Electrical Engineering ⇒ Topic : By Phasor Diagram

By Phasor Diagram

In this method, we find the magnitude and phase angle of each branch current. We then draw the phasor diagram taking voltage as the *reference phasor. The circuit or line current is the phasor sum of the branch currents and can be determined either (i) by parallelogram method or (ii) by the method of components. The second method is prefen-ed because it yields quick results.

Consider a parallel circuit consisting of two branches and connected to an alternating voltage of V volts (r.m.s.) as shown in Fig. (a)

The current I₁ in branch 1 leads the applied voltage V 'by Φ° as shown in the phasor diagram in Fig. (b).

The current I₂ in branch 2 lags behind the applied voltage V by Φ²° as shown in the phasor diagram in Fig (b).

                                figure  (a)                                                                                           figure   (b)

The line current I is the phasor sum of /₁ and /₂. Suppose its phase angle is Φ as shown in Fig.(b). The values of I and Φ can be determined by resolving the currents into rectangular components.

The phasor diagram method is suitable only when the parallel circuit is simple and contains two branches. However, if the parallel circuit is complex having more than two branches, this method becomes very inconvenient. In such a case, use of phasor algebra is recommended to solve parallel circuit problems