Electrical Engineering ⇒ Topic : Components of admittance

Components of admittance. Depending upon the nature of reactance, the impedance of

an a.c. circuit can be expressed in the complex form as

                                      Z = R + j X_L or Z =R - jX_c

Here, R is the resistive or in-phase component of Z while X_L or X_c is the reactive or quadrature component of Z. Let us find the components of Y. We shall discuss two cases by way of illustration.

(1) R and L in parallel. Fig. a (i) shows the circuit. Here V is the applied voltage and Z is total circuit impedance.

                                                                          figure (a)

Fig. a (ii) shows the components G and B_L of Y. Here, G is the in-phase component of Y while B_L, is the quadrature component of Y. Note that G (conductance) is positive and B_L (inductive susceptance) is negative.

(ii) R and C in parallel. Fig. a (i) shows the circuit. Here V is the applied voltage and Z is total circuit impedance.

                                                                                   figure (a)

Fig. a (ii) shows the components G and B_c of Y. Here, G is the in-phase component of Y while B_c is the quadrature component of Y. Note that G (conductance) is positive and B_c (capacitive susceptance) is also positive

Note. Conductance G is always positive. However, B_L (inductive susceptance) is negative while B_c, (capacitive susceptance) is positive. Moreover, it is a usual practice to omit the suffix L or C with susceptance B. The positive sign with B indicates capacitive susceptance and the negative sign with B implies inductive susceptance