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nobody talking about switching PS wasting power on input filter caps?

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soldar:

--- Quote from: radiolistener on August 24, 2019, 11:02:36 am ---yes, but this "returned back" energy creates impedance change for power source. So, a power source (power plant) needs to spend more energy in order to fight with this "returned back" energy. Because this "returned back" energy will works against power source. Isn't it?
--- End quote ---

No. You do not understand the process. Two voltage sources in parallel are not working "against each other". They are "helping" each other.


--- Quote from: radiolistener on August 24, 2019, 11:02:36 am ---Also, there is additional power loss in the capacitor and power loss in the wire, due to higher current. All this energy is lost and cannot be consumed. Yes, not all this loss happens inside capacitor, but this energy is wasted due to capacitor :)
--- End quote ---

Unless the capacitor is placed to compensate inductive rectance. But yes, poor power factor uses energy in the transmission wires regardless of the cause.

radiolistener:

--- Quote from: soldar on August 24, 2019, 11:54:37 am ---No. You do not understand the process. Two voltage sources in parallel are not working "against each other". They are "helping" each other.
--- End quote ---

There is no two voltage sources with the same voltage in parallel. 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. Mains voltage and capacitor voltage always shifted by some phase. So, they always working against each other.

Capacitor doesn't consume that energy. It just returns it back to AC generator. And AC generator needs to make an extra effort to charge and discharge this capacitor. It just waste some part of energy in order to charge and discharge this capacitor.

You can fix it by placing inductor, so it will make phase shift in the opposite direction. In such way AC generator will not needs to make an extra effort to charge and discharge capactior. But you will needs additional expenses on this inductor and heat loss in the wire between capacitor and inductor.

Exactly the same thing will happens with inductor connected to the mains. AC generator will needs to make an extra effort to fight against inductor. Inductor don't consume energy it just will return it back to AC generator (we don't talk about heat loss in the wire). And AC generator will needs to fight agains "returned back" energy from inductor. In order to fix it you will need to place capacitor to make phase shift in the opposite direction.

radiolistener:

--- Quote from: soldar on August 24, 2019, 11:54:37 am ---Unless the capacitor is placed to compensate inductive rectance.

--- End quote ---

The same you can place inductor to compensate capacitive resistance. But this compensating inductor or capacitor requires additional expenses and needs to be connected together with reactive load. If you don't place such capacitor/inductor, AC generator will needs to make additional effort to work against your reactive load. Who will pay for that? :)

JohnG:
Wikipedia is your friend: https://en.wikipedia.org/wiki/Power_factor

John

Ice-Tea:

--- Quote from: radiolistener on August 24, 2019, 12:40:59 pm ---
--- Quote from: soldar on August 24, 2019, 11:54:37 am ---Unless the capacitor is placed to compensate inductive rectance.

--- End quote ---
If you don't place such capacitor/inductor, AC generator will needs to make additional effort to work against your reactive load. Who will pay for that? :)

--- End quote ---

Depends on your definition of effort. A genset consists of some kind of motor and the actual generator. The motor doesn't care. Whatever extra effort it needs to do is returned. The generator *does* care, but only because of the current. It's the current that heats up the winding and it's the maximum temperature of that winding that will determine the maximum VAR of that generator. So in theory, you can load the generator up to its maximum while the attached motor is still idling (except for the I²R losses and provided the motor has sufficient inertia to load/unload).

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