Re: [LAD] A little quiz about audio measurements...

From: Gene Heskett <gene.heskett@email-addr-hidden>
Date: Sat May 29 2010 - 19:18:32 EEST

On Saturday 29 May 2010, Ralf Mardorf wrote:
[...]

>I found no Wiki for "Überferquenz", increased frequency. At what value
>was the voltage, when there were 100 Hz?

The 100 HZ component is what you get by rectifying both halves of the sine
wave, effectively inverting the lower half to become another pulse, with
lots of distortion so there will be harmonics of the 100HZ also displayed on
the spectrum display. In most power generators, the voltage at the output
is regulated by the current through the rotating armature being controlled,
so the voltage, should the armature overspeed, is generally fairly stable.

In what we call standby power systems here, the throttle of the engine doing
the turning is usually controlled by the output frequency, with a drop in
frequency being assumed to be an increase in the load, and an increase being
a drop in the load, generally achieving about a +- 1 hz tolerance. In much
larger systems, there will be a fixed frequency reference derived from a
master clock, and the phase angles of the power are compared to this
reference, with a very high gain so the phase errors are usually within a
degree. So the system is said to be phase locked. The input energy to turn
the machinery, water gates, whatever, are where the control is actually
exerted. Should any one 'generator' get more than a few degrees out of
lock, it will usually disconnect itself, or reduce its excitation current to
allow it to catch up or increase it if it needs to slow minutely, this may
cause a few millivolts of a voltage change to the whole grid. Somewhere in
here the load shedding also comes into play if it is a controllable item for
that section of the grid.

Where the grid idea fails in places like the US, is when the light speed
propagation delays begin to play with the phase reference. Because of this
the USA is broken into smaller pieces grid wise.

>So if anybody wants to program a virtual Hammond B3, should he take care
>about tuning effects caused by the power line?
>Btw. is the motors speed for a B3 depending to the voltage or is it
>synced by the frequency?
>
>Ralf

They are synch motors Ralf. Its a different motor for me at 60hz on this
side of the pond.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Windows 98 is the most popular virus on the market today.
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Received on Sat May 29 20:15:04 2010

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