This applet demonstrates the loss of commutation which might occur if the thyristor converter operates in inverter mode with the triggering angle too close to 180 degrees. As an example we selected the three-phase half-bridge thyristor rectifier. If the commutation process is not finished before reaching 180 degrees, the commutation fails, and the phase remains in the conduction state. The converter output voltage does not balance the load voltage any more, and the quickly rising voltage drives the phase current to extremely high values.

• Increase the stray inductance to increase commutation time and finally reach loss of commutation.
• Reduce the mains voltage amplitude (drag red point on the u1-curve) or increase the load side DC voltage (drag the red horizontal line with label 'u0') to drive the converter system into loss of commutation.
• Increase the triggering angle to reach loss of commutation.
• Drag the time slider from left to right. After passing the triggering point, the trigger pulse is animated. After triggering, the thyristor is in the on-state and the load current keeps flowing.