| Positive Temperature Coefficient of Resistance(PTCR)elements have three basic characteristics:resistance temperature characteristics,volt-ampere characteristics and current-time characteristics,and are widely used in many fields.In practical applications,it is found that under a certain temperature,the zero power resistance of the PTCR element will show an obvious downward when applied with the increased voltage.This phenomenon is the voltage effect.In this research,the test data of voltage effect test can simultaneously reflect the influence of the applied voltage and temperature on its performance.Voltage effect has a great negative influence on the work of PTC thermistor,especially under high voltage.If this influence cannot be limited to a controllable range,it will show an unstable performance or even cause damage to the equipment.Nowadays,with the rapid development of new energy vehicles,the demand for PTCR components,which can withstand high voltage,has surged.Therefore,the test equipment of high withstand voltage PTCR voltage effect has important research significance.The high withstand voltage PTCR voltage effect test needs to be completed under zero power conditions,so there are higher requirements for test voltage and data acquisition.The innovative design of this article uses millisecond-level high-voltage pulse sources to provide voltage(50～1000 V).The programmable peak voltmeter with sampling rate collects data in real time,so that the whole test process is in full compliance with the zero power condition.In the case of high voltage loading,the partial voltage of the sampling resistor fluctuates drastically due to the excessive change of the PTCR’s own resistance(10~3～10~7Ω).Therefore,in this research,we designs the multi-stage dynamic switching of the sampling resistor to reduce the error,so that the load is loaded on the PTCR.The high voltage above fluctuates is limited in a small range.We also designs an electric furnace to provide a varied test temperