Exploring Marx Generator Physics: Seeking Answers

[MasonJ1989]

https://en.m.wikipedia.org/wiki/Marx_generator

I chose the prefix to get an educated answer. I am not school educated but rather self taught, also instead of focusing primarily on electronics I have studied for the past several years the broader spectrum of electromagnetic phenomena including magnetism, electronics, light, etc.. and I have scoured forums, pdf, books, mathematical structures etc.. I have some questions about the above referred to link and schematics therein but not specifically from that site but in general reference to the Marx generator and my understanding of physics involved, I cannot find the answers and have come here for help.

1. If capacitor1 positive on the left is charged to source, say 4kv,which starts the cascade through the spark gap1 and current travels to capacitor2 negative and releases capacitor2 at which point the current being blocked by the capacitor2 will have 2 options. Travel through R1 or R2. Beyond R1 is ground and beyond R2 is more resistance. Current should go to ground, In this the current cannot add to any other current. What's happening here?
2. When current from capacitor1 discharges through gap1 and discharges capacitor2, capacitor2 had the same source charge so therefore should discharge at source voltage regardless of the charge on its negative plates. What's happening here?
3. I have looked around and some numbers were 4kv at 20mA as a charge source and P=IV.. I=v/r.. R=1m ohm that the power dissipated into any R should be 16 watts but the guy was using 2watt resistor.. What's happening here?

I risk feeling stupid but I feel that I'm missing something with this, please feed my brain.

 

[MasonJ1989]

I guess I don't understand voltage multipliers. This example he tells me one side is grounded and then proceeds to tell me how current travels on that side even through the diode resistance (small but nonetheless) instead of going to ground. If the grounded side is at 0v then how could it possibly charge the capacitor to a peak voltage?

https://hackadaycom.files.wordpress.com/2017/03/multipliera.png?w=400&h=234

How Does It Work?

The multiplier circuit needs an AC power supply in order to work. For the sake of simplicity let´s assume that one side of the power supply is grounded and remains at zero potential, and the other varies between plus and minus U (100 V in the example). Here’s what happens:

Capacitor C1 charges through diode D1 at the voltage U (100 V) of the power supply, which is at its negative peak. Note that this leads the capacitor to be positive at its right side and negative at its left. The yellow line indicates the direction of current flow

 

[anorlunda]

See if this article's description helps. https://en.wikipedia.org/wiki/Voltage_multiplier#Operation

 

[MasonJ1989]

See if this article's description helps. https://en.wikipedia.org/wiki/Voltage_multiplier#Operation

When I Google a question wikipedia is there, this was in my first 5 sites after pdfs. My lack of understanding is in basic principles of electricity. If I add 2 voltages of the same potential into a single rail my output voltage is equal to either of the input voltage. The only time voltage doubles is in series power source but I'm failing to see how the capacitors are acting as a series power source. Even when charged or discharged while source is in action should just result in adding two rails.

 

[anorlunda]

Those capacitors are not in parallel where the voltages are the same. They are connected in series where the voltages add.

Try thinking of those diodes as switches that open and close. Does that help?

 

[phyzguy]

I got interested in these types of circuits a while ago, so I built a SPICE simulation of the simple Cockroft-Walton voltage doubler. Perhaps it will help you to see the node voltages as the capacitors charge up so you can see it working. The plots are attached

 

[anorlunda]

@phyzguy , I can't open any of those PDF files

 

[phyzguy]

@phyzguy , I can't open any of those PDF files

Interesting. I see them fine in Adobe Reader. What happens when you try to open them? What application are you using? I was even able to see them on my Samsung phone.

 

[MasonJ1989]

I was able to open them but the information gained was that the voltage doubles power stage, I understand that but I'm not understanding the image from Wikipedia or the why it's happening based on what physically observed principle of E. -100 at c1 which means that +100 goes through the one way to charge the capacitor equally with the opposite charge. However they have it represented as 0v. Since it's forward biased, the current even in a second should continue before reverse cycle to charge the bottom of c3 and charge the top of c2 and since like charges repel discharges the bottom of c2 which is source voltage and does not effect the voltage overall. Then the top during the rest of the half cycle prevents the bottom of c2 from being charged. During the reverse half cycle c1 cannot discharge through the diode1 and so continues through diode 2 into capacitor 2 as a finite charge since the half cycle cannot continuously travel through D1 as the positive half cycle can..

