Variable speed motor drive generated magnetic fields

Variable speed motor drives produce nonsinusoidal currents and generate periodic magnetic fields with significant frequency content. This paper describes measuring techniques and an evaluation method to characterize the generated fields. The study involved three drives rated from 1-150 hp. They produced field strengths up to 100-200 mG and had harmonic distortion factors of 50-60% in the 15-60 cm range from the motor. The dominant frequency range is 15-1000 Hz. The results emphasize the importance of the characterization of electronic device generated magnetic fields.<
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