| Electronics > Beginners |
| nobody talking about switching PS wasting power on input filter caps? |
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| Circlotron:
--- Quote from: radiolistener on August 24, 2019, 12:10:47 pm ---On rise edge of sine wave, capacitor always have less voltage than mains and consume mains current for charging. On fall edge of sine wave capacitor always have higher voltage than mains and consume mains current for discharging. --- End quote --- No. On the falling edge of the sine wave the capacitor supplies current back to the mains, it does not consume current. It only consumes current on the rising edge of the mains. |
| radiolistener:
--- Quote from: Circlotron on August 24, 2019, 02:01:10 pm ---No. On the falling edge of the sine wave the capacitor supplies current back to the mains, it does not consume current. --- End quote --- On falling edge capacitor prevents AC generator to decrease voltage. Because when AC generator trying to decrease voltage, capacitor provides it's own voltage and prevents voltage drop in such way, so AC generator needs to apply more power in order to overcome capacitor resistance. --- Quote from: Circlotron on August 24, 2019, 02:01:10 pm ---It only consumes current on the rising edge of the mains. --- End quote --- It consume current on both edges. You're forgot that we're talking about AC voltage. AC voltage means that current change it's direction in a loop. On rise edge AC generator provides +current, and capacitor consumes -current in order to charge. On falling edge AC generator provides -current, and capacitor consumes +current in order to discharge. In simple words, capacitor prevents AC generator to change voltage in both direction and AC generator needs to consume more mechanical power in order to make AC voltage. Capacitor don't consume energy (except heat loss in the wires), but it makes phase shift, so AC generator will needs to fight with it's own energy returned back (which creates additional load for AC generator). This returned voltage prevents AC generator to change voltage in order to make AC voltage. The same issue with inductor. Inductor don't consume energy (except heat loss in the wires), but it makes phase shift in opposite direction, and it leads to the same result as with capacitor - AC generator will needs to fight with it's own energy returned back (which creates additional load for AC generator). When you connect capacitor and inductors together, they will compensate phase shift of each other, and it will reduce power load on AC generator. But even in this case it still has higher heat loss on wires between capacitor and inductor. |
| Ice-Tea:
I appologise for the crudity of the drawing (and thank you darling for lending me your crayons) but this may help you understand. Or not. |
| radiolistener:
Ice-Tea, AC generator needs to change voltage from + to - and then again to + and then again to - in a loop. Capacitor prevents that voltage change, it trying to make constant 0 V from AC voltage. Try to understand that when AC generator trying to reduce voltage (on the falling edge of sine wave), the capacitor will prevent that by providing it's accumulated energy. Capacitor will use it's accumulated energy in order to prevent voltage change (basically to stop AC generator). This energy returned by capacitor will be consumed by AC generator to stop rotation of AC generator rotor. And you will need to apply more mechanical power to AC generator rotor. For example it will leads to higher gasoline consumption, if you're using gasoline AC generator. As you can see, capacitor doesn't consume this energy, but when you connect it to AC generator it lead to waste additional power in the AC generator, because capacitor prevents AC generator to make voltage change in any direction. In short, capacitor uses AC generator energy against AC generator. So, AC generator first needs to waste some power in order to charge capacitor and then it needs to waste some power again to discharge capacitor. And this happens 50 times per second. |
| soldar:
--- Quote from: radiolistener on August 24, 2019, 02:15:30 pm --- On falling edge capacitor prevents AC generator to decrease voltage. Because when AC generator trying to decrease voltage, capacitor provides it's own voltage and prevents voltage drop in such way, so AC generator needs to apply more power in order to overcome capacitor resistance. --- End quote --- You are totally wrong here but this thread has degenerated into such confusion that I am going to bow out and let others deal with the confusion because this is like shooting at clouds. I do not know what your qualifications are but I can tell you are not an Electrical Engineer. There are some of us on this board who are engineers. You should listen to them. |
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