Editing Talk:2642: Meta-Alternating Current
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Long distance links, especially those between separate unsynchronized grids, use high voltage DC. There is a 2,000-mile link in China running at 1 MV. [[User:Arachrah|Arachrah]] ([[User talk:Arachrah|talk]]) 11:32, 7 July 2022 (UTC) | Long distance links, especially those between separate unsynchronized grids, use high voltage DC. There is a 2,000-mile link in China running at 1 MV. [[User:Arachrah|Arachrah]] ([[User talk:Arachrah|talk]]) 11:32, 7 July 2022 (UTC) | ||
:That's because at great distances, relatively high frequency AC loses a lot of ("active" = actually useful) power as ... reactive power, I think (didn't learn the terminology in English, unit seems right though). A typical grid has a lot of generators and load. A long distance connection results in a phase shift according to the transmission time (speed of light in medium x distance) in about the order of magnitude of the AC period (usually somewhere between 1/10 to 1/60 seconds) wastes a portion equal to the sine of the phase shift angle (up to 90° = all of it) as reactive power. DC isn't quite as easy to use but on long distances there is no power loss to reactive power. [[User:627235|627235]] ([[User talk:627235|talk]]) 12:25, 7 July 2022 (UTC) | :That's because at great distances, relatively high frequency AC loses a lot of ("active" = actually useful) power as ... reactive power, I think (didn't learn the terminology in English, unit seems right though). A typical grid has a lot of generators and load. A long distance connection results in a phase shift according to the transmission time (speed of light in medium x distance) in about the order of magnitude of the AC period (usually somewhere between 1/10 to 1/60 seconds) wastes a portion equal to the sine of the phase shift angle (up to 90° = all of it) as reactive power. DC isn't quite as easy to use but on long distances there is no power loss to reactive power. [[User:627235|627235]] ([[User talk:627235|talk]]) 12:25, 7 July 2022 (UTC) | ||
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Let's face it, the thing should be called an alternator. Of course that name's taken as a redundant word for (electrical) generator. [[User:627235|627235]] ([[User talk:627235|talk]]) 12:26, 7 July 2022 (UTC) | Let's face it, the thing should be called an alternator. Of course that name's taken as a redundant word for (electrical) generator. [[User:627235|627235]] ([[User talk:627235|talk]]) 12:26, 7 July 2022 (UTC) | ||
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It always bothered me that UPS battery backups take the wall AC and convert it to DC to charge the battery, but then have to turn it back to AC to send it to the computer, so the power supply can convert it to DC to run the thing. I picture some connector that goes directly from the UPS to the power supply so that if power is lost it can just pull 12V directly from the battery. [[User:Andyd273|Andyd273]] ([[User talk:Andyd273|talk]]) 12:47, 7 July 2022 (UTC) | It always bothered me that UPS battery backups take the wall AC and convert it to DC to charge the battery, but then have to turn it back to AC to send it to the computer, so the power supply can convert it to DC to run the thing. I picture some connector that goes directly from the UPS to the power supply so that if power is lost it can just pull 12V directly from the battery. [[User:Andyd273|Andyd273]] ([[User talk:Andyd273|talk]]) 12:47, 7 July 2022 (UTC) | ||
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:Where do you propose the extra current to make up for such difference would come from? [[Special:Contributions/172.70.206.213|172.70.206.213]] 21:38, 7 July 2022 (UTC) | :Where do you propose the extra current to make up for such difference would come from? [[Special:Contributions/172.70.206.213|172.70.206.213]] 21:38, 7 July 2022 (UTC) | ||
::When you convert AC to DC or DC to AC, you can't qualify either with single number for voltage OR current. You need to examine whole graph, because both voltage and current are changing with frequency of (original) AC. I'm pretty sure that 81% figure is related to the different way how voltage is computed for AC and DC. That said, regarding the gloving power supply ... usually, power supply contains fan, and while it's partially used to cool the case interior, the power supply might not like it being stopped either. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:24, 7 July 2022 (UTC) | ::When you convert AC to DC or DC to AC, you can't qualify either with single number for voltage OR current. You need to examine whole graph, because both voltage and current are changing with frequency of (original) AC. I'm pretty sure that 81% figure is related to the different way how voltage is computed for AC and DC. That said, regarding the gloving power supply ... usually, power supply contains fan, and while it's partially used to cool the case interior, the power supply might not like it being stopped either. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:24, 7 July 2022 (UTC) | ||
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