High precise, high voltage pulse generator made up of high-power IGBT and pulse transformers controlled by a computer are described. A simple main circuit topology employed in this pulse generator can reduce the cost ...High precise, high voltage pulse generator made up of high-power IGBT and pulse transformers controlled by a computer are described. A simple main circuit topology employed in this pulse generator can reduce the cost meanwhile it still meets special requirements for pulsed electric fields (PEFs) in food process. The pulse generator utilizes a complex programmable logic device (CPLD) to generate trigger signals. Pulse-frequency, pulse-width and pulse-number are controlled via RS232 bus by a computer. The high voltage pulse generator well suits to the application for fluid food non-thermal effect in pulsed electric fields, for it can increase and decrease by the step length 1.展开更多
Due to overvoltage produced by inverter output,inverter-fed motor insulation systems often experience fast electrical aging process,especially when partial discharge(PD) is incepted.Before putting into use,the PD dete...Due to overvoltage produced by inverter output,inverter-fed motor insulation systems often experience fast electrical aging process,especially when partial discharge(PD) is incepted.Before putting into use,the PD detection should be performed on inverter-fed motors at repetitive square voltages to avoid the PD caused insulation deterioration when the motors are collected to inverters having specific characteristics.However,unlike PD tests at AC/DC voltages proposed in IEC 60270,the PD detection at repetitive square voltages is much more complex because of serious interference generated by impulse generator.To solve the problem,ultra-high frequency(UHF) method seems recommendable for its preferable signal-to-noise ratio(SNR).The chief aim of this study is to investigate PD pulse and statistical characteristics of turn-to-turn insulation for inverter-fed traction motors.A square-shaped Archimedes antenna,specially designed for the PD detection at repetitive square voltages of fast rise times,was used to perform PD tests on turn-to-turn insulation models.Time and frequency analysis results indicate that energy component of generator disturbance and PD pulses are mainly distributed in the 0-0.5 GHz and 0.6-1.5 GHz range,respectively.Based on the results,suitable filter was designed for power disturbance suppression.Additionally,resorting to the sensor unit(i.e.antenna and filter) and the PD test system,the PD statistical features at square voltages of different frequencies were obtained.Experimental results show that higher frequency will give rise,statistically,to PD of lower magnitudes distributing at smaller phases.A reasonable interpretation of this phenomenon was presented.Lastly,according to the PD statistical features,some suggestions for the PD detection system design,generator parameter optimization and the PD pulse extracting were given.The results of this work would be beneficial to the increase of the sensitivity when performing the PD detection on insulation systems for inverter-fed motors at repetitive square voltages and thus,improving the reliability of inverter-fed motors.展开更多
A new experiment-library least-squares(experiment-LLs) method used in the neutron inelastic-scattering and thermal-capture analysis(NITA) technique for on-line coal analysis was developed,which has significantly decre...A new experiment-library least-squares(experiment-LLs) method used in the neutron inelastic-scattering and thermal-capture analysis(NITA) technique for on-line coal analysis was developed,which has significantly decreased the non-linear radiation effects.In this method,sixty samples with preset elemental contents were made,from whose experimental spectra twenty single-element spectrum libraries corresponding to twenty kinds of coal were built using the least-squares method.The spectrum of the unknown sample was analyzed based on these twenty libraries to estimate its element contents.With the initial estimated result,the procedure of developing library and analysis was iterated to build a new library with the closest element contents to the unknown sample.Hence the experiment-LLs method can reduce non-linear radiation effects.The experiment-LLs method was performed on an improved coal analysis system which was equipped with a long-life 14 MeV pulsed-neutron generator,a bulk BGO detector with a temperature controller,a moisture meter and coal-smoothing device.The precisions of this system for ash content,water content,volatile content and calorific value have reached 1.0wt%,0.5wt%,1.0wt%,350 kJ/kg,respectively.展开更多
文摘High precise, high voltage pulse generator made up of high-power IGBT and pulse transformers controlled by a computer are described. A simple main circuit topology employed in this pulse generator can reduce the cost meanwhile it still meets special requirements for pulsed electric fields (PEFs) in food process. The pulse generator utilizes a complex programmable logic device (CPLD) to generate trigger signals. Pulse-frequency, pulse-width and pulse-number are controlled via RS232 bus by a computer. The high voltage pulse generator well suits to the application for fluid food non-thermal effect in pulsed electric fields, for it can increase and decrease by the step length 1.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51177136,50377035)Zhuzhou Electric Motor Company of South China Locomotive & Rolling Stock Corporation Lim-ited
文摘Due to overvoltage produced by inverter output,inverter-fed motor insulation systems often experience fast electrical aging process,especially when partial discharge(PD) is incepted.Before putting into use,the PD detection should be performed on inverter-fed motors at repetitive square voltages to avoid the PD caused insulation deterioration when the motors are collected to inverters having specific characteristics.However,unlike PD tests at AC/DC voltages proposed in IEC 60270,the PD detection at repetitive square voltages is much more complex because of serious interference generated by impulse generator.To solve the problem,ultra-high frequency(UHF) method seems recommendable for its preferable signal-to-noise ratio(SNR).The chief aim of this study is to investigate PD pulse and statistical characteristics of turn-to-turn insulation for inverter-fed traction motors.A square-shaped Archimedes antenna,specially designed for the PD detection at repetitive square voltages of fast rise times,was used to perform PD tests on turn-to-turn insulation models.Time and frequency analysis results indicate that energy component of generator disturbance and PD pulses are mainly distributed in the 0-0.5 GHz and 0.6-1.5 GHz range,respectively.Based on the results,suitable filter was designed for power disturbance suppression.Additionally,resorting to the sensor unit(i.e.antenna and filter) and the PD test system,the PD statistical features at square voltages of different frequencies were obtained.Experimental results show that higher frequency will give rise,statistically,to PD of lower magnitudes distributing at smaller phases.A reasonable interpretation of this phenomenon was presented.Lastly,according to the PD statistical features,some suggestions for the PD detection system design,generator parameter optimization and the PD pulse extracting were given.The results of this work would be beneficial to the increase of the sensitivity when performing the PD detection on insulation systems for inverter-fed motors at repetitive square voltages and thus,improving the reliability of inverter-fed motors.
基金supported by the National Basic Research Program of China (Grant No. 2007CB815005)the National Natural Science Foundation of China (Grant No. 11075064)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No.20050183008)
文摘A new experiment-library least-squares(experiment-LLs) method used in the neutron inelastic-scattering and thermal-capture analysis(NITA) technique for on-line coal analysis was developed,which has significantly decreased the non-linear radiation effects.In this method,sixty samples with preset elemental contents were made,from whose experimental spectra twenty single-element spectrum libraries corresponding to twenty kinds of coal were built using the least-squares method.The spectrum of the unknown sample was analyzed based on these twenty libraries to estimate its element contents.With the initial estimated result,the procedure of developing library and analysis was iterated to build a new library with the closest element contents to the unknown sample.Hence the experiment-LLs method can reduce non-linear radiation effects.The experiment-LLs method was performed on an improved coal analysis system which was equipped with a long-life 14 MeV pulsed-neutron generator,a bulk BGO detector with a temperature controller,a moisture meter and coal-smoothing device.The precisions of this system for ash content,water content,volatile content and calorific value have reached 1.0wt%,0.5wt%,1.0wt%,350 kJ/kg,respectively.
