The current waveform in the load depends on the load components. For the
resistive load, the current waveform matches the shape of the output voltage. An
inductive load will have a current that has more of a sinusoidal quality than the
voltage because of the filtering property of the inductance. An inductive load presents
some considerations in designing the switches in the full-bridge circuit
because the switch currents must be bidirectional.
For a series RL load and a square wave output voltage, assume switches S1
and S2 in Fig. 8-1a close at t=0. The voltage across the load is Vdc, and current
begins to increase in the load and in S1 and S2. The current is expressed as
the sum of the forced and natural responses