Re: transformer measured L, etc.

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

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

Hi Jim,

On 3 Feb 2003, at 18:33, Tesla list wrote:

 > Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
<jimlux-at-earthlink-dot-net>
 >
 > It occurs to me that for an idealized transformer, you can measure just the
 > open circuit inductances to get the turns ratio.  Both windings have
 > essentially the same core, and in most power transformers, the windings are
 > reasonably compact, so the inductance will be proportional to the square of
 > the number of turns.
 >
 > Therefore: N2/N1 = sqrt(L2/L1)

For ideal, yes. But none are ideal in practice. The test frequency
must be well below any self-resonant frequencies present and from
experience, I advise placing a signal voltage source across the
winding with the higest inductance to de-Q the transformer as much as
possible.

Regards,
Malcolm