Inverter charger

[nicknorman]

On 07/06/2018 at 16:27, Tony Brooks said:

Well http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_pre_2011/electric_circuits/mainsproducedrev1.shtml

 

says near the bottom:

 

Increasing the induced voltage

To increase the induced voltage:

• move the magnet faster
• use a stronger magnet
• increase the number of turns on the coil
• increase the area of the coil

Now, the speed of the magnet is fixed by the engine speed. The number of turns and the area of coil is fixed by the design of the machine. That leaves strength of magnetic field and that is what is altered but pulse width modulation so I stand by my statement that its the voltage that is controlled and that any current control is, in part, a result of that voltage control. In other words the opposite of what you argue.

 

Current flowing in any circuit depends upon the voltage pushing it and the resistance of that circuit. Curreent does not determine the voltage trying to push it.

I did “report” this post 2 days ago and asked it to be moved to a new thread to avoid cluttering up this thread, but it seems the mods are too busy slashing and burning elsewhere. So, with this thread in a lull here goes:

 

Above is Faraday’s law, which relates to an emf being induced into a conductor by changing magnetic flux. But it only works in an open circuit scenario. Once you draw current, Lenz’s Law is also invoked which says that the current creates an EMF so as to oppose the current. So Faraday’s law and Lenz’s law kind of balance out to give a certain current at a certain voltage. Faraday’s law taken on its own for say a short circuited conductor (a loop) would predict an extremely high current (EMF as per formula, into the tiny resistance of the loop) which is clearly not what happens.

With those balancing effects in place the system becomes pretty much a current source.

 

Another way of looking at it is, consider the alternator charging 2 batteries in parallel at something like 80-90% SoC. The regulator is operating on a certain duty cycle to keep the voltage at say 14.4v. Let’s say 50% duty cycle. Now by magic, fix that regulator duty cycle at 50%. Now disconnect one of the batteries. If the regulator was regulating voltage as stated, nothing would change. But in fact, since the battery now only wants 1/2 the current, the output voltage will rise substantially to pretty much push the same power into the one remaining battery.

 

So clearly the regulator wasn’t regulating voltage directly (and no regulator ever does) it was controlling the current such that, with the demand placed on it, the voltage was the desired one. All types of regulator that I can think of, regulate voltage by controlling the current into the instantaneous load.

Edited June 9, 2018 by nicknorman

[Tony Brooks]

Go your own way then.

 

In your example something would change, the mark space ration of the rotor current would change i response to the voltage trying to rise as you have just halved the current flow but it would still be regulating at its set voltage.

 

Lenz's law is what results in a reducing charging voltage as the current rises and it relates to the pulsing magnetic fields interacting with the stator coils. That is the magnetic fields induced by the current flow so trying to create a voltage in opposition to the one we are generating.

 

When there is current regulation designed into a generator's control gear as in the RB340 it is in effect a second voltage regulator that limits the voltage when the current is too high.

 

I note you ignore the accepted theorem that current is caused to flow by the EMF (voltage) and its value will be determined by the resistance and Voltage. Increase the voltage and the current rises. Decrease the voltage and the current falls. Decrease the resistance and the current rises, increase the resistance and the current falls. Nothing about altering the current by some magical means and the voltage altering.

 

I will not say more than this or try to convince you based on past experience. I will leave other members to decide who is more likely to be correct.

[nicknorman]

It's a shame you have to turn it into a war but never mind. My comments in red:

 

1 hour ago, Tony Brooks said:

Go your own way then.

 

In your example something would change, the mark space ration of the rotor current would change i response to the voltage trying to rise as you have just halved the current flow but it would still be regulating at its set voltage. Yes of course, if the "magic" wasn't there the regulator would reduce the field current which would reduce the output current such that the voltage remained the same. It would be regulating at its set voltage, by controlling the current to match the load at the regulated voltage.

 

Lenz's law is what results in a reducing charging voltage as the current rises and it relates to the pulsing magnetic fields interacting with the stator coils. That is the magnetic fields induced by the current flow so trying to create a voltage in opposition to the one we are generating.

 

When there is current regulation designed into a generator's control gear as in the RB340 it is in effect a second voltage regulator that limits the voltage when the current is too high. No you are confusing a current limiting system (typically for thermal protection ends) with a voltage regulation system which operates by controlling current.

