7 inch arcs from modified MOT - im happy / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

7 inch arcs from modified MOT - im happy

1 2 next

Move Thread

LAN_403

dmg

Sun Jan 17 2010, 06:07AM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

here's some pictures of a mot, the shunts and filament winding are removed, as well as the bottom mounting plate,
(trying to elliminate core losses as much as possible). as a size reference, the wood post terminal is about 6 inches
tall. on a side note:
PFC cap of 5Î¼F is on the mains,
6kv 0.33Î¼F capacitor on the secondary,
running from a standard house mains (15-20A).
core doesn't saturate too much now.

eniyuki

Sun Jan 17 2010, 07:03AM

Registered Member #2148 Joined: Tue Jun 02 2009, 02:22AM
Location:
Posts: 62

do you have schematic diagram? can you measure current draw? im afraid to test mine cuz the CB might pop. but someday i will try it.

dmg

Sun Jan 17 2010, 07:21AM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

you do not need to worry about your breaker "popping" it is resetable, also, the wiring is not too complicated;
it is a motor run capacitor (370V 5Î¼F) in parallel for mains (power factor correction)
the secondary's tap is connected to the arc stick (the thing i'm holding)
and the core ground is connected to 3 Microwave capacitors in series (rated 6kv at 0.33Î¼F)
the breaker WILL trip if you hold an arc for too long, as the core slowly becomes saturated.
also you might benefit running this on a 20-30A outlet (do as I say not as I do).
I usually dont run my MOTs with current limiting, but if you run more then 1 MOT you might
want to consider either air cooling or mineral oil submersion or a resistive or inductive ballast
I lost a mot before to primary overheating, the secondary usually stays fairly cold.
sanding away the laquer on the sides of the transformer makes the core a bit colder and will
disapate more heat, if you choose to do this, be carefull not to damage the primary or secondary coils.
hope this helps.

eniyuki

Sun Jan 17 2010, 07:47AM

Registered Member #2148 Joined: Tue Jun 02 2009, 02:22AM
Location:
Posts: 62

if i have 30A CB, all outlets in the house is 30A also? or did you run this directly on 30A CB?

dmg

Sun Jan 17 2010, 07:56AM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

no, in my setup (originally i just wanted a picture for a desktop) i was running this off a standard 120V 15A outlet,
commonly found in households, typically, high amperage outlets are found in garages, along with 240V service, what i suggested though, was to run it with a 30A service rather then 15A because if you have sufficent cooling, you can draw an arc for longer periods of time, usually for 1 mot (unmodified) a 20A breaker is more then enough to handle the current draw. like I said before, your main concern is the MOTs overheating,
MOTS are usually rated to opperate at 200 degrees C but the longer you draw an arc, the more your primary
will heat due to resistance.

also never run a 120 mot or a 240 outlet, the saturation will most likely kick your breaker immediately.

as of current draw, I recomend using Power factor correction, as it makes your load (MOT) behave like a resistive load rather then inductive, allowing you more time before kicking your breaker, you can put power factor correction in parallel with mains, if you do not have a capacitor for that, you can put microwave oven capacitors in series with the HV secondary, this will partially correct the power factor and if your value is right, induce resonance, which means bigger arcs.

just my 2 cents.

eniyuki

Sun Jan 17 2010, 08:03AM

Registered Member #2148 Joined: Tue Jun 02 2009, 02:22AM
Location:
Posts: 62

ok thanks, will take care of my mots! will be running 2 mots in series with voltage doubler as my PSU in dc resonant tc

dmg

Sun Jan 17 2010, 08:08AM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

thats cool, I too am working on a DC resonant coil, it has a mot setup 180 degrees out of phase (assuming they are wiring core to core) like yours and will eat up about 2KW, I am almost done building my fancy-shmancy PLC controller and will utilize and ARSG controlled with PWM, it still has ways to go though, anyway good luck with your MOTs.

note: when collecting mots, try not to get caught by those who threw out the microwave....awkward situation.

Dr. Dark Current

Sun Jan 17 2010, 09:39AM

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

hm, 0.33uF cap? In parallel to the secondary?

If you leave the MOT alone and put 2-3 paralelled microwave capacitors in series with the HV output, you can probably draw over 10" from one MOT.

dmg

Sun Jan 17 2010, 04:35PM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

no, the HV 0.33Î¼F capacitor is NOT parallel with secondary, it is in SERIES, there is a 5Î¼F 370V capacitor in parallel with the incoming mains though, for Power factor correction. (this is my setup)

the 0.33Î¼F cpacitor bank is made out of microwave oven capacitors, 3 X 2000V at 1Î¼F resulting in a 6000V 0.33Î¼F bank.

also i tried the capacitor setup before and after modifing the MOT, the arcs are bigger with the mot modified the it is without modifications, not by much though, probably and inch or two.

Dr. Dark Current

Sun Jan 17 2010, 05:29PM

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

Here is what I got from 2 MOTs and 6 microwave caps:

(its in the bathroom because the mains socket there is connected to a more powerful breaker).

How long can you run it before overheating? exactly how is it connected, 3 caps in series with the output? I got no arcs that way, even with an unmodified mot.

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob