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Registered Member #1656
Joined: Wed Aug 27 2008, 03:28PM
Location: Pittsburgh PA
Posts: 53
Hey all. I was playing around with a MOT running a 12vdc line to the primary to make a powerful electromagnet. Just low amperage from my power supply. Anyways, there are three coils. The primary, secondary, and a third coil that just under the secondary, but insulated with a clothish cover. I put current to the two wires coming out from the third coil (12vdc at 4-6amps). When I apply voltage to it, high voltage AC current comes out of the secondary. Enough to light up a neon sign. I'm just wondering....why is this happening. I didn't think DC current worked that way. Here is a video to show what is happening.
Thanks all for any information you can supply me :)
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
Because your power supply didn't die, I assume there is some sort of short-circuit protection built in, so it is probably causing current pulses in the winding (which is only a few turns, meant to power a filament).
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608
this is just pulsed DC which acts like dc. you can do this by running a wall wart transfomer backwards with a 9v and a nail file. It make "AC" out of DC current.
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
Does it go away if you put a resistor in series with the coil you are connecting to the power supply? maybe a power resistor of a few ohms to limit the current to something under the power supply's maximum output current.
If it goes away then it will be the current limiting like Sulaiman said, if not then it will probably be caused by high ripple voltage like kimbomba posted.
If it is ripple causing it then put a large electrolytic capacitor of a few thousand uF onto the output of the power supply to smooth out the ripple.
Other than that maybe this will become a thing now, using a high ripple supply as a quick way to drive MOT's!
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
dexter wrote ...
something like this for double the line frequency?
Lol, this will not work in any way. With the cap in place it will just charge to the peak input voltage and do nothing. If it is removed, the primary winding of the MOT will be saturated by DC voltage and trip the breaker. You guys should really learn some circuit / component basics
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Strange AC discharge with DC input on a MOT
