----- Original Message -----
From: Alexandre Domingos F. Souza <xandinho@INTERLINK.COM.BR>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Saturday, November 18, 2000 11:58 AM
Subject: Re: [EE]: Cheap and easy 100 Hz MPU clock? (prefix added)


>Once the breaker is closed in, there is no way the generator can get out of
>phase/frequency lock with the grid.

        Why? The frequency of the line is generated by a switcher (as I
learned, the mains voltage is generated in DC, and switched to AC in a HUGE
bank of SCRs), and there is a PLL locked to the external line frequency?

        It seems to be an interesting subject :o)


No, DC is only used for _very_ high voltage (typically 500,000Kv and up),
long distance transmission lines (in the US only found spanning the large
distances in the midmest).

Everything else is done with AC.

Once the generator breaker is closed, the low impedence to the grid prevents
the generator from running at any but the exact correct speed.

Actually, the generator tries to 'push' the frequency a little bit, but that
is regulated by the energy control center by adjusting generation system
wide.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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