A basic 3-phase question
So in the coffee bar this morning chat pondered on 3-phase and how to
know which of the 3 wires was which phase. I've done some googling and would like the experts to confirm: 1. It doesn't matter which wire is which phase providing the sequence of 1-2-3 2-3-1 or 3-1-2 is maintained when connecting, or any pair swapped if that is what is required. 2. The voltage between any two phases is 440v and it doesn't matter which two and 3. The voltage between any phase and ground/neutral is 240v Is that correct? Are there any conditions when the phase needs to be known? If so how is it detected? -- AnthonyL Why do scientists need to BELIEVE in anything? |
A basic 3-phase question
In article ,
AnthonyL wrote: So in the coffee bar this morning chat pondered on 3-phase and how to know which of the 3 wires was which phase. I've done some googling and would like the experts to confirm: 1. It doesn't matter which wire is which phase providing the sequence of 1-2-3 2-3-1 or 3-1-2 is maintained when connecting, or any pair swapped if that is what is required. 2. The voltage between any two phases is 440v and it doesn't matter which two and 3. The voltage between any phase and ground/neutral is 240v Is that correct? Are there any conditions when the phase needs to be known? If so how is it detected? when connecting up a 3 phase gennerating plant to the grid. Can't remember, I never became a poer engineer. -- from KT24 in Surrey, England "I'd rather die of exhaustion than die of boredom" Thomas Carlyle |
A basic 3-phase question
AnthonyL wrote:
So in the coffee bar this morning chat pondered on 3-phase and how to know which of the 3 wires was which phase. I've done some googling and would like the experts to confirm: 1. It doesn't matter which wire is which phase providing the sequence of 1-2-3 2-3-1 or 3-1-2 is maintained when connecting, or any pair swapped if that is what is required. 2. The voltage between any two phases is 440v and it doesn't matter which two and 3. The voltage between any phase and ground/neutral is 240v Is that correct? Are there any conditions when the phase needs to be known? If so how is it detected? Totally ignorant comment he Surely there is no absolute phase (in power distribution at least), just phase in relation to the other two phases. So no real life equipment could know the difference as long as you can swap any two if it is wrong. Is it good practice in real life to keep the same colour wires throughout the whole installation for each incoming phase? -- Roger Hayter |
A basic 3-phase question
On 01/03/2020 13:37, AnthonyL wrote:
So in the coffee bar this morning chat pondered on 3-phase and how to know which of the 3 wires was which phase. I've done some googling and would like the experts to confirm: 1. It doesn't matter which wire is which phase providing the sequence of 1-2-3 2-3-1 or 3-1-2 is maintained when connecting, or any pair swapped if that is what is required. 2. The voltage between any two phases is 440v and it doesn't matter which two and 3. The voltage between any phase and ground/neutral is 240v Is that correct? Yes Are there any conditions when the phase needs to be known? If so how is it detected? As long as you know the 1-2-3, 2-3-1 or 3-1-2 rotation you should be OK. -- Adam |
A basic 3-phase question
charles wrote:
In article , AnthonyL wrote: So in the coffee bar this morning chat pondered on 3-phase and how to know which of the 3 wires was which phase. I've done some googling and would like the experts to confirm: 1. It doesn't matter which wire is which phase providing the sequence of 1-2-3 2-3-1 or 3-1-2 is maintained when connecting, or any pair swapped if that is what is required. 2. The voltage between any two phases is 440v and it doesn't matter which two and 3. The voltage between any phase and ground/neutral is 240v Is that correct? Are there any conditions when the phase needs to be known? If so how is it detected? when connecting up a 3 phase gennerating plant to the grid. Can't remember, I never became a poer engineer. As long as they were in the right order wouldn't they just slip into sync? -- Roger Hayter |
A basic 3-phase question
Jethro_uk wrote:
