electrical question.

Had the machinists beleiving that when we ugraded the electricial in the machine shop.

steveormary

A 240 volt nameplate motor for 60 Hz would run fine on 200 volts 50 Hz. 220 volt namplate would want about 181 volts at 50 Hz. Either case the torque would be as rated but since the shaft speed is 5/6th rated, the horsepower will be 5/6 nameplate.

So it depends on the details of the motor design an construction.

Gerald J.

60 cycle just makes sense, since minutes, hours, seconds, etc are in mutiples of 60, clocks, etc are easy to make that operate on 60 hz. 50 cycle just never seemed right to me. Large aircraft use 115V/400hz but that is for a special reason, and not something you are distributing across power grids.

Charles

Charles

There used to be a lot of industry around here on 25 hz, but that was all changed over years ago.

Gerald J.

That's all very interesting stuff. I had no idea that any utilities in North America produced anything other than 60 Hz power (excepting DC transmission lines).

Regarding generation at the Falls, I read once that when the first Tesla-designed (Westinghouse) generators were installed there, they tried to operate them at 50 cycles, but the generators wouldn't work right. The utility told Tesla that his generators were no good, and he responded by saying "I designed them to work at 60 cycles per second, not 50." The utility sped up the generators to humor Tesla, and sure enough the generators worked as designed at the higher speed. And that is supposedly why North America is on 60 Hertz while most of the rest of the world uses 50 Hz power.

16-2/3 was a handy frequency easy to generate from 50 Hz with rotating machinery as was 25 though many power plants primarily for traction used those low frequencies in their steam engine or steam turbine driven alternators. I looked through an abandoned 25 Hz plant about 35 years ago and the laminations were over 3/16" thick where 60 Hz laminations would be on the order of .015" thick or less. It wasn't rare for traction companies in the country to sell power at their standard low frequencies to farmers along the line. I've seen a couple radios with 25 Hz power transformers that came from the factory that way. The iron core stack is over twice as tall as the normal 60 Hz power transformer. They run fine on 60 Hz.

Lots of southern California ran on 25 or 50 Hz from Boulder Dam and early sound movies had that hum frequency recorded on the sound track.

I've seen equipment made for 133 Hz and I think something in the 90s.

Lots of aircraft equipment runs at 400 Hz and higher because motors and transformers are smaller for the same power the higher the frequency. Many aircraft factory tools have been made as 120 Hz 3 phase which gives them light weight and good shaft speeds (7200 synchronous speed for a 2 pole motor) and makes them totally useless when stolen. I've seen a very sturdy double spindle shaper (essentially a couple mouted routers on a table, but with 1-1/2" shafts) with 3 phase 120 Hz motors. They were 240 volt, but ran fine at half speed on 120 volts three phase 60 Hz.

I used to have a book from the 1930s with articles collected and written by an electrical engineer of the era and one of the articles was on the question of frequency and associated history. That article I recall was published in an AIEE periodical. I wish I had that book, it may be here but I think I loaned it out and it never came back.

One of the arguments for 50 and more so for 60Hz is that our eyes don't notice flicker at those frqeuencies while at 25 Hz every body does. There are some that notice flicker, especially from fluorescent lamps at 60 Hz.

Gerald J.