The theorems prove that a voltage source with an output series impedance is indistinguishable from an equivalent current source with an output parallel admittance. All real voltage sources have some output impedance and all real current sources have some output admittance.
A question:
We have two black boxes, one containing a voltage source and the other containing a current source. The boxes cannot be opened. When measured from the output terminals, the open-circuit voltage is 1V and the short-circuit current is 1A. Which box contains which source?
In electrical engineering, when one refers to something as a "current source", what do they typically mean:
A - the simple most basic interpretation, which is that any circuit with a power source has current flowing, eg battery, cap, lightning bolt.
B - that the power source they are talking about behaves similar to an ideal current source, ie where the current is fixed, ie it doesn't vary or doesn't vary much with respect to any load?
I vote for B. In which case, an alternator does not look like a current source. Is it still sourcing current, just like a battery, cap, or lightning bolt? Sure.
"You seem to have forgotten that altenators are current sources, incapable of producing more than the rated current."
OK, what does that mean? If he's saying an alternator supplies current, then it's pretty silly. So too does any power source, so why make that statement? It sure seems that he was saying that an alternator behaves similar to an IDEAL CURRENT SOURCE, where the output current if fixed, or in a tight range, regardless of the load.
You replied with:
"If it is a current source, then it can be equated to a voltage source with a high value series resistor. "
So, clearly you interpreted his post the same way I did, that he means it behaves like a ideal current source. Otherwise you would not have to say "if it's a current source", because we all know that there is current flowing in any alternator.
And then you claimed that if it's a current source, then it can be equated with a voltage source in series with a high value resistor. Just think what that means. What's a "high value" resistor? 1K ohms? An alternator putting out
100 amps would then produce a voltage of 100kv across that resistor. Your voltage source wouldn't be 12 - 15V, it would have to be 100KV, across a 1K resistor, to give you a current source of 100A. The open circuit voltage would be 100KV. That sure isn't any car alternator I've ever seen.
The bottom line is an alternator/VR behaves similar to an ideal voltage source, it tries to maintain constant voltage, not constant current, which is what an ideal current source would do. And if you want to model it, you can do it with an ideal voltage source in series with a very low value resistor or you can do the Norton equivalent, which would be a current source with a very low value resistor in PARALLEL.
Whoey Louie wrote in news: snipped-for-privacy@googlegroups.com:
What is it with you where you feel so compelled to include a lightning bolt? They have durations measured in sub-second values. In case you did not pay attention, that falls into electrostatic class, NOT a "current source".
A current source is a POWER SUPPLY FEED, from whatever transducer generated it, that can supply a constant current value to a load, regardless of its value, and they are rated at just how high that value can get. That current 'setpoint' is set by the operator.
A voltage source supplies a set, pinpoint (specified granularity) voltage to a load, and depending on that load, the current fed through it varies.
I think you got confused over the years. Ideally, you should rehash the entire NEETS course, for starters.
Mumbling about "sourcing current". Sure.
An alternator feeding into a car battery sees the battery as a load and presents a voltage to it, If said voltage exceeds that of the battery, 'charging' can take place on those storage cells whose technology supports recharging in the form of current flow. The current varies into that battery depending on the difference between the battery's current charged voltage and the voltage of the charging device. Automotive alternators are for the most part designed to charge a lead acid liquid electrolyte 12V battery at no more than
14.2 Volts. That choice was made so that alternators did not get taxed too much, and that batteries did not get charged at too high a rate (and commonly explode). With the industry selecting 14.2 volts, they held the max charge current on batteries in good operating condition to a known number that fell inside the window of a typical alternator's max output CURRENT. They ALL put out 14.2 volts, but the current varies according to load, which is a function of the current charge state of the battery in volts. So a little bitty car alternator on a huge array of truck batterries WILL *eventually* cahrge them, but that sucker will run hot as a firecracker and fail far earlier than desired. And the batteries will take longer to charge because at the max rate, the alternator still unable to provide full current at 14.2 volts droops a bit until the batteries begin to top off.
The time period is irrelevant of course. Leave it to you to start squabbling though.
It's still current flowing. The point, which obviously went right over your head, is that in electrical engineering, when someone talks about a "current source", they typically mean that it behaves similar to an IDEAL CURRENT SOURCE. Otherwise what's the point to calling something a current source? It was about an alternator. It isn't already obvious to everyone here, with no need to state it, that an alternator supplies current?
No confusion here. You're the one wandering in the wilderness.
Thank you for all that, Capt Obvious. It added nothing.
Well, that gets back to what one means by a "current source". In any circuit that has current flowing, of course there is a source for the current. It does not have to be constant.
On the other hand, if one says an alternator behaves like a current source, then if you're an electrical engineer, that would mean that you're saying it behaves similar to an IDEAL CURRENT SOURCE. And BTW, of course that can vary too. I can draw a circuit with a
you are retrenching by trying to ignore what you posted.
age
made the claim you say I did. You meanwhile incorrectly said a current so urce is not equivalent to a voltage source in series with a high value resi stance.
The recap is above. Just read that!
th a high value series resistor. "
Who cares? What Jason said is not relevant.
More divarication.
I posted the quotes that were relevant. You are doing the typical Always W rong thing of micro analyzing every word and twisting the conversation to s uit your wants.
I only responded that if he were talking about an ideal current source it c
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valents.
Why not just give up and stop back peddling?
Whatever. I generally treat you the same as DLNU, I ignore you both. I'm not sure why I responded. Guess I'm over this pointless discussion with yo u. Just like Always Wrong you can't admit when you make a mistake, Always Wronger.
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Rick C.
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e, you are retrenching by trying to ignore what you posted.
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er made the claim you say I did. You meanwhile incorrectly said a current source is not equivalent to a voltage source in series with a high value re sistance.
with a high value series resistor. "
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Wrong thing of micro analyzing every word and twisting the conversation to suit your wants.
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ROFL
I know that the Thevenin model for an alternator isn't a voltage source in series with a high value resistor.
How's that all that Tesla spamming working for you? Make any money yet?
here's another way to think about it, imagine a gapped transformer where the primary is fed with a constant AC current. the secondary is going to see pretty-much the same as what the altenator stator sees.
Whoey Louie wrote in news:5fefe6c9-17c4-4aee- snipped-for-privacy@googlegroups.com:
No, it is not. The very term "current" and "bolt" are mutually exclusive when the end product is "work". Current connotes constance.
The time period is NOT irrelevant.
If it were useable for work, we would have huge lightning capacitors down in Florida grabbing up the cloud juice so we could put it to use over a longer period than a single strike event
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