Thanks all for the advice and experience stories, even the CW rectified
schematic to get DC HV from the output of a MOT.
Are there any circuit diagrams or basic description for how I would use
microwave oven caps (and possibly diodes) to have a capacitive ballast,
since it sounds like it may have the least amount of power loss? While
still keeping the current draw to 10 amps or so? It also sounds easier
and
less expensive than making an inductive ballast since I have most of the
good innards of four or five microwaves. I want to probably start
simple,
maybe a 12 to 18 inch high secondary with a 1:4 ratio on its cylindrical
dimensions, driven from a single MOT. Could I get by with a single
static
spark gap where its only 1 to 2 kv? Or would it even help to get a higher
HV out using the MOT, MOC and diode straight from the microwave to get a
higher voltage, if the diode can handle the power from the bigger HV out
and not just from the little cloth covered wire for the magnetron? Has
anyone popped a microwave diode before from putting it straight on the 1
to
2 kv output of the MOT?
----------------------------------
Brian Hall
> From: cn@xxxxx
> To: tesla@xxxxxxxxxx
> Subject: Re: [TCML] MOT ballasting options
> Date: Thu, 3 Jan 2013 13:20:38 -0700
>
> Hi, David,
>
> Your incandescent resistor warming your garage proves that every cloud
has a
> silver lining. Kind of like the old vacuum tube oscilloscopes. A
couple of
> Tek 517s would keep a garage pretty warm, too. What do you use for an
> inductive ballast?
>
> Cheers---
> Carl
>
>
>
>
>
> -----Original Message-----
> From: drieben
> Sent: Thursday, January 03, 2013 5:51 AM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] MOT ballasting options
>
> Hi Carl,
>
> Yes, you do bring up a good point as to the power waste of
> resistance ballasting in large coils. I have a large power resistor in
the
> control panel of my Green Monster coil that I can add in series to my
> everpresent inductive ballast, if I so choose to help in smoothing
> the output or just for additional attentuation. I believe the mea-
> sured resistance of my power resistor is only 0.5 ohms, so you'd
> think thaere wouldn't really be that much in the way of voltage
> drop here. However, when you're typically running ~60 amps
> that translates to 1/8 of the total circuit impedance at 240 volts
> input (240/60 = 4 ohms), so that's 30 volts dropped out. I have
> the option of switching the resistive ballast on or off while the
> coil is in operation and the difference in the output sparks is
> definitely noticable! The sparks become noticable dimmer and
> weaker looking when I add the resistance. Also, the resistor
> will gradually warm to incandesence if ran in this manor, as
> 30 volts x 60 amps = 1800 watts of wasted power! On the
> bright side, the resistive heating does contribute to warming
> my garage on these cold winter days ;^)
>
> David
>
> ----- Original Message -----
> From: "Carl Noggle" <cn@xxxxx>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Sent: Wednesday, January 02, 2013 10:19 PM
> Subject: Re: [TCML] MOT ballasting options
>
>
> > It would be good to stick to capacitors or inductors for ballasting,
since
> > they don't dissipate any power (ideally). A resistor such as light
bulbs
> > or salt water will reduce the power available from the source. It
would
> > only be practical for small coils. The most efficient resistive
ballast
> > would dissipate half the power in the resistor and half in the TC.
Using
> > a DC supply and controlling the firing rate is probably the best ide,
> > needing no ballast. Have to watch out for the large energy storage in
the
> > C-W capacitors, though.
> >
> > BTW, the rectifier circuit in the drawing is a center-fed
Cockroft-Walton.
> >
> > ---Carl
> >
> >
> >
> >
> >
> >
> > -----Original Message-----
> > From: Jim Lux
> > Sent: Wednesday, January 02, 2013 8:53 PM
> > To: tesla@xxxxxxxxxx
> > Subject: Re: [TCML] MOT ballasting options
> >
> > On 1/2/13 6:58 PM, Andy Cobaugh wrote:
> >> On 2013-01-02 at 17:17, Jim Lux ( jimlux@xxxxxxxxxxxxx ) said:
> >>>
> >>> the "500 ft spool of wire" as an inductor has some simplicity and
> >>> appeal.. I can't recall what it's inductance is, but it's on the
list.
> >>> (copper being expensive these days, it's not as cheap as other
> >>> means)
> >>
> >> I think the 500ft spools of #12 THHN stranded copper measure around
9mH.
> >> The mostly complete spool that I use with my potential transformers
> >> measures 8.5mH.
> >>
> >
> > 9mH = 3.4 ohms at 60 Hz, 2.8 @ 50
> >
> > 1 spool = 35 Amps at 120 V, 60 Hz
> >
> >
> >
> > _______________________________________________
> > Tesla mailing list
> > Tesla@xxxxxxxxxx
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> > _______________________________________________
> > Tesla mailing list
> > Tesla@xxxxxxxxxx
> > http://www.pupman.com/mailman/listinfo/tesla
>
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