Canoe tell me more, is it being pulled around by another force or do I have this wrong as well?
yes I do know that lifts have speed controls and brakes
yes I do know that lifts have speed controls and brakes
A Thought Experiment
- Thread starter Sidewinder
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Help Support Talk Electrician Forum:
Good grief !!Canoeboy said:
Does the world slowly go into reverse and then time as we know it go backwards???
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I thought about this last night; I think I have a solution based
upon "Black Box" analysis.
Sidewinder is right; my previous method would NOT work
because too many assumptions need to be made.
The Black Box analysis is more reliable because if you have
two such boxes, the same test has to be applied to both;
the outcome is determined by HOW the boxes behave when the
test is applied.
And yes, the kit is unutterably simple. I have to go out but will post
the method later.
upon "Black Box" analysis.
Sidewinder is right; my previous method would NOT work
because too many assumptions need to be made.
The Black Box analysis is more reliable because if you have
two such boxes, the same test has to be applied to both;
the outcome is determined by HOW the boxes behave when the
test is applied.
And yes, the kit is unutterably simple. I have to go out but will post
the method later.
I have been keeping an eye on this thread it really rings a bell in my head but its years since doing any 3phase let alone motors...
My tutor at college was evil and he would set us tasks way beyond those of c&g level hence its ringing a bell.
Im going to do some more reading but for now do we have access to an oscilloscope?
My tutor at college was evil and he would set us tasks way beyond those of c&g level hence its ringing a bell.
Im going to do some more reading but for now do we have access to an oscilloscope?
well,
I dont really have a clue,
started to think a bit about trying to measure inductance, but I cant see how we could do that effectively,
and then thought about volt drop, but the variables would be too small and more affected by our influences more than coil differences, I think,
even if it were viable.
as for most other thoughts,
above my head,,,,,,,, :|
I dont really have a clue,
started to think a bit about trying to measure inductance, but I cant see how we could do that effectively,
and then thought about volt drop, but the variables would be too small and more affected by our influences more than coil differences, I think,
even if it were viable.
as for most other thoughts,
above my head,,,,,,,, :|
This storeman is a very unhelpful chap perhaps he works part time in BnQ?
I'm off to steal one from my local schools science dept....
:coat
I'm off to steal one from my local schools science dept....
:coat
Yes we have access to an oscilloscope.
Steps, inductance is about as much use as resistance and capacitance on its own.
I still think it needs a combination approach.
I honestly don't yet have an answer, which is why I posted the thread, I could not immediately "see" an answer, so I thought it worthy of more thought.
Not sure if I will get one yet.
Been mental today, just been catching up on emails & stuff for a couple of hours whilst popping in and out of here.
Had an unusual one tonight, a Co. in the USA interested in using my abilities on their behalf across Europe and beyond perhaps!
Got to sort out a rate now, hmm...
Steps, inductance is about as much use as resistance and capacitance on its own.
I still think it needs a combination approach.
I honestly don't yet have an answer, which is why I posted the thread, I could not immediately "see" an answer, so I thought it worthy of more thought.
Not sure if I will get one yet.
Been mental today, just been catching up on emails & stuff for a couple of hours whilst popping in and out of here.
Had an unusual one tonight, a Co. in the USA interested in using my abilities on their behalf across Europe and beyond perhaps!
Got to sort out a rate now, hmm...
Do you have an actual answer to this or is it an exercise that doesn't necessarily have an answer.
I have 2 methods that spring to mind. The one that's no so elegant involves connecting a car battery to two of the terminals and using a FLIR camera to see if two or all 3 of the windings are heating up. Not sure how well this would work in real life though.
The other method is so simple I'm almost convinced I'm missing something obvious.
*Edit* Just wanted to clear up any confusion by letting you know panel builder are superior beings in every way. The only thing that might trump being a panel builder is being voted sparky of the year .
I have 2 methods that spring to mind. The one that's no so elegant involves connecting a car battery to two of the terminals and using a FLIR camera to see if two or all 3 of the windings are heating up. Not sure how well this would work in real life though.
The other method is so simple I'm almost convinced I'm missing something obvious.
