Electric Circuits and Networks

9.6 SUMMARY

• A set of three sinusoidal quantities, all at the same frequency, with equal peak (and hence equal r.m.s) values and shifted successively by 120° in phase is defined as a Balanced Three-Phase Quantity. Therefore, if x₁(t), x₂(t) and x₃(t) is a three-phase set, then,

   

  

   

  If the peak values are unequal and/or successive phase shifts are different from 120°, the set will be called an Unbalanced Three-Phase Quantity. A three-phase source is specified by specifying line-to-line voltage r.m.s values.

• Each limb or branch of a three-phase system (source or load) is termed as a phase. R, Y and B are used to designate the line terminals of ...