Power Frequency

From: Hans Franke <Hans.Franke_at_mch20.sbs.de>
Date: Sat Apr 17 11:59:22 1999

> The key item is that motors and transformers are physically smaller
> for same or similar VA capability with increasing frequency. there is a
> corner you turn as you go higher though as the iron in the course gets
> lossier and line radiation increses losses. So power distrubution has
> the 50/60 as a good bet. Note aircraft use 400nz for the compact
> transformers and reduced filtering in rectifiec circuits.

Jep, when it comes to internal systems of vehicles often higher
frequencies are used - for example, the 'new' (already 10 years
old) Siemens low floor tram cars (2 phases motors, electronicly
converted from 750V DC) now offer some 240V outlets for maintanance
equippment - but with 100 Hz .. so some eq will behave different :)

> There were also
> 25, 30 and 40hz systems. The NY subway at one time was 25Hz and the DEC
> mill prior to refurb in the 80s was 40hz (that power also lighted part of
> the town.) at one point in history.

Now, if we are going for exotic ideas (from todays point of viev),
we have to mention the German Overhead wire system with 15kV and
16 2/3 Hz (Also used in Swizerland, Austria, some parts of Poland,
Czech Republik, Luxembourg, Netherlands and Denmark).

The key idea has been to develop a AC system (to allow transformation),
while still using AC motors - remember, the German system was developed
very early, and speed controll of AC motors was still a problem - at
this time, most Countries decided to go for pure AC, with all problems -
Received on Sat Apr 17 1999 - 11:59:22 BST