Single Phase Bridge DC-AC Inverter with R-L Load

The function of the inverter in case of R-L load can be explained as follows:

Case 1 : At time t = T₁, the switches S₁ and S₂ are turned off and the pair of swithces S₃ and S₄ are turned on . Due to the inductive load, the current through the load (i_L) will not change its direction at t = T₁ and will continue to flow through the load from point a to b , through the diodes D₃ and D₄, till it becomes zero as shown in Figure 10a . Once i_L = 0 , S₃ and S₄ start conducting and the load current i_L builds up in opposite direction (point b to a ).

Case 2 : At time t = T₂, the switches S₁ and S₂ are turned on and the pair of swithces S₃ and S₄ are turned off . Just as in case 1 , the current takes time to become zero and diodes D₁ and D₂ conduct as long as its non-zero . This condition is shown in Figure 10b .

The instantaneous current through the R-L load is given by

                                                            (15)

The current and voltage waveforms for R-L load are shown in Figure 11 .In this figure the conduction is didvided into 4 distinct zones. In Zone I the diode D₁ and D₂ conduct until i_L becomes zero. Once i_L equals zero , the switches S₁ and S₂ conduct and it is marked as Zone II . At time t = T₂, the didoes D₃ and D₄ conduct and this is marked as Zone III in Figure 11 . Finally, in Zone IV the switches S₃ and S₄ conduct.