believe they have 415/240V, but that is because the EU cheated them :) The nominal EU voltage is 230V with some percent allowed up and down. The British upper and lower voltage limits basically equals the EU limits, but they don't know it. :)
AFAIK it's exactly opposite. They nominally have 230/400V but for legacy reasons in reality it's often 240/415V.
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I think people here argue often more about semantics, than technical content these days. The voltage could be as high as 440V but signs normally state the nominal, rather than maximum possible voltage.
Irrespective of whether the air conditioning unit uses an inverter or not. Three phase is probably more efficient because it's nicer on the electrical grid. It's better for the power plant and the distribution transformers if the current drawn from each phase is equal. Having huge loads on one or two phases, causes excessive copper losses and vibration in alternators. Generally there are so many loads connected to the power grid, that everything evens out in the end, but I imagine it's still better for local transformers, especially in a rural setting.
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I imagine someone doing maths before opening electric box :). How do you know for sure that you must calculate, BTW? What if there is true 3 phase 240V like in US? or 3ph 230V like is still common in some mainly 3rd world countries. Or there is step down transformer used.
1:
Never imagine anything about mains.
2:
What is the definition of "true 3 phase"?
You have several different wiring systems that will give you three phases. If you intend to do any work on a three phase system you must know and understand how it works. If not, you will face severe trouble.
You can start with the easy one. IT, TT and TN-C. Keep on with TN-S and TN-C-S.
3:
If you have a TN-system of any kind, the voltages relate to each other as described. If anything else that a TN-system, other calculations will apply.
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The britons believe they have 415/240V, but that is because the EU cheated them :) The nominal EU voltage is 230V with some percent allowed up and down. The British upper and lower voltage limits basically equals the EU limits, but they don't know it. :)
Nah, this has come up before.
UK mains continues to be 240V +/- 6% and I doubt there are really plans to change that.
The EU "harmonised" the voltage at 230V +10% - 6% - nobody really changed a thing but we now all adhered to the same standard which was obviously A Good Thing(C) TM :)
It was a good thing because anyone who designs and makes electrical goods knows what voltages their equipment will encounter and the range over which it must function.
However his does have some disadvantages for us as equipment designed with a nominal 220-230V supply in mind will consume more power in the UK, potentially putting your bill up.
There was supposed to be a later "harmonisation" to 230V +/- 10%, this has not (yet?) been put into practice.
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However his does have some disadvantages for us as equipment designed with a nominal 220-230V supply in mind will consume more power in the UK, potentially putting your bill up.
On the other hand, my electric kettle is marked 2520 W / 220 V, 2750 W / 230 V, 3000 W / 240 V. I know which voltage gives me the fastest cup of tea! :)
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A 3 phase install may cost a small fortune to install, leaving you not much choice but to stick to a single phase unit,
preferably branching from the incoming main with its own dedicated oversize/THICK cabling and isolation switch and RCOB etc
so it doesn't affect the rest of the house power too much
In WA, 3ph is quite common.
Many electric water heaters are 3ph, & ovens are, strangely, 2 ph.
I have a honking great 3ph socket in the carport, so a previous owner must have had a fairly serious bit of
gear out there.
Not my "cup of tea", though, as the rain beats in there in the winter.
I haven't seen a 3 phase domestic electric water heater on this side of roo, YET... ???
nor an oven running on 2 phases at 415v potential,
I'd keep mum or the little lady away from scrubbing the insides of that :o
Sir, are you 100% certain they are both not wired from separate phases, with separate/split neutral and earth/grounding wire going to each ?
i.e. single phase + neutral operation, branched off from a three phase mains with 3 separate neutral bussbars
The "3ph socket in the carport", is that a 4 pin or 5 pin socket? 20 amp or 32 or ??
The mystery deepens... :-// at the edge of my seat in suspense here :popcorn:
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FWIW Ladies and Gents:
These are fresh readings taken on a "TN-C-S" system on this side of Kangaroo Land,
3 phase (4 wire) domestic install (L1, L2, L3 with pretty colours :-* and black Neutral)
and a recent 3 phase 'Smartass Meter" -involuntary upgrade- from the utility company.
To be fair, the meter has been behaving afaik, with no BSOD, flat BIOS battery/date change, 'ERRor' or firmware update flashing notices..
415 volts phase to phase, voltage freakingly on the money today!
240 volts any phase to neutral or phase to earth/ground (neutral and earth/ground LINKED at the switchboard as per regulations)
Reading taken with two True RMS meters with no power sucking devices operating on the premises (heater, kettle, washing machine, Photonicinduction kit etc)
Fluke 87V GENUINE Made in USA model, and a Fluke 114 Made in China,
both meters in agreement, give or take half or one volt either way :-+
Meter sockets and probes cleaned with WD-40, as per old school Fluke recommendations, to be sure of awesome contact :box:
I'm not sure I can do a phase to phase rotation check with my Fluke T100 volt thingie due to the Neutral/Earth connections,
I have tried it but no change in the rotation change LEDs, no matter which way I tried.
Perhaps the meter has issues with that function, though all the other functions work well,
or more likely a function that works at the motor end with 3 phase and earth/ground, but no neutral to alter the rotation :-//
Someone here more familiar with that side of 3 phase delta vs star operations may be able clue us up a bit better on that. :)
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FWIW Ladies and Gents:
I have tried it but no change in the rotation change LEDs, no matter which way I tried.
