保护用电流互感器全自动伏安特性试验仪研制

Development of automatic volt-ampere characteristic tester for current transformer

介绍一种全自动伏安特性试验仪的研制过程。装置的强电和弱电环节在单片微计算机的控制下协调工作。内置的升压器由伺服电机驱动,具有不同的升、降压速率。电压和电流双通道测量,2路A/D同时转换,体现了真正的实时性。采样前对被测电量进行真有效值变换,避免了试验中互感器铁芯磁饱和时,电压、电流波形的畸变对测量准确性的影响。切换量程通道的电子模拟开关中导通电阻的处理和仪器的数字式校准技术提高了测量的准确度,各通道全量程精度均高于0.5%。为在伏安特性曲线图中体现出铁芯饱和前电流值的细微变化,试验数据的尺度变换技巧实现了特性曲线在对数坐标中的显示和打印。

The development of an automatic voh-ampere characteristic tester is introduced. Controlled by MCU,the electrical part and the electronic part of the tester work in phase. The inner auto -transformer is driven by servomotor;with different speeds in voltage rising and falling. The voltage and current are measured and converted simultaneously through dual channds and A/D converters to reach the real time performance. The RMS/DC transform before sampling avoids the influence of voltage/current waveform distortion on measurements,which is caused by the iron core saturation of transformer. The proper disposition of the on-resistance of analog switch and the application of digital calibration technique improve the veracity of tester. The precision is better than 0.5 % all over the scale. Using the skill of scale transform,the characteristic curve can be displayed and printed in logarithmic coordinates to show the tiny change of current before saturation.