Flyback diode

In a three-phase inverter, a bridge circuit is configured by six rectifying diodes. This is a 3-phase full-wave rectification circuit and it causes the current due to the back-emf of the motor winding to fly back to the DC side. In fig. (a), the resistor R is placed on the DC side, and this is used as a feedback path. Figure (b) illustrates the appearance of pulsating DC voltage across the resistor R, through the two diodes in the path with the highest back emf (e_A – e_B), (e_B – e_C), (e_C – e_A) .

Three-phase rectifier circuit constructed in an inverter. Two of six diodes are conducting a current. The highest back-emf of (e_A – e_B), (e_B – e_C), (e_C – e_A) supplies current to R via two of the six diodes.