Perhaps the meter has issues with that function, though all the other functions work well,
or more likely a function that works at the motor end with 3 phase and earth/ground, but no neutral to alter the rotation :-//
Someone here more familiar with that side of 3 phase delta vs star operations may be able clue us up a bit better on that. :)
Seems like the third electrode is your body. The manual suggest a firm grip around the tester.
www.elso.sk/media/download/pdf/fluke/man/Fluke-T100-VDE_iseng.pdf (http://www.elso.sk/media/download/pdf/fluke/man/Fluke-T100-VDE_iseng.pdf)
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FWIW Ladies and Gents:
I have tried it but no change in the rotation change LEDs, no matter which way I tried.
Perhaps the meter has issues with that function, though all the other functions work well,
or more likely a function that works at the motor end with 3 phase and earth/ground, but no neutral to alter the rotation :-//
Someone here more familiar with that side of 3 phase delta vs star operations may be able clue us up a bit better on that. :)
Seems like the third electrode is your body. The manual suggest a firm grip around the tester.
www.elso.sk/media/download/pdf/fluke/man/Fluke-T100-VDE_iseng.pdf (http://www.elso.sk/media/download/pdf/fluke/man/Fluke-T100-VDE_iseng.pdf)
Thanks, will try again :-+ I was in a bit of a hurry to close it up and no time for thinking when it starts raining hard :o
Edit: and I had gloves on, so the rotation feature wasn't going to happen anyway, lol ;D
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This is what is described as 3 phase 240V - as it is measured with respect to the neutral. Anybody in Australia that has any idea of 3 phase will completely understand what is being described by this.
There is not confusion about this. There is no argument about this. It is correct.
I seriously doubt that. In the UK, that system would be described as 3 phase 415 V. Since Australia broadly follows the UK pattern I think it will be the same there.
As to why, it is because anyone working with the system needs to know the highest voltage they can encounter in that system. This is a convention that I think is followed world wide, for fairly logical reasons.
If you doubt me, do an image search for "danger 415 volts" and see all of the red and black signs that show up following Australian standards.
"that system would be described" .... by whom?
After sleeping on it, I must clarify that point in what I was saying - and it can be attributed to semantics.
Certainly, reference to the power network will refer to phase to phase voltages, but in the domestic environment, most people are only familiar with a single phase. That, quite obviously, has to be taken with respect to neutral - unless you want to start talking about a single phase as 1 phase 415V. Since there's no way you will be able to measure 415V at this installation, that doesn't make a lot of sense.
When a second phase is presented to the property - do we start talking about 2 phase 415V? We now have a way to measure 415V - but is that how it is discussed by the general populace? Not that I have noticed. They started out with a neutral and one active for 240V - and now they have two. As I said before, the phase angle is something that many would not know - or care about.
Add the third phase and without changing anything about the previous 2, what would you expect the general public to understand?
Telling them it's no longer 240V - but 415V would freak a lot of people out - and some would start yanking appliances out of the sockets. (Tell me you've never come across someone like that...)
As such, within the typical suburban household service where 240V is the norm, while the reference to 240V 3 phase is technically incorrect, it can be understood.
This is exactly how the OP presented it:
Existing system is 3 phase, 240v Sydney, Australia.
Like Dave - and a few other members here - I, too, live in Sydney Australia ... and I knew exactly what he was talking about.
This is all that I was saying.
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Come on guys, it's not rocket science, the typical measurements found in most of Australia I posted above are as simple as it gets,
and confident our UK bros have the same deal over there too :-+
415 volts phase to phase
240 volts any phase to neutral or phase to earth/ground (neutral and earth/ground LINKED at the switchboard as per regulations)
i.e. You're either running 3 separate lots of 240 volt lines, measured with respect to Neutral, and each can have it's own RCD/GFCI with no issues
or running rotating machinery etc with the 3 Lines WITHOUT a Neutral reference connected, and 415 volts measured between each or any two Line/Phase
There are caveats to the above of course, which may be beyond the scope of this post
OP needs to supply a bit more info perhaps, are there currently a few air con units or one? :-//
If there are a few air con units are they single phase units being run as such from a 3 phase + Neutral switchboard split up as 3 lots of 240 volt lines to the air cons?
Is the installer suggesting to dump those, and install 3 phase air cons into the current 3 phase installation ?
Let's clear up some of the grey please first, before going the full 360 degrees here :phew:
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Telling them it's no longer 240V - but 415V would freak a lot of people out - and some would start yanking appliances out of the sockets. (Tell me you've never come across someone like that...)
I think it should freak them out. It's scary.
For instance, in the UK, if any panel or item of switch gear has more than one phase conductor inside it, it will have a label on the outside saying "Danger 415 V". This will cause electricians to take special care when working on that system and should cause ordinary people to stay far away.
It is, in the UK, exceedingly rare to find more than one phase in a domestic property, although it is not all unusual on farms or in light industrial premises. If that happens I think the "Danger 415 V" signs will be found, to warn people that they are not dealing with the ordinary 240 V mains. (Not only is there a higher voltage, but there is also likely to be a higher fault current.)
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Indeed, people in the UK seem pretty careful whenever two phases are close together. In our university computer lab there are dire warnings not to interconnect benches with extension leads as they're on different phases and have 415V between them.
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Indeed, people in the UK seem pretty careful whenever two phases are close together. In our university computer lab there are dire warnings not to interconnect benches with extension leads as they're on different phases and have 415V between them.