On Sun, 01 Mar 2020 13:37:47 +0000, AnthonyL wrote: Are there any conditions when the phase needs to be known? If so how is it detected? If you connect a 3-phase motor up wrong, it won't work. Does that count ? From a position of no theoretical knowledge and little practical experience, I thought it would go backwards. Am I wrong? This has the suggestion of leading to a bridges of Koenigsberg puzzle ... what's the minimum number of wires you'd need to swap to get it working :) -- Roger Hayter |
A basic 3-phase question
On Sun, 1 Mar 2020 14:12:25 +0000, Roger Hayter wrote:
Jethro_uk wrote: On Sun, 01 Mar 2020 13:37:47 +0000, AnthonyL wrote: Are there any conditions when the phase needs to be known? If so how is it detected? If you connect a 3-phase motor up wrong, it won't work. Does that count ? From a position of no theoretical knowledge and little practical experience, I thought it would go backwards. Am I wrong? The motors at work did - switch on, look at the fan or feel the airflow, sod's law... Can't remember (30 years ago) what happened with the 3-phase fridge motors. The condensr fan might have been the indication, but it might have been single phase. We had a 3-phase USP but that was just for providing 3-off 1-phase supplies. -- Peter. The gods will stay away whilst religions hold sway |
A basic 3-phase question
On Sunday, 1 March 2020 14:12:27 UTC, Roger Hayter wrote:
Jethro_uk wrote: On Sun, 01 Mar 2020 13:37:47 +0000, AnthonyL wrote: Are there any conditions when the phase needs to be known? If so how is it detected? If you connect a 3-phase motor up wrong, it won't work. Does that count ? From a position of no theoretical knowledge and little practical experience, I thought it would go backwards. Am I wrong? This has the suggestion of leading to a bridges of Koenigsberg puzzle ... what's the minimum number of wires you'd need to swap to get it working :) It depends. A 3ph motor can be connected in "star" or " delta/mesh" (Mesh=USA) Reversing any two phases reverse the motor. However if you swop the connections on one of the windings, (ie reverse the Live and Neutral connections,) it won't run. |
A basic 3-phase question
On 01/03/2020 13:37, AnthonyL wrote:
So in the coffee bar this morning chat pondered on 3-phase and how to know which of the 3 wires was which phase. I've done some googling and would like the experts to confirm: 1. It doesn't matter which wire is which phase providing the sequence of 1-2-3 2-3-1 or 3-1-2 is maintained when connecting, or any pair swapped if that is what is required. 2. The voltage between any two phases is 440v and it doesn't matter which two 400v +10% - 6% and 3. The voltage between any phase and ground/neutral is 240v 230v +10% -6%. Are there any conditions when the phase needs to be known? If so how is it detected? -- Colin Bignell |
A basic 3-phase question
On 01/03/2020 13:37, AnthonyL wrote:
So in the coffee bar this morning chat pondered on 3-phase and how to know which of the 3 wires was which phase. I've done some googling and would like the experts to confirm: 1. It doesn't matter which wire is which phase providing the sequence of 1-2-3 2-3-1 or 3-1-2 is maintained when connecting, or any pair swapped if that is what is required. 2. The voltage between any two phases is 440v and it doesn't matter which two and 3. The voltage between any phase and ground/neutral is 240v Is that correct? yes Are there any conditions when the phase needs to be known? If so how is it detected? The only time you need to know is when connecting to a true AC motor when reversing any two phases will reverse the motor direction -- Future generations will wonder in bemused amazement that the early twenty-first centurys developed world went into hysterical panic over a globally average temperature increase of a few tenths of a degree, and, on the basis of gross exaggerations of highly uncertain computer projections combined into implausible chains of inference, proceeded to contemplate a rollback of the industrial age. Richard Lindzen |
A basic 3-phase question
On 01/03/2020 14:01, Roger Hayter wrote:
