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Effects of low frequencies on three phase induction motor performance operating in close proximity t
The calculation of harmonics torques in induction motors is carried out in similar manner to the fundamental taking into consideration the frequency of the harmonic order and its sequence with respect to the fundamental. Torque pulsation is estimated on different bases. Such estimation can be misleading due to nearness of the harmonic torques and torque pulsation frequencies and their interactive effects on the speed of induction motors.
The problems associated with sub-harmonics had not been investigated thoroughly in the same manner higher harmonics have been studied. Hence, with the increase of sub-harmonics injection in networks and the consequent voltage distortion, it is quite important now to study the effects of lower frequencies on induction motors performance.
The work in this paper is to investigate the effects of low order harmonics (sub-harmonics) in the range from 1 to 10 Hz on the performance of induction motor operating in proximity to rated speed. This paper explains the speed fluctuations that might result from sub-harmonics voltages present in the supply voltage. The sources of sub-harmonic currents are diverse and swelling in power consumption like arc furnaces, cycloconverters ...
Theoretically, it is possible to analyze the affects of cascaded ac sources of different frequencies and amplitudes by implementing the superposition method.
