Abstract
Objective. This paper presents the results of investigation of the distorted current and voltage waveforms on the output of LS800-42K2-TD frequency converter with dc-link that were obtained by the АКТАКОМ АСК-2034 digital oscilloscope, the scalograms of the investigated signals (graphic interpretations their time-frequency representation), and their wavelet transforms as 3D dependencies obtained in Wolfram Mathematica by the simplified complex Morlet wavelet. Technique. The phase current oscillograms on the output of frequency converter with dc-link and linear voltage oscillograms on the outlets of driven motor were received in result of laboratory investigations. Wolfram Mathematica program to obtain the frequency and amplitude values for particular frequency components of the distorted current and voltage waveforms together with graphic interpretations their time-frequency representation (scalograms) was developed. Results. The high-frequency components in the 0.76-97.31 kHz range with voltage amplitudes up to 199% and current amplitudes up to 78% (with respect to power frequency) were identified on the output of frequency converter with dc-link using developed Wolfram Mathematica program. Duration of these high-frequency components reaches up to tens microseconds-only a few milliseconds while their pulse edge is similar to square-wave signal. Scientific novelty. The animated frequency spectra of the phase current on the output of frequency converter with dc-link and linear voltage on the outlets of motor that demonstrate the variations in the frequency content of the investigated signals for any time moment within all period of their registration were obtained by means of a special algorithm for identifying the frequencies and amplitudes of the individual harmonic components based on the simplified complex Morlet wavelet. A special Wolfram Mathematica subprogram to represent the wavelet transforms of the investigated signals as 3D dependencies was developed also. Practical value . The presented results can be used to estimate the negative effect of high-frequency components on the dc-link capacitors, winding insulation of driven motor and insulation of connecting cable, and for investigation of resonant effects causing the failures of the frequency converter and motor elements. Results of this paper would be useful for choosing the parameters of passive and active filters to suppress the high-frequency components.
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