Totally ignorant comment he Surely there is no absolute phase (in power distribution at least), just phase in relation to the other two phases. So no real life equipment could know the difference as long as you can swap any two if it is wrong. yes. Is it good practice in real life to keep the same colour wires throughout the whole installation for each incoming phase? yes. -- Future generations will wonder in bemused amazement that the early twenty-first centurys developed world went into hysterical panic over a globally average temperature increase of a few tenths of a degree, and, on the basis of gross exaggerations of highly uncertain computer projections combined into implausible chains of inference, proceeded to contemplate a rollback of the industrial age. Richard Lindzen |
A basic 3-phase question
On 01/03/2020 14:08, Jethro_uk wrote:
On Sun, 01 Mar 2020 13:37:47 +0000, AnthonyL wrote: Are there any conditions when the phase needs to be known? If so how is it detected? If you connect a 3-phase motor up wrong, it won't work. Does that count ? This has the suggestion of leading to a bridges of Koenigsberg puzzle ... what's the minimum number of wires you'd need to swap to get it working :) one pair -- Future generations will wonder in bemused amazement that the early twenty-first centurys developed world went into hysterical panic over a globally average temperature increase of a few tenths of a degree, and, on the basis of gross exaggerations of highly uncertain computer projections combined into implausible chains of inference, proceeded to contemplate a rollback of the industrial age. Richard Lindzen |
A basic 3-phase question
On 01/03/2020 14:12, Roger Hayter wrote:
Jethro_uk wrote: On Sun, 01 Mar 2020 13:37:47 +0000, AnthonyL wrote: Are there any conditions when the phase needs to be known? If so how is it detected? If you connect a 3-phase motor up wrong, it won't work. Does that count ? From a position of no theoretical knowledge and little practical experience, I thought it would go backwards. Am I wrong? depends if its CAPABLE of going backwards -- €śThose who can make you believe absurdities, can make you commit atrocities.€ť €• Voltaire, Questions sur les Miracles Ă* M. Claparede, Professeur de ThĂ©ologie Ă* Genève, par un Proposant: Ou Extrait de Diverses Lettres de M. de Voltaire |
A basic 3-phase question
It matters quite a bit if you close an interconnector without the two sections being synchronised.
|
A basic 3-phase question
In message , ARW
writes On 01/03/2020 13:37, AnthonyL wrote: So in the coffee bar this morning chat pondered on 3-phase and how to know which of the 3 wires was which phase. I've done some googling and would like the experts to confirm: 1. It doesn't matter which wire is which phase providing the sequence of 1-2-3 2-3-1 or 3-1-2 is maintained when connecting, or any pair swapped if that is what is required. 2. The voltage between any two phases is 440v and it doesn't matter which two and 3. The voltage between any phase and ground/neutral is 240v Is that correct? Yes Are there any conditions when the phase needs to be known? If so how is it detected? As long as you know the 1-2-3, 2-3-1 or 3-1-2 rotation you should be OK. Synchronising a generator? -- Tim Lamb |
A basic 3-phase question
On Sun, 1 Mar 2020 17:59:00 +0000, The Natural Philosopher
wrote: On 01/03/2020 13:37, AnthonyL wrote: So in the coffee bar this morning chat pondered on 3-phase and how to know which of the 3 wires was which phase. I've done some googling and would like the experts to confirm: 1. It doesn't matter which wire is which phase providing the sequence of 1-2-3 2-3-1 or 3-1-2 is maintained when connecting, or any pair swapped if that is what is required. 2. The voltage between any two phases is 440v and it doesn't matter which two and 3. The voltage between any phase and ground/neutral is 240v Is that correct? yes Are there any conditions when the phase needs to be known? If so how is it detected? The only time you need to know is when connecting to a true AC motor when reversing any two phases will reverse the motor direction What about when it's being connected to the grid? -- AnthonyL Why do scientists need to BELIEVE in anything? |
A basic 3-phase question
On Sunday, 1 March 2020 20:10:43 UTC, Cynic wrote:
It matters quite a bit if you close an interconnector without the two sections being synchronised. All you need is three lamps. Eg:- https://www.nuclear-power.net/nuclea...oscope-method/ |
A basic 3-phase question
On Mon, 02 Mar 2020 00:37:10 -0800, harry wrote:
