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Current Controlled Battery Charger

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I still don't see how it putting out a constant voltage and variable current during its normal operating conditions could remotely be considered acting as a constant current source. :confused:
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You obviously have never open-circuited a running alternator. Look up and study a "load-dump". Come back when you understand that a load dump is a consequence of an alternator acting as a constant-current source.
 
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If using the wrong terminology, formulas, and theories for a basic electronics related actions, functions, or devices in their normal intended design state of being is semantics then yes I am being nit picky! :p
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I challenged you to come up with a mathematical formulation that shows an alternator acts as a constant voltage source, and all you have done is run your mouth (keyboard). Put your money where your mouth is...
 
Actually I have open circuited alternators dozens of time with no ill effects. Its pretty common to have that happen with farm machinery when a battery cable gets knocked off while jump starting anther tractor or when a clamp goes bad.

I am not sure what mathematical formula you want. As far as I know mathematically modeling a common no brand or model specific alternator is not possible.
can you mathematically model a IC and circuit without any references to its design or anything else other than to say it blinks on and off?

So far I have given multiple links to definitions of constant current constant voltage and how an alternator is defined and used in practical application.
Wheres yours defending your constant current description based on the relatively constant voltage and widely variable current output that an alternator works in in its intended applications of charging a batteries and maintain system voltages in an automotive application? :confused:

The whole point of this forum is to help people by instructing and educating them and to do so requires the use of agreed upon definitions actions, devices, and how circuits work along with properly applied usage of said terminology along with schematic that use standardized symbols.

So far I have at least given half an effort to defend my stand and provide articulate and reasonable term definitions that apply to common electronics and electrical system device applications relating to this subject.:D

As I have said before and will say again how do you come to the conclusion that an electrical power source device that in its stock form puts out a stable and constant voltage value regardless of what the load current drawn from it does anywhere from zero up to what ever its peak intended design limit is can be constituted as a constant current device?

I am not asking for how it may operate when subjected to tampering modification or during conditions not standard to its normal and intended purpose and application. :)
 
Well now that I have had time to ponder a bit more on this at work tonight while out fueling trains I would say that to properly mathematically model a theoretical alternator without any voltage control circuits I would say that the numbers are going to show it as being more of a constant wattage device with similar numerical characteristics to those of an typical constant wattage lighting ballast opposed to that of an ideal constant current source. :p

Here is why I think that.
Given a fixed input RPM the output voltage will be limited by the combination of rotational speed plus the effective energy of the magnetic field of the rotor. Due to that the natural inductance of the windings and iron core will limit how much current can be drawn off without the output voltage dropping which will at the upper voltage and lower current end of the scale equal a zero wattage output condition..
Now if things are reversed while given the same mechanical RPM input and rotor magnetic field strength with the output in a dead short condition the output again will now show zero wattage due to the output voltage essentially being zero and the current being limited by the resistance of the stator windings.

Given those two limits as being zero watts any point in between will begin to rapidly show itself as being of near equal wattage due to the combined integration of the winding Resistance winding inductance and the load resistance. What I would expect from that is a mathematical model of the output wattage that resembles a sort of trapezoid shaped operating area defined by V x I =W with a slightly rounded top. ;)

As far as the mechanical power being imparted thats a whole different set of equations where zero amps on the load will give a near zero mechanical loading effect and a dead short on the output will give the maximum mechanical loading effect with essentially all that mechanical energy being dissipated in the alternator itself as heat despite the output wattage being essentially zero.

But thats just me. :eek:

(I hope the OP can pull something useful out of this.) :eek:
 
Great links! Good photos and explanations to help show how things work too! :D

Any chance you could get that perma linked into the RE section some place?
 
Quoting Bryan's signature line:

" NEVER argue with stupid people, they will drag you down to their level and then beat you with experience"- Mark Twain

I 'm not sure why I'm bothering, but lest Tcmtech's postings leave the wrong idea about how alternators really work, this might teach a thing or two:



Here is a very simple simulation of an automotive charging system that models a 14V car alternator as a current-controlled current source. The Voltage Regulator is modeled as a voltage-controlled switch, which opens when it senses an input voltage exceeding 14.2V, with a tiny bit of hysteresis (just like a real car Voltage Regulator). The battery is modeled as a huge capacitor because it ACTS like one. No, I'm not advocating calling a battery a capacitor...

Look at the first plot. To start, the voltage of the battery (red trace) is initialized to 12.6V. Initially, the alternator supplies its full output current (lt. blue trace) to charging the battery. As the system voltage reaches 14.2V, the Voltage Regulator begins switching on/off the alternator's field voltage (Pink trace), thereby reducing alternator's field current (dark Blue trace). As the battery becomes fully charged, its current goes to zero, so all that is left for the alternator to do is to supply the static load of the system (~2A).



The next two plots show expanded time scale, the second just as the system voltage reaches 14.2V where the PWM duty cycle is still high, and the third, where after the battery stops accepting any charge current, all the alternator has to do is to supply about 2A to the 7Ω static load. Note that initially, the alternator is going flat out, with the field current limited only by the DC resistance of the field winding. Once the PWM gets going, note that it is the field inductance and amount of hysteresis built-in to the Voltage Regulator that determines the PWM rate.

