[time-nuts] Maser 0.7 nsec jumps solved

Andy AI.egrps+tn at gmail.com
Wed May 25 23:13:19 EDT 2016


On Wed, May 25, 2016 at 12:59 PM, Mike Monett <timenuts at binsamp.e4ward.com>
wrote:

LTspice shows  switching  at 0V is the best point in  time.  ...



Bzzzt!  Your simulation is seriously flawed, and your conclusions are
wrong.  What you forgot, or may not have realized, is that SPICE's initial
transient solution is obtained by having the signal sources already turned
on (at the moment of the Big Bang) and set to their initial value, so the
current through L2 is limited by DC conditions.  That is not anything close
to switching the driving voltages on.  It is having one waveform sit at
+169.7V DC for a very long time ('forever'), and then letting it follow a
cosine wave.

Re-run the simulation with "UIC" added to the .tran statement (.tran 50ms
uic) and see what it shows.  Using UIC forces the initial voltage to be 0V
at time=0, the start of the simulation.  That's like having the switch
initially open.

Or if you don't like that, multiply the sources by a PWL waveform that
starts both voltages at 0V and then switches them on, a few milliseconds
into the simulation, with the appropriate phase.

Or use an actual switch.  LTspice has a switch element you could use.

I guarantee you, the case with the voltage switching on at the 0V point in
the voltage waveform, causes greater currents.

The smaller surge current happens when the source is connected at the
moment when the current i(t) would be 0A if it were a continuous waveform.
For an inductive load, this happens when the voltage v(t) would be +/- peak
(or near peak, for a real load which has both inductance and a little
resistance).  This condition also results in no surge, thus no L/R decay.

All of this might not be relevant to a mechanical system, where surge
current is caused by rotational inertia, rather than anything electrical.

Regards,
Andy


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