Alternator Paralleler Circuit

[Timleech]

It's a bit like god, it's no use to anyone, can't be detected but it gives chris some comfort.

 

I suppose it's almost a philosophical question, rather than an engineering one, as to whether they 'exist'.

They clearly don't exist as potential differences, and being a bit pedantic is it correct to describe a theoretical emf as a Voltage when it can't be measured? (even though it's described in volts).

Answers on the back of a postage stamp, please

 

Tim

Edited May 20, 2009 by Timleech

[chris w]

I suppose it's almost a philosophical question, rather than an engineering one, as to whether they 'exist'.

They clearly don't exist as potential differences, and being a bit pedantic is it correct to describe a theoretical emf as a Voltage when it can't be measured? (even though it's described in volts).

Answers on the back of a postage stamp, please

 

Tim

If you open circuit the alternator, run the engine then hold the B+ lead in one hand whilst touching earth with the other hand, you will discover they really do exist.......although you may not, after trying this.

 

Chris

Edited May 20, 2009 by chris w

[Gibbo]

They clearly don't exist as potential differences, and being a bit pedantic is it correct to describe a theoretical emf as a Voltage when it can't be measured? (even though it's described in volts).

Answers on the back of a postage stamp, please

 

<postage stamp>

 

No

 

</stamp>

 

.... they don't exist.

 

Any two (or indeed any other number) terminal device (say one of the stator windings) can be simulated and analysed easier by replacing it with various other components. In this case an EMF and a series resistance (to be completely correct we would need to add series inductance, parallel capacitance and mutual same to the other windings etc but one can go on for ever with this game).

 

That allows the effects at the two terminal ends to be predicted and calculated very simply. But, what happens inbetween the two temrinals in all the simulation components is in no way related to reality. They are a modelling device. Any voltages/currents/waveforms etc shown mathematically to exist inside the model simply do not exist in the real world.

 

You were spot on when you wrote....

 

So you're saying the voltages to which you referred don't actually exist, they're just computed to fit in with circuit analysis?

 

To say that the high voltage does exist because it can be measured if the alternator is open circuited is incorrect because then we are discussing a completelty different circuit.

 

Gibbo

 

My hot question is why it's no working from D.... but cheers guys!

 

Well it's getting confusing because you wrote in post #284...

 

With D connected there is 7.2 volts at the live side of the latch relay coil. With D connected there's 14.3 at the same terminal.

 

Which kinda baffled me!

 

I will add the diode, which admittedly I've failed to do, and go from there. But I'm still baffled as to why it doesn't work from D??

 

Well it won't work from D+ until the alternator is up and running.

 

Gibbo, I am working from 168, and in my last post stripped it back and tested all the connections, i felt quite swanky typing results in as I tested However the lamp 1 diode isn't there... Yet!

 

Why can't I use D... in words of less than 2 para's with no-one falling out please...

 

I can't remember. There's been too much toing and froing and diversions with b*ll*x..

 

Gibbo

[chris w]

To say that the high voltage does exist because it can be measured if the alternator is open circuited is incorrect because then we are discussing a completelty different circuit.

 

Gibbo

They DO exist and are the EMF's driving the current into the charging battery. However, they are not accessible normally.

 

Remove the regulator (which holds the voltage below 14.2 ish normally) and the rectifier (which convertes the AC to DC) and you have an AC generator which will run at about 120VAC.

 

I appreciate this is not how WE would normally run them, but these are real voltages. Open circuit the alternator whilst it's running and these high voltages will usually fry your alternator diodes.

 

Chris

[Gibbo]

They DO exist and are the EMF's driving the current into the charging battery. However, they are not accessible normally.

 

NO THEY DO NOT

 

Remove the regulator (which holds the voltage below 14.2 ish normally) and the rectifier (which convertes the AC to DC) and you have an AC generator which will run at about 120VAC.

 

That is now a different circuit. You cannot try to use the figures from one circuit to show what the figures are in a completely differtent circuit. We're back to electronics for 6 year olds.

 

Gibbo

[carlt]

NO THEY DO NOT

Yes they do.

 

Chris has made them exist, merely by mentioning them.

