Behavior of the Scheme Source - Capacitor - Induction Motor when Voltage Sags and Short Interruptions Take Place

The self-excitation phenomenon was investigated by the presence of capacitors connected in the proximities of induction motors, when voltage sags and short interruptions take place. The investigation was carried out in analytic form using Matlab and experimentally in the laboratory of the IPSEP. This phenomenon has been reported as the origin of numerous damages inside industrial facilities. From the investigation can be concluded that in the event of short interruptions, the mentioned phenomenon is not excited provided the capacitor doesn´t exceed a certain value of reactive power. Transients of considerable magnitude are presented, being its energy function of the induction motor shaft load. For higher number of capacitors or higher reactive power, a smooth voltage fall takes place showing also an important reduction of speed, being followed by high overvoltages previous to the voltage restoration. The overvoltage surge takes place with higher reactive power, what leads to the damage of the capacitors. The same phenomenon but in smaller scale is presented with three phase voltage sags