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A Practical Primer On Motor Drives (Part 15): Low-Pass And Harmonic Filtering Of Power Measurements Focus: Most power analyzers utilize an analog-to-digital conversion system to digitize the
voltage and current waveforms, and then perform power calculations on each acquired cycle.
By default, the instrument’s analog bandwidth and digital sample rate combine to determine
the maximum (full-spectrum) frequency of the acquired voltage and current signals, and
thus the number of harmonic orders present in the power calculations. One may employ
analog or digital low-pass filters, complex harmonic filters, or any combination of these,
to achieve filtering of the acquired full-spectrum signals. This part explains how these
different filtering options work and shows how they are configured on Teledyne LeCroy’s
Motor Drive Analyzer. Measurement examples of motor drive waveforms that have been
processed using a discrete Fourier transform (DFT) digital harmonic filter demonstrate the
impact of filter settings on calculated power values. Finally, the last section in this
part discusses the impact of line-to-reference voltage probing of PWM signals on drive
outputs and how the analyzer’s harmonic filtering can be used to remove the high common-
mode voltage present on such measurements.
What you’ll learn: - How to understand the different filter options for motor drive power measurements
- How to apply analog or digital low-pass filters, complex harmonic filters or a combination
of these to motor drive measurements made using Teledyne LeCroy’s Motor Drive Analyzer
View the Source
Author & Publication: Ken Johnson, Teledyne LeCroy, Chestnut Ridge, N.Y., How2Power Today, Apr 17 2017
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