| DPF | Displacement Power Factor. DPF is used to measure the effect of inductive (motor, transformer) and capacitive loads on the efficiency of an AC distribution system. Such loads have a reactive component (see VARs) which must be taken into account when sizing system capacity, but they are still linear loads (current is drawn as a sine wave). DPF therefore does not include the effect of non-linear harmonic currents. However, a low DPF will be a major cause of a low PF (Total Power Factor), and would indicate the need for corrective measures. |
| PF | Power Factor or Total Power Factor. Active Power divided by Apparent Power. PF is a measurement of the efficiency of an AC power transmission and distribution system, including the effects of harmonics. Harmonic currents cause PF to be lower than DPF. |
| % THD-F | Percent Total Harmonic Distortion-Fundamental reference. This reading represents the ratio of the harmonic components of voltage (or current) to the voltage (or current) of the fundamental alone. All measurements are true-rms. |
| % THD-R | Percent Total Harmonic Distortion-RMS reference. This reading represents the ratio of the harmonic components of voltage (or current) to the total voltage (or current), including the fundamental and all harmonics. All measurements are true-rms. |
| (k)W | (kilo) Watts. Active power, also known as Real/True Power. Watts measure that portion of electrical power which does work, which by definition includes heat losses. |
| (k)VA | (kilo) Volt-Amperes. Apparent power. VA is computed by taking the product of the rms values of voltage and current. It is a measure of the total electrical power capacity of a distribution system or component equipment. In addition to Watts, it includes the contributions of VARs and harmonic currents. This term is of interest because utility and facility engineers must size their system equipment in VA, in effect providing the current-carrying capacity to handle the worst-case situation. |
| (k)VAR | (kilo)Volt-Amps Reactive. Reactive Power. VARs are the reactive component of VA (Apparent Power), caused by a phase shift between AC current and voltage in inductors (coils) and capacitors. In inductors, current lags voltage (in time), while in capacitors, current leads voltage. VARs are typically first present in a distribution system as a result of inductive loads such as motors, reactors and transformers. VARs are then used in sizing power factor correction capacitors, which are used to offset the effects of these inductive loads. |
