[Milsurplus] LM-18 and AC PS Questions.. More

[J Forster]

All well and good, but the early CQC-23ACP Power Control Boxes have three
toggle switches that select additional capacitors in parallel with a main
series capacitor in the 800 CPS power line.  The reactance of the generator
is not going to change, except possibly for an increase in the real part
with temperature as the winding heats up.

Front panel toggle switches, within inches of the switch controlling the
transmitter,  and a voltmeter clearly imply to me a need for OPERATIONAL
adjustment of the settings.  There is also a caution in the manual not to
exceed 125 Volts because of possible capacitor damage.  Why would that
caution be in the manual if the operator could not DO something about the
voltage, other than shut off the radar? It seems to me the capacitors are
intentionally used to alter the input voltage to the set by selecting a less
than optimal value.

Later versions of the Power Control Box have neither the switches nor the
capacitor and the meter seems to have been deleted even later in the war.

FWIW,
-John



Mike Hanz wrote:

> brunneraa1p at comcast.net wrote:
>
> > Think of the generator as a perfect generator with a series reactor,
> > and the carbon-pile regulator regulating the field current to maintain
> > the output voltage. As the load increases there is voltage drop
> > through the series reactor which must be compensated by raising the
> > generator voltage. When maximum possible generator voltage is reached,
> > voltage output will unavoidable drop with increased load, as it cannot
> > be compensated. The series capacitor neutralizes the generator (mostly
> > armature) reactance, eliminating the reactance voltage drop, and
> > greatly increases generator output at rated voltage. This is mostly
> > load-independent, and definitely not for line voltage adjustment. All
> > this, and carbon pile adjustment, is on Mike Hanz's web site, but I
> > can't find it just now...
>
> Excellent description of the process, Richard.  The documents are under
> docs  :-)   at the bottom of the left column at http://aafradio.org/
>
>  - Mike