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# Re: Flyback and Q (fwd)

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From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Thursday, July 17, 1997 3:09 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Re:  Flyback and Q (fwd)

Hello Richard (Smit),

> From: Richard Smit <esmit-at-ilink.nis.za>
> To: tesla-request-at-pupman-dot-com
> Subject: Flyback and Q
>
> Hi,
>
> I only have two questions.
>
> 1. How do you calculate Q?

For a series-resonant circuit Q = (SQRT(L/C))/R  where R is the
Effective Series Resistance and is a monster to calculate because
it is comprised of wire resistance (modified by skin and proximity
effects), ground path resistance, radiation resistance, dielectric
losses in the coil former, core losses if a core is being used etc.
etc.  You normally measure Q and calculate R after the fact. To get
even close to an accurate measurement of Q for a TC secondary, it
must be totally isolated from its surroundings and the ground path
resistance should be zero. In practical terms, you can measure Q for
the situation in which it will be used (surrounded by all the normal
clutter). Under these conditions, Q will be considerably less than
the isolated value. This is measuring unloaded Q anyway.

> 2. What is the voltage and current of a flyback transformer

How long is a piece of string?

> 3. The EMF around a Tesla Coil, is it like a magnets magnetic field only
> much    weaker, therefore it doesn't attrack objects like nails to it or what?

It is oscillating and can be quite strong if the currents are high.

Malcolm

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