On Wed, 8 Apr 2009 21:26:07 -0400, "Phred" wrote:
"Richard Knoppow" wrote in message
...
25hz is used for
industrial purposes, particularly for electric railways
because core losses are lower in motors and transformers
(less heat dissipated).
Richard,
I believe the real reason for 25 Hz power near Niagara Falls was the
large number of chlor-alkali plants in the area. The Castner
Electrolytic Alkali Company began operation at Niagara Falls in
1897. Eventually this became the Olin Niachlor plant. Chlor-alkali
plants are a major consumer of electricity, and it was plentiful and
cheap at Niagara Falls. Other companies in the same area with
chlor-alkali plants are DuPont and Hooker (later to be Occidental
Chemical).
The reason for using 25 Hz AC is related to the need for high
current DC for use in the process. In the early days, mechanical
(rotary) rectifiers were used to convert the AC to DC. Essentially
a synchronous motor was used to turn large disks broken into
sections. AC was fed to these disks. Brushes would rub on the disk
producing a unipolar output. Operating at 1500 RPM this system was
quite efficient. But at 50 or 60 Hz, rotating the disks at 3000 or
3600 RPM, the efficiency was less (the off time, essentially the
insulating space between the disk sections, became a larger portion
of the total period) and the brushes wore out faster. Operating at
lower frequencies would have been even more efficient but
transformer size became excessive.
Unfortunately the early electrolytic cells used mercury for one
electrode leading to a major pollution problem. You might recognize
the name Hooker Chemical from their waste being dumped in the Love
Canal.
73, Dr. Barry L. Ornitz WA4VZQ
I vaguely remember my father (an electrician) telling me that power at
the very beginning of WW II in the Gary Indiana area was 25 Hz.
Does anyone know anything about that? Would the presence of steel
mills and other heavy industry have anything to do with it.
I have no reason to doubt what my father had said (but I can't ask
him anymore.)
Were there other places in the US that had non standard Hz. Also I'd
be interested in knowing when 60 Hz became the US standard and why?
The Gary, Hammond, East Chicago area and Southern parts of nearby
Chicago is, of course, one of the more heavily industrialized areas in
the US, or at least it was in the first half of the 20th century. Gary
(which happens to be my birthplace though I only lived there 10 weeks,
at the beginning of WW II) was founded specifically as a "Company
Town" in 1906 for US Steel and is named for an early president of the
company.
Jon Teske, W3JT [And as I found out on the only visit I ever made to
Gary aside from bypassing it on the tollways when I stopped to get an
Indiana Birth Certificate, my claim to fame is that I was born in the
same hospital as the Jackson family kids...Michael, Janet, Tito etc.
Sheesh! ]