Re: [TCML] MOT Measurements

[futuret@xxxxxxx]

Bart,

Various NST's behave in various ways regarding resonant points with 
various
sized caps, etc.  Lou Balint of PA did some work on this a few years 
ago.
He wrote up a paper of his findings.  It's not on the internet though.  
In any
case it would seem that some resonant charging does occur using our
cap values in some cases, perhaps especially when the NSTs are
overvolted if I remember correctly.  It's been years since I reviewed 
the work
so I don't remember much about it.  I don't remember if he loaded the
transformers, I don't think he did.

John
--


-----Original Message-----
From: bartb <bartb@xxxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Mon, 12 Jan 2009 10:58 pm
Subject: Re: [TCML] MOT Measurements


Hi All, 
 
I hope I'm not boring you with this (I'm sure some are). But I think 
the next step is to look at a 15/30 NST which has not been modified. I 
have a couple on hand (Franceformers). I have a "gut feeling" that we 
really don't know where shunted transformers (NST's, MOT's, etc.) are 
truly at. Some resonant charging may or may not be occurring with our 
tank cap values. All the programs (including my own Javatc) are looking 
at Cres of non-shunted transformers. The shunted transformer is a 
different beast and without measurements, only guesses. 
 
These transformers force leakage inductance via the shunts to apply 
regulation.
This changes the transformer as we assume it to be as far 
as currents, voltages, Cres, etc. The load also changes the output. 
NST's will begin to suffer a voltage drop even with a small load. MOT's 
are current beasts, and they will require larger loads before 
significant change in output voltage is seen. Load impedance of shunted 
transformers is yet another set of tests that should be performed at 
some point. 
 
I'll run through my normal 10V increment routine with one of my 
15/30's. I'll set a variac to as near 10V as I can get, then measure 
the open and short circuit primary currents as well as open secondary 
voltage. Then head up to 20V and do all again. This is my routine as it 
keeps the source voltage unchanging, and thus, the numbers for Ioc, 
Isc, Vin, and Vout are all in very good agreement. My plan is to first 
do this unloaded (basic transformer testing). But loading is yet 
another issue. 
 
If anyone has any additional thoughts, please let me know. For the NST, 
considering it's low power, I can will also measure true power as well 
as VA. 
 
Best regards, 
Bart 
 
 
bartb wrote: 
> For an unmodified NST (shunts in tact), I expect Cres to be somewhat 
> near what we would expect (maybe), but Cres will change depending on 
> magnetizing current and current through the magnetic shunts. The > 
shunts have inductance with the AC
cycle, and as current is increased, 
> the leakage inductance is increased. The result is a rather > 
significant changing reactance dependent ultimately on the input > 
voltage, and thus Cres will not be a constant throughout a voltage > 
range (such as driving an NST with a variac). The impedance of a > 
shunted transformer is not constant with varying input voltages (which 
> is counterintuitive to non-shunted power transformers). 
>  
> Best regards, 
> Bart 
 
_______________________________________________ 
Tesla mailing list 
Tesla@xxxxxxxxxxxxxx 
http://www.pupman.com/mailman/listinfo/tesla ;

_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla