Operation with RL Load:

With an inductive-load, the output voltage waveform is similar to that with a resistive-load, however the load-current cannot change immediately with the output voltage. The operation of half-bridge inverter with RL load is divided into four distinct modes. Voltage and current waveforms are shown in Fig. 2 . $D_{1}$ and $D_{2}$ are known as the feedback diodes.

Mode $\boldsymbol{I}\left(t_{1} \lt t \lt t_{2}\right) :$ $S_{1}$ is turned-on at instant $t_{1},$ the load voltage is equal to $+E_{\mathrm{dc}} / 2$ and the positive load current increases gradually. At instant $t_{2},$ the load- current reaches the peak value. Switch $S_{1}$ is turned-off at this instant. Due to same-polarity of load voltage and load current, the energy is stored by the load $[\text { Fig.3(a)}].$

Mode $\boldsymbol{II}\left(t_{2} \lt t \lt t_{3}\right) :$ Due to inductive-load, the load current direction will be maintained even-after S is turned-off. The self-induced voltage in the load will be be negative. The load current flows through lower half of the supply and $D_{2}$ as as shown in $[\text { Fig.3(b)}].$ In this mode, the stored energy in load is fed back to the lower half of the source and the load voltage is clamped to $-E_{\mathrm{dc}} / 2 .$.

Mode $\boldsymbol{III}\left(t_{3} \lt t \lt t_{4}\right) :$ At instant $t_{3},$ the load-current goes to zero, indicating that $a_{1},$ the stored energy, has been returned back to the lower half of supply. At instant $t_{3}, S_{2}$ is turned-on. This will produce a negative load voltage $e_{0}=-E_{\mathrm{dc}} / 2$ and a negative load current. Load current reaches a negative peak at the end of this interval $[\text { Fig.3(c)}].$

Mode $\boldsymbol{IV}\left(t_{0} \lt t \lt t_{1}\right) :$ Switch $S_{2}$ is turned-off at instant $t_{4} .$ The self induced voltage in the inductive load will maintain the load current. The load voltage changes its polarity to become positive $E_{\mathrm{dc}} / 2,$ load current remains negative and the stored energy in the load is returned back to the upper half of the d.c source $[\text { Fig.3(d)}].$ At $t_{5},$ the load current goes to 0 and $S_{1}$ can be turned-on again. This cycle of operation repeats.