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Comment by Animats | Hacker News Reader

Until the 1990s, Grand Central Station in New York had almost everything - 60Hz commercial power, 40Hz LIRR power (Pennsylvania Railroad standard) 25Hz NYC Subway power, 700VDC Metro North power, 600VDC subway third rail power, and some old Edison 100VDC power. There was a huge basement area full of rotary converters to interconvert all this. Various ancient machinery and lighting ran on different power sources.

In the 1990s, Grand Central was rewired, and everything except railroad traction power was converted to 60Hz. All conversion equipment was replaced with solid state gear. It took quite a while just to find everything that was powered off one of the nonstandard systems.

It wasn't until 2005 that the last 25Hz rotary converter was retired from the NYC subway system. (Third rail power is 600VDC, but subway power distribution was 13KV 25Hz 3-phase.)

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> 60Hz commercial power, 40Hz LIRR power (Pennsylvania Railroad standard) 25Hz NYC Subway power, 700VDC Metro North power, 600VDC subway third rail power, and some old Edison 100VDC power.

The only thing missing is 400Hz power!

Isn't that usually used just for ships and aircraft?

There's a fair amount of ground military equipment that uses 400Hz also. Radar, microwave radios, satcom, etc.

And old IBM computers!

With a motor-generator units in each rack frame. Also used by xerox/SDS computers

>"Until the 1990s, Grand Central Station in New York had almost everything - 60Hz commercial power,..."

Do you mean 50Hz there?

I really don't understand the downvotes, this was a sincere question. Please note, the OP states:

>"Until the 1990s, Grand Central Station in New York had almost everything - 60Hz commercial power, 40Hz LIRR power (Pennsylvania Railroad standard) 25Hz NYC Subway power, 700VDC Metro North power, 600VDC subway third rail power, and some old Edison 100VDC power."

and then subsequently states:

."In the 1990s, Grand Central was rewired, and everything except railroad traction power was converted to 60Hz."

I am asking because I am trying to make sense of the entire comment. They also mention 4 or 5 other electrical frequencies and voltages, so there's a lot packed into that comment. I am genuinely interested in the comment and trying to learn something.

>a lot packed into that comment.

A summary: once upon a time, Grand Central Station had AC at multiple frequencies in addition to 60hz (also it had some DC power). In the 1990s it was rewired so that the AC only used the (American) standard 60hz.

I suppose its hard to make sense of if you didn't know that 60Hz is the standard in the U.S.?

I don't think 50Hz was ever used in the US. What are you curious about?

They probably had some old 60Hz three phase supply, maybe something weird like a "wild leg" configuration, but when everything was modernized they likely switched to 480V three phase for the big stuff like the ventilation motors, and 240V single phase with neutral for supplying smaller motors and 120V systems.

> I don't think 50Hz was ever used in the US

I think Before 1948, LA's Power Grid Ran at 50hz :)

Haha, geez... That's what I get for picking my phone up to the comments hours later. Embarrassing.

The whole article is about 50Hz AC being generated and used in California until 1948, so it was used in the US

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