A Thought Experiment

[Sidewinder]

No I am NOT saying ANYTHING different to what I have said before.

You have 3 unknown resistances.

You have one in parallel with two.

How do you know what the current division is between the three resistances to get the voltage?

Look at the diagrams I have drawn, I can't see yours at this end as they have not come through well., not your fault, but a limitation of the method I suspect.

In the delta configuration in your example you have an unknown current dividing between 3 resistors, of equal value, one in parallel with two in series, now if you don't know the current flowing, how can you derive the current division?

If you don't have the current division, how can you have the voltage division?

 

[steptoe]

ah, but, I think in specs theory you can identify the coil resistance by moving the added resistor to each of the wires in turn,

thereby being able to work out the coil resistance,

its late, bikes been on today, beer been cold, time for the pub, 

:coat

 

[SPECIAL LOCATION]

Going round in circles here...

Look at the drawings I have done..

it is all explained...

Two equal value resistances in series across placed a known test voltage will divide to a calculable voltage half of the known test volatge..

The parallel aspects is irrelevant as the voltage will be across the two identical resistances now matter how many other known or unknown loads you put across the voltage...

and I will say again the coil resistance will be only one of two possible values form a test resistance taken at the very begining..

either 0.5r  or  1.5r where r= resistance between any two of your three wires..

meets all the criteria of the initial question

Unless we are not allowed to measure the initial resistance???

This is getting daft...

I have provided the drawings and the calcs that that work out ... 

But now it seems we could not measure initial resistance and we cannot use a known voltage source ..

or an infinitely variable resistor....

(use ANY test equipment)

as part of this theoretical excersie...

:coat

 

[Sidewinder]

Steps,

You cannot use numbers to prove things, you have to use theory, you can ONLY use numbers to disprove things, that is not my ideas, or opinion, or my rules, that is fact.

You have too many unknown values to calculate the required items IMHO, you have unknown resistances and an unknown current so how can you dervie the voltage?

 

[SPECIAL LOCATION]

Steps,

You cannot use numbers to prove things, you have to use theory, you can ONLY use numbers to disprove things, that is not my ideas, or opinion, or my rules, that is fact.

You have too many unknown values to calculate the required items IMHO, you have unknown resistances and an unknown current so how can you dervie the voltage?

1/  we have three wires,  A, B, C,  can we measure the resistance between each and every pair of these three wires?

YES/NO

2/ is it a balanced load either Star or Delta?

YES/NO

3/ will not A-B = B-C =C-A ?

YES/NO

4/ if the answer to 3 is YES lets call this value 'r'

4a/ if a star configuration coil resistance will equal 0.5*r   YES/NO?

4b/ if a delta configuration coil resistance will equal 1.5*r YES/NO?

If the answers to any of the above are NO...

then you have changed the rules form the original question IMHO....

Otherwise..

we do not have UNKNOWN resistances..

We have TWO possible correct solutions to the coil resistance.

p.s.

my three sheets were NOT using numbers...

just proportional values!!

 

[Sidewinder]

1/  we have three wires,  A, B, C,  can we measure the resistance between each and every pair of these three wires?

YES/NO

Yes

2/ is it a balanced load either Star or Delta?

YES/NO

Yes

3/ will not A-B = B-C =C-A ?

YES/NO

Yes

4/ if the answer to 3 is YES lets call this value 'r'

4a/ if a star configuration coil resistance will equal 0.5*r   YES/NO?

4b/ if a delta configuration coil resistance will equal 1.5*r YES/NO?

I can't tell you as I don't believe that the value can be derived from resistance values only.

You are proposing using a voltage source, thus the current is unknown.

From Ohms law then you have an unknown resistance and an unknown current, but a known voltage, so how can you derive two unknown values from one known value, once you can give me the solution for two unknown values from one known value then I will perhaps agree with your reasoning, however, at this time, I can see no known solutions to an Ohms Law equation where you have two unknown values that can present you with one known value, else I am reading your posts incorrectly, or I am missing a piece of information that you have that I don't?