 

I note you ignore the accepted theorem that current is caused to flow by the EMF (voltage) and its value will be determined by the resistance and Voltage. Increase the voltage and the current rises. Decrease the voltage and the current falls. Decrease the resistance and the current rises, increase the resistance and the current falls. Nothing about altering the current by some magical means and the voltage altering. No I am absolutely not ignoring ohms law. Although one has to be careful, ohms law only completely applies to DC and alternators are AC! But with the 3 variables voltage, resistance and current, one can be variable according to outside influences, one can be controlled, resulting in the third being as desired. So in the case of an alternator, the resistance (or load, if you like) is the external variable (related to the battery's SoC etc). If the current is controlled then the voltage can be as desired ( by controlling the current). Show me a circuit that controls voltage, not current. (Don't spend too long on it because you can't).

 

Incidentally, don't feel to bad about this new concept. It was something I had not really thought about and it was Gibbo who pointed it out. Yes he is not always right but in this instance he was.

 

I will not say more than this or try to convince you based on past experience. I will leave other members to decide who is more likely to be correct. If this was a thread about BMC engines etc, I would bow to your superior knowledge. But it isn't.

 

[Chewbacka]

9 hours ago, nicknorman said:

It's a shame you have to turn it into a war but never mind. My comments in red:

 

 

If you view the alternator/power supply as a source of charge, then charge will flow out into the load.  If the load demand is low (determined by it’s resistance) then the charge will flow out slower than the charge available.  For a given output capacitance as charge rises so does voltage.   Likewise if load demand is higher than supply the charge in the output capacitor will fall and so the voltage across it will fall.  The regulator controls the flow of charge, however in the real world trying to directly measure charge is difficult so we measure volts and amps, but actually we control energy.  So I think you are both right and wrong in that you are both viewing the result of energy transfer.  

[nicknorman]

46 minutes ago, Chewbacka said:

If you view the alternator/power supply as a source of charge, then charge will flow out into the load.  If the load demand is low (determined by it’s resistance) then the charge will flow out slower than the charge available.  For a given output capacitance as charge rises so does voltage.   Likewise if load demand is higher than supply the charge in the output capacitor will fall and so the voltage across it will fall.  The regulator controls the flow of charge, however in the real world trying to directly measure charge is difficult so we measure volts and amps, but actually we control energy.  So I think you are both right and wrong in that you are both viewing the result of energy transfer.  

If we can clear up some of your dimensional inconsistencies I think I can agree. Charge is the integral of current and thus has no concept of power or energy. Therefore replace “charge” with “power” in the first sentence. I then get confused when you start talking about capacitors! (There aren’t any!).

 

So I would rephrase thus:

 

View the alternator as a source of power which flows into the load. If the load demand is low (determined by its resistance) the current will be less and the voltage will rise to increase the current and maintain the power. Likewise if the load demand is higher than the supply the voltage will decrease to reduce the current and maintain the power. The regulator controls the flow of power.

 

The important point is that voltage can’t be directly regulated, it can only be regulated by adjusting the power in accordance with the load so that by ohm’s law, the voltage becomes correct. I said earlier “by controlling the current” but in fact I should have said “by controlling the power”.

 

Of course in the above, the alternator isn’t a true constant power source, but over a modest range of load resistance it is a fairly close approximation to it.

[Chewbacka]

39 minutes ago, nicknorman said:

If we can clear up some of your dimensional inconsistencies I think I can agree. Charge is the integral of current and thus has no concept of power or energy. Therefore replace “charge” with “power” in the first sentence. I then get confused when you start talking about capacitors! (There aren’t any!).

 

So I would rephrase thus:

 

View the alternator as a source of power which flows into the load. If the load demand is low (determined by its resistance) the current will be less and the voltage will rise to increase the current and maintain the power. Likewise if the load demand is higher than the supply the voltage will decrease to reduce the current and maintain the power. The regulator controls the flow of power.

 

The important point is that voltage can’t be directly regulated, it can only be regulated by adjusting the power in accordance with the load so that by ohm’s law, the voltage becomes correct. I said earlier “by controlling the current” but in fact I should have said “by controlling the power”.

 

Of course in the above, the alternator isn’t a true constant power source, but over a modest range of load resistance it is a fairly close approximation to it.

Agree that an alternator does not have a capacitor as a discrete component but it does have a capacitance (and inductance) and so if you open circuit an alternator under load the voltage will rise very rapidly.  However I am just being pointlessly pedantic. 

[WotEver]

2 hours ago, Chewbacka said:

However I am just being pointlessly pedantic. 

As is this entire branch of this thread. 

[nicknorman]

6 minutes ago, WotEver said:

As is this entire branch of this thread. 

That’s why I wanted it moved to a new thread, but it wasn’t to be.