*Edit* Just wanted to clear up any confusion by letting you know panel builder are superior beings in every way. The only thing that might trump being a panel builder is being voted sparky of the year
.
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Marvo,
I don't have an answer yet, and I was going to do some work on this before one of my dogs went walk about!
Just found her and got her home, so nowt been done since last post, sorry.
There is a real answer, and I do know that there is a member here that has it.
Your attempt is a valiant one, but, it used numbers, we have to avoid numbers because then we have to prove it works for every possible number,
We really need a theoretical answer that uses symbols to prove that the evaluation works, it can be illustrated with numbers after that, but it must work in algebra to be a reasonable proof.
As an aside, seeing as Canoe has drifted off topic!
I ended up lifting vinyl flooring today in a domestic dwelling, very glamorous for a sparky NOT!
That was after removing an EM light & 2 socket outlets, the waste water pipework & the cold supply.
Then making good all the decoration after the removal.
Still got paid the same rate though, not something I would normally do, but it helped the client out on a medical job.
Tomorrow.
Fitting power, tacho & encoder plugs to analogue servo motor cabling in a packaging manufacturer!
A change is as good as a rest & all that!
Knackered today though, 8 hours absolutely flat out, totally seriously, non-stop, without, any, breaks with an hour travel either side.
I don't have an answer yet, and I was going to do some work on this before one of my dogs went walk about!
Just found her and got her home, so nowt been done since last post, sorry.
There is a real answer, and I do know that there is a member here that has it.
Your attempt is a valiant one, but, it used numbers, we have to avoid numbers because then we have to prove it works for every possible number,
We really need a theoretical answer that uses symbols to prove that the evaluation works, it can be illustrated with numbers after that, but it must work in algebra to be a reasonable proof.
As an aside, seeing as Canoe has drifted off topic!
I ended up lifting vinyl flooring today in a domestic dwelling, very glamorous for a sparky NOT!
That was after removing an EM light & 2 socket outlets, the waste water pipework & the cold supply.
Then making good all the decoration after the removal.
Still got paid the same rate though, not something I would normally do, but it helped the client out on a medical job.
Tomorrow.
Fitting power, tacho & encoder plugs to analogue servo motor cabling in a packaging manufacturer!
A change is as good as a rest & all that!
Knackered today though, 8 hours absolutely flat out, totally seriously, non-stop, without, any, breaks with an hour travel either side.
well,
you could transpose Marvos answer into
>6x
or
5x
I cant do the proper fancy x
you could transpose Marvos answer into
>6x
or
5x
I cant do the proper fancy x
The numbers in the solution were just for illustration. It will work for any motor because it's the percentage difference between the two tests that gives the answer. If the 2 tests give a 33.3% difference in their results the motor will be internally delta connected, if the difference between the two test results is 25% the motor will always be internally Y connected.
I kinda like the FLIR method although I think it would be a long shot. If it did work you'd also see if the motor is 2-pole, 4-pole or 6-pole.
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I don't think you would see winding heating in a TEFC motor TBH connected to a car battery for example.
Plus how would you know which windings were heating through the case of the motor?
You would just see the case heating, possibly.
Don't know about the tests/results, I'd again have to have some time to think about it.
Got to go tonight, early start tomorrow, got to travel to the job.
Plus how would you know which windings were heating through the case of the motor?
You would just see the case heating, possibly.
Don't know about the tests/results, I'd again have to have some time to think about it.
Got to go tonight, early start tomorrow, got to travel to the job.
I like the thermal imaging idea too
Would delta create more heat due to drawing more current when connected?
Just... stabbing in the dark.
Would delta create more heat due to drawing more current when connected?
Just... stabbing in the dark.
Nope, I haven't tried either test. The only thermal camera I have is at work,
I'm pretty sure you could see the definition of the windings and pole arrangement through a thermal camera but you probably need one that's better quality than the one I have.
This is an image I pulled from the net which kinda suggests it plausible.
The method I scribbled on the paper was just the result of trying to dream up different tests that would give varying comparative differential answers. If you're not keen on the resistance test percentage difference you could do pretty much the same with an applied voltage and testing the current flow with all terminals open and again with any two terminals linked. It's much of a muchness, you'd be still looking at the percentage difference in the displayed results so the resistance test would be the preferred method for me.
