Use of logarithmic sensitivity in power system analysis: the example of lighting circuits (hot filament, LED and fluorescent lamp circuits)

Logarithmic sensitivity characteristics were widely employed by Ch. P. Steinmetz in his classical studies of magnetic systems. In the present case, the authors deal with power sensitivity, K(U) = (dP/P)/(dU/U), where U is the amplitude (scaling factor) of the applied voltage and P is the averaged power. That such characterisation can be suitable for non-linear power systems is demonstrated for lighting systems: incandescent lamp circuits (i.e. the hot filament), LEDs and fluorescent lamp (FL) circuits. For FL circuits, the problem of minimisation of K(U) is shown to be practically and methodologically very important. On the pedagogical regard, the opinion is expressed that the described use of K(U) should be taught in basic courses of circuit theory and power systems.