Apparent Power and Efficiency of Three-Phase Four-Wire System

The differences between Buchholz's formula of apparent power and proposed formulation were demonstrated in the case of three-phase four-wire power system. It was shown that voltage integral from proposed formula of apparent power is the value of power losses in active resistances of power cable, which is due to load line-to-neutral voltages and short circuit mode of load. A new physical sense of apparent power was established, it is a geometric mean value of short-circuit power and power losses, caused by line currents. This definition of apparent power of three-phase power supply system is completely equivalent to definition standardized by IEEE. Conditions to achieve unit power factor and maximum efficiency of three-phase four-wire power system were established. The formula for determining efficiency of three-phase four-wire power system for unbalanced non-sinusoidal mode with a given load power factor and the known load factor has been derived. Computer simulation in MATLAB Simulink showed good agreement between the experimental data and the theoretical curves for efficiency both in the presence of the SAF, or without it. Ref. 8, Fig. 5, Таb. 1