An Experimental Investigation of Power Quality Effects on Torque Pulsations in an Induction Motor

Voltage disturbances occur frequently in power systems. The most important voltage disturbances are voltage unbalance, voltage deviation, and voltage waveform distortions. Voltage waveform distortions are usually considered harmonics, but subharmonics and interharmonics may also occur. Voltage subharmonics are components with frequencies lower than the fundamental frequency. In contrast, voltage interharmonics are components of the frequency spectrum that are higher than the fundamental frequency and are not integer multiples of it. Voltage fluctuations are the superposition of the first voltage harmonic and subharmonic components. This work analysed the shaft torque pulses of an induction motor under single-subharmonic action or under periodic voltage fluctuations combined with voltage unbalance. The experimental results were compared with results from previous work. We also analysed the influence of voltage disturbances on the selection of the coupling connecting the induction motor to the working machine.