All you need in a dual phase situation is one flipped active+neutral reverse wired d!ckhead engineered DIY extension lead, to get the party started >:D
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Completely different in Germany. Never seen a warning label on a standard distribution panel, and most flats got a 3-phase socket in the kitchen. The three phases are evenly distributed across all rooms to keep the load about the same for each phase.
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It's obvious a few people here are going to get bitten one day, armed with a half baked understanding and unclear assumptions on what 3 Phase is, how it works,
and how it's applied to devices with or without the Neutral.
It's a job for electrical contractors that know what they are doing,
not DIY newbs that hit on forums asking big questions pretending they are in the know
Darwin Awards and Boot Hill await... :clap: :clap:
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Dunno if Australia is somewhat special in this regard but everywhere I know it's not described like this. All I can google about Australia says 415V. If there is mentioning of 240V, it's written like 240V single ph / 415V 3ph
This is my domestic Melbourne, Australia 3-phase meter box. Pretty unusual for a normal house but I just gotta be different. :scared: 60A per phase capacity instead of normal 80A single phase. Note the writing on the smart meter. Sorry about the lousy pics. Taken by torch light 8pm on a cold winters night (tonight).
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if you have a power outlet in star configuration it's 400(415) V between phases, and the only way to make it a delta power outlet is a 3phase transformer , and that will yield 230(240)V between phases but at higher current.
If the transformer has a delta primary and secondary then yes.
If the transformer has a star primary and delta secondary then also yes, but the three outlet wires are shifted in phase by 30 degrees wrt the primary. Just to add to the confusion, of course.
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A 3 phase install may cost a small fortune to install, leaving you not much choice but to stick to a single phase unit,
preferably branching from the incoming main with its own dedicated oversize/THICK cabling and isolation switch and RCOB etc
so it doesn't affect the rest of the house power too much
In WA, 3ph is quite common.
Many electric water heaters are 3ph, & ovens are, strangely, 2 ph.
I have a honking great 3ph socket in the carport, so a previous owner must have had a fairly serious bit of
gear out there.
Not my "cup of tea", though, as the rain beats in there in the winter.
I haven't seen a 3 phase domestic electric water heater on this side of roo, YET... ???
nor an oven running on 2 phases at 415v potential,
I'd keep mum or the little lady away from scrubbing the insides of that :o
Sir, are you 100% certain they are both not wired from separate phases, with separate/split neutral and earth/grounding wire going to each ?
i.e. single phase + neutral operation, branched off from a three phase mains with 3 separate neutral bussbars
The "3ph socket in the carport", is that a 4 pin or 5 pin socket? 20 amp or 32 or ??
The mystery deepens... :-// at the edge of my seat in suspense here :popcorn:
As far as I remember, the stove has a common Neutral, & different elements & other components connected
between that Neutral & one or other of the two phases.
The 3ph socket is 5 pin & I would guess 20 amp--- it certainly looks smaller than the ones at my old work.
When we bought this house, the HWS was a unit made by "Everdure""
This was an instantaneous unit, where three mercury switches, one for each phase, were operated by the drop in water pressure when the "Hot" tap was turned on.
The "party trick" these things had was to drop a phase,so that the HWS still "sort of" worked------if you liked lukewarm showers!
We replaced it with a Solar unit------the "booster" on that is, I believe, single phase.
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Indeed, people in the UK seem pretty careful whenever two phases are close together. In our university computer lab there are dire warnings not to interconnect benches with extension leads as they're on different phases and have 415V between them.
All you need in a dual phase situation is one flipped active+neutral reverse wired d!ckhead engineered DIY extension lead, to get the party started >:D
One of the good justifications for test and tag on devices before they enter service, and after any repairs.
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Completely different in Germany. Never seen a warning label on a standard distribution panel, and most flats got a 3-phase socket in the kitchen. The three phases are evenly distributed across all rooms to keep the load about the same for each phase.
Why have the german flats a 3-phase plugs in the kitchen? I don't understand because with a PIA 25A is enough for a normal oven ("2500 W"),besides it still can plug a vitroceramic.
Dunno if Australia is somewhat special in this regard but everywhere I know it's not described like this. All I can google about Australia says 415V. If there is mentioning of 240V, it's written like 240V single ph / 415V 3ph
This is my domestic Melbourne, Australia 3-phase meter box. Pretty unusual for a normal house but I just gotta be different. :scared: 60A per phase capacity instead of normal 80A single phase. Note the writing on the smart meter. Sorry about the lousy pics. Taken by torch light 8pm on a cold winters night (tonight).
I don't know which is the electrical reglament in Australia, but i am surprising that the support where is hung the smartmeter and fuse holder is of wooden or plywood. Here, for new building has to be the fireproof plastics.
That's is the reason:
https://youtu.be/kxcxmmYmhvo (https://youtu.be/kxcxmmYmhvo)
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Why have the german flats a 3-phase plugs in the kitchen? I don't understand because with a PIA 25A is enough for a normal oven ("2500 W"),besides it still can plug a vitroceramic.
A typical oven got around 3kW and the ceramic glass cooktop 7kW. 10kW / 230V = 43.5A. A 25A breaker won't be happy about that ;)
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Completely different in Germany. Never seen a warning label on a standard distribution panel, and most flats got a 3-phase socket in the kitchen. The three phases are evenly distributed across all rooms to keep the load about the same for each phase.
