New to MOT's how to configure for some arc's? / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

New to MOT's how to configure for some arc's?

Move Thread

LAN_403

Sparkie

Mon Jul 07 2008, 11:16PM

Registered Member #627 Joined: Thu Apr 05 2007, 04:05PM
Location: London
Posts: 32

Hi all...

OK, i've played with NST's, jacobs ladders and ZVS Flyback circuits etc, but not yet tried anything with an MOT.
I managed to get an old 530w microwave, and would like to use the transformer to draw some arc's. I tried to search the forums for 'MOT' but it wants at least 4 characters so its a bit hard.

So, im looking for information on how to configure this simply to get some arcs or run a jacobs ladder from it.

So, I am wondering..

a) what im able to use as a ballast. Can I use a light bulb (500w or so) in series with the primary?

b) Do I use the HV cap thats in here in series on the secondary?

c) As one side of the the secondary is earthed, do I draw arcs against this (maybe obvious lol)

d) There is a rectifier diode going from the cap to ground. Do I remove this?

There is a schematic of the whole microwave inside the case, so I have taken a pic of the transformer section if it helps...
And some pics of the transformer and cap.

Cheers for the help! John.

Microwave Schematic

Myke

Tue Jul 08 2008, 12:54AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

You can start with the light bulb in series with the primary but don't expect huge arcs. You can get another MOT and short the secondary and it can be used as a ballast (connections are made to the primary). The leakage inductance from the shorted MOT should limit the current enough. You don't need any of the other components in this setup. I would save them if I were you though because they can be useful in the future.

Billybobjoe

Tue Jul 08 2008, 01:00AM

Registered Member #396 Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176

a) A 500 watt bulb would be good. You say this is a 530 watt MO so ballasting probably won't be necessary for "breaker tripping" prevention purposes, but will keep your MOT cooler. Personally I would try it for a short time without one and see how hot things get or what kind of current it draws.

b) You do not need to use it but it with others can be used for a resonant setup (search "resonant MOT").

c) Yes, connect the earthed side to your ground on the power coming in and draw arcs off of it (make sure it is large wire, preferable carbon or something that won't melt as easily).

d) Remove it unless you plan on modifying the arrangement and using the DC output or setting up a doubler arrangement like in the oven

EDIT - ahh, Myke beat me to things . . .

Ultra7

Tue Jul 08 2008, 04:26AM

Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307

There is always our HvWiki over on the sidebar to your left.
It has all kinds of useful info, even some on MOT's.
Try this link.

quicksilver

Tue Jul 08 2008, 03:27PM

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

Myke wrote ...

You can start with the light bulb in series with the primary but don't expect huge arcs.

I agree with Myke; a single MOT, alone is just not all that impressive for drawing an arc, making a little Jacob's ladder, etc. But here is where the other experiments can help if you care to get creative. I saw your picture and I even think I recognize the type of MOT you have. It's got quality windings and I personally would keep that one and get another less well-made one to short or alter. But my point here is that IF you can get others or parts you can have some choices to develop a voltage multiplier, etc. You have 60Hz output so the use of the original caps keeps things simple. If you've experimented with making Jacob's ladders you can make some in unique shapes for the arc to follow. Just my opinion but the higher current level seems to hold that arc through turns that a NST will drop off at.

Sparkie

Tue Jul 08 2008, 08:43PM

Registered Member #627 Joined: Thu Apr 05 2007, 04:05PM
Location: London
Posts: 32

Many thanks for the replies guys! So, heres what ive came up with...

I tried the 500w bulb as a ballast, and yes, it was pretty tame. So then I put a fan heater in line, that has a choice of low and high (1kw or 2kw). 2kw produced some nice arcing, so then I had the 2kw heater, and the 500w bulb as a ballast, and it worked ok. Transformer got quite warm after 10 mins of playing, but I think it will be ok once you dont run it constantly for ages!

So, I made a small video to show you what I achived with your help: http://www.youtube.com/watch?v=jIEAh8ruha8

I kept all the bits from inside, platter motor, fan, cap, I even kept the magnetron, dunno why

Thanks for all your pointers, and i'll update you with any further progress, such as when I get another MOT ;)
I haven't tried the cap in series with the secondary yet. Would this be safe? its a 0.92uf 1800VAC cap.
And quicksilver yes, it might be pretty good quality, its from an old microwave, stamped 1987! And the transformer says 'made in UK' hah, thats rare enough nowdays! Oh, im in UK so have 240v mains @ 50Hz

Cheers, John.

Myke

Tue Jul 08 2008, 11:12PM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

It wouldn't resonate so I think it would be fine to put the cap there. 1800VAC? They usually are rated at 2000VAC or 2100VAC right? All of mine are...

The fan is a good source of magnet wire and the magnetron is good for the big magnets in it.

In the link in my signature, there are videos of MOTs with and without resonant caps and one video of a MOT with a resistive ballast.

Dr. Dark Current

Wed Jul 09 2008, 07:33AM

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

Myke wrote ...

It wouldn't resonate so I think it would be fine to put the cap there. 1800VAC? They usually are rated at 2000VAC or 2100VAC right? All of mine are...

It wouldn't resonate so I think there is no sense in putting it there

Really, you can try it, but you'll pobably get just little sparks. With two parallel caps is where the magic begins.

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