## Friday, January 13, 2023

Power factor (PF), as described briefly on the Power Quality page, can be represented by the power triangle to show the relationship between real power in kilowatts (A), reactive power in kilovolt-amps reactive (B) and apparent power in kilovolt-amps (C):

Real power performs actual work such as heating a burner element or illuminating an incandescent bulb.  Reactive power does not perform work but energizes magnetic fields in motor windings or power supplies which create inductive loads.  Apparent power is the result of combining real power and reactive power.  It measures the true load of an electrical distribution system.

If real power and reactive power exist simultaneously, why can't we just add them together to get apparent power?  The reason is that purely reactive current (inductive load) is ninety degrees out of phase with real current (resistive load).   Thus, we use the power triangle vectors to graphically represent this 90 degree relationship.

Another way to look at this relationship is to compare the sine waves, or oscillograms, of voltage and current for resistive and inductive loads.   In a purely resistive load the current sine wave and voltage sine wave are in sync with one another. The PF in this case is 100 percent or unity.

In a purely inductive load the current sine wave lags 90 degrees behind the voltage sine wave.  The PF in this case would be zero.

In the real world there are no purely inductive loads because there is always some amount of work being done by the device even if it is only the generation of heat.  On the other hand, purely resistive loads do exist in the real world such as a burner element or incandescent bulb.   When energized they have a PF of unity.

Power factor (PF), as described briefly on the Power Quality page, can be represented by the power triangle to show the relationship between real power in kilowatts (A), reactive power in kilovolt-amps reactive (B) and apparent power in kilovolt-amps (C):

Real power performs actual work such as heating a burner element or illuminating an incandescent bulb.  Reactive power does not perform work but energizes magnetic fields in motor windings or power supplies which create inductive loads.  Apparent power is the result of combining real power and reactive power.  It measures the true load of an electrical distribution system.

If real power and reactive power exist simultaneously, why can't we just add them together to get apparent power?  The reason is that purely reactive current (inductive load) is ninety degrees out of phase with real current (resistive load).   Thus, we use the power triangle vectors to graphically represent this 90 degree relationship.

Another way to look at this relationship is to compare the sine waves, or oscillograms, of voltage and current for resistive and inductive loads.   In a purely resistive load the current sine wave and voltage sine wave are in sync with one another. The PF in this case is 100 percent or unity.

In a purely inductive load the current sine wave lags 90 degrees behind the voltage sine wave.  The PF in this case would be zero.

In the real world there are no purely inductive loads because there is always some amount of work being done by the device even if it is only the generation of heat.  On the other hand, purely resistive loads do exist in the real world such as a burner element or incandescent bulb.   When energized they have a PF of unity.