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Re: [TCML] Advice on MMC



I wind power reactors on old pole xmfrs cores.  Just strip off all the wire
down to the core.  If it's an E-I type core, I usually use approx 80 turns
of #6 AWG hi-temp wire on the core for good current limiting at around 60
Amps.  If you need less current just use more turns.  You can usually pick
up lightning damaged xmfrs from local electric utility companies for around
$25 (scrap prices).

Dr. Resonance




On Sat, Jan 2, 2010 at 12:57 PM, andrew <andrew@xxxxxxxxxxxxxxxxxxxxx>wrote:

> Hi Claude
> I have made the safety gap part of my Terry Filter so that is good news if
> I
> dont have to buy the rest of it.
>
> Very interesed in the welding rod reactor idea. Any photos? (worth a
> thousand words!)
>
> The other possibility that has been sugested is a MOT with the shunts and
> secondary removed and varying the gap in the core
> to modify the iductive reactance.
>
> Thanks Andrew
>
>
> -----Original Message-----
> From: claudio masetto [mailto:claudmas@xxxxxxxxxxxxxxx]
> Sent: Saturday, 2 January 2010 9:32 a.m.
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Advice on MMC
>
> H i Andrew,
> I've been using a 4 MOT stack without a filter on many coil configurations
> and have not had any problems.
> Just make sure to have a safety gap across the stack. MOT's are virtually
> indestructible.
> I also made a variable inductor using a stack of welding rods for the core.
> Can't remember where I saw the
> design but someone on the list may know the site.
>
> Claude.
> ----- Original Message -----
> From: "Thomas Ryckmans" <thomas.ryckmans@xxxxxxxxxx>
> To: "'Tesla Coil Mailing List'" <tesla@xxxxxxxxxx>
> Sent: Thursday, December 31, 2009 3:13 AM
> Subject: RE: [TCML] Advice on MMC
>
>
> > Andrew,
> >
> > As for ballasting using a variable reator with iron wire in a tube, try
> > asking Phil Strauss on the TCUK mailing list (tcbouklist at yahoogroups
> > dot
> > com). He has build a very smart one
> >
> > tcbouklist@xxxxxxxxxxxxxxx
> >
> > cheers
> >
> > Thomas
> >
> > -----Original Message-----
> > From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf
> > Of andrew
> > Sent: 29 December 2009 20:20
> > To: 'Tesla Coil Mailing List'
> > Subject: RE: [TCML] Advice on MMC
> >
> > Thanks David
> > Yes, I have 4 MOTs primaries in parallel at 240v 50hz, secondaries in
> > series, output voltage, 9200 as far s I can tell.
> > I fed 24 volts ac into primaries and measured 920 v total accross
> > secondaries, as turns ratio will be constant. I imagine it will change
> > under
> > load though.
> >
> > Not quite sure how to measure the s/c current though. The ratings of the
> > microwave ovens were all in the 1300/1400 watt range and 240v 50 hz 6.5
> to
>
> > 7
> > Amps so I would guess that in microwave operation they would be running 6
> > amps through the magnitron as virtually a short circuit limited by
> > resistance and the saturation of the shunted transformers. If that is the
> > case then my primary current would be in the 20~ 24 amp range. It would
> be
> > more manageable if it were 18 to 20A max and I have tweaked JavaTC to see
> > how this affects things.
> >
> > How can I get a more precise answer on s/c current or is this close
> > enough?
> > ie how do you measure this? I have a fluke digital meter but I am a bit
> > leary of shorting out the 9000v secondary lest there be smoke! Is it
> > really
> > ok to do that?
> >
> > And yes regarding Ballast. I think I need something there. At the moment
> > for
> > testing things and to stop it blowing fuses. I have just been using a 3
> kw
> > oil column heater in series with the primaries. (very big resistor!)
> >
> > I don't have a variac but am keeping my eye out for one of suitable
> rating
> > but there are not many for sale around here.
> >
> > I like the idea of building a variable reator with iron wire in a tube
> but
> > not quite sure how to do that.
> >
> > Andrew
> >
> >
> > -----Original Message-----
> > From: David Dean [mailto:deano@xxxxxxxxxxxxxxxx]
> > Sent: Wednesday, 30 December 2009 5:37 a.m.
> > To: Tesla Coil Mailing List
> > Subject: Re: [TCML] Advice on MMC
> >
> > Hi Andrew
> >
> > I guess I did not read your post carefully enough.
> > Until Chip Ford ask:
> > He states that he will be using 4 x MOT. In that case, is a terry filter
> > needed???
> > In answer to *that* question, my guess would be that a Terry filter is
> > probably not needed, but a properly optimized Terry filter with the right
> > number of MOVs for the voltage and possibly increased wattage rating for
> > the
> > resistors to handle the extra current would certainly not hurt anything.
> >
> > Will try to address some of your original questions, comments
> > interspersed:......
> >
> > On Monday 28 December 2009 04:48:41 pm andrew wrote:
> >> Hi
> >> I have been using Javatc to help me design my coil. I am currently
> >> trying  to decide on the correct capacitance value for the tank cap
> >> but am a  little confused about all the different capacitor values
> > mentioned.
> >>
> >> They are:-
> >> Primary Capacitor uF  ; I am asuming this is the actual tank cap used.
> >>
> > Yes
> >> Resonant Cap Size, I think this is the capacitance value that
> >> resonates  with the transformer at 50 hz.
> >>
> > Yes, if you have 50Hz in New Zealand
> >> Power factor cap size,  To correct the PF.
> >>
> > Yes, but that is the mains resonant value for the primary of the
> > transformer
> > with the secondary shorted. Informational purposes, actual value required
> > for any given setup may vary considerably. 1st place a TC is a non-linear
> > load, 2nd tank cap adjusts power factor during charging part of cycle.
> > Best
> > to not use power factor correction unless you really need it, then start
> > with small value and add incrementally till best result found.
> >
> >> Static gap LTR cap size,   Is this the same as the Tank Cap?
> >>
> >> srsg LTR cap size.       ditto but for a Sync gap.
> >>
> > Yes, these are suggested values for use with a NST to maximize power
> > throughput while protecting the NST from overvoltage.
> >> I was planning to use an asynchronous spark gap but from what I have
> >> read this is not recommended for coils designed with Java TC,
> > Asynchronous rotary spark gap is not recommended for coils powered by NST
> > Java TC is designed for NST coils Probably why you read that
> >> so for simplicity I will go with a multi pipe static gap. My
> >> transformer is 4x MOT.  I am building a Terry filter for it.
> >>
> > Fine
> > Question:
> > I assume when you say "My transformer is  4x MOT." you mean a stack of 4
> > MOTs in series to output approximately 9kV open circuit?
> > Another Question:
> > Are you using, or planning to use, any external ballasting for the MOTs?
> > And yet Another Question:
> > Are you using, or planning to use, a Variac, or other variable
> > autotransformer to adjust the input voltage to the MOT stack?
> >
> > What you need to know:
> > Open circuit voltage (measured is best)
> > Short circuit current (measured is best) If using external ballast
> > measurements are made with ballast in place Input that data into the
> boxes
> > marked "Rated V out" and "Rated mA"
> > in the transformer design section of JavaTC
> >
> > Know that the MOT is not linear, and the impedance will change depending
> > on
> > the applied voltage, so the result you get will only be valid for the
> > conditions you have used for inputs. If you are not planning to use a
> > Variac, it should be close enough. If you *are* going to vary the input
> > voltage you might want to measure your open circuit voltage and short
> > circuit current at different input levels and recalculate to see if there
> > are any gross anomalies that might change the value you choose for a MMC
> > capacitor.
> >> When I know that, I can order my caps for the MMC.
> > Yep
> >>
> >> Many thanks
> >> Andrew Buxton
> >> Newbie Kiwi Coiler
> >>
> >>
> > later
> > deano
> >
> >
> >
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