On Sunday, 1 March 2020 20:10:43 UTC, Cynic wrote: It matters quite a bit if you close an interconnector without the two sections being synchronised. All you need is three lamps. Eg:- https://www.nuclear-power.net/nuclea...ysics/reactor- operation/reactor-startup/synchronizing-lamps-synchroscope-method/ I remember reading of a case where the lamps were wired incorrectly. On the first attempt to sync, there was an expensive bang. -- My posts are my copyright and if @diy_forums or Home Owners' Hub wish to copy them they can pay me ÂŁ1 a message. Use the BIG mirror service in the UK: http://www.mirrorservice.org *lightning surge protection* - a w_tom conductor |
A basic 3-phase question
AnthonyL laid this down on his screen :
1. It doesn't matter which wire is which phase providing the sequence of 1-2-3 2-3-1 or 3-1-2 is maintained when connecting, or any pair swapped if that is what is required. Yes. Which is which phase will normally be decided and checked at the incomer (with the instrument I). The phase marking will then be maintained throughout the installation. If a 3ph motor is already marked for the correct phases to ensure the correct direction of rotation, if connected with the correctly marked phases, it will run the desired way. Swapping over any two of the three phase wires, will reverse the direction of rotation. 2. The voltage between any two phases is 440v and it doesn't matter which two Yes. 3. The voltage between any phase and ground/neutral is 240v Yes. Are there any conditions when the phase needs to be known? If so how is it detected? There is no way to determine on an unmarked 3ph cable, which wire is which phase apart from the obvious belling method of comparing the voltage to the known incoming other end. To ensure, or check correct phase rotation, engineers use a tiny 3ph handheld (I), three wire motor. |
A basic 3-phase question
On Mon, 2 Mar 2020 00:37:10 -0800 (PST), harry
wrote: On Sunday, 1 March 2020 20:10:43 UTC, Cynic wrote: It matters quite a bit if you close an interconnector without the two sections being synchronised. All you need is three lamps. Eg:- https://www.nuclear-power.net/nuclea...oscope-method/ Lamps were last used in anger in the 1980's, where there was still some generation connected at distribution voltages Syncroscopes were always used for synchronisation at main generation sites. You still had a single check light but the pointer showed the rate of slip relative to the grid But both methods are wholly reliant on the skill of the operator and the speed of breaker closure, get it wrong and you can very easily wreck the generator rotor. Everything (as in post 1987 ish in the UK ) is now done electronically such that it is impossible to synch incorrectly, even with a total system split and a large disparity on phase rotation rates and voltages. You prime the breaker with the appropriate sync mode and just wait, for up to 30 mins if necessary at which point it will time out. Generation just runs the governor against the reference voltage and frequency and autocloses within preset voltage and slip parameters. The level of operator skill required is near zero. -- |
A basic 3-phase question
On Sun, 1 Mar 2020 12:10:41 -0800 (PST), Cynic wrote:
It matters quite a bit if you close an interconnector without the two sections being synchronised. All interconnectors with the exception of the one from Lancashire to the Isle of Man are DC and as such there is no concept of synchronisation. Coupling sections of busbar or overheads is also in the main performed with both ends in synchronisation because the system is always operated as one frequency zone. If a system split happens or there is a phase shift due to reactive components then the breaker is closed under an automated procedure but only when the rate and magnitude of the vectors are within preset parameters. -- |
A basic 3-phase question
In article ,
Jethro_uk wrote: Are there any conditions when the phase needs to be known? If so how is it detected? If you connect a 3-phase motor up wrong, it won't work. Does that count ? They generally just run in reverse. -- *If you try to fail and succeed, which have you done? * Dave Plowman London SW To e-mail, change noise into sound. |
All times are GMT +1. The time now is 04:25 PM. |
Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004 - 2014 DIYbanter