 

Have you not read Sartre?

[alan_fincher]

Ah, possibly the first time I have seen the Sartre move played in an electical thread.

 

Smart move!

[carlt]

Ah, possibly the first time I have seen the Sartre move played in an electical thread.

 

Smart move!

Oh, sorry, I thought this was an eclectical thread.

[chris w]

NO THEY DO NOT

 

Gibbo

So what's driving the say 50A charge current through the battery........ magic!!!!

[Gibbo]

So what's driving the say 50A charge current through the battery........ magic!!!!

 

Where can this voltage be measured?

 

In macroscale electronics, If it can't be measured, it doesn't exist. It's a basic fact.

 

Gibbo

[chris w]

Where can this voltage be measured?

 

In macroscale electronics, If it can't be measured, it doesn't exist. It's a basic fact.

 

Gibbo

"Macroscale electronics"????????? I don't think you know what that means.

 

Also, one can't measure the true battery voltage of a lead-acid battery whilst it's connected into a circuit, so are you saying that doesn't exist either or are you arguing for aguing's sake? One can calculate it just as one can calculate the driving EMF of an alternator.

 

Anyway........................what's driving the say 50A charge current through the battery........ magic!!!!

Edited May 20, 2009 by chris w

[Timleech]

Anyway........................what's driving the say 50A charge current through the battery........ magic!!!!

 

The Voltage at the alternator terminals?

 

Tim

[chris w]

The Voltage at the alternator terminals?

 

Tim

No....the voltage at the alternator terminals is clamped at the battery voltage. There is a (higher) internal voltage that is driving the current through the battery and overcoming the battery voltage and the rectifier diodes forward voltage drop and the voltage drop across the stator coils.

 

Chris

PS: Smelly: did you get my PM?

Edited May 20, 2009 by chris w

[Timleech]

No....the voltage at the alternator terminals is clamped at the battery voltage. There is a (higher) internal voltage that is driving the current through the battery and overcoming the battery voltage and the rectifier diodes forward voltage drop and the voltage drop across the stator coils.

 

Chris

 

If it were truly 'clamped at the battery voltage', the battery would never charge

 

Tim

[chris w]

If it were truly 'clamped at the battery voltage', the battery would never charge

 

Tim

That's so wrong......... it is clamped at whatever the battery voltage is at that moment - which rises as ithe battery charges. The alternator's internal voltage is what is DRIVING the current through the battery and charging it.

 

Chris

[Smelly]

Well it's getting confusing because you wrote in post #284...

At D it 7.2 Volts and at D it's 14.3

 

Which kinda baffled me!

 

 

 

Well it won't work from D+ until the alternator is up and running.

 

 

 

I can't remember. There's been too much toing and froing and diversions with b*ll*x..

 

Gibbo

 

I meant to say that at W its 7.3 and at D it.s 14.3

 

As to diversionary b*ll*x... fair play

Edited May 20, 2009 by Smelly

[Gibbo]

"Macroscale electronics"????????? I don't think you know what that means.

 

So, because you don't understand something (as is very clearly evidenced by this thread) you try to make out other people don't? Interesting tact.

 

Also, one can't measure the true battery voltage of a lead-acid battery whilst it's connected into a circuit, so are you saying that doesn't exist either

 

Yes, that is exactly what I am saying. Clearly you disagree with that which again shows that you put all your faith in maffs without ever trying to stop to understand that the maffs is just a device to be used for calculating numbers. It doesn't represent reality.

 

The voltage measured on the terminals of a battery is the actual battery voltage. The fact that it drops when a load is applied means the voltage drops. It does not mean that the internal voltage remains and somehow gets magically transformed between your sums and the battery posts.

 

The natural battery voltage and the internal battery resistance are representative devices to allow the real world voltage to be calculated at the outside terminals. That does not mean that the internally calculated parameters actually exist. It is a device, not reality.

 

or are you arguing for aguing's sake? One can calculate it just as one can calculate the driving EMF of an alternator.

 

Anyway........................what's driving the say 50A charge current through the battery........ magic!!!!