I'm pretty sure you could see the definition of the windings and pole arrangement through a thermal camera but you probably need one that's better quality than the one I have.
This is an image I pulled from the net which kinda suggests it plausible.
The method I scribbled on the paper was just the result of trying to dream up different tests that would give varying comparative differential answers. If you're not keen on the resistance test percentage difference you could do pretty much the same with an applied voltage and testing the current flow with all terminals open and again with any two terminals linked. It's much of a muchness, you'd be still looking at the percentage difference in the displayed results so the resistance test would be the preferred method for me.
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Hi Marvo,
Errrr, no.... I went through all that in post 29. Difference is exactly the same for both star and delta. The difference between 15 and 20 is NOT 25% it is 33% . What is 33.333% of 15??? 5.. add 5 to 15... 20!!!!
john...
You could use a thermal camera all you liked too, would not work either, cos the windings are still in the same place. Have to be, otherwise a motor could not be operated in both star and delta. Windings in same place, connections to ends different is all....
john...
Errrr, no.... I went through all that in post 29. Difference is exactly the same for both star and delta. The difference between 15 and 20 is NOT 25% it is 33% . What is 33.333% of 15??? 5.. add 5 to 15... 20!!!!
john...
You could use a thermal camera all you liked too, would not work either, cos the windings are still in the same place. Have to be, otherwise a motor could not be operated in both star and delta. Windings in same place, connections to ends different is all....
john...
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I looked at this "all ends up" yesterday. I wondered about looking
at it as a "black box" so I did the following.
I wondered what might happen to the reads on the ends of the wires
coming out, as Sidewinder says, there are only three and the centre
point, if there is one, is hidden.
So; Take reads of the resistance around the motor. The three should
be the same. Note it and call it step 1.
Now, short any two of the conductors and then take reads around the
other two, they will be the same and less than step 1.
Calculate the drop in resistance as a percentage betwen step 1 and
2.
I did this, wondering if there would be any difference between the star
and delta configuration with regard to the percentage decrease of the
read.
I did the algebra, worked examples, and finally a rig on a bread board.
Irrespective of the configuration, the drop (expressed as a percentage)
is the same - 25%.
at it as a "black box" so I did the following.
I wondered what might happen to the reads on the ends of the wires
coming out, as Sidewinder says, there are only three and the centre
point, if there is one, is hidden.
So; Take reads of the resistance around the motor. The three should
be the same. Note it and call it step 1.
Now, short any two of the conductors and then take reads around the
other two, they will be the same and less than step 1.
Calculate the drop in resistance as a percentage betwen step 1 and
2.
I did this, wondering if there would be any difference between the star
and delta configuration with regard to the percentage decrease of the
read.
I did the algebra, worked examples, and finally a rig on a bread board.
Irrespective of the configuration, the drop (expressed as a percentage)
is the same - 25%.
Yes, so did i, back in post 29. You can express it as a drop of 25% or an increase of 33%. You can express the increase/ decrease as a ratio if you want; Either 1.333 or 0.75 depending again, on which end you are looking from...
john
john
Hi Again.
What about powering up the motor by DRIVING it with a second motor so as to run it as a generator. Yes, i know you would have to think of some means of exciting the rotor, say an external voltage across one winding, or capacitors???
Anyway, run it up to speed [plus a bit for slip] and see what voltage you get out.
You could perhaps connect it up to 230 3p and measure the current it draws, and see how quick it starts, then [ if it seemed sluggish] connect it to 400V 3p and again, check the current and starting performance against a motor in the same size range
john..
What about powering up the motor by DRIVING it with a second motor so as to run it as a generator. Yes, i know you would have to think of some means of exciting the rotor, say an external voltage across one winding, or capacitors???
Anyway, run it up to speed [plus a bit for slip] and see what voltage you get out.
You could perhaps connect it up to 230 3p and measure the current it draws, and see how quick it starts, then [ if it seemed sluggish] connect it to 400V 3p and again, check the current and starting performance against a motor in the same size range
john..
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