Ok, so I know this might open a can of worms on electrical/electronics theory but I need to understand this....
I just took a class on VFDs. I understand how it works but I'm hung up on something. How exactly do the IGBT's in the inverter section create both polarities of the sin wave? Here are my references: (see attached graphics)
My questions are: isn't current always flowing from + to - on the DC bus (negative current flow?) or will it flow in the other direction through the energized IGBT if the diode is checking it (my best guess at how it works)? From that, do the IGBT's conduct through the diode if the gate is not energized? If the gate is energized will current go around the diode in positive current flow? What is the significance of the orientation of the collecting and emitting ends of the IGBT's?
I know these might not be easy concepts to explain, but anything to explain the original question would help. I'm going nuts trying to understand this.
Any graphics of current flow superimposed on a diagram of the inverter section, with corresponding references to the cycle and states of the IGBT's would be lovely!