Just for comparison, ditto in Finland. All newer-than-ancient houses have 3 phase TN-S system (5 wires) with 400V main voltage (i.e. 230V phase voltage). Entry fuses are usually just 3x25 or 3x35 A which will appear tiny for our lower voltage / phase challenged friends but actually is plenty enough with the higher voltage 3 phase system.
Same thing with distributing the load across phases. Most common wiring is 2.5 mm2 copper for a 16A max phase current. But some heftier stoves may go with 20 or 25 A fuses too with correspondingly heavier wiring. You did know that practically every house in Finland has at least one sauna. Many of those with electrical stoves.
Additionally, current code requires RCD's in all circuits.
Why have the german flats a 3-phase plugs in the kitchen? I don't understand because with a PIA 25A is enough for a normal oven ("2500 W"),besides it still can plug a vitroceramic.
A typical oven got around 3kW and the ceramic glass cooktop 7kW. 10kW / 230V = 43.5A. A 25A breaker won't be happy about that ;)
A 3 phase cooktop can put out some 10 kW from a 3 phase 16 A supply. My Bosch induction hob will bring a half kettle of water to boiling point almost faster than you can fetch the eggs from a fridge on the other side of the kitchen :)
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Why have the german flats a 3-phase plugs in the kitchen? I don't understand because with a PIA 25A is enough for a normal oven ("2500 W"),besides it still can plug a vitroceramic.
A typical oven got around 3kW and the ceramic glass cooktop 7kW. 10kW / 230V = 43.5A. A 25A breaker won't be happy about that ;)
Then the power term hired with electrical corporation would have to be 13,5kW 3-phase. I am surprised how my family had been able to live on a flat(gas kitchen) with 3.3kW 1-phase with HVAC and electrical stoves.
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As such, within the typical suburban household service where 240V is the norm, while the reference to 240V 3 phase is technically incorrect, it can be understood.
This is exactly how the OP presented it:
Existing system is 3 phase, 240v Sydney, Australia.
Like Dave - and a few other members here - I, too, live in Sydney Australia ... and I knew exactly what he was talking about.
This is all that I was saying.
Just curious.
How is this connected since it is technically incorrect?
I have 230V 3-phase. Transformer is connected in star with each winding giving 134V and 230V between the phases. The center connection is floating. All three phases are evenly distributed in the house as 230V. Three wires into the house, no neutral and floating local ground. This is known as"IT". Is it something like that?
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As such, within the typical suburban household service where 240V is the norm, while the reference to 240V 3 phase is technically incorrect, it can be understood.
This is exactly how the OP presented it:
Existing system is 3 phase, 240v Sydney, Australia.
Like Dave - and a few other members here - I, too, live in Sydney Australia ... and I knew exactly what he was talking about.
This is all that I was saying.
Just curious.
How is this connected since it is technically incorrect?
I have 230V 3-phase. Transformer is connected in star with each winding giving 134V and 230V between the phases. The center connection is floating. All three phases are evenly distributed in the house as 230V. Three wires into the house, no neutral and floating local ground. This is known as"IT". Is it something like that?
Yes, IT is the correct term. Are you sure it's completely unearthed? If not there can be problems with it floating at a higher voltage than expected. Suppose you connect an auto transformer to it, with 230V at the primary and a few kV on the secondary. If an earth fault occurs on the secondary winding, then the whole mains circuit will float at a few kV, with respect to earth and bad things will happen.
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As such, within the typical suburban household service where 240V is the norm, while the reference to 240V 3 phase is technically incorrect, it can be understood.
This is exactly how the OP presented it:
Existing system is 3 phase, 240v Sydney, Australia.
Like Dave - and a few other members here - I, too, live in Sydney Australia ... and I knew exactly what he was talking about.
This is all that I was saying.
Just curious.
How is this connected since it is technically incorrect?
I have 230V 3-phase. Transformer is connected in star with each winding giving 134V and 230V between the phases. The center connection is floating. All three phases are evenly distributed in the house as 230V. Three wires into the house, no neutral and floating local ground. This is known as"IT". Is it something like that?
Yes, IT is the correct term. Are you sure it's completely unearthed? If not there can be problems with it floating at a higher voltage than expected. Suppose you connect an auto transformer to it, with 230V at the primary and a few kV on the secondary. If an earth fault occurs on the secondary winding, then the whole mains circuit will float at a few kV, with respect to earth and bad things will happen.
Yes, it is unearthed from the transformer. IT = isolated terra. The center of the transformer is connected to a spark gap in case of lightning. Local earth is a ground rod.
If it is an IT-system, it is techincally three phases. Nothing strange there.
Most of Norway is wired like this. We have a very few TT- systems with local earth on the transformer too. If they develop a new area for buildings with a new transformer, it will usually be wired as TN-C-S as most of Europe.
Yes, it can be some challenges, but they are mostly related to short circuits to earth because IT will not trip a fuse if only one phase is earthed. Since there is no common earth between houses, you can infact have a short on more than one phase if the shorts are far away from each other.
In older days houses was connected together with steel water pipes in the ground, so two shorts would trip a fuse. Those pipes has rusted away since long ago, and the plastic replacements are rather poor conductors.
Many houses have no RCD's so it is possible with some very interesting current-paths in the soil. I guess this will improve now when we get new smart meters that will monitor earth leakage from each house.