 

 

The driving force is the EMF. As shown earlier in this thread, you can't quite get your head round the difference between a potential difference and an EMF. No doubt you will now go and look it up and come back with a big mathematical proof but you still won't be able to get your head round it. And until you do you simply won't get this subject.

 

Gibbo

[RLWP]

Ah, possibly the first time I have seen the Sartre move played in an electical thread.

 

Smart move!

 

Ah yes, but did Sartre not say "A lost battle is a battle one thinks one has lost"

 

Seems apposite

 

Richard

[carlt]

Ah yes, but did Sartre not say "A lost battle is a battle one thinks one has lost"

 

Seems apposite

 

Richard

No he was, himself quoting a French General (forget the name) who said it, originally.

 

He was probably retreating or unpacking the white flag, at the time.

 

Edited to say: Google says, Ferdinand Foch.

Edited May 20, 2009 by carlt

[RLWP]

No he was, himself quoting a French General (forget the name) who said it, originally.

 

He was probably retreating or unpacking the white flag, at the time.

 

Why does your avatar say you are going to sue me?

 

Richard

[chris w]

The voltage measured on the terminals of a battery is the actual battery voltage. The fact that it drops when a load is applied means the voltage drops. It does not mean that the internal voltage remains and somehow gets magically transformed between your sums and the battery posts.

 

Gibbo

Yes I agree with that when the battery is OPEN CIRCUITED - I don't have a problem with that. But the voltage that appears when the battery (or alternator) is IN circuit is not the actual true voltage of the battery. It is the battery's true voltage LESS the voltage drop across its internal resistance owing to the current it is delivering to the circuit to which it is attached.

 

 

The voltage at point V when the switch is closed is NOT the same as the battery charger voltage of 12.6v. It's also not the same as the open circuit voltage of the battery being charged. You would only see the 12.6v at the battery charger if the charger were open-circuited. The bits within the boxes are not accessible but still exist.

 

Chris

Edited May 20, 2009 by chris w

[carlt]

Why does your avatar say you are going to sue me?

 

Richard

It doesn't, it's just a photo of Chris w's car (allegedly).

 

He tells me he is suing me for libel.

[Gibbo]

Chris this is an old one and I'm sure you'll have heard it before but it perfectly demonstrates the situatrion that maffs is a tool and should not be relied on to represent reality because it is often very wrong if that is attempted.

 

Man has to travel from A to B

 

Nothing can travel infinitely fast (including our man) therefore it will take a certain amount of time to travel from A to B

 

Before man gets to B he has to get halfway there. Before he gets halfway there he has to get a quarter of the way there, before he gets a quarter of the way there he has to get an eigth of the way there etc etc etc.

 

Mathematically we can keep dividing this down forever. And as it is impossible for man to travel infinitely fast this means that it is impossible for him to travel from A to B. He will simply never get there. That's what maffs proves.

 

Yet we know he can get there.

 

Gibbo

[Bridget]

Sorry to go back over old ground, but:

 

That's as maybe, but what about the log paper? You will have to end up admitting that was a red herring or the maths holds up. The maths only falls if log paper is not needed. Then we can explore whole new vistas. C'mon just admit that was an RH.

 

Chris

 

You both raised some (genuinely) interesting points in this arguement. Did you ever resolve it?

 

Bridget

[nb Innisfree]

Chris this is an old one and I'm sure you'll have heard it before but it perfectly demonstrates the situatrion that maffs is a tool and should not be relied on to represent reality because it is often very wrong if that is attempted.

 

Man has to travel from A to B

 

Nothing can travel infinitely fast (including our man) therefore it will take a certain amount of time to travel from A to B

 

Before man gets to B he has to get halfway there. Before he gets halfway there he has to get a quarter of the way there, before he gets a quarter of the way there he has to get an eigth of the way there etc etc etc.

 

Mathematically we can keep dividing this down forever. And as it is impossible for man to travel infinitely fast this means that it is impossible for him to travel from A to B. He will simply never get there. That's what maffs proves.

 

Yet we know he can get there.

 

Gibbo

Unless he's already there? Quantum stuff and all that, spooky

Edited May 20, 2009 by nb Innisfree