**broken link removed**

**broken link removed**

To anybody who works on automotive and aircraft charging system (like me), this is a faithful simulation of what actually happens with the exception of the time scale along the bottom. I just sped up the time it takes to charge a battery so the simulation doesn't have to run as long as the physical system....

The reason I posted it is to show that even a simplistic model can show the workings of a physical system. I especially wanted to show that the alternator ACTS as a current-controlled constant-current source. It is the feedback provided by the Voltage Regulator that turns it into a constant-voltage system, contrary to all the blather by tcmtech.
 
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You have way too much time on your hands. :p

The reason I posted it is to show that even a simplistic model can show the workings of a physical system. I especially wanted to show that the alternator ACTS as a current-controlled constant-current source. It is the feedback provided by the Voltage Regulator that turns it into a constant-voltage system, contrary to all the blather by tcmtech.

BTW, from this description it could be taken that all switch mode based power supplies and the like are also constant current devices as well because they too have feedback loops that sample their output voltage and in a way are thus constantly adjusting their output currents in order to to keep their output voltage levels stable. ;)

I still don't see how feedback loop circuit that reads the output voltage and adjusts the control circuitry to keep the final output voltage stable as the level of current being supplied by it can vary by any amount at any time even remotely fits under a the definition of being a constant current source. :confused:
 
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Well I ran this question of alternators being defined as constant voltage or constant current source past the engineers at another site I hang out at and here is what they have to say,
https://cr4.globalspec.com/thread/8...s-Constant-Current-or-Constant-Voltage-Source

Also apparently Michel Faraday made a law about it as well. :p
https://en.wikipedia.org/wiki/Faraday's_law_of_induction

Seems that they are indeed voltage sources by physical action and operating principals not current sources being voltage leads current in all steps of their function and its only the regulation systems that can control them in a way to make them act as a constant current source when being operated within their normal designed range. ;)

As for the OP of this thread if he want more help and info on alternators and possibly refining his design I would suggest getting set up over at the forum in the first link. Loads of actual highly skilled, experienced, and educated engineers and the like over there. (Plus me too.) :p:eek:

So for the next big debate what do you define someone as that gets reeducated by stupid people? :rolleyes:

Here's a new quote for you as well.

"Learning the wrong definitions is easy. Convincing someone that they are using the wrong definitions is much harder. " :p
 
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Well since we are comparing references, here is one I like:

www.rle.mit.edu/per/conferencepapers/cpconvergence00p583.pdf

Please read the paragraph just below Figure 4 on page 3:

"in a typical automotive alternator, back voltages in
excess of 80 V may be necessary to source rated current
into a 14 V output at high speed. An appropriate dc-side
model for the alternator system is thus a large opencircuit
voltage in series with a large speed- and current dependent
output impedance."

Sure sounds like a constant-current source to me.

Actually, that report is worth reading. It has a lot of useful information...

btw-the alternator model I used in my LTSpice simulation was done for a Ford automotive alternator (with an external Voltage Regulator) installed in an aircraft where engine speed is constant for the duration of the flight, so I didn't bother modelling speed dependencies.
 
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You can a call it what ever you want but I and the rest of the educated world of science engineering and physics base our descriptions of an alternators intrinsic actions and functions by what Faraday's Law of Induction and other similar laws state it as and describe it as which would make you the odd man out. :p

Somehow I rather have doubts that the whole of science engineering and physics is wrong in what and why they chose to describe devices that generate electrical power by conversion of mechanical force into electromotive force as voltage sources not current sources.

After all you can not get current to flow without voltage being there first and besides current dependent is not constant current. ;)

The whole issue comes down to the simple fact that in an automotive electrical system the currents as in amperage flow is always varying and never constant and the voltage regulator in an alternator is continually adjusting the rotors magnetic field strength to keep the system voltage constant based on the specific working voltage range that the battery works at.

So how are you getting that an electrical system that regulates it self to stay at at constant voltage independent of what ever the system impedance or resistive values change by is producing a constant current? :confused:

If they were truly working as constant current sources they would be putting out a constant specific current regardless of what ever they system voltage has to change to do so which they do not unless they are broken.

Any electrical power source able to adjust its output current flow to keep the voltage level of the electrical system or circuit no mater what other electromagnetic, electrochemical or other principals are at work constant is not a constant current source and you can measure and test and measure that yourself on you own airplane just by putting a volt meter and an amp meter on the output of your alternator and turning on different loads. Does your alternators output voltage greatly change from no load to high load voltage change or does the current coming out of the alternator change as the load values change? :eek:


BTW I read the full link you gave, https://www.electro-tech-online.com/custompdfs/2012/11/cpconvergence00p583-1.pdf ,and your quote of

Please read the paragraph just below Figure 4 on page 3:

"in a typical automotive alternator, back voltages in
excess of 80 V may be necessary to source rated current
into a 14 V output at high speed. An appropriate dc-side
model for the alternator system is thus a large opencircuit
voltage in series with a large speed- and current dependent
output impedance."

Sure sounds like a constant-current source to me.

is being taken way out of context not only in regards to the whole of the report but even just to the very paragraph it came from. :eek:

You are not going to declare yourself irrefutable now are you? We all know were and to whom that leads to. :rolleyes:
 
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