[time-nuts] Maser 0.7 nsec jumps solved

Gerhard Hoffmann dk4xp at arcor.de
Wed May 25 23:25:26 UTC 2016


Am 25.05.2016 um 18:59 schrieb Mike Monett:
>
> This analysis shows switching at 0V is the best option.
>
No, it doesn't. :-)

First, the single inductor does not represent a transformer; the second 
inductor
and the coupling declaration ( style: K1 L1 L2 0.99 or so) and the load are
missing.

The most important thing is that the Inductor is nonlinear which is not
represented in the model. If there has remained some magnetism in
the core from previous operation, the transformer won't be able to further
increase the magnetism as needed to induce an opposing voltage
in the primary winding. When the core saturates, the inductance
collapses and leaves only the copper resistance to limit the current.

The catastrophe builds up in the first 90 degrees of the source wave,
not right at the start.

In the simulation, the current at t=0 is at its maximum already when at
t=0 the input voltage is just switched on. You'd expect that from a
capacitor, never from an inductor.

The reason is that the simulation does not really start at t=0, but
much earlier. The simulator computes the conductance matrix,
applies the initial sources and waits until everything has calmed down.
That may require repeated recalculation of the matrix to respect
nonlinearities.

Your circuit must contain hidden resistors btw, otherwise the computation
of the initial condition at "t<=0" would result in numeric overflow
as required by an assumed initial DC voltage across an inductor, before
the transient simulation.

One can enforce initial conditions with statements like  .IC v(my_node) = 0V

regards, Gerhard


BTW I've got the first 20 pcs. of the VCXO carrier / voltage regulator /
lock to reference / squarer / iso amp or frequency doubler / 1pps board.
That won't be soldering for beginners or jittery hands.  :-)









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