4 ms·

I'm not an EE so maybe this is all wrong, but from my understanding, Nikola Tesla determined that the optimum way to transmit power in the early days of AC was

by jordanb 16y ago

I'm not an EE so maybe this is all wrong, but from my understanding, Nikola Tesla determined that the optimum way to transmit power in the early days of AC was 240V@60HZ. 240V was the best tradeoff between safety and voltage drop, and 60HZ was the most efficient frequency for generators and motors. The United States ended up on 120V because of Thomas Edison's lobbying, but took Tesla's recommendation of 60HZ. Europe took Tesla's recommendation of 240V but adjusted the frequency to the "more metric" 50HZ.

Luc 16y ago
The 'more metric' 50Hz made me smile. The Wikipedia article on the history of these frequency choices suggests it was increased from 40Hz to 50Hz to stop visible flickering of lamps. It's an entertaining read: http://en.wikipedia.org/wiki/Utility_frequency#History http://en.wikipedia.org/wiki/Utility_frequency#History
masklinn 16y ago
And Japan went with all of the above at once (they have 120V/50Hz, 120V/60Hz, 240V/50Hz and 240V/60Hz)
- dicemoose 16y ago
  Japan's actually got 100V/50Hz and 100V/60Hz. http://en.wikipedia.org/wiki/List_of_countries_with_mains_power_plugs,_voltages_and_frequencies http://en.wikipedia.org/wiki/List_of_countries_with_mains_po...
brudgers 16y ago
In the US power transmission is three phase at high voltage (which is where voltage drop is really a big concern). Voltage drop within a building is rarely a concern in the vast majority of buildings. Typical electrical service for small buildings is 240v using two of the three legs. At the service panel each of the legs is available separately as 120v or in combination as 240v. Larger buildings and industrial applications will often use 208v three phase services for power efficiency. Higher 3 phase voltages are also used on a more limited bases
- DrJokepu 16y ago
  This is also the case in Europe just with different numbers. There are three 230V legs, each within 120 degrees of phase difference from each other. If two are combined, you get 230V * (sin 60) * 2 = 400V which can be used for industrial applications.
  - iuygthyjuk 16y ago
    Not quite - the US has a unique split neutral where an incoming 240V single phase is divided into +/- 120V to drive either 120V to earth or 240V heavy duty appliances. But the dryer supply in the US isn't a multi phase
    - mikey_p 16y ago
      That is the single phase that is common in most residential service in the US. It is separate from the 3 phase service you find in light industrial and large office buildings.
- lutorm 16y ago
  Actually, at least in Sweden, 3-phase 380/400V is available in most homes for power-hungry things like electric stoves, water heaters, etc. I've never seen this in the U.S, so combined with the lower voltage, you need really thick wires to support the 20+A you need to run a 2500W stove. Seems like a waste of copper. I wonder if the U.S. resistive losses are noticeably larger than in Europe. Certainly you notice extension cords for things like vacuum cleaners get very warm in the U.S.
  - dmm 16y ago
    In the USA dryers and electric stoves are connected to 240V, and use different plugs. I have never seen an electric dryer that operates from 120V.
    - billswift 16y ago
      Ranges are 240V and 50 Amps; clothes dryers are 240 V and 30 Amps. Both have 3 prong plugs that are much larger than 120 V outlets, the dryer plug has an L-shaped prong so it can't be inserted into a range outlet. (The reason you don't want the dryer plugged into a range outlet, is the internal wiring is inadequate for 50 amp loads, and can burn out without tripping the 50 amp breaker on range circuits.)
iuygthyjuk 16y ago
There isn't really an optimal - it was mostly a set of accidents to do with already installed turbines and the number of generator poles in a particular design. Lower frequencies were easier to build for early components, 50Hz is about the lowest frequency that you didn't notice flicker on a lamp. Almost all the early non-industrial use of electricity was for lighting - industry tended to generate their own power on-site using whatever equipement they happened to buy. Telsa picked 60hz apparently because it allowed him to reuse clock mechanism in test gear. He also felt that 60sec/60min so 60hz was a 'natural' solution

by jordanb 16y ago

Luc 16y ago

The 'more metric' 50Hz made me smile. The Wikipedia article on the history of these frequency choices suggests it was increased from 40Hz to 50Hz to stop visible flickering of lamps. It's an entertaining read: http://en.wikipedia.org/wiki/Utility_frequency#History http://en.wikipedia.org/wiki/Utility_frequency#History

masklinn 16y ago

And Japan went with all of the above at once (they have 120V/50Hz, 120V/60Hz, 240V/50Hz and 240V/60Hz)

dicemoose 16y ago
Japan's actually got 100V/50Hz and 100V/60Hz. http://en.wikipedia.org/wiki/List_of_countries_with_mains_power_plugs,_voltages_and_frequencies http://en.wikipedia.org/wiki/List_of_countries_with_mains_po...

brudgers 16y ago

In the US power transmission is three phase at high voltage (which is where voltage drop is really a big concern). Voltage drop within a building is rarely a concern in the vast majority of buildings. Typical electrical service for small buildings is 240v using two of the three legs. At the service panel each of the legs is available separately as 120v or in combination as 240v. Larger buildings and industrial applications will often use 208v three phase services for power efficiency. Higher 3 phase voltages are also used on a more limited bases

DrJokepu 16y ago
This is also the case in Europe just with different numbers. There are three 230V legs, each within 120 degrees of phase difference from each other. If two are combined, you get 230V * (sin 60) * 2 = 400V which can be used for industrial applications.
- iuygthyjuk 16y ago
  Not quite - the US has a unique split neutral where an incoming 240V single phase is divided into +/- 120V to drive either 120V to earth or 240V heavy duty appliances. But the dryer supply in the US isn't a multi phase
  - mikey_p 16y ago
    That is the single phase that is common in most residential service in the US. It is separate from the 3 phase service you find in light industrial and large office buildings.
lutorm 16y ago
Actually, at least in Sweden, 3-phase 380/400V is available in most homes for power-hungry things like electric stoves, water heaters, etc. I've never seen this in the U.S, so combined with the lower voltage, you need really thick wires to support the 20+A you need to run a 2500W stove. Seems like a waste of copper. I wonder if the U.S. resistive losses are noticeably larger than in Europe. Certainly you notice extension cords for things like vacuum cleaners get very warm in the U.S.
- dmm 16y ago
  In the USA dryers and electric stoves are connected to 240V, and use different plugs. I have never seen an electric dryer that operates from 120V.
  - billswift 16y ago
    Ranges are 240V and 50 Amps; clothes dryers are 240 V and 30 Amps. Both have 3 prong plugs that are much larger than 120 V outlets, the dryer plug has an L-shaped prong so it can't be inserted into a range outlet. (The reason you don't want the dryer plugged into a range outlet, is the internal wiring is inadequate for 50 amp loads, and can burn out without tripping the 50 amp breaker on range circuits.)

iuygthyjuk 16y ago

There isn't really an optimal - it was mostly a set of accidents to do with already installed turbines and the number of generator poles in a particular design. Lower frequencies were easier to build for early components, 50Hz is about the lowest frequency that you didn't notice flicker on a lamp. Almost all the early non-industrial use of electricity was for lighting - industry tended to generate their own power on-site using whatever equipement they happened to buy. Telsa picked 60hz apparently because it allowed him to reuse clock mechanism in test gear. He also felt that 60sec/60min so 60hz was a 'natural' solution