From:  David Dean [SMTP:deano-at-corridor-dot-net]
Sent:  Thursday, April 09, 1998 3:45 PM
To:  Tesla List
Subject:  Re: diode

>From:  Sulaiman Abdullah [SMTP:sulabd-at-hotmail-dot-com]
>Sent:  Thursday, April 09, 1998 11:09 AM
>To:  tesla-at-pupman-dot-com
>Subject:  Re: diode
>>From:  David Dean [SMTP:deano-at-corridor-dot-net]
>>Sent:  Wednesday, April 08, 1998 11:01 AM
>>To:  tesla-at-pupman-dot-com
>>Subject:  diode
>>I picked up a diode
>> So- does anyone know what it is?
>>What are the specs?
>>On another note:
>>I'm planning to make a new secondary for a microwave oven
>>transformer. The present sec. is shorted. I have cut the core
>>apart and removed the windings. The present sec. is wound of 25
>>gauge wire and has approx. 1369 turns (calculated). Another MOT
>>of the same size (both have a label that says Warning 4000 Volts!)
>>measures 1.8kv on the output of the sec. Both primary windings
>>are 13awg and have the same dc resistance with a DMM. The second
>>MOT sec. is wound with 26awg and has a calculated 2725 turns.
>>I got some 32awg magnet wire surplus and am going to try to put
>>as many turns on this thing as  I can...My question is- if I insulate
>>very well, and install an arc shield of .020 copper sheet between
>>the pri. and the sec. can I leave out the shunts? This would give
>>3/8 inch extra width for the sec windings. More turns = more volts!
>>Shooting for 7.5-8kv-at-150ma or better. the core and pri are rated
>>1kva with margin left over.
>>Any thoughts?
>My thought (one a day is enough strain!)...
>If you remove the shunts then you will have no short-circuit
>protection at all, and resonant charging will not work.
>I'd leave the shunts in place!  bye ... Sulaiman
AS far as short circuit protection is concerned, the volt-ampere rating of
transformer is greater than that of the circuit supplying power, ie 125vac
circuit breaker. (I'm talking here about the max. safe current rating of the
in the windings.) When I short the sec. on a non- modified MOT plugged into
125V outlet with a 20A breaker the pri. current pegs the needle on my
ammeter on the 40A scale for about a second then the breaker trips.
when people bring in microwave ovens to be repaired the complaint is "when I
the start button it just trips the breaker". Usually in such a case the
problem is a
defective diode which in effect grounds the output terminal of the
So I am not concerned with that.
The point about resonant charging- as I understand it you get resonant
when Xc = Xl ; that is when the output impedance of the transformer is equal
to the
impedance of the capacitor in this case at 60hz. Since Xr is "assumed" to be
neglegable, and Xc and Xl are 180 degrees out of phase, the resultant Vo
would be
2*Vin. Of course in real life there is always some resistance so it never
gets that high
but...sometimes close. I would expect to have to use some type of current
limiting in
series with the pri. as they do with distribution transformers, potential
transformers, etc.
Perhaps I'm missing something?