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

[J Forster]

brunneraa1p at comcast.net wrote:

> From: J Forster <jfor at quik.com>
> > Maybe not. The load is essentially constant and there is feedback on the
> > generator output which would compensate for line changes and windage change with
> > altitude (if that's an issue).    I can think of no alternate reason for the operator controls.
>
> The reason for the controls (capacitor selection) is to set the capacitance value as near to optimum as possible to neutralize armature reactance.

Yes

> Thereafter there is no need to touch them.

Then WHY are they front panel controls with a voltmeter monitoring their effect??

> The carbon pile then compensates for changes in windage or input voltage by varying generator field excitation.  Note that they also used saturated-pole generators which were inherently self-regulating, (no carbon pile) but they still used the series capacitors.

Yes

> In initial setup the voltage level is set by a carbon pile setting, and thereafter only small adjustment is possible with a pot on the M-G chassis.  A saturated pole generator of course sets itself, and is not adjustable
>
> Richard Brunner, AA1P

That still does not answer the question why are the capacitors switchable, when, if properly set up, there is no need to change them. It it a design error?

-John