Power Factor Questions in AC Circuits

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Discussion Overview

The discussion revolves around the concept of power factor in AC circuits, particularly focusing on the roles of capacitors and inductors, the implications of apparent versus real power, and the operational considerations for power generation and distribution. Participants explore theoretical and practical aspects of power factor, its impact on energy consumption, and the technical requirements for generators and wiring.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that energy associated with capacitors and inductors does not contribute to actual energy usage, raising questions about how this affects the power factor.
  • One participant notes that apparent power is not the same as real power supplied by generators, emphasizing that power companies charge for low power factor due to the impact on amperage.
  • A question is raised about whether generators can be designed to supply only real power, or if apparent power must always be considered.
  • Another participant explains that power in three-phase systems can still flow even if the phases deviate from their ideal configuration, which affects usable power and voltage between phases.
  • There is mention of using capacitors to correct phase shifts and the potential for distributed generation to help manage power factor on the grid.
  • One participant highlights that real power is directly related to fuel consumption in power plants, while the power factor affects the amperage, influencing the size of wires and generators needed.

Areas of Agreement / Disagreement

Participants express various viewpoints regarding the relationship between apparent power, real power, and power factor, indicating that multiple competing views remain without a clear consensus on the best approach to managing these concepts in AC circuits.

Contextual Notes

There are unresolved questions about the design of generators in relation to wattage versus apparent power and the implications of different power factors in distribution systems. The discussion also reflects a dependence on specific definitions of power factor and its components.

daredevil
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In AC circuits, it seems that there is no energy used for capacitors and inductors.

I was wondering how is the energy used causing it to increase and decrease the power factor?. And also, why does the power provider have to supply power(apparent power) for something that is ultimately not even used

Thanks..
 
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Apparent power is not supplied as real power by the generator. The reason the power company gets annoyed at (and charges you for) low power factor is that the capacity of generators and wires is based on amperage, not wattage.
 
Thankss..

So, aren't there are generators made based on wattage??.. or can we ignore the apparent power and use a generator to supply for the real power only?

And also when the current returns to distribution point.. different cables with be with different power factors.. so will there be any problem caused by that
 
Pwr comes to us in three phases, each 120 degrees out of phase with the next. We derive pwr by flowing current between the phases. If the phases change from their ideal 120 degrees, you still have full pwr flowing thru each phase, which is what we get charged for. But we now have slightly less voltage between the phases at each instant in time, so we get less usable pwr between the phases.

Correcting this phase shift normally means adding capacitors. But with expanded use of distributed generation; we can run the DG generators out of phase in the opposite direction to help correct the PF on the grid. This is how generator owners sell VARS to the power company.
 
Last edited:
daredevil said:
Thankss..

So, aren't there are generators made based on wattage??.. or can we ignore the apparent power and use a generator to supply for the real power only?
The real power is "real" in the sense that it directly relates to how much fuel the power plant burns. That's why it is the main component of a commercial bill. But how hot a wire or generator gets is a function of amperage, so the worse the power factor the higher the amperage so the larger the wires and generator need to be or the higher the losses will be.
 

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