With IT we can get anything between 0V and 230V between a given phase and earth (if we don't add voltage as you describe), but in a TN-C-S we can get anything up to 400V between one phase and neutral if the PEN-wire from the power company manages to work itself loose. It does sometimes happen, and is quite expensive if it kills a lot of equipment. All systems have pros and cons.
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For the same power output, three phase motors are definitely smaller, lighter, more reliable and all things being equal, more efficient than single phase primarily due to more efficient use of the stator core and windings. Whether it makes economic sense, I can't say.
I've got a question about power distribution. In other jurisdictions, is power provided as true delta, ie. floating vis-a-vis ground/earth? I understand that the user's circuits are not supposed to be floating in case there is a failure that may unintentionally make the line to ground/earth voltage a hazard. eg. a primary to secondary short in the PoCo's transformer.
I'm in Canada and we tend to follow the US system. I haven't personally encountered any of the unusual configurations such as corner grounded delta. As far as I know, the PoCo always provides power to the small user as Wye referenced to ground/earth with both a neutral and local grounding/earthing. We have circuits and receptacles that can be single phase pole to neutral, single phase pole to pole, three phase no neutral and three phase + neutral.
All circuits and receptacles have a safety ground/earth that is not to be used to carry current except under fault conditions. Is this pretty much the case elsewhere too? (Excepting older systems)
Cheers,
Duane
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I've got a question about power distribution. In other jurisdictions, is power provided as true delta, ie. floating vis-a-vis ground/earth? I understand that the user's circuits are not supposed to be floating in case there is a failure that may unintentionally make the line to ground/earth voltage a hazard. eg. a primary to secondary short in the PoCo's transformer.
For the most part the final delivery to retail consumers is with a star and neutral/earth system. Light loads might take just one phase plus the neutral, but heavier loads could use the three phases. I think it is very unlikely that modern installations would deliver power to non-industrial consumers from a delta wound transformer secondary.
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As such, within the typical suburban household service where 240V is the norm, while the reference to 240V 3 phase is technically incorrect, it can be understood.
This is exactly how the OP presented it:
Existing system is 3 phase, 240v Sydney, Australia.
Like Dave - and a few other members here - I, too, live in Sydney Australia ... and I knew exactly what he was talking about.
This is all that I was saying.
Just curious.
How is this connected since it is technically incorrect?
I have 230V 3-phase. Transformer is connected in star with each winding giving 134V and 230V between the phases. The center connection is floating. All three phases are evenly distributed in the house as 230V. Three wires into the house, no neutral and floating local ground. This is known as"IT". Is it something like that?
Our 240V comes from a phase and neutral combination. That's about as sophisticated as a lot of people's thinking gets, so when there are 3 such combinations available, it is often referred to as 3 phase 240V. This is technically incorrect, as it is really 3 phase 415V
You have 230V 3-phase. Transformer is connected in star with each winding giving 134V and 230V between the phases.
We have 415V 3-phase. Transformer is connected in star with each winding giving 240V and 415V between the phases.
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I have encountered a data center that ran on 240V to neutral. The UPS setup accepted 277V to neutral, the idea being that bucking that down to 240V to neutral is simpler and more efficient than designing it to be able to step up or down.
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I've got a question about power distribution. In other jurisdictions, is power provided as true delta, ie. floating vis-a-vis ground/earth? I understand that the user's circuits are not supposed to be floating in case there is a failure that may unintentionally make the line to ground/earth voltage a hazard. eg. a primary to secondary short in the PoCo's transformer.
For the most part the final delivery to retail consumers is with a star and neutral/earth system. Light loads might take just one phase plus the neutral, but heavier loads could use the three phases. I think it is very unlikely that modern installations would deliver power to non-industrial consumers from a delta wound transformer secondary.
I don't see why not. Delta is very good for high currents at low voltages. There can still be a neutral, in a system with a delta wound transformer, which can either have a tertiary winding or there could another transformer can be nearer the load(s) requiring the neutral. The neutral current would be limited by the winding providing it, which could be much smaller than the main transformer, if the phase imballace/neutral current is small.
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I have encountered a data center that ran on 240V to neutral. The UPS setup accepted 277V to neutral, the idea being that bucking that down to 240V to neutral is simpler and more efficient than designing it to be able to step up or down.
I imagine the power company wanted the use of the 277V for balance of the windings more or not have to change/add another transformer from 480V. What data centre uses a lot of 480V though?
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I imagine someone doing maths before opening electric box :). How do you know for sure that you must calculate, BTW? What if there is true 3 phase 240V like in US? or 3ph 230V like is still common in some mainly 3rd world countries. Or there is step down transformer used.
2:
What is the definition of "true 3 phase"?
It means 3 phase 240V, not 3 times of 240V single phases / 3 phase 415V.
(https://ctlsys.com/wp-content/uploads/2016/10/3_phase_4_wire_delta_240.png)
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I think this point was not mentioned yet:
On the one hand, a three phase grid delivers power continuosly because
power = va*ia + vb*ib + vc*ic = constant
in spite of va, vb, vc, and ia, ib, ic, being sinusoidal phase voltages and currents, respectively.
Therefore the three phase motor does not have torque ripple and it runs smooth.
On the other hand, in a sinle phase grid
power = v*i= constant + ac_term
and the ac tern has a frequency which is twice the grid frequency (100Hz europe, 120Hz usa,...) [sin(50f) sin(50f) =1/2 (cos(0) + cos(100 f) ]
This ac term causes low frequency ripple in the torque delivered by the motor.
