1 Feb
2011
1 Feb
'11
2:25 p.m.
On 1 Feb 2011 at 16:49, William Donzelli wrote:
I think this is all finally gone, apart from the
NorthEast Corridor.
The only reason the NEC is still 25 Hz is due to railroad
ultra-conservative engineering.
In my younger days, I worked at Inland Steel in various plants and
departments. There were three power distribution frequencies in use;
DC, 25Hz and 60 Hz. The 25Hz was generated locally from waste heat;
the 60 Hz was purchased and the DC could come from either source (via
large rotary converters).
The DC made sense as it was used for the overhead cranes (and
electromagnets), traction motors as one might find on an ingot buggy,
welding and for the large motors that powered the rolling mills.
Since the 25Hz was the cheapest power source, it was used for
lighting, ventilation, running various control instruments and as
general utility. A side effect of this was that new equipment was
being ordered at a significant premium to make use of 25Hz.
My tenure occurred when the plants began shifting from incandescent
to mercury vapor lighting. While the incandescent lighting had a
distinct pulse to it on 25Hz, the mercury vapor flicker was probably
sufficient to induce a seizure.
--Chuck