[Prev][Next][Index][Thread]
Re: (Fwd) Re: Formula for self C of a Coil (not Medhurst)
Tesla List wrote:
>
> Original Poster: "Malcolm Watts" <malcolm.watts-at-wnp.ac.nz>
> All lines I tried were seven section (h'ware limitations). This is the
> model that I submitted to the Corums for their consideration.
> However, I now think that this model is not valid as it would
> exhibit a phase shift of 90 degrees between the input and output
> voltages. ?? (Can someone with SPICE running please give it a whirl?)
> Reason - it lacks the turn-turn coupling of the real thing.
The 90 degrees difference between the input and output voltages at
the resonances only appear because there are resistive losses in the
system. With an ideal lossless coil, no matter if lumped or distributed,
the phase difference between voltages at any points can only be 0 or
180 degrees. If you observe the phase difference between voltages at
the bottom and top of a coil with a signal generator
connected to the bottom of a coil, as you vary the frequency you see
a series of notches at the input side and a series of simultaneous
maxima at the output side. At each one the phase difference between
input and output crosses 90 degrees in a small frequency range, while
changing between 0 and 180 degrees. At the limit case of a lossless
coil, the notches would go all the way to 0, the maxima all the way
to infinity, and only 0 or 180 degrees phase differences would
be observed.
Antonio Carlos M. de Queiroz