Bottom line: to achieve a continuous power transfer and a smooth operation of the motor by means of an AC signal, 3 phases are at least required.
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I imagine someone doing maths before opening electric box :). How do you know for sure that you must calculate, BTW? What if there is true 3 phase 240V like in US? or 3ph 230V like is still common in some mainly 3rd world countries. Or there is step down transformer used.
2:
What is the definition of "true 3 phase"?
It means 3 phase 240V, not 3 times of 240V single phases / 3 phase 415V.
(https://ctlsys.com/wp-content/uploads/2016/10/3_phase_4_wire_delta_240.png)
So "true 3 phase" is what is known as 3-phase in west and some 3rd world countries use 3x1-phase systems?
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Our standard is 230V P/N (+10% - 6%), and not 240V, and it has been for 25 years or so, if you measure it at 240V or 250V it is just a fluctuation.
IMO The best way to describe the voltage is 230V 'phase to neutral', though sometimes i say 'phase voltage'.
or 400V 'phase to phase' or sometimes I say 'line to line'.
Describing the voltage on it's own is not really enough.
Wraper was right early on when he said it wouldn't matter if you connect it as star or delta, as a motor it will still be the same voltage.
Though he stated the voltage ambiguously, I knew what the OP meant because I am subject to the same electrical rules as him.
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It means 3 phase 240V, not 3 times of 240V single phases / 3 phase 415V.
(https://ctlsys.com/wp-content/uploads/2016/10/3_phase_4_wire_delta_240.png)
Oh, how I cringe when I see that diagram get pulled out when we are having issues with basic Star and Delta.
Our standard is 230V P/N (+10% - 6%), and not 240V, and it has been for 25 years or so,
I thought that standard changed in 2000 - so not quite 25 years.
Also, it was more of a paper change, anyway. 240V +6%/-10% versus 230V +10%/-6%. Do the math ... and smile like I did.
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I thought it was 25 years as my teacher was the one who told me, about 25 years ago. Seems to be 2000 though.
Yeah it was a paper change of a paper number that brought us into line with many countries.
So 230V p/n it is.
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So 230V p/n it is.
...and if you believe that I may have a bridge, or a gold brick, or a golden egg to sell you.
I've worked in the power industry for a few *cough* years and the voltages I've measured have on average not deviated one jot (technical term) over those few years. When I measure phase to neutral I expect to see 240V. When phase to phase I expect to see 415V.
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For the most part the final delivery to retail consumers is with a star and neutral/earth system. Light loads might take just one phase plus the neutral, but heavier loads could use the three phases. I think it is very unlikely that modern installations would deliver power to non-industrial consumers from a delta wound transformer secondary.
I don't see why not. Delta is very good for high currents at low voltages.
Bear in mind I am talking about final delivery (domestic utility service) to homes and offices. This supply will follow the local electrical code and modern electrical codes will nearly always require a solidly grounded neutral.
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For the most part the final delivery to retail consumers is with a star and neutral/earth system. Light loads might take just one phase plus the neutral, but heavier loads could use the three phases. I think it is very unlikely that modern installations would deliver power to non-industrial consumers from a delta wound transformer secondary.
I don't see why not. Delta is very good for high currents at low voltages.
Bear in mind I am talking about final delivery (domestic utility service) to homes and offices. This supply will follow the local electrical code and modern electrical codes will nearly always require a solidly grounded neutral.
There can still be a neutral, in a system with a delta wound transformer, which can either have a tertiary winding or there could another transformer can be nearer the load(s) requiring the neutral.
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Soon you all start to talk about Zigzag transformers. :-DD
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So 230V p/n it is.
...and if you believe that I may have a bridge, or a gold brick, or a golden egg to sell you.
I've worked in the power industry for a few *cough* years and the voltages I've measured have on average not deviated one jot (technical term) over those few years. When I measure phase to neutral I expect to see 240V. When phase to phase I expect to see 415V.
That's good, cause that's in the specified range.
Now when people talk about the specified mains voltages in Australia I expect to hear them say 230V and 400V.
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Soon you all start to talk about Zigzag transformers. :-DD
Yes, zigzag transformers are often used to create a neutral, in a delta system.
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I have encountered a data center that ran on 240V to neutral. The UPS setup accepted 277V to neutral, the idea being that bucking that down to 240V to neutral is simpler and more efficient than designing it to be able to step up or down.
I imagine the power company wanted the use of the 277V for balance of the windings more or not have to change/add another transformer from 480V. What data centre uses a lot of 480V though?
The point is that 480V phase to phase is 277V to neutral. Some data centers are even using PSUs that run direct off 277V, while others are looking at HVDC power distribution. All of which are trying to improve on the most common 208V phase to phase used in almost all the smaller data centers and some large ones.
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Soon you all start to talk about Zigzag transformers. :-DD
Yes, zigzag transformers are often used to create a neutral, in a delta system.
Yes. But can you point to a country in the world where new installations of domestic low voltage supply to people's homes is provided with a delta system?
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So "true 3 phase" is what is known as 3-phase in west and some 3rd world countries use 3x1-phase systems?
:palm:
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So "true 3 phase" is what is known as 3-phase in west and some 3rd world countries use 3x1-phase systems?