If the answers to any of the above are NO...

then you have changed the rules form the original question IMHO....

No I have NOT changed the rules, I simply cannot see how you can derive a single definitive known value from three unknown values, which your argument seems to be suggesting?

Now IF you can give me two definitive KNOWN values for your arguments, definitions, and equations that will give us a definitive difference between the two configurations, that stand up to independent scrutiny, that will definitively prove the values from theory, without any measurements, then I will admit "defeat" and say that my suggestions were incorrect, however, as far as I read this thread at the moment, my theory with respect to the voltage divider and a single unknown in the star configuration giving a single answer is correct, and, I have yet to see a theory that disproves this that has a single unknown, thus, is calculable and thus provable.

Two unknown values with a single equation linking them is an insolvable system of equations, thus an unsolvable system of equations, and I cannot see an answer, equation or argument that you have posted, that has a single unknown in its formation, thus, I believe your arguments are flawed and cannot be proven.

Now IF you can provide TWO known values to back up your Ohms law arguments and prove them in theory to back them up, then I will back down and say that you are correct. 

Otherwise..

we do not have UNKNOWN resistances..

Wrong we do.

We have TWO possible correct solutions to the coil resistance.

Wrong, we have NO idea what the coil resistances are. They could be anything.  They are a total unknown.#

The combination of coil resistances are in two distinct configurations, however, we have no idea what the base values of each winding are.

p.s.

my three sheets were NOT using numbers...

just proportional values!!

Perhaps, but I feel your arguments and examples are flawed, so thus incorrect as you are relying on two unknown values to prove your arguments.

I am not convinced that you can calculate and derive this answer from resistance values only and no one has provided an argument yet that can convince me, because there are too many unknown values in the arguments that have been provided.

Until this can be narrowed down to one unknown out of three then the laws of mathematics and, if you like physics say that the answer is incalculable.

Unless that is anyone else can prove over a thousand years of maths and physics wrong?

 

[SPECIAL LOCATION]

1/ we have three wires, A, B, C, can we measure the resistance between each and every pair of these three wires?

YES/NO

Yes

2/ is it a balanced load either Star or Delta?

YES/NO

Yes

3/ will not A-B = B-C =C-A ?

YES/NO

Yes

1/  So when I say can we measure this resistance....

I am suggesting I use an ohmmeter of suitable range that can measure the continuity of the coils..

(ANY TEST EQUIPMENT)

The ohmmeter does the bits of applying voltages and currents to work out an unknown resistance... 

so for the sake of arguments lets say my ohm meter gives me a reading of 200ohms for the resistance between  A-B  and  200ohms  B-C and 200ohms  C-A....   {r=200ohms}

2/  If it is a balanced Star the coil resistances  (call it three lots of 'x' in a star) will be...

x+x = r

Therefore x=r/2

or x = 100ohms  {200/2}

So for my reading A-B, B-C, C-A  (200ohms)

I know if it is star the coils must be 100ohms!

(or 0.5r)

If it is a balanced Delta the coil resistances (call it three lots of 'x', 2x in parallel with 1x) will be...

(2x*1x)/(2x+1x)=200ohms     {product over sum parallel resistance}

or

2x/3x=r

2x/3x=0.6667x

so

0.6667x=r

or

x=r/0.6667

or

x=300ohms  (200/0.66667)

So for my reading A-B, B-C, C-A (200ohms)

I know if it is delta the coils must be 300ohms!

(or 1.5r)

So how are either or those UNKNOWN values???

unless you are saying I cannot actually use and ohmmeter to read across the three wires to start off with????

Which IS changing the original question.

:C

 

[Sidewinder]

No, I am not saying that you cannot use an Ohm Meter, I am saying that in true scientific form that you cannot use numbers to prove a theory, you HAVE to use THEORY to prove a theory.

