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i need sleep (sh.itjust.works)
submitted 9 months ago by to c/science_memes@mander.xyz
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[–] 14 points 9 months ago (8 children)

High frequency is generally bad for transmission line losses, so getting power from A to B is better at lower frequency

DC is a great option here.

If we switched to DC, many things would still flicker though as they would presumably use switching power supplies, but those could be relatively high frequency like you said.

Interestingly, airplanes use 400Hz, as transmission over distance doesn't matter, and transformers can be made much smaller/lighter.

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  • [–] 8 points 9 months ago (5 children)

    Also if we switched to DC, you'd need costly dcdc transformers to step up the voltage for transmission and back down again for domestic usage

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  • [–] 2 points 9 months ago (4 children)

    Aren't switching mode power supplies smaller and more efficient than regular AC transformers anyway?

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  • [–] 5 points 9 months ago (2 children)

    As far as I understand, a DCDC converter is less efficient and more expensive than an equivalent ACAC converter. I don't know about switching power supplies, and whether that's true or extendable to the transformer case, sorry.

    Long distance point to point power transmission (like internationally) is often DC because transmission losses become more important.

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  • [–] 1 point 9 months ago (1 child)

    I don't think that's actually true. To do AC to AC conversion at grid frequencies normally requires large inefficient transformers. A PC power supply is an example of a switch mode power supply. Basically what happens is: AC mains -> DC (at mains voltage) -> AC (high frequency, mains voltage) -> transformer -> AC (low voltage, still high frequency) -> DC (low voltage). Why do all this? Because doing the voltage conversion at grid frequency would need a much bigger transformer. They could just do the voltage conversion at grid frequency and only have to rectify once with no conversion back to ac, but it's actually less efficient and requires more expensive hardware. So actually DC to DC conversion is more efficient, even if it means using high frequency AC in the middle. Not all switch mode supplies use this AC trick, though they do all involve switching current. buck and boost converters are used in smartphones, laptops, motherboards don't have any transformer and are incredibly compact and efficient.The fact that many many things also need DC would be a bonus. Recitifying single phase AC at low frequency is not the most efficient thing in the world. Three phase is better, but having straight DC and only needing to change voltage would probably be best.

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  • [–] 2 points 9 months ago

    They’re more efficient than old school ac-dc linear supplies (of which an ac transformer is just a part of). However if you just want to step up or down ac voltage, transformers are quite efficient.

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  • [–] 3 points 9 months ago

    Even a switch mode power supply doesn't really flicker since they have a rectification and smoothing stage on the output to produce a DC voltage. The switching is done on the input to set the duty cycle which controls the voltage/current ratio at the output.

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