"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