AC Power and Energy Measurements based on Physical Definitions

The article presents the AC power measurements based on physical definitions as introduced by the draft German standard DIN 40110 in 1970 and its practical application as a power signal processor. The power processor is an electronic device allowing separation of the measured power signal (obtained from the multiplier circuit of voltages and currents) in two components: P+ and P- defined as the input power Pv and return power Pr. The separation is obtained by shifting the phase angle between the current and voltage. The value of return power is negative. Such separation is natural because it is based on physical phenomena of delivered, useful energy and harmful return energy flows. Return power is considered harmful because it causes heating of cables and sources of AC power (as transformers). Presented concepts and meters can be useful for accurate billing purposes for delivered electrical energy as well as for dynamic compensation of nonlinear loads to reduce the return power. Experiments realized using the power meter WL-1 synchro (operating according to physical definitions) confirms high percentage of return power for nonlinear loads, as AC powered LED light sources where the amount of return power can reach 70% of delivered power