Summation of harmonic currents of variable-speed induction motor drives

In this paper, the problem of the summation of harmonic currents of induction motor variable-speed drives (IM VSDs) is analyzed based on computer simulations and field measurements. As a first step, the influence of different parameters on the phase angles of current harmonics of different orders is analyzed using computer simulations. Secondly, harmonic currents of several drives working in parallel were measured on two locations for a period of one week, with a time resolution of 1 s. The measured locations included drives with 6-pulse and 12-pulse rectifier front ends. From the measurements, coefficients for simplified harmonic current summation were calculated, together with their limit values.