:palm:
:-// What is the so called non-true 3 phase system in the first place. US 120/120/240 ???
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So "true 3 phase" is what is known as 3-phase in west and some 3rd world countries use 3x1-phase systems?
:palm:
:-// What is the so called non-true 3 phase system in the first place. US 120/120/240 ???
There is no "non true" 3 phase. I was talking about the voltage rating if you don't get it. I was talking about 3 phase with "true 240V" or "true 230V" voltage rating which can be found around the world. No to be confused with 3 phase 400/415V which have 230/240V between phase and neutral. Wrote that when someone said it's fine to call 3 phase 415V as 240V (which is voltage between phase an neutral in 415V 3 phase systems) because :
As to why, it is because anyone working with the system needs to know the highest voltage they can encounter in that system. This is a convention that I think is followed world wide, for fairly logical reasons.
If you have a three-phase system based on TN-wiring, the voltages are related by math. In domestic wiring, the most usual will be 400V/230V (actually 398.3V/230V) because we get normal mains between one phase and neutral. The voltage between two phases is the voltage between one phase and neutral multipled with the square root of 3 (1.73).
The britons believe they have 415/240V, but that is because the EU cheated them :) The nominal EU voltage is 230V with some percent allowed up and down. The British upper and lower voltage limits basically equals the EU limits, but they don't know it. :)
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Some potentially confusing things have been posted about using two phases of a three phase system, so I thought I'd clarify.
ovens are, strangely, 2 ph.
I doubt it. They're most likely single phase. Unless the supply in your area is two phase, which I don't believe is the case anywhere in the world. It will either be split phase or two phases of a three phase supply.
When a second phase is presented to the property - do we start talking about 2 phase 415V?
If there's no neutral, then it can be regarded as single phase.
If there is a neutral, then it's two phases of a three phase system, as they're 120o out of phase. The desired missing phase could be generated using a transformer, if needs be.
Two phase is 90o.
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I think this point was not mentioned yet:
On the one hand, a three phase grid delivers power continuosly because
power = va*ia + vb*ib + vc*ic = constant
in spite of va, vb, vc, and ia, ib, ic, being sinusoidal phase voltages and currents, respectively.
Therefore the three phase motor does not have torque ripple and it runs smooth.
On the other hand, in a sinle phase grid
power = v*i= constant + ac_term
and the ac tern has a frequency which is twice the grid frequency (100Hz europe, 120Hz usa,...) [sin(50f) sin(50f) =1/2 (cos(0) + cos(100 f) ]
This ac term causes low frequency ripple in the torque delivered by the motor.
Bottom line: to achieve a continuous power transfer and a smooth operation of the motor by means of an AC signal, 3 phases are at least required.
two should be enough, like a stepper motor
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Some potentially confusing things have been posted about using two phases of a three phase system, so I thought I'd clarify.
ovens are, strangely, 2 ph.
I doubt it. They're most likely single phase. Unless the supply in your area is two phase, which I don't believe is the case anywhere in the world. It will either be split phase or two phases of a three phase supply.
When a second phase is presented to the property - do we start talking about 2 phase 415V?
If there's no neutral, then it can be regarded as single phase.
If there is a neutral, then it's two phases of a three phase system, as they're 120o out of phase. The desired missing phase could be generated using a transformer, if needs be.
Two phase is 90o.
I am not sure of this, just speculating.
Local meanings, practices, again are probably causing confusion.
Sometimes here, in rural areas with low load down a long road they often run 2 phases of a 3 phase HV system. (No neutral, no third phase. )
This would go to pole top transformers along the road which would bring it down to single phase 230V and a standard TN-C-S system.
I am guessing that is how somebody gets a 2 phase meter like this. So in this case it might mean single phase. But it does say polyphase? and it does say 2 x 230V? and it does say 3 wire, so maybe its 2 phases and neutral.
Alternatively with a three phase supply, if an oven is large there is no reason you could not run 2 phases and neutral to it if it was designed that way.
For the same power rating 3 phase cables will probably have a smaller current rating, and doing this would help balance the phases.
Or it could be one phase to the cooktop and one phase to the oven.
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Some potentially confusing things have been posted about using two phases of a three phase system, so I thought I'd clarify.
ovens are, strangely, 2 ph.
I doubt it. They're most likely single phase. Unless the supply in your area is two phase, which I don't believe is the case anywhere in the world. It will either be split phase or two phases of a three phase supply.
Our ovens are flexible regarding the power supply. The different heaters and the cooking plates are distributed across three phases (Y/star with neutral), but you can add metal bridges to the terminal block to power the oven from two phases or a single phase.
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So "true 3 phase" is what is known as 3-phase in west and some 3rd world countries use 3x1-phase systems?
:palm:
:-// What is the so called non-true 3 phase system in the first place. US 120/120/240 ???
There is no "non true" 3 phase. I was talking about the voltage rating if you don't get it. I was talking about 3 phase with "true 240V" or "true 230V" voltage rating which can be found around the world. No to be confused with 3 phase 400/415V which have 230/240V between phase and neutral. Wrote that when someone said it's fine to call 3 phase 415V as 240V (which is voltage between phase an neutral in 415V 3 phase systems) because :
Yes, well that I thought, but there seems to be so exotic solutions around (like the US domestic split phase setup). There is no non-true 3-phases as the phase term itself means (in here that..) there is a time difference between of 3.333 ms between peaks in symmetrical three phase system if the phase frequenzy is 50Hz (edit. non logical this phrase sorry. ). This makes the so called angle 120 geometrical degrees between each and results the line-to-line voltage of aprox. 400 Vrms sinusoidal if the line-to-neutral voltage have given value of 230 Vrms sinusoidal nominal. The right standardised notation of the voltage is propably given in IEC 60038 standard (= International Electrotechnical Commission since 1906) and its local translations (which I do not have in my disposal).
