"Jack Zeal" wrote in message
...
NSM wrote:
That makes more sense. Planes use 400 Hz to save weight. Some of the old
Niagara alternators were 25 cycle. But I can see no reason for 600 Volt
400
Hz for any part of the subway system. That'd be weird.

Many of the rail systems are reliant on extremely old (first half 20th
century) infrastructure. I think, for example, the overhead
electrification in the northeast US was an odd setting (possibly 12kv?)
until like the 1970s, replaced with a common industrial voltage
(possibly 25kv?) Also, Grand Central Terminal still serves locomotives
over 40 years old (the FL9s) and the corresponding third-rail
electricity must remain compatible.

The 400Hz's odd; ISTR there were some DC fittings in New York.

Back home some of the old elevators used to run off the DC for the street
cars. I'm sure they've all long since been replaced.

N