Also, you are still not giving me the required unknown values.you are only quoting resistances, what are the voltages and currents that you are applying, or at least ONE of them so that you ONLY have ONE unknown.

The resistances are known values, but at what current and voltage?

Without at least the current or voltage the resistance values are irrelevant to prove the argument.

Your voltage source in your diagrams is irrelevant as you have no idea what current it delivers, without this I cannot see how you can calculate the unknown values.

You have done nothing in your last post to give any more of the unknown values, you have simply provided resistances, that IMHO are worthless without voltage and current values and, you have done nothing to prove they are.

I have provided a theory with a diagram and an "argument" in post #110, which you have not yet disproved, so, I feel that this is absolutely correct as there is ONLY ONE unknown, plus by the theory posted there with regard to the load and measurement currents it makes an absolute proof, yet your arguments only so far provide ONE measurement and expect us to "assume" one of the other two to prove Ohms Law.

No, I am not saying that you cannot use an Ohm Meter, I am saying that in true scientific form that you cannot use numbers to prove a theory, you HAVE to use THEORY to prove a theory.

Also, you are still not giving me the required unknown values.you are only quoting resistances, what are the voltages and currents that you are applying, or at least ONE of them so that you ONLY have ONE unknown.

The resistances are known values, but at what current and voltage?

Without at least the current or voltage the resistance values are irrelevant to prove the argument.

Your voltage source in your diagrams is irrelevant as you have no idea what current it delivers, without this I cannot see how you can calculate the unknown values.

You have done nothing in your last post to give any more of the unknown values, you have simply provided resistances, that IMHO are worthless without voltage and current values and, you have done nothing to prove they are.

I have provided a theory with a diagram and an "argument" in post #110, which you have not yet disproved, so, I feel that this is absolutely correct as there is ONLY ONE unknown, plus by the theory posted there with regard to the load and measurement currents it makes an absolute proof, yet your arguments only so far provide ONE measurement and expect us to "assume" one of the other two to prove Ohms Law.

 

[steptoe]

mmmm,

paradox then sidewinder,

you have already stated that numbers cannot be used,

but now you are insisting on using numbers,

ie, voltage and current values,

voltage = V

current = C

is that better ?

 

[Sidewinder]

No Steps, I have NOT said that numbers must be used, I am saying exactly the opposite from where I am writing, it is obviously not coming across correctly.

You MUST describe the current, voltage and resistance in KNOWN values, these are NOT numbers they can be perfectly legitimately be expressions in algebraic form, however, for Ohms Law to work we have 3 unknowns, and the laws of mathematics can only solve for one unknown with one equation, this unknown can be derived from an algebraic expression though.

I have seen no arguments bar mine where there are only one unknown in the expressions provided.

Now IF you can describe a system of two simultaneous equations then these can be solved for two unknowns, but I have yet to see an argument that describes a system of two related equations that can be used to solve this scenario either.

 

[SPECIAL LOCATION]

No, I am not saying that you cannot use an Ohm Meter, I am saying that in true scientific form that you cannot use numbers to prove a theory, you HAVE to use THEORY to prove a theory.

Also, you are still not giving me the required unknown values.you are only quoting resistances, what are the voltages and currents that you are applying, or at least ONE of them so that you ONLY have ONE unknown.

So you are actually changing the question then....

If you CAN use an ohm meter.....then that will give me two possible resistances

one for a star and one for a delta solution..... 

You don't need to know what the voltage or current the ohm meter uses...

Thats why I use the ohmmeter!!!!

and either way..

the ratio of the star or delta resistances will be proportional; to the formula I have given..

coil=o.5 reading

or coil=1.5 reading...

(ohms law resistance in series or parrallel....)

Unless you are honestly telling me that you cannot calculate a resistance value from a known meter reading assuming two possible resistor configuration of equal valued resitances..???