[WotEver]

Whatever, it’s a pointless argument based on pedantry. The field current only exists because of the voltage applied to the field. But the voltage only exists because of the current flowing through the field control transistor. So which is it? Use whichever is easiest to understand - generally voltage. 

 

If you want to be truly pedantic then move down to the quantum level, where voltage and current are the same thing viewed from a different perspective. Current is related to magnetic fields, voltage is related to voltage fields but move past either fast enough and they become the other as both Maxwell and Einstein wrote equations to prove.  

[Dr Bob]

3 hours ago, WotEver said:

Whatever, it’s a pointless argument based on pedantry. The field current only exists because of the voltage applied to the field. But the voltage only exists because of the current flowing through the field control transistor. So which is it? Use whichever is easiest to understand - generally voltage. 

 

If you want to be truly pedantic then move down to the quantum level, where voltage and current are the same thing viewed from a different perspective. Current is related to magnetic fields, voltage is related to voltage fields but move past either fast enough and they become the other as both Maxwell and Einstein wrote equations to prove.  

I don't think you are considering String theory.?

[WotEver]

16 minutes ago, Dr Bob said:

I don't think you are considering String theory.?

Is the string for wrapping round the pulleys if the belt breaks?

[MtB]

15 minutes ago, Dr Bob said:

I don't think you are considering String theory.?

 

There are people frightened of string. 

 

Linonophobia is the fear of string.

 

http://common-phobias.com/linono/phobia.htm

[Dr Bob]

22 hours ago, WotEver said:

Is the string for wrapping round the pulleys if the belt breaks?

Only if you are good at tying knots.

[WotEver]

1 hour ago, Dr Bob said:

Only if you are good at tying knots.

Knots? No more than 3.476 on the canals. 

[rusty69]

9 minutes ago, WotEver said:

Knots? No more than 3.476 on the canals. 

KnotEver! 

[Dr Bob]

9 hours ago, WotEver said:

 No more than 3.476 on the canals. 

Is that volts or Amps?

[Dr Bob]

On 10/06/2018 at 22:50, Mike the Boilerman said:

 

 

Linonophobia is the fear of string.

 

 

I thought that was the fear of Lino. Mrs Bob doesn't like Lino. The duck doesn't like Lino either.

[rusty69]

1 hour ago, Dr Bob said:

Is that volts or Amps?

You'd have to ask Machpoint00469034

Edited June 12, 2018 by rusty69

[MtB]

58 minutes ago, Dr Bob said:

I thought that was the fear of Lino. Mrs Bob doesn't like Lino. The duck doesn't like Lino either.

 

Don't be silly, that would be linophobia, innit. We are discussing linonophobia. 

 

Or is she frightened of Linono too?

[mrsmelly]

3 hours ago, Dr Bob said:

I thought that was the fear of Lino. Mrs Bob doesn't like Lino. The duck doesn't like Lino either.

How is Duck? havnt heard about him of late. Any recent pics so we know you havnt killed and eaten him? preferably reading a daily somett or other so we can date the foto ?

[rusty69]

1 minute ago, mrsmelly said:

How is Duck? havnt heard about him of late. Any recent pics so we know you havnt killed and eaten him? preferably reading a daily somett or other so we can date the foto ?

Good point mrsmelly. Donald the duck hasn't been heard of for some time. 

 

No photoshopary either Dr Bob,as we Will know! 

[Dr Bob]

3 hours ago, mrsmelly said:

How is Duck? havnt heard about him of late. Any recent pics so we know you havnt killed and eaten him? preferably reading a daily somett or other so we can date the foto ?

 

3 hours ago, rusty69 said:

Good point mrsmelly. Donald the duck hasn't been heard of for some time. 

 

No photoshopary either Dr Bob,as we Will know! 

Yes, he has been a bit quiet hasnt he. We will be going down the Stockton flight tomorrow so I will try and get some photos. What is a newspaper?

[Dr Bob]

6 hours ago, Mike the Boilerman said:

 

Or is she frightened of Linono too?

No,of course not. Linono is great on toast and not bad in a spag-bol sauce washed down with a Brains SA Gold.

[mrsmelly]

21 minutes ago, Dr Bob said:

 

Yes, he has been a bit quiet hasnt he. We will be going down the Stockton flight tomorrow so I will try and get some photos. What is a newspaper?

Who mentioned " Newspaper "?

[Dr Bob]

5 minutes ago, mrsmelly said:

Who mentioned " Newspaper "?

You did. 'reading the daily sumit'.