| The technology of alternating variable frequency adjustable speed has developed rapidly since the 80's last century. The motor of alternating transmission system has so many specialties, such as small cubage, lightweight, high speed and high-power that the technology of alternating transmission leads the direction of the development of locomotive transmission technique. Now, our domestic railway is promoting the "ten-year conversion" project which is to realize the transition from direct current traction and transmission to alternating. The research how to develop a high performance and price ratio testing device, which samples, analyze and processes the main electric parameters, and makes scene maintenance and examine and repair easy is very important.Voltage traction converter which consists of 4qs and PWM inverter is the elementary circuit of electric locomotive's main converter. The input voltage of this converter is PWM wave with fixed frequency, and the output voltage is PWM wave with variable frequency. Compared with 50Hz electric signal, PWM wave has severe aberration, and the waveform has several across-zero points, so it is difficult to get its cycle by ordinary data processing methods, which will affect the computation of current and voltage. What's more, because the middle direct voltage is high up to 2800V, the sensors need higher insulated voltage and wider frequency band. Data acquisition commonly requests 16 channels and 10 kHz sampling frequency. Based upon what has been mentioned above, the paper has accomplished the following work.Firstly, the paper analyzes the principle and testing request of domestic modern locomotive alternating traction and transmission systems, and the paper analyzes and discussed the choice of the sensors with high insulated voltage. In addition, the paper analyzes the effects of A/D conversion accuracy and sampling frequency on testing accuracy. Based on the conclusion, PCL-1800 is used to configure data acquisition system. Secondly, MATLAB off-line sampling data analysis is introduced. Fundamental wave frequency can be obtained from sampling data by across-zero point method. Then, the author accomplishes electric parameters calculation and spectrum analysis. Stockadeeffect, frequency aliasing and spectral leakage issues are also discussed. The spectrum testing results have higher accuracy by the technology of spectrum emendation. Lastly, the paper analyzes the effects of finite register length by simulation.
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