If I am then using a KNOWN voltage source to continue my tests..

(after first reading with an ohmmeter to calculate possible resistances)

then I will know what voltage I am applying to either of two possible series resistors placed across the volatge..

To say I need to know the current as well is irrelevant ..

I have a known voltage source.....

So to say I don't know what the voltage is daft.. 

e.g.

If I have a known 100v supply  v

a known 20ohm resistor   r1

in series with another resistor that could be 10ohm or 30ohm  r2

and a measured known output voltage v2 across our known resistor..

so if

40v across the 20ohm  {r1}

and 60v across the unknown  {r2} (30 ohm option)

We know v2=(v/(r1+r2))*r1

Therefore  r2=((v*r1)/v2)-r1     Theory no numbers!

put numbers back in

r2=((100x20)/40)-20

r2=30ohms 

or

66.66v across the 20ohms

and 33.33 across the unknown  (10ohm option)

So with A known resistor, A known voltage and an unknown resistor..

and a known measured output

again

We know v2=(v/(r1+r2))*r1

Therefore r2=((v*r1)/v2)-r1 Theory no numbers!

put numbers back in

r2=((100x20)/66.6)-20

r2=10ohms

From your own initial description 

Any test equipment can be used...

and

I can use an ohm meter to measure resistance

so..

I can also use a KNOWN test voltage source....

and a suitable volt meter to measure a potential difference across a known or unknown resistor

With a known test voltage and some known and unknown resistances simple voltage division formula can give predicted measured voltage outputs....

I can do this with absolutely NO requirement to measure or calculate any currents at all

And I only have one unknown in any of my calculations..

 

[SPECIAL LOCATION]

It is now morning.....

Yesterdays beer is gone....

Todays beer is still chilling...

So been back over my musings with a clean sheet of paper and coloured pens.....

I still stand by my assertion that two possible coil resistances can be known by measurement

and voltage diving ratios can be used to predict an output voltage relative to a test input voltage via a known test resistor value proportional to our measured resistance.....

BUT....

after going back through I noticed my previous theory needed a measurement at the STAR point of the star winding!!!!!!!!!!!!

Redoing my ratios and calcs re voltage dividers...

I now confirm that BOTH star and delta give equal ratios and readings for my previous method....

So I have proved bugger all....

But I had a go and did a bit of colouring in the process!!

:slap

if anyones interested my amended sketches are as follows...

First my delta potential divider...



Then Star potential divider...



Expand out star to get ratios...



So there you go...  

No doubt SideSnake can see what I was trying to do..  and where my clanger was dropped.. :innocent

Always good to get the old brain ticking though...

But I think I will let someone else have a go now....

:Blushing

.

 

[apprentice87]

All interesting stuff...!!

 

[Steve3948]

The amount of time in man hours in this thread, it would be cheaper to buy a new one  :innocent

I will look in my little Red Brooks Motors booklet from the early 90's for direction, don't wait though  :facepalm:

 

[Andy™]

I will look in my little Red Brooks Motors booklet from the early 90's for direction, don't wait though  :facepalm:

well thats screwed up the job hasnt it, now after we eventually find out if its star / delta, how do we know what direction its going to spin

yes i know there is a method to find this out, but im sure we suddenly dont have the equipment necessary to do so...

 

[Andy™]

but we dont have access to ths 'speshul metre'

 

[Andy™]

And he wasn't asking how to tell what way it revolves !

yet. one question at a time. dont want to confuse us mere mortals

 

[Sidewinder]

I have the rotation meter!

I DON'T have the speshul meter that he has that tells him Y or D!

 

[steptoe]

I have the rotation meter!

I DON'T have the speshul meter that he has that tells him Y or D!

ah,

well, thats the answer then,

sub this motor job out to him, with his speshul meter , 

 

[Sidewinder]

I still think my voltage divider on post #110 theory will work.

Anyone want to analyse the maths?