Muller Dynamo

[mariuscivic]

Hi konehead!

Thanks again for all the info 
Right now the results are a bit different. The speed up effect is gone; it was the FWBR that was not working soo well( it doesn't like HV). After replacing it i got better results:
-the 330uF cap goes to 300V  in less than 60 sec without droping rpm and still rising. The driving coil sucks only 15 mA more when shorting the gen coil
-12V 55mA rotor spining free
-12V 70mA rotor spining with shorting the gen coil
I have used IRFP460 just like you said and they work great! Now i have to find this MIC4421 driver and see if there is any difference in everything.
For now i want to get to the point where there is no droping in rpm when shoring the coil
Konehead what was your result with this circuit?

[konehead]

Hi Mariu
Sounds good glad you like the IRFP460s...are there two bidirectional now too with gates and source leads connected?.....
try 4 in paralell, and annother 4 in paralell with the two clusters of 4 hooked bidirectional....this would be ultra low resistance this way...they have some 40A 500Vmosfets about same price as the IRFP460s cant remember the number for them but you can google "40A 500V NPN mosfets" and find them...
I dont think the driver will make that much difference for you right now actually its just something that you "should" have whenever working with mosfets - the driver will make for a very very fast cut-off and turn-on, and they can make it so the mosfets will do high frequencies without any glitches too,
Basically you are supposed to use a driver with mosfets or the engineers will scream at you is real reason!  (Romero didnt use them either)
I cant say the difference with driver and no driver really - it seemed pretty much the same to me with or without like I did two summers ago without them, but I will say the driver improves performance 15% but this is sort of imaginary since I never did side by side tests to check...I am sticking with always drivers with mosfets in future so that is all I can say...
you might want to try a 80uf or 60uf or 40uf AC type cap IN SERIES on one of your AC legs of the FWBR.....a "high bypass filter" is official designation of this cap....Tesla used to do this with his spark-gaps too....shorting coils is very similar to spark gap stuff since they both create the ringing...When you use one of those AC caps in series, they also "Absorb" the backemf/lenzlugging too on the output to a load,  so they serve a dual-purpose....
this means you can get by with NO "two-stage output circuit" by using the AC cap and just plug in your load on the DC side output of the FWBR...I sort of consider this cheating nowadays, and the two-stage or diode plug is much better way to go but you might want to check it out maybe you can really nail it down better than I ever did using the AC caps - its basically a matter of trying lots of UF sizes in the AC cap and see what doesnt affect the speed of filling the cap, and also makes it so the load doesnt affect draw so its a balancing act of finding the best compromise of speed of cap filling up and no lenz lugging at same time.....
for examples: 6uf will make absolutely no lenz lugging (and now you cna go with wide pusle width too) but the cap will fill up slow...
100uf will let lots of power go through to fill cap very fast, but you will get some lenz lugging probably - so now you would want to change pulse width....it goes like that....

I cant really say what the results are but you will get 3 times the votlage instantly and 20times the votlage in cap over time when it is working good - seems like you are already there......so your results right now are pretty mcuh what I get too
There really are two sides to this: filling the cap without affecting draw, or affecting it very little --- and then there is discharging caps to load without affecting draw, or affecting draw very little....
try AC cap in series on AC leg of FWBR maybe is good next step for you since then you can start testing with a load too..
You might not want to worry too much about any small amount of extra draw when shorting you get - the extra power made is worth it.... to make it totally lenz-free, you are probably going to have to have a finite adjust to the pulse width...and cap size will always be different for the different pulse widths too....

[Khwartz]

It looks good news to me.
i couldn't find the 4421 driver but i've adapted the romero's driving circuit to those mosfets and this is the result:
- The coil without shorting  is giving me around 24V
- when the shorts occurs the rpm drops a bit but it gives me instant 70V and rises around 200V
- free spining rotor 1513 rpm
-spining rotor with shorting without charging cap 1345rpm
-spining rotor with charging cap connected 1433 rpm  ( i've tryed 56....330uF/400V)

The spikes are going off the scale of my small scope

[Khwartz]

Also its going to be hard to measure watts-output from the cap, when you cant jsut do a lump reistive load on it, like what Crazycut, and most any engineer would want to see.
So you need to calculate watts-out from this cap-discharge formula which any EE worth their salt will agree with:
FARADS of cap /2
X
(Cap voltage before discharge SQUARED  minus the cap voltage after discharge SQUARED)
X
cap-discharge events per second
= WATTS

:-bd

example:
100uf cap, that has 200V in it before discharge, and 100V in it after discharge, pulsing to load 4 times per second...
So:
100uf = .0001f
.0001f / 2 = .00005

200 X 200 = 40,000
100 X 100 = 10,000
40,000 - 10,000 = 30,000
so put those numbers in the formula to find watts:
.00005 X 30,000 X 4 = 6 watts

[konehead]

Hi Mariu
I did some coil shorting tonight with a new big Muller-type generator I built recently and its going around 275rpm with 8 farily large magnets in rotor - the thick-wire genrator coils dont make much voltage at all on purpose since I want to coil short them for the voltage, instead of speeding up rotor to get more voltage...this particular generator makes 60hz at 275 rpm so am trynig to keep the rpms at that speed..
anyways it wasnt so impressive until I went down to a 22uf "capture" cap then the voltage really zings right up to 100V near instantly from only 10V being made without shorting  - and climbs to 300V over some time....all with no effect at all to motor coil draw...
I was usng 1000uf and also470uf  before and the volts-clmb was pretty slow....anyways besides low resistance in the swtiching, and no resistance across cap when it fills, the size of the cap is very important for good results I think too... can you try a 22uf cap or 10uf and see what happens for you with cap that size?