Another general industrial load may be modeled as a series resistance, inductance, and a dc voltage source, as shown in Fig. 4-5a. A dc motor drive circuit
and a battery charger are applications for this model. There are two possible
modes of operation for this circuit, the continuous-current mode and the
discontinuous-current mode. In the continuous-current mode, the load current
is always positive for steady-state operation (Fig. 4-5b). Discontinuous
load current is characterized by current returning to zero during every period
(Fig. 4-5c).