Full Bridge Inverter with R-L Load : Working and Output Waveforms+
Full Bridge Inverter is Voltage source inverter that converts input DC voltage into AC output voltage.
The ac output voltage is twice that obtained with half-bridge VSI topologies.
The operation of Full Bridge Inverter with R-L Load is divided into 4 modes of Operation :
Mode 1 : t1 to t2
At instant t = t1 ⇒ S1 & S2 is turned ON simultaneously and S3 & S4 is turned OFF .
Load current starts increasing exponentially due to inductive nature of load.
Energy will be stored in inductive load.
The instantaneous current through S1 & S2 will be equal to instantaneous load current .
V0 = +VS
Mode 2 : t2 to t3
At instant t = t2 ⇒ S1 & S2 is turned OFF simultaneously and D3 & D4 is turned ON .
Load current doesn't reduce to zero instantaneously due to inductive nature of load.
Self induced emf across the load maintains the direction of load current as before.
The polarity of this voltage will be exactly opposite to that of Mode 1 voltage.
V0 = -VS
Load current continues to flow in the same direction through diodes D3 & D4 .
The stored energy in the laod is returned back to source
Mode 3 : t3 to t4
At instant t = t3 ⇒ S3 & S4 is turned ON simultaneously and D3 & D4 is turned OFF .
The direction of Load current will reverse and increases exponentially and load again stores energy.
But the polarity of this voltage will remain negative .
V0 = -VS
Mode 4 : t4 to t5
At instant t = t4 ⇒ S3 & S4 is turned OFF simultaneously.
The inductive load tries to maintain the load current in the same direction by inducing positive load voltage.
This will forward bias the diodes D1 and D2
The energy from the load is returned back to supply.
Load voltage remains positive V0 = +VS
The load current remain negative and decreases exponentially towards zero.
At t5 the load current reduces to zero and S1 and S2 can be turned ON again.
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