MH's ideal coil and voltage question

[Grumage]

Hi Chet.

For some reason I can't use the quote to reply function on this thread, strange.

The video that Brad linked to was of a Blackstone " Lamp start " hot bulb ignition semi Diesel from the mid 1920's. It's fuel would have been lamp oil now commonly known as Kerosene with you and Paraffin over here.

Not very fuel efficient compared to modern day but still running despite the serious cylinder blow by and nearly 100 years of active service.

I have attached a picture of my attempt at a quarter scale Hornsby Akroyd from 1891 engine number 193.These were the first engines to successfully operate on the hot bulb ignition system, it's so early that the starting lamp pre dates the pressure blow lamp hence the strange looking object under the bulb shroud. Sadly it never ran very well so nine months work of scaling and patternmaking were for nought.

https://www.youtube.com/watch?v=rZanAMesCeY

It makes you think........... Perhaps in this area of research trying to scale down things is a mistake? My own experience in the model engineering world is the smaller they are the harder they are to get going.  Well apart from steam......

Cheers Grum.

[Grumage]

Loner wrote.

"
As to all the posts between your question and this reply, I think think the thread has been fully hijacked.  Interesting stuff I suppose.  I don't visit the forum enough to keep up, these days.

How a discussion of ideal Inductor and voltage came to this...  "

Dear Loner.

My apologies for the hijack. If my posts seem irrelevant, please advise, I can remove them far quicker than it took to post them.

Resonance and tuning both play a great part to the efficient running of an ICE both internally and externally.

Cheers Grum.

[MileHigh]

The thread is long since done, you can hijack it all you want.

[poynt99]

In an attempt to enlighten the non-believers (those having difficulty understanding currents through voltage sources), let's alter/simplify MH's question to the following:

- same ideal voltage source and ideal 5H inductor connected across each other.
- between t=0 and t=3, V=+4V
- between t=3 and t=6, V=-4V
- from t=6 to infinity, V=0V
(see scope shot)

We know from previous discussions that between t=0 and t=3, the circuit current will ramp up linearly to 2.39A. I think everyone agrees with this, even the non-believers. We can also calculate the power and conclude that the power delivered by the voltage source ramps up from 0W to 9.56W during the same period of time. But since we know that the current and voltage in a voltage source are 180º out of phase, the power will actually ramp down to -9.56W.

What happens between t=3 and t=6 when the voltage inverts from +4V to -4V? Well, the non-believers have stated the following:

Loner
I would not bother with this question based around a voltage source that dose not exist.
MH is also not able to understand that an ideal voltage cannot be placed across a conductor that has 0 ohms of resistance,and current flowing against that that the ideal voltage wants to create.This is like placing an ideal voltage across an ideal capacitor.
At T=3 seconds--kaboom--bye bye equipment and components.

But how can that be? Real world experiments certainly don't result in the catastrophic end of the earth, and a simulation debunks this notion as well. Well, the non-believers argue that the L/R ratio of 5000:1 is not close enough to ideal (5H/1m), yet I have shown via sim that a ratio of even 100:1 is close enough for a 5% error. That converts to a total series resistance of 50m Ohms.

The fact is, most high quality high power audio amplifiers have an output damping factor of about 400:1, which means the output resistance is on the order of 20m Ohms (based on 8 Ohm load). So a big audio power amp is a good ideal voltage source.

The other fact is that we can indeed short out an ideal inductor that has current flowing through it, by ideal wire or ideal voltage source. If in our example the inductor is shorted by an ideal wire right at t=3, what happens? does the inductor and the world blow up? I think we all agree that the current would remain at 2.39A. If the voltage source went to 0V rather than -4V at t=3, we know that it would act the very same way as the previous case of the ideal wire, and the current would remain at 2.39A and there would be no explosions.

But my example switches the voltage from +4V to -4V, right at the instant 2.39A is flowing in the coil and voltage source. What happens next is the opposite from the period between t=0 and t=3; the current ramps down from 2.39A to 0A, and the power instantly changes from -9.56W to +9.56W, and ramps back down to 0W. The energy stored in the inductor is returned to the voltage source. No energy was dissipated when the inductor was energized, and none is dissipated when it de-energizes.

Green=voltage Source
Red= Circuit Current
Purple= Voltage Source Power

[tinman]

Loner wrote.

"
As to all the posts between your question and this reply, I think think the thread has been fully hijacked.  Interesting stuff I suppose.  I don't visit the forum enough to keep up, these days.

How a discussion of ideal Inductor and voltage came to this...  "

Dear Loner.

My apologies for the hijack. If my posts seem irrelevant, please advise, I can remove them far quicker than it took to post them.

Resonance and tuning both play a great part to the efficient running of an ICE both internally and externally.

Cheers Grum.

Aint that the truth


Brad