Re: determining transformer characteristics

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Mark,

On 18 Jul 01, at 12:58, Tesla list wrote:

> Original poster: "Mark Broker by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<broker-at-uwplatt.edu>
> 
> List,
> 
> Although my uses for this information is not directly related to Tesla
> Coils, the information IS directly useful to TCs.
> 
> Without the aid of a Henry meter, I would like to determine the inductance
> for a tightly coupled transformer.  I've run across an excellent paper on
> the Net that explained how to calculate the inductance of an NST.  This 
> proceedure involved shorting the secondary while mearsuing the primary
> current.  On a loosly coupled transformer, like an NST, this proceedure
> works sufficiently well.  On a tightly coupled transformer (PT, pig, high-
> power MOTs), this proceedure won't really work.  Is there a way (without a
> Henry meter) to find the inductance of a tightly coupled transformer?

Which inductance? Primary, secondary or leakage? 

Primary: energize without the secondary connected, measure the 
primary current and calculate L from the Xl figure you get by: Xl = 
V/I
Secondary: can be done the same way as long as the pri-sec turns 
ratio => 1
Leakage: a bit more tricky. If the transformer is tightly coupled 
there won't be much of it which is why the NST procedure won't work 
and also why you need an external ballast for this type of 
transformer.
 
> Also, can anyone hazard a guestimate as to the coupling coefficient of a
> 500VA, 2:1 toroidal transformer?

About 0.99

Regards,
Malcolm