Why is the power factor needed in ac circuits and hence its correction?

[sreekant]

why is the power factor needed in ac circuits and hence its correction?-explain to a beginner.

[avm]

Power factor is actually a factor which decides how much power can be taken in at the receiving end. All the power from the sending end will not reach the receiving end. It is dependent on the resistance and impedance.

[Fahad Bhatti]

In a purely resistive network, the voltage and current are always in phase, means both sine waves rise and fall at the same time, But in practice the household and industrial loads are inductive such as motors, fans etc. This makes the current lag the voltage and the product of VI = POWER is no more valid.

More the load is inductive more the current lags... which must be corrected,
This correction is called Power Factor Correction.

In above discussed case of inductive load the power factor correction should be made by adding a capacitor which would cancel the effect of indcutor.

Thus power factor correction is all about bringing Voltage and Current in phase.

[ashuashi]

Originally Posted by sreekant

why is the power factor needed in ac circuits and hence its correction?-explain to a beginner.

Adding to above post...

Poor power factor may cost you more. As in some places Electricity board charge on KVAH. KWh is independent of power factor. Thus poor power factor make KVAH more & hence you pay more. If you keep good p.f. you pay less as well as Electricity Board provides rebate also.

[sauravgoswami]

To make things simple,losses in AC is more than DC.power factor is one of the ways to monitor the loss,AC is preferred over DC since it is cheaper and easier to generate compare to DC

[ashuashi]

Originally Posted by sauravgoswami

To make things simple,losses in AC is more than DC.power factor is one of the ways to monitor the loss,AC is preferred over DC since it is cheaper and easier to generate compare to DC

Hi Saurav,

Does this mean... We improve losses by improving power factor, adding capacitor bank to our system?

[sauravgoswami]

nothing as such,but ofcourse we check the health of our system and maintain it at a right time,thus decreasing the losses.pls correct if i am wrong

[ashuashi]

Originally Posted by sauravgoswami

nothing as such,but ofcourse we check the health of our system and maintain it at a right time,thus decreasing the losses.pls correct if i am wrong

No doubt our system gets improved with good power factor. But I have a doubt on improving losses... bcoz if we improve P.F., we install capacitor banks which draw extra current from the system.

Please also correct me if I am wrong...

[frodo.rok]

Originally Posted by ashuashi

Hi Saurav,

Does this mean... We improve losses by improving power factor, adding capacitor bank to our system?

We can minimize reactive losses by improving power factor.
And we can do that by adding capacitor bank of course.
But we generaly choose a moderate value of power factor becuase of cost associated with adding capacitors.
We can also improve power factor using condensers or overexcited induction motors.

[avm]

The actual amount of power generated is the apparant power. But due to the inductive effect of the circuit the power delivered at the receiving end (load) will be a percentage of the apparent power. So the power factor is actually an indication of the percentage utilization of the generated power. If we say that the powerfactor of a circuit is 0.8, then the amount of utilization of the apparent power is 80%.

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