TABLE OF CONTENTS It may seem odd to treat these two quantities together, but power factor correction in the presence of harmonic currents poses special problems, and correction of harmonic problems may affect the circuit power factor. The two are best considered together so their interactions can be better understood. The author had the pleasure of presenting tutorial sessions on power factor and harmonics for several years at national meetings of the IEEE Industry Applications Society.
Power factor, as everyone knows, is defined as the ratio of real power to volt-amperes and is the cosine of the phase angle between the voltage and current in an AC circuit. These are neatly defined quantities with sinusoidal voltages and currents. Power factor can be improved by adding capacitors on the power line to draw a leading current and supply lagging vars to the system. Power factor correction capacitors can be switched in and out as necessary to maintain var and voltage control.
As mentioned in Chapter 1, many utilities charge industrial customers a certain rate for kilowatt-hours of energy consumed in a month, and another charge related to the infrastructure necessary to supply that power under the customer's conditions of operation. If the customer is operating with a low power factor load, the demand charge is higher, because the current requirement is higher. Table 14.1 shows the differences between energy and demand.
| Energy | Demand |
|---|---|
| Kilowatt-hours from: | Kilovoltamperes from: |
| Tons of coal | Generators |
| Acre-feed of water | Transmission lines |
