What is the average power factor

In between these two extreme cases, pf is said to be leading or lagging. Leading power factor means that the current leads voltage, which implies a capacitive load.

Lagging power factor means that current lags voltage, implying an inductive load. Power factor affects the electric bills consumers pay the electric utility companies. We will learn how to fix the power factor using the power factor correction. For better understanding let us review examples below : 1. Find the apparent power and the power factor of the load. Determine the element values that form the series-connected load.

Solution :. The apparent power is. The power factor is. The pf is leading because the current leads the voltage. The pf may also be obtained from the load impedance.

A plot of p t for various circuit elements is shown in Figure. For a resistor, i t and v t are in phase and therefore always have the same sign see Figure. For a capacitor or inductor, the relative signs of i t and v t vary over a cycle due to their phase differences see Figure and Figure. Consequently, p t is positive at some times and negative at others, indicating that capacitive and inductive elements produce power at some instants and absorb it at others.

Because instantaneous power varies in both magnitude and sign over a cycle, it seldom has any practical importance. It is defined by the time average of the instantaneous power over one cycle:. With the substitutions and this integral becomes. Using the trigonometric relation we obtain. In engineering applications, is known as the power factor , which is the amount by which the power delivered in the circuit is less than the theoretical maximum of the circuit due to voltage and current being out of phase.

For a resistor, so the average power dissipated is. A comparison of p t and is shown in Figure d. To make look like its dc counterpart, we use the rms values of the current and the voltage. By definition, these are. With we obtain. This equation further emphasizes why the rms value is chosen in discussion rather than peak values. Alternating voltages and currents are usually described in terms of their rms values.

Re: average power factor IanP said:. Arithmetic mean - the sum of all measurements divided by the number of observations in the data set.. Re: average power factor Hi Bigjoe, In an electrical system the impedance can vary from purely capacitive to resistive to purely inductive. Therefore the cosine of the angle can never be negative and the power will always be positive. When you make the calculation of the average power you should use the absolute value, the sign is only an indication for you to indicate if the current is leading or lagging and should not be taken into account for the actual calculation of the power.

A simple average doesn't work, because the signs are a convention, but I don't think absolute value works well either because no extra credit is given for the sign change. I don't know what the standard method is, but it would be easier for me anyway to think in terms of the "average phase angle" instead of average power factor and then calculate the power factor of the average phase angle.

In your case, the angles are: This makes sense, the fact that the load leads some of the time would suggest "don't add compensation capacitance, leave it alone" and average power factor is near unity. Average the real and reactive powers seperately leaving the negative signs. Then finally convert back to average apparent power and average power factor. If all your apparent powers are the same like 1 VA then the reactive powers are: 0. Re: average power factor hi, thank you guys for your replies.

Similar threads J. In this case, the average power in an ac circuit with pure capacitive load is. According to equation 2c , the power dissipated by the pure capacitor circuit is zero. Power only floats back and forth between the source and the capacitive load. We have seen in the above section that if power dissipation depends upon the cosine of the phase angle along with the amplitude of voltage and current.

For example, if the phase angle is 90 no power will dissipate and if it is zero or somewhere between theme the load will dissipate power. The cosine term very important and is called the power factor PF. An AC circuit containing multiple elements like a resistor, inductor, and capacitor can have a power factor between zero and one. The power factor has no unit but it is usually expressed as a leading or lagging power factor. If the current leads the voltage, the power factor is called leading, and if the current lags, the power factor is called the lagging power factor.

The PF of a capacitive circuit is leading and that for an inductive circuit is lagging. The power factor in an ac circuit helps us in finding how much energy is actually utilized for performing the desired work. A power factor of less than one causes over-current and voltage drop because of power flow back and forth flow.