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Registered Member #5208
Joined: Thu Jun 07 2012, 06:12PM
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Posts: 86
One more thing, can I glue the MOT core after dissassembling it with some strong glue, or epoxy? I know it should be welded, but maybe glue/epoxy will work too?
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
If you are making a ballast out of it, you must reassemble it with an air gap and use some kind of a clamp. If you still intend to use it as a transformer, then I would not even disassemble the core because the air gap after reassembling will always be bigger (and the no-load current which is already huge will increase). Also the MOT almost always hums or buzzes after reassembling...
Registered Member #5208
Joined: Thu Jun 07 2012, 06:12PM
Location:
Posts: 86
Yeah it hums alright, when I said noise I ment the sound when you draw an arc out of it. It just sounds mean, lol. Also, I noticed the primary is smaller than on my other MOT which is rewound. That means it has lower power, yes? I will remove the secondary, but how to do it quickly? The space between prim and sec coils is relatively small, any way to get rid of it without damaging the prim coil?
By the way, when shorted, the ~22volt MOT shakes like ballerina on ecstasy. I never saw MOT do it with original windings when shorted.
Registered Member #3343
Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311
Zippo !
The info from Dr Dark Current , Steve and KugleSmith are really usefull / valuable.
MICROWAVE TRANSFORMERS (MOT) works very well as a ballast. Typical homemade simple MOT ballast with mimimal modifications give you a 4 to 40 ohms (0.01H to 0.1H) using a 120V 60 Hz primary winding of 125 turns. As your MOT primary is 230V rated (+- 250turns), the expected reactance will be 16 to 160 ohms.
The secondary may or not may be removed. (I recomend remove, because the hi voltage that will appears ate sec is dangerous , and guive you more space inside steel core for more turns. As Steve said you may add a second piimary coil gettng a higher reactance.
You will separate the E core block of the I core block using a hand hacksaw making a 3mm deep cut along the block weld easy, it will take 20 minutes... It is a surgical incision that requires pacient and precision!
Take care with the E and I blocks to avoid the laminated sheets lost fron the blocks, keep it as a block. Close again the core, as it was before the surgical work,
WITHOUT the above separation ( no space between the E and I ) you have 160 ohms reactor, with 2-3 mm separation between the E block and the I block you get 16 ohms ballast. The separation may be done using fiber or cardboard all along the I core .
You may clamp the I and E using 4 bolts 100mm long by 3mm and using the BASE PLATE that are welded to the MOT tranformers. In this way, no noise after clamped.
By the way someone has a good sketch for assembling the I and E air gap to work as a adjusting reostat ?
Registered Member #3343
Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311
Hi, I was wondering if I could use a MOT PSU (currently 22 turns of 18AWG wire,230V) as a ballast for another MOT with secondary intact. If yes, how to do it?
I thik your primary have 220 to 250 turns, for good induction of 1.7~1.8T at 230V...
Registered Member #5208
Joined: Thu Jun 07 2012, 06:12PM
Location:
Posts: 86
Thanks for detailed info Newton, I will try it today . I have unrelated question though. What would happen if I would parallel few mosfets or igbts in a ZVS and feed it with rectified mains? Would a standard flyback stand it?
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Depends where you live, if in a 120V land you can use 1200V IGBTs. The problem with IGBTs in a "ZVS" driver is their saturation voltage, because of this the other transistor can partially turn ON while it should be OFF and produce a lot of heat. If you live in a 230V land, you would need to use >1600V transistors, which have such a huge saturation voltage that the driver would probably not work properly without modifications. And of course I'm not mentioning redesigning the primary circuit (increase of turns, decrease of tank cap size etc)
Registered Member #5208
Joined: Thu Jun 07 2012, 06:12PM
Location:
Posts: 86
Hm, so a MOSFET would be better idea? Supposedly they're faster, but I never saw a MOSFET with >1600v ratings. I remember someones vid on youtube, he kicked his ZVS to more than 2kW. If I remember well he used several IRFPs250.
Registered Member #5208
Joined: Thu Jun 07 2012, 06:12PM
Location:
Posts: 86
Since I don't want to start a new thread or pester other users via PM's I wanted to confirm if I connect all the stuff correctly. My aim originally was 8kV but quad stack doesn't seem to work. Probably phased something wrong. All I got was static like "arc". Pic- .Click "Continue to the media".
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Quick MOT question.
. I have unrelated question though. What would happen if I would parallel few mosfets or igbts in a ZVS and feed it with rectified mains? Would a standard flyback stand it?
