PIC18F2550 AC Harmonik Bozulma Ölçer

Harmonik bozulma ölçer AC beslemesinin kalitesini ölçmek için tasarlanmış. Daha önce paylaşılan PIC18F2550 proje geliştirme kartı ve tam dalga doğrultucu devresi ile uygulanmış.

AC güç hattı, 220VAC düşürücü izolasyon trafosu ile ölçülüyor. 10-bit ADC’ye giriş sinyali tam dalga doğrultularak uygulanıyor. Yazılım, temel frekansın (50Hz) genliğini ve 3. harmoniği (150Hz) bulmaya yarayan DFT (Ayrık Fourier Dönüşümü) hesaplamasını gerçekleştiriyor. DFT hesaplaması ADC verileri 32 noktalı 10 bit çözünürlükte.

Ayrıca PIC18F2550 AC Harmonik Bozulma Ölçer projesinin Alarm ve aşırı yük göstergesi olan ikinci versiyonu bulunuyor. Uydulamaların kaynak Mikro-C kodları var.

The 3rd harmonic distortion meter has been designed for measuring the quality of AC supply. The meter is built with a PIC18F2550 project board and the full wave rectifier front-end circuit. The AC power line, 220VAC is measured through the step down isolation transformer. The input signal to the 10-bit ADC is full wave rectified. The software performs DFT calculation finding the amplitude of the fundamental frequency and the 3rd harmonic. The distortion is computed by the ratio of the amplitude of the 3rd harmonic to the fundamental frequency. The meter has been tested with the square wave signal resulting 33% distortion. For low voltage AC utility, 220V, the reading showed approx. 3%. The meter can be applied for high voltage application with the appropriate signal conditioning.

Nowadays an increasing of the electronic devices having nonlinear characteristics are many used at home and office. Such devices mostly are computer based equipment with a low power factor switch mode power supply. The input circuit of the power supply uses a diode-capacitor at the front-end circuit. The current drawn is charging capacitor only near the peak voltage. Thus for a given feeder having finite impedance, there will be a lost from voltage dropped near the peak voltage resulting flattened top distortion of the AC voltage. To measure how high the distortion of AC voltage is, we may decompose it into the summation of sinusoid waves using DFT. The PIC harmonic distortion meter shows a method for finding the amplitude of the fundamental frequency and the 3rd harmonic. The reading shows percentage of the 3rd harmonic distortion.

Kaynak: http://chaokhun.kmitl.ac.th/~kswichit/

Alternatif Dosya indirme LINK listesi (TXT formatında) link-25668a.zip