High voltage MOT VS flyback whats more dangerous?

Discussion in 'General Electronics Chat' started by electronis whiz, Apr 28, 2015.

  1. electronis whiz

    Thread Starter Well-Known Member

    Jul 29, 2010
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    I'm just kind of curious about this. I can't say I've heard of anyone getting a zap from either, but curious if you dealt with these what would you be more scared of.

    MOT make like 2KV at like 1A a flyback will make 25KV at a couple hundred MA. I understand both are dangerous, but it seems some people that mess with flybacks seem to think you would get more an RF burn than a real shock.

    The oddest thing I find with this is based on ohms law it would seem that something that put out 25KV would have more amperage than something that put out 2KV. I suppose it depends on the wire losses and other design factors possibly.
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Flyback has very poor current regulation. So more is a burn and a nasty shock. I get these every now and then.
    MOT can kill you. I am not saying flyback can't kill.
     
  3. dl324

    Distinguished Member

    Mar 30, 2015
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    High voltage at low current is less dangerous than high voltage at high current.
    Ohm's Law doesn't apply to current or voltage limited situations.
     
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
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    flybacks "Q" is reduced under load, and it puts out less power. that is what makes them less
    reulated. also, rf from flybacks is at higher frequency, and skin effect is higher.
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    If both supplies have adequate current outputs and if all of the wiring is sized to prevent affecting the results and if the resistor is big enough, then yes, a 25 kVDC power supply will push 12.5 times more current that a 2 kVDC power supply would in the same resistor. But that has nothing to do with what happens with high voltages contact skin. 25 kV hurts - a lot. But I would not want to tangle with 2 kV at 10 times the power level.

    ak
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
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    The microwave oven transformer can shift its 2kV at around 500mA - your very own common or kitchen "Old sparky". The voltage doubling rectifier doubles as a current limiting source - but still lethal!

    You could probably do a solid state CRT TV as much damage as yourself if you shunted the final anode cap with your hand.

    With a valve horizontal output type flyback - you could probably make the horizontal valve anode glow red - but you probably wouldn't be paying much attention by then!

    Way way back before flyback EHT; the EHT came from a big fat winding on the mains transformer - similar lethality to a microwave transformer.
     
  7. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    It also depends greatly on how each transformer is driven. A mains transformer draws its current directly from mains, which is only limited by your fuse/circuit breaker (and your transformer's insulation). MOTs do not have any built-in current limiting features, meaning if they are shorted, they will continue to draw more and more current from mains until either the breaker trips or the insulation burns out. This means it can deliver far more than one amp if given the right conditions. Flyback transformers are generally driven by batteries or small DC-powered oscillator circuits. There is a lot more circuitry between a flyback transformer and mains, and the output current is going to be limited. I can tell you first-hand that the output of a flyback transformer hurts like the dickens, but I don't think there's anyone in the world who's felt a zap from an MOT and is still alive to describe it.
     
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  8. electronis whiz

    Thread Starter Well-Known Member

    Jul 29, 2010
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    Now that you say that I have seen that on youtube. Photonicinduction did something with a microwave seems like dumped like 480 into it instead of 220. Transformer started smoking then burst into flames.
     
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  9. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Yep, I have seen that one as well :p
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
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    There was a science abuse programe that did much more fun things with microwave ovens.

    One show did an assortment of alcoholic drinks still in the bottle/can etc.

    The bottle of champaign blew the whole microwave metal casing open like it was a soggy cardboard box.

    They set up a portable generator so they could do it in the middle of a field - the camera crews used telephoto lenses so they were out of range of the shrapnel.
     
  11. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Owing to (low) frequency and (high) current availability, MOTs are, in all cases, extremely dangerous...

    That said, the potential shock, even electrocution, hazards of flyback (case in point LOPT) circuits should not be dismissed - especially where resonant and/or current-mode drivers are employed! --- Moreover a significant hazard is presented by unintentional or unwitting coupling of high current to the HV winding/output (as is the case, for instance, in flybacks wired as 'auto-transformers' --or-- via arcing or other leakage to the primary [or other source of high current]) -- the latter consideration being the rationale for inclusion of 'strike rings' in HV demonstration apparatus...

    Please be advised that a few tens of milliamps may be lethal (via. ventricular fibrillation) -- 40mA being generally regarded as the 'LD50' (if you will) --- although the pronounced 'skin-effect' attendant to the LOPT circuit's (relatively) high operating frequency offers a greater margin of safety, it is folly to wager your life on same...

    All of which is to say: good safety habits are essential even, (and, indeed, especially) where their necessity is equivocal!!!

    Best regards and be safe:)
    HP
     
    Last edited: Apr 28, 2015
  12. James Wang

    New Member

    Apr 28, 2015
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    Just wondering how that works out finally.
     
  13. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Are you referring to my 'running' edit of my response? --- Well ya see it's sorta like the US congress -- I've gotta post it before I get to see what's in it!;););)

    Best regards
    HP:D
     
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