Three‐Phase Power

Summary

This chapter describes the three‐phase concept—how it works, why it was chosen, and basic techniques for analyzing three‐phase circuit. There are two reasons for configuring alternating current in three phases: economy of transmission, and efficiency of power conversion in rotating machines. The choice of delta or wye connection offers one way to select different voltage levels for loads from the same three‐phase power supply. Symmetrical components is the summary term for positive‐, negative‐, and zero‐sequence components. The benefit of symmetrical components is that they allow us to describe an imbalanced three‐phase situation in terms of three separate, superimposed balanced situations. The dqz transformation converts a set of rotating phasors into a set of stationary vectors in a rotating reference frame. This is especially useful for the analysis of voltages and currents within three‐phase machines.