Jack, I'm happy there are people on the list which have ideeas and
experience. Definitely you are one of them. When I have posted the
question I have already playing around this methode. It has the greatest
disadvantage of a fast inductance saturation with the active signal and
an important changing of the Q factor. I haven't solved yet the
isolation between the control winding and the signal. Even I'm using a
high output impedance constant current generator the control is killing a
large part from the signal output. Probably I need a filter which will be
huge...

thank you,
Vasile

BTW, your name remains me about two persons: a writer (Jack London)and
a killer on the London bridge :)
thank's again !


On Wed, 13 Aug 2003, Jack Smith wrote:

> One way I've seen an electronically variable inductor designed is to put a
> DC control current through an extra winding. The control current moves the
> operating point up or down on the B-H curve and thus changes the inductance.
>
> This technique has advantage of being fast and inexpensive, but may not give
> you the control range you need. It may also cause change Q with L, which may
> or may not be a problem for your application. You also may need to
> experiment to find an appropriate core material.
>
> Of course the DC control voltage must be fed through an isolating choke, or
> else it will look like a shorted turn to the 1-25 KHz signal.  If you are
> using a toroid inductor, you can wind the magnetizing control winding on the
> outside of the toroid, so that it is isolated from the internal signal.
> Sort of like this:  (((o))) where the o is the toroid core with the windings
> made in the normal fashion where the flux is constrained within the core,
> and the ((())) represents a control winding made around the outside of the
> core.
>
>
> Jack
>
>
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Vasile Surducan
> Sent: Wednesday, August 13, 2003 7:42 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [EE]: my chalenge: 2KVrms sinusoidal in 1...25KHz range
>
>
> I need to generate 2KVrms into a small capacitive load (below 1nF).
> So far I have good results with a resonant output, voltage to current
> converter. The problem I have is that I need a precise way to control
> the generator output inductivity (other than changing the coil wires
> numbers or the air gap in the ferrite core) to cover the whole frequency
> range. Do you know other methodes to get such high voltage in the
> frequency range required ?
>
>
> top 10 wishes,
> Vasile
> http://surducan.netfirms.com
>
>
> On Wed, 13 Aug 2003, Wouter van Ooijen wrote:
>
> > > However, even though I have inserted the guards into my
> > > header files as above, I am still getting multiple
> > > definition errors relating to globals that are defined
> > > within those header files.
> >
> > Global what's? Variables? A variable in a .h file should in most cases
> > be declared external, and only appearing in one .c file as not external.
> >
> > Wouter van Ooijen
> >
> > -- -------------------------------------------
> > Van Ooijen Technische Informatica: www.voti.nl
> > consultancy, development, PICmicro products
> >
> > --
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