Edit. Hopefully I got right english terms at last.
To ovens... continuing Madires last line: ..or three phases (if available).
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When we deal with three phase systems, it is most important to be very specific about what we talk about.
There are a lot of definitions flaoting around, some of them are based on local conventions.
One problem is how to distinguish between 230V mains from the 400/230V TN-system and 230V mains from the IT (or TT) systems in buildings were they co-exist.
All of them are in use, and especially IT is common in for instance hospitals and some industries where continous power supply is more important than the benefits of a separate neutral conductor.
In Norway they decided upon this:
(https://www.eevblog.com/forum/chat/3-phase-is-more-efficent-than-single-phase/?action=dlattach;attach=338409;image)
Because of the therm 2-phase, some people believe that a normal incandescent lamp is a 2-phase load. It is not. It is always a 1-phase load because it does not need a rotating magnetic field to function.
How do they do this in other countries? Is there anyone here with real knowledge about it? Any electrician with hands-on experience from IT or TT-systems?
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Some potentially confusing things have been posted about using two phases of a three phase system, so I thought I'd clarify.
ovens are, strangely, 2 ph.
I doubt it. They're most likely single phase. Unless the supply in your area is two phase, which I don't believe is the case anywhere in the world. It will either be split phase or two phases of a three phase supply.
When a second phase is presented to the property - do we start talking about 2 phase 415V?
If there's no neutral, then it can be regarded as single phase.
If there is a neutral, then it's two phases of a three phase system, as they're 120o out of phase. The desired missing phase could be generated using a transformer, if needs be.
Two phase is 90o.
I am not sure of this, just speculating.
Local meanings, practices, again are probably causing confusion.
Sometimes here, in rural areas with low load down a long road they often run 2 phases of a 3 phase HV system. (No neutral, no third phase. )
This would go to pole top transformers along the road which would bring it down to single phase 230V and a standard TN-C-S system.
In that case, I believe the two phases just go to either ends of the primary and the secondary is single phase.
I am guessing that is how somebody gets a 2 phase meter like this. So in this case it might mean single phase. But it does say polyphase? and it does say 2 x 230V? and it does say 3 wire, so maybe its 2 phases and neutral.
Yes, it looks like 2 of 3 phases + neutral. 2 phase in that case is a misnomer. I would suspect the two phases come of a three phase transformer.
All of them are in use, and especially IT is common in for instance hospitals and some industries where continous power supply is more important than the benefits of a separate neutral conductor.
How do they do this in other countries? Is there anyone here with real knowledge about it? Any electrician with hands-on experience from IT or TT-systems?
I am not an electrician and do not have any direct experience with IT systems but studied them at college, as part of a course on the 17th Edition (UK wiring regulations). An IT system is usually provided by a local transformer and has to have an insulation monitoring system, which generates a warning, if one of the conductors develops an earth fault. I haven't seen it used for domestic power but there might be some old installations with an IT system and no insulation monitoring circuit.
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All of them are in use, and especially IT is common in for instance hospitals and some industries where continous power supply is more important than the benefits of a separate neutral conductor.
How do they do this in other countries? Is there anyone here with real knowledge about it? Any electrician with hands-on experience from IT or TT-systems?
I am not an electrician and do not have any direct experience with IT systems but studied them at college, as part of a course on the 17th Edition (UK wiring regulations). An IT system is usually provided by a local transformer and has to have an insulation monitoring system, which generates a warning, if one of the conductors develops an earth fault. I haven't seen it used for domestic power but there might be some old installations with an IT system and no insulation monitoring circuit.
What about the naming convention? 1-phase and 2-phase? Do they distinguish between this in other countries? We do, because IT is the normal from old days, and TN is the new. To avoid electricians messing up and ending up with 400V in the wrong place they found it necessary to distinguish.
From what I understand, IT is more widespread than many people believe because of the hospital / industrial use.
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All of them are in use, and especially IT is common in for instance hospitals and some industries where continous power supply is more important than the benefits of a separate neutral conductor.
How do they do this in other countries? Is there anyone here with real knowledge about it? Any electrician with hands-on experience from IT or TT-systems?
I am not an electrician and do not have any direct experience with IT systems but studied them at college, as part of a course on the 17th Edition (UK wiring regulations). An IT system is usually provided by a local transformer and has to have an insulation monitoring system, which generates a warning, if one of the conductors develops an earth fault. I haven't seen it used for domestic power but there might be some old installations with an IT system and no insulation monitoring circuit.
What about the naming convention? 1-phase and 2-phase? Do they distinguish between this in other countries? We do, because IT is the normal from old days, and TN is the new. To avoid electricians messing up and ending up with 400V in the wrong place they found it necessary to distinguish.
From what I understand, IT is more widespread than many people believe because of the hospital / industrial use.
Here we have single and three phase. I don't think I've ever encountered the expression "two phase", other than here. I have seen equipment which uses two phases of a three phase supply but it's provided with a three phase connector, with only two of the phases used.