Power Quality and Electromagnetic Compatibility Aspects at Personal Computers

In this article, issues related to electromagnetic compatibility and energy/power quality for a laptop are addressed. Power quality problems are outlined. Testing frameworks (developed by authors) are presented and discussed for a laptop when two different sampling frequencies are used: 80 kHz and 19.2 kHz. Waveforms corresponding to the voltage across the laptop's terminals and current absorbed by it were acquired. Recordings and numerical processing, based on original software using Fast Fourier Transform, are discussed, and the analysis of waveforms in both cases is performed. Various power quality indices were calculated. Theoretical and practical aspects related to the determination of power quantities, power flows, and power factor are presented. Some conclusions concerning different ranges of frequencies are presented, along with some considerations for power quality problems. Tests for conducted emissions (single phase and neutral wire respectively) and for the radiated emissions (for horizontal and vertical polarizations) are presented. Comparisons to the emission standards were made. The immunity behavior for a laptop is discussed according to immunity standards. It is shown that new measures (e.g., active filters) are necessary for network protection when connecting a laptop to the network. Some considerations, based on the authors' observations concerning new standards for power quality and electromagnetic compatibility, are outlined.