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RE: [TCML] Advice on MMC
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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