Electrical Engineering ⇒ Topic : 3-phase Balanced Loads in Parallel

3-phase Balanced Loads in Parallel

In a 3-phase supply system, it is quite common to have balanced A and Y loads connected in parallel. Rarely the loads are all A-connected or all Y-connected. The problems on such parallel loads can be solved by one of the following three ways :

(1) All the Y-loads in the problem may be converted into equivalent A loads. Then these loads in parallel (all now being A loads) can be treated on a single-phase basis (line-to-neutral) to find the various circuit values e.g., currents, power factor etc.

(2) All the A loads in the problem may be converted into equivalent Y loads and treated as in (i) above.

Out of the above two methods, usually the latter is prefered because it is more convenient to handle Y-connection.

(3) A still shorter and more commonly used method is to treat each load on a complete 3-phase basis. The active, reactive and apparent powers in each 3-phase load are determined. The active powers (watts) of the parallel loads can be added directly to give the total active power P. The reactive powers (VAR) of the parallel loads can be added algebraically (with due regard to the *signs of inductive VAR and capacitive VAR) to give the total reactive power Q. Then total apparent power S (in VA) is given by

The various characteristic quantities (e.g., power factor, line current etc.) can be easily,determined for the combined loads