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Just another resonant mot thread

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Steve Conner

Mon Jul 14 2008, 11:52AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

That's interesting Dr. kV, so is the circulating energy limited by magnetic saturation or something? I guess when things start to saturate, the resonant frequency will shift and that's what will limit the current. So maybe it's acting as a constant-current source like your theory says, and that's why it works so well.

I'm wishing I hadn't sold my MOT and cap collection now. :(

Dr. Dark Current

Mon Jul 14 2008, 12:21PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Dr. Conner wrote ...

That's interesting Dr. kV, so is the circulating energy limited by magnetic saturation or something? I guess when things start to saturate, the resonant frequency will shift and that's what will limit the current. So maybe it's acting as a constant-current source like your theory says, and that's why it works so well.

I'm wishing I hadn't sold my MOT and cap collection now. :(

Yes it is limited by saturation. Actually most of the inductive energy is stored in the shunts of mots and of course they cannot take infinite energy

I have measured the secondary current and it actually increases as you draw the arc out! It may be just my meter, the waveforms probably get wild, but I'm sure it does not decrease noticably.

A note to "resonant" transformers: properly tuned resonant transformer will draw up to 4 times less current for the same arc length than the same xformer with just inductive ballast, this is why I like them so much

Theory is that as the transformer starts to saturate, it cannot take any more energy by itself (or by other inductive components in the circuit) and the left-over energy is "recycled" back to the primary winding and to mains.

quicksilver

Mon Jul 14 2008, 03:13PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

Experimental: Set up one shape, shunt design of MOT with / of equal energy to another of deferring physical geometric construction. Compare arc output under equal conditions/saturation....
IF I am correct; those (at least one) are a "DONG YANG" MOT & is a cube. In a thread sometime back someone made a comment relating to saturation and cuboid shape & it's relationship to the shunt. My totally non-scientific experimentation-playing around: Largest single MOT arc (with single cap) when compared to half dozen differing examples; cube wins every time.

Dr. Dark Current

Mon Jul 14 2008, 04:43PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Sometimes the arc with a MOT and 2 caps is very unstable and likes to go out soon, sometimes it works right. The capacitance of different microwave caps is similar most times, so the difference is down to the MOT used. And I believe it has something to do with the core shape and shunts.
From what I saw, "open" and slim-core MOTs make more stable arcs, while with the compact "cubes" it's often unstable.

teslacoolguy

Mon Jul 14 2008, 09:57PM

Registered Member #1107 Joined: Thu Nov 08 2007, 10:09PM
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Yes those mots are "cubes". I do have 2 similar slim-core mots that i could try and see if the arc is any better.

Dr. Dark Current

Tue Jul 15 2008, 07:29AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

teslacoolguy wrote ...

Yes those mots are "cubes". I do have 2 similar slim-core mots that i could try and see if the arc is any better.

if you use the third MOT with shorted primarylike you did, they are almost always stable. But I warned you of popping caps and the shorted mot's primary overheating

teslacoolguy

Tue Jul 15 2008, 02:19PM

Registered Member #1107 Joined: Thu Nov 08 2007, 10:09PM
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Posts: 792

I could make a 3x3 moc bank?

Dr. Dark Current

Tue Jul 15 2008, 02:23PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

teslacoolguy wrote ...

I could make a 3x3 moc bank?

yea that would be better.

Mads Barnkob

Wed Jul 16 2008, 02:29PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

Just got a shipment of MO parts from a colleague, we got 24 MO at 2$ a piece, some where brand new but we salvaged it all anyway, he didnt want his share after a few experiments so now I have most of it.

I am open for suggestions, but limited by 230V / 10A or if I remove my oven I can get 230V / 16A

In the picture you can see 21 MOTs (12 are the same) and there is also 21 MOCs and about 12 diodes left, some where blown.

Dr. Dark Current

Wed Jul 16 2008, 03:08PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

MadsKaizer wrote ...

Just got a shipment of MO parts from a colleague, we got 24 MO at 2$ a piece, some where brand new but we salvaged it all anyway, he didnt want his share after a few experiments so now I have most of it.

I am open for suggestions, but limited by 230V / 10A or if I remove my oven I can get 230V / 16A

In the picture you can see 21 MOTs (12 are the same) and there is also 21 MOCs and about 12 diodes left, some where blown.

OMG.

I don't even want to know where did he get them. (but really, I do

) I can't even imagine what would be possible with that and a 400V 30A 3ph outlet

With 10A you cannot do much, I would suggest the standard "2 MOT 4 cap" resonant circuit.
Do you have access to a three phase outlet?

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