The effect of harmonic torque to torsional vibration of induction machines

An increasing number of industrial control applications and home appliances employ power electronic devices which cause large concomitant harmonic cur rents. These harmonic currents distort the waveform of the voltage source a nd, in doing so, the distorted voltage can induce harmonic pulsating torque in the air gap and rotor harmonic torque of an induction machine. This har monic pulsating torque generally causes torsional vibration. In addition, w hen the natural frequency of the mechanical system is in the proximity to t he frequency of the rotor harmonic torque, the magnitude of the vibration b ecomes amplified and deteriorates rapidly; the torsional resonance occurs a s well. In this investigation, we analyze the phenomena of torsional resona nce caused by rotor harmonic torque and torsional vibration caused by harmo nic pulsating torque.