Re: MOT power supply ??

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Hhchicken1-at-aol-dot-com>

Hi list, 
The design I use does work, in fact it works very well, although the diodes 
do get quite hot. I've no idea why, though - I have very limited knowledge of 
the subject, being 13, but am interested in how it works.  I will try 
grounding the cores of the MOTs (effective centre tap) and the centre of the 
diode string, perhaps that will make them run safer and cooler.  Maybe I've 
just been lucky... Also the transformers I was using were absolutely 
identical and so were tha capacitors and diodes. 
Chris - I use the fan from inside the microwave to cool the gap - seems to 
work quite well for me. 

Thanks, Henry 

In a message dated 03/01/01 05:00:03 GMT Standard Time, tesla-at-pupman-dot-com 
writes: 


>
> Hi 
>
> I agree that the diagram at 
> http://hot-streamer-dot-com/temp/mot.bmp 
> is interesting. If the connection between the cores were to be connected 
> to the point between the diodes, it would be a "back to back level shifter" 
> which would work OK. Marco, and I believe some others have used this 
> topology 
> with success. This is exactly the "voltage doubler" circuit used in 
> microwave 
> ovens, except in the oven there is a magnetron which is of course a diode 
> (vacuum tube diode with a _very_ complex impedance characteristic) which 
> completes the circuit forming a "true" voltage doubler of the classic 
> design. 
> The level shifter circuit will give a half wave of a peak voltage of 1.4 X 
> VRMS 
> of the transformer on top of a DC voltage of 1.4 X VRMS of the transformer 
> for 
> a total peak voltage of 2.8 X VRMS of the transformer. If two of these 
> circuits 
> are connected together (core to core), one positive and the other negative, 
> and 
> they are phased so that the peaks are simultaneous, then the output can be 
> 5.6 
> X VRMS of the transformer, assuming both transformers have the same voltage 
> rating. 
> Assuming each transformer is rated at 2KV then the output can be 11.2KV at 
> 60pps. 
> It the transformers are 2.3KV, the output can be 12.8KV. 
>
> Of course in the diagram at http://hot-streamer-dot-com/temp/mot.bmp , there is 
> no 
> connection between the cores and the midpoint of the diodes. Someone 
> reported 
> recently trying the design and loosing some diodes. That makes sense, 
> especially if 
> the transformers were phased so that the peaks were not synchronized. 
>
> later 
> deano 
>
> > -----Original Message----- 
> > From: Tesla list [mailto:tesla-at-pupman-dot-com] 
> > Sent: Tuesday, January 02, 2001 6:59 PM 
> > To: tesla-at-pupman-dot-com 
> > Subject: MOT power supply ?? 
> > 
> > 
> > Original poster: "J. B. Weazle McCreath by way of Terry Fritz 
> > <twftesla-at-uswest-dot-net>" <weazle-at-hurontel.on.ca> 
> > 
> > 
> > Hello all & Henry, 
> > 
> > I'm confused about Henry's description and diagram of the MOT voltage 
> > doubler power supply that he's using with his Tesla coil. 
> > 
> > It doesn't look like any voltage doubler circuit that I've ever seen 
> > in my years of toying with electronics.  I've checked numerous ARRL 
> > publications, and my collection of electronic texts and I just can't 
> > see how that circuit works as a voltage doubler. 
> > 
> > The most common circuit that I'm familiar with consists of two diodes 
> > in series which are in turn paralleled with two capacitors in series. 
> > The D.C. is drawn from across the diodes/caps with the A.C. applied 
> > at the junction of the two diodes for one leg and the junction of 
> > the two caps for the other.  See my rather crude ASCII art below. 
> > 
> >                     --------------------------------------0 Pos. out. 
> >                     |                  | 
> >                     |                  | 
> >                     -                  - 
> >                     -  Cap             ^  Diode 
> >                     |                  | 
> >      A.C. in 0------|                  |------0 A.C. in 
> >                     |                  | 
> >                     -                  - 
> >                     -  Cap             ^  Diode 
> >                     |                  | 
> >                     |                  | 
> >                     --------------------------------------0 Neg. out 
> > 
> > In Henry's circuit are the cores, which in reality represent the center 
> > tap of the two seriesed secondaries, connected to anything?  At the 
> > least I would expect the cores to be grounded for safety. 
> > 
> > Please clue me in as to how his circuit works, as I just don't get it! 
> > 
> > 
> > 73, Weazle, VE3EAR/VE3WZL 
> > 
> > Listening: 147.030+ and 442.075+ 
> > E-mail:    weazle-at-hurontel.on.ca 
> >            or ve3ear-at-rac.ca 
> > Web site:  www.hurontel.on.ca/~weazle 
> > 
> > 
> > 
>
>