Power Frequency

From: Geoff Roberts <geoffrob_at_stmarks.pp.catholic.edu.au>
Date: Fri Apr 16 12:54:37 1999

----- Original Message -----
From: Hans Franke <Hans.Franke_at_mch20.sbs.de>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Sent: Saturday, April 17, 1999 3:59 AM
Subject: OT: Power Frequency


> > 240V was chosen to be the standard to reduce line losses??? Why 50cyc?
>
> Short answer:
> Why not.
> Or: Why 60 ?

Good question.

> Long Answer:

> A willingfull decision of a single person (or group) in the past.

Dead right.
AFAIK, in our case we simply adopted the British standard, we only ceased to
be a Crown colony in 1901, and were still fairly anglicised in our
orientation. Still true to a point. We drive on the LEFT side of the road
with RH drive cars too. Upsets some visitors. :^)

>The 60 Hz decison might have
> been based on the idea to continue the line: one minute is 1/60th of
> a hour, and a second is 1/60th of a minute, and a cycle is 1/60th of
> a second ... while the 50Hz idea was based on geting a simple number,
> In fact any number could have been involved.

I think you are spot on there, I am led to believe the 60hz decision in the
US and some other countries was made to facilitate the use of the
(relatively) precise mains frequency for clocks and other timing functions.
This is also possible, even for motor driven clocks, with 50hz mains simply
by careful motor design. Though it may have been less simple when the
decision was made.
I'm not even sure when 240v 50hz became the standard, though I think it was
around 1920 or so, at least in this country.
Television systems for particular countries usually have a frame rate
equivalent to the mains frequency. This reduces/eliminates mains hum
strobing, though it is more of a historical problem with modern TV designs I
think.
US NTSC is 525 line 60hz PAL 625 line 50hz. We use PAL. (There are all
kinds of wierd variations, including a version of PAL with a 60hz field rate
in South America somewhere - Brazil I think)

Cheers

Geoff Roberts
VK5KDR
Computer Systems Manager
Saint Marks College
Port Pirie, South Australia
geoffrob_at_stmarks.pp.catholic.edu.au
Received on Fri Apr 16 1999 - 12:54:37 BST