 

[MasonJ1989]

There's more to gain from the pdf but I have only had a bit to study them thank you for them

 

[phyzguy]

What you need to realize is that the voltage across a capacitor cannot change unless you supply charge. Suppose I have a capacitor charged up to 100V, where side A of the capacitor is at 0V and side B is at 100V. Suppose the capacitor is in the air and not connected to anything. Now I take a wire connected to side A and connect it to a power supply at 100V. Side B will (basically instantaneously) move to 200V, maintaining the 100V voltage difference across the capacitor.

 

[MasonJ1989]

Is voltage strictly a measure of difference or does it also represent a quantity of charge?
Q=cv
V=q/c
As v increases either q increases or c decreases so if voltage represents a real quantity then per Wikipedia image the top of c1 maintains difference by increasing voltage as a representation of difference but then transfers that voltage to c2 as a physical quantity that has no source. I will continue to think about your post, you guys are the first qualified people I have talked to since I started studying so I will consider seriously what you have given to me

 

[phyzguy]

In the equation Q=CV, the V is the voltage across the capacitor, i.e. the difference in voltage between one side and the other.

 

[anorlunda]

Interesting. I see them fine in Adobe Reader. What happens when you try to open them? What application are you using? I was even able to see them on my Samsung phone.

I found them under downloads. Thanks.

 

[phyzguy]

I added a plot of the currents through the four diodes.

 

[anorlunda]

Is voltage strictly a measure of difference or does it also represent a quantity of charge?

A lot of people get confused about that. Voltage is always a difference between two points. So in a circuit you must be careful to pay close attention to which two points are being discussed. @phyzguy is giving you good coaching. Good luck.

 

[MasonJ1989]

@phyzguy in reference to the schematic you gave to me, and basics to be clear. Between the leads of the source we have a 100v difference which could be -50v and +50v right? Or any combination that has an absolute value of 100v? Let's call the left side of any capacitor side A and the right side B. D1 is forward biased in respect to c1. In the first half wave side A of capacitor gets charged with peak +v and side A of capacitor 2 with peak - v. D1 will not conduct - v when forward biased towards c1 due to the physical properties of dopants used in its junction. So physically nothing energy wise goes through the circuit until the second half wave in which the polarities on side A of c1 and c2 reverse and the D1 conducts the +v and charges c1.. Am I right so far?

 

[phyzguy]

@phyzguy in reference to the schematic you gave to me, and basics to be clear. Between the leads of the source we have a 100v difference which could be -50v and +50v right? Or any combination that has an absolute value of 100v? Let's call the left side of any capacitor side A and the right side B. D1 is forward biased in respect to c1. In the first half wave side A of capacitor gets charged with peak +v and side A of capacitor 2 with peak - v. D1 will not conduct - v when forward biased towards c1 due to the physical properties of dopants used in its junction. So physically nothing energy wise goes through the circuit until the second half wave in which the polarities on side A of c1 and c2 reverse and the D1 conducts the +v and charges c1.. Am I right so far?

No. Print out the node voltages and currents so you can see what's happening. First, of all, the source is 100V peak, so N1 goes from -100V to +100V. Also, node N0 is tied to ground so it is always at 0V. Look at the voltages and currents. All of the nodes start out at 0V. As node N1 ramps up, the capacitor voltage can't change instantaneously, so it pulls N2 up with it. This forward biases D2 and causes current to flow through D2. This pulls up N3,N4 and N5. At around 8 ms, N1 goes negative. N2 tries to follow, but D1 clamps it and prevents it from going below ground. So all of the current flowing through D1 is charging capacitor C1. So when the next cycle starts, capacitor C1 has charged up part way and node N2 is more positive than N1. So when N1 goes positive again, it pulls up N2 further than it did the first time. See how N2 is getting larger and larger after each cycle? The same types of things happen to the other capacitors down the line.

 

[MasonJ1989]

-100 to 0v is 100v different and 0v to +100 is 100v different peak to peak is then 200v total. Also I do standard model so + runs to negative. Nothing biases the diodes because they are already fixed in circuit either cathode to anode or vice versa and therefore conduct accordingly. Also any rail tied to ground having a ground potential cannot pass current as all current is then at 0v and I have only seen a separation in center tap windings. As n1 starts to decrease n2 likewise starts to decrease but since D1 does not conduct in that direction the only place current to go is through d2 into c2. I guess I run into problems because I don't believe currents just sit and jitter back and forth I believe they run forward. My theory is based on what I see I guess I will have to play with these components to understand

 

[MasonJ1989]

Ac, dc, electron theory therein lies my hang up but all electrical energy can be produced my magnetism and current being a magnetizing force only reinforces this. Up till now I was able to conceptualize and a unique way almost all electrical phenomena but this one is requiring more effort

 

[phyzguy]

@MasonJ1989 Wow. It sounds like you have a lot of misconceptions. I urge you to throw away your misconceptions and get a good elementary textbook and study it. Electromagnetism is well understood, and you would do well to learn the accepted methodology rather than invent a new one, which will almost certainly be wrong.

 

[anorlunda]

Ac, dc, electron theory therein lies my hang up but all electrical energy can be produced my magnetism and current being a magnetizing force only reinforces this. Up till now I was able to conceptualize and a unique way almost all electrical phenomena but this one is requiring more effort

You're making it harder than necessary. Forget electrons. Think of AC as just a DC voltage that varies in time instead of being constant.

 

[phyzguy]

@MasonJ1989: Look at it this way. Gauss' Law was formulated in 1773, Coulomb's Law in 1784, Ampere's Law in 1823, and Faraday's Law of induction in 1831. Then Maxwell pulled it all together in 1865. So some of the greatest minds of the human race took about 90 years to figure this stuff out. So even if you are as smart as these guys (unlikely - look at the histories of Gauss' and Maxwell's lives), your life is too short to "start from scratch". On top of that, there are all of the advances that have been made (semiconductors for example) since Maxwell gave it all a theoretical underpinning. In other words, don't try to figure this out for yourself. Read what others have done and take advantage of their genius.

 

[MasonJ1989]

I have been studying exactly those texts and following exactly that math and I still believe the full picture has not been realized. All those people came to their conclusions within their lifetime which is the important time consideration. Money can biase ideas, opinions, history, health, and truth. Benjamin Franklin, Nicola tesla, Edward leedskalnin these are free thinkers who discovered physical effects and interpreted those effects as theory. They invented theory. I'm just following suit. A ball falling to the ground has no difference from a magnetics attraction (not to say its not different but following logic I would first explore the possibility first before jumping to another force that is not measurable) , even maxwell saw this in his original equations before heaviside chopped them up. Electrons cannot be seen and observed Plancks constant will never be observed.. But I have misconceptions because I follow physical effects and then make math versus following a mathematical loop. Also
@anorlunda sometimes to visually conceptualize "energy" its good to think about fields, particles, streams, analogies, vibrations, strings, waves, time variations etc sometimes its good to fix variables and see the others move. Fields are exceptional because energy physically manifests as fields. Anyways with these caps in series as the mechanism for voltage duplication. I think I gained something here but it's too bad I can't find any correlative texts for it. If you have 2 charged caps in series but not connected to anything just charged and connected to one another as two voltage sources in series, I then connect a volt meter to the outsides I would have 2v(c) but there will be no texts for understanding the charges in the center where you have positive touching negative, of course they are attracted to each other but at the same time held in place by the opposite plate of the capacitor, then you would have 2 sets of attraction and a voltage increase. Where are the tests the physical tests?? What happens if I add or subtract, what happens if I set a third charged cap with only one side touching this center? What happens if I add different material type, or magnetism? All we have is a math model but without physical experimentation we don't know. Google long ago started giving me repeated surface information or no information for my questions and who is doing tests? My taxes pay scientists to experiment and improve qualities of life instead they are playing with the Lhc which has done very little to relieve my curiosity and improve my day to day.

 

[anorlunda]

@anorlunda sometimes to visually conceptualize "energy" its good to think about fields, particles, streams, analogies, vibrations, strings, waves, time variations etc sometimes its good to fix variables and see the others move.

I agree. But please read the PF Insights article below. In it, I argue that the sometime for fields/particles etc. should not overlap with the sometime to study closed circuits. It would be like designing a bridge one atom at a time.

https://www.physicsforums.com/insights/circuit-analysis-assumptions/

 

[phyzguy]

@MasonJ1989: I see that you are not willing to take the time to understand what is already understood, and insist on ignoring what others already know. Believe me capacitors are well understood, and the thousands of working electronic circuits surrounding you every day are proof of that. I have tried to push you in that direction, but it sounds like I am wasting my time. I am bowing out of this thread. Good luck.

 

[anorlunda]

The original question had been answered. It is time to close this thread.