Re: MOT power supply

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jason Johnson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <hvjjohnson13-at-hotmail-dot-com>

Current limiting is not needed, but when running on small breakers may be
nice because it limits it down alot. To find out about how much current
you'll draw take the microwave output power double it and then take about
1.2 to 2 times that. The amount depends on the oven it came out of, the
transformer and what you are running on the other side. The ballast does
work well and is simply one (or more) MOTs run in series with the primary of
the two MOTs.

So if you have two MOTs that came from 450 watt ovens you will be able to
series these and run about 2000 va through them unballasted. Ballasted with
a third MOT this will be around 1000 to 1200 va. (these are rough
guesstimates based on some of the MOTs I have and will vary). The way you
hook them up is by placing the two primaries in parallel, attach the cores
together (unless you can easily remove the wire connecting one side of the
secondary to the core, and want to float or ground the cores) and put the
secondaries in series. You may need to reverse the primary connection of one
the transformers if you get no output. For the ballast transformer you just
short the secondary (just attach the secondary wire to the core, be sure to
attach it securely and remove any varnish where you attach) and place the
primary in sereies with the other two. You'll want to place the transformers
in an oil bath to help cooling and insulation, just be sure to use the
cheapest, non-detergent motor oil you can get. SAE 30 works well for the oil
and can be had for 74 cents a quart at Wal-Mart. I run two largish MOTs out
of 750 watt ovens for about 4800volts on a 120 volt 15 amp breaker with over
five foot of spark. These are damn near indestuctible, cheap, and give great
performance (they also regularly trip the breaker when on full power).

Jason Johnson

----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, January 01, 2001 2:29 PM
Subject: MOT power supply


> Original poster: "Christopher Telford by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <christophertelford-at-yahoo-dot-com>
>
> Hello All,
>
> I am considering using two MOT's to replace my 450W
> NST power supply. I have heard that two MOT's can be
> put in series to gain 4000V, and that this is enough
> for a Tesla coil. If this was done would current
> limiting be needed? I don't have access to a variac so
> i can't use that. Would a third MOT work? Any help
> and/or diagrams would be very much appreciated.
>
> Thanks,
>
> Chris Telford
>
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