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Re: [TCML] Advice on MMC

To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Subject: Re: [TCML] Advice on MMC
From: cobus Duvenhage <cobusduven@xxxxxxxxx>
Date: Sat, 2 Jan 2010 23:41:22 +0200
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Hi
I think you got the wrong Person
Regards

On Sat, Jan 2, 2010 at 9:57 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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References:
- Re: [TCML] Advice on MMC
  - From: claudio masetto
- RE: [TCML] Advice on MMC
  - From: andrew

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