The phase relationship between voltage across and the current thru a true
inductor is always
90 degrees. It may be less due to series resistance in the inductor but in
an High Q inductor it should
be very close to 90 degrees.
Phase angle depends on your reference. It always takes two signals to
establish phase.
And in your case one is the anode and not the voltage across the inductor
itself.
Perhaps this will help clear some of the confusion.
73
Bill wa4lav
At 10:41 AM 3/3/2003 -0500, Tom Rauch wrote:
> > Mr. Rauch -- 80% of 4000V = 3200V. 90% of 4000V = 3600V. What's the
> > problem with 3500V?.
>
>Your normal diversion is to lift things out of context. The rest of my
>answer explains the difference.
>
> > >which would translate to 3kV or more across the tank inductance.
> > >The exact value depends on tank loaded Q, which sets phase shift across
>the
> > >inductance. Q's of 10-12 result in about 130-degree shift,
> >
> > And I thought the phase shift in an inductor was 90?.
>
>You thought wrong.
>
>Phase shift depends on reactance and circuit impedances. A series inductor
>only causes a 90-degree shift when the load impedance is zero and the
>inductor is infinite in value.
>
>In a pi-network tank system we have shunt capacitive reactances at each end,
>and a series inductance. The ratio of those reactances and the termination
>impedance of the network determines the phase shift. It is 90-degrees in a
>minimum Q network that matches two impedances, because the network behaves
>like a 1/4 wl transmission line with a surge impedance equal to the
>geometric mean of the load and source impedances. The same formula that
>would apply to a 1/4 wl transmission line applies to the CLC or LCL system.
>
>In a pi, that is behaving like a pi, the network is two back-to-back L's.
>This allows us to set phase delay over a wide range when matching two
>impedances. There is no difference in talking about phase shift or Q. Either
>one can be translated into the other.
>
>This is why some engineers baffle people by speaking about phase shift in
>tanks. They are really describing Q.
>
>Thank goodness things work the way they do, and not the way you thought
>Rich! We would be in big trouble designing tank circuits and variable phase
>shift networks!!
>
> > >http://www.w8ji.com/demonstation.htm
> >
> > "In a 3000V PA stage, this would be 10,000V peak! It should make sense
> > that amplifiers arc from grossly excessive drive power." -- Tom Rauch.
> >
> > - ... but it doesn't. In a worst case test with a SB-220 (a 3000V
> > stage), the max peak V across the Tune-C was 3500V - which is c. 100V
> > from flashing over. The idea of overdrive producing triple V does not
> > make sense since 3-500Zs are emission limited.
>
>Once again you totally miss a very important point.
>
>The capacitor and other components limit the peak voltage, not the tube
>emission. A tank is an energy storage system. Unless something removes
>energy at a rate faster than which it is applied, the voltage and currents
>will increase.
>
>Even a very small low-emission tube could build up extreme voltages if
>nothing is draining off the stored energy faster at a higher rate than
>energy it is being added.
>
> > >You'd better insulate appropriately for worse-case conditions, which is
>the
> > >maximum breakdown voltage of the tank tuning capacitor times at least two
>or
> > >three or whatever other component limits the peak voltage under a fault
> > >condiution.
> >
> > Kenwood used a 6000V Tune C in the TL-922 and the Tune-C does not protect
> > the 5000V bandswitch from arc-over. Kenwood apparently sells a heap of
> > 922 bandswitches.
>
>Yes, and the reason is explained in my web site. Your idea that emission
>limits voltage is wrong. It is breakdown of some component, causing that
>component to consume the excess energy, that eventually limits stored energy
>in a tank. Either that or the system reaches equalibrium before a failure
>occurs, becuase there is something loading the tank (like an antenna).
>
>This is all explained at:
>
>http://www.w8ji.com/Vacuum_tube_amps.htm
>
>where I walk through the PA system step by step.
>
>73 Tom
>
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