美國供電規格

經常見到有人提及美國的電子用品,但點睇都唔明佢到底係乜野制式,上網查過後,知道有三個規格,不過就真係講到一舊舊!
第一個係高壓系統,13.2KV,不是一般民用接觸到的level,可以不理。
第二個係460-480V Line to Line,277V Phase voltage。(三相四線)
第三個係115-120V,但這個就最離奇,係單相電壓,咁240V又點走出來?兩相供電?定係三相供電(假如係三相,電壓又唔岩規矩!)假如係三相,係三相三線,定係三相四線?
頻率:全部應該係60Hz吧。

問題關鍵,其實係無一個標稱的基準電壓,全部係一個range,變成可以有好多個計法和變數,希望有師兄可以賜教。

http://zhidao.baidu.com/question ... EA%D7%BC&ie=gbk

回覆 1# diy-apprentice

一圖解千語

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謝謝!低效率的供電系統。

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Quote:
Since the residential power line voltage coming into all U.S. homes is rated at 220V, it must be reduced inside the home to 110V. The power is brought in as three phase 220V AC, which means it comes in as two 110 volt lines and a central neutral tap line. With this system you can tap each leg to provide 110 volts where it is needed. At the same time you can connect both 110 volt lines to an appliance along with the neutral leg to supply a full 220 volts where needed. In this manner your home gets all of the power it needs for all of your appliances and fixtures.
Unquote.

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回覆 3# diy-apprentice

如果呢張圖呢 ?

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三條電纜只提供兩相電,假如係三相三線或三相四線,就可以提供更大的功率。

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本帖最後由 diputs 於 2015-7-16 23:46 編輯

或可參考以下資料取材自:
https://en.wikipedia.org/wiki/Split-phase_electric_power
A variation is the 240 V delta 4-wire system, also known as a high-leg or red-leg delta. This is a three-phase 240 V delta connected system, in which one winding of the transformer has a center tap which is connected to ground and used as the system neutral. This allows a single service to supply 120 V for lighting, 240 V single-phase for heating appliances, and 240 V three-phase for motor loads (such as air conditioning compressors). Two of the phases are 120 V to neutral, the third phase or "high leg" is 208 V to neutral.

Multiwire systems split more than two ways are possible with both AC and DC but have the significant disadvantage that no matter which point is tied to ground some of the wires will have a higher earth relative voltage than the utilisation voltage; therefore, such systems are not used in normal power distribution.

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佢要用120V係點連?
若用Earth做回路
咪好易觸電

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佢要用120V係點連?
若用Earth做回路
咪好易觸電
YES_MAN 發表於 2015-7-16 23:35


上邊圖係neutral 嚟㗎,另earth同Neutral 本身都係通㗎,又點易觸電d

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如果這樣要接四條;
也即是兩相四線;

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