Dynamic Measurements of the Main Electrical Parameters of a Dc Machine

Since in many applications of dc machines an accurate knowledge of the dynamic mathematical model is necessary, it is desirable to have simple measurement methods to obtain the different parameters required. A new approach of defining the electrical parameters of a dc machine is shown. The measurement techniques provide dynamic resistance and inductance characteristics which are shown to be very much off the usual values taken from a linear approximation. Resistance values are measured by modified voltage drop methods, and inductance values are measured by load current variations. In case of transient behavior, like sudden short circuits or sudden load variations, the linear model cannot be applied, and the dynamic resistance and characteristics used in the nonlinear differential equations describing the system provide a good model within experimental error. The results show in particular how the armature inductance is dependent on the load as well as on the speed of rotation.