Challenges in electrical power measurements of adjustable speed drives and motors
- Univ. of Florida, Gainesville, FL (United States)
- Polytechnic Univ., Brooklyn, NY (United States)
The numerous advantages of adjustable speed drives (ASDs) have caused a rapid growth of their applications in HVAC equipment. Power electronic converters, which are the heart of ASDs, shape current and voltage waveforms both at power-grid--ASD and ASD--motor terminals making the waveforms nonsinusoidal. The character of waveform distortion is different for various types of ASDs. Accurate measurements of electrical power under nonsinusoidal waveform conditions pose a serious challenge for engineers and scientists. The power information is, however, very important for efficiency optimization of HVAC equipment. There are two kinds of problems associated with power measurements. One is to select an instrument best suited to precisely measure electrical quantities under a particular type of distortion, the other is to interpret correctly the results, in the instrumentation area, this paper presents the principle of operation of modern solid-state power analyzers, their parameters and technical limitations. Accuracy of three selected meters in ASD efficiency measurements is experimentally investigated. The pitfalls of the fast Fourier transform (FFT) method used for harmonic analysis are discussed. Regarding the theoretical interpretation of the measurements, power definitions under nonsinusoidal conditions are reviewed. Particular stress is put on reactive power, compensation of which increases equipment efficiency. Nowadays, there is no commonly agreed upon reactive power definition. Several definitions are presented, discussed and illustrated by an ASD waveform example. Conclusions and suggestions for further research are given.
- OSTI ID:
- 479418
- Journal Information:
- ASHRAE Journal, Journal Name: ASHRAE Journal Journal Issue: 2 Vol. 39; ISSN 0001-2491; ISSN ASHRAA
- Country of Publication:
- United States
- Language:
- English
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