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08-22-2013 10:51 PM

Power factor improve capacitors, what about resistor?

A lot of students come here to ask their doubts, now I have a question for the future engineers to whom early or later the world will deposit the future.

Power factor is improved by using capacitors but what about to use a resistor?

Assume an equivalent load with an impedance of 25 ohms with an angle of 25°
This yields to a power factor of the load equal to 0.9 (aprox.)

If I put a 25 ohms resistor in shunt with the previous load I get that from the source point of view the power factor now is 0.97

Why not to use resistors instead of capacitors to improve power factor?

Right answer = GE Industrial Power Systems Data Book copy.
08-22-2013 10:54 PM
Top #2
08-22-2013 10:54 PM
my opinion is that we don't use resistors for improving of power factor because, in case of resistors, we have additional active power losses which are equal with R*I*I, so, in that case, we need to produce additional active power with purpose to cover those additional active power losses and, on that way, we need to overload feeder which supply mentioned consumer area with additional active power which we need to transmit to consumer area.
08-24-2013 09:35 PM
Top #3
08-24-2013 09:35 PM
No further comment for that... just to repeat my simple answer... if you will increase resistance at constant Q, then P will increase, S will increase, pf will improve and but energy required will also increase... (just relate P, Q & S as a triangle in a Cartesian plane)

before you install capacitors to improve power factor, do some power quality analysis to consider other parameters like harmonics, distortions, voltage unbalances, etc..
08-24-2013 09:35 PM
Top #4
08-24-2013 09:35 PM
This concept and theory sounds logical, but whenever you connect a resistor, whether in parallel or in series with an existing load, this resistor will surely affect the current
flow to this load or the voltage applied to this load. Consequently, this will affect the performance characteristic of the existing load. Shunt capacitors are still the most effective method of improving power factor.
08-24-2013 09:36 PM
Top #5
08-24-2013 09:36 PM
As you know reactive power come towards load in half cycle then return in the next half cycle so it cause occupy power transfer capacity of line.Capacitors by neutralizing inductive effect,increase active power transmission capacity. Resistor don't solve this problem and you should pay more for more active power.
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