Inverter - presentation of the switching operation in case of pulse width modulation (PWM)

Description:
The following simulation shows the switching operation between the transistors (e. g. IGBT's) and free-wheeling diodes of an inverter. The control of the transistors (switches) is executed by means of a PWM, so that consequently sinusoidal current flows are generated in the motor phases. The sinusoidal fundamental oscillation is superimposed by harmonics of higher frequency. The higher the switching frequency of the inverter the more the parts of the harmonics decrease.

Commutation:
In certain phases of the PWM the transistors of the inverter are switched on and off. The current flow in the motor phase is not interrupted abruptly, but it is maintained due to the motor inductance and searches the way via the free-wheeling diodes - the current commutates from the transistor to the free-wheeling-diode. The transistor switching and the current flows between the transistors, free-wheeling diodes and motor phases are well-presented in the following presentation (operating points of the PWM in motor and generator mode):  

• Simulation of the commutation processes and current flows in case of a one-phase PWM inverter with voltage link: https://www.ipes.ethz.ch/ipes/Inverter/e_H_Bruecke.html

The simulation is controlled by means of the mouse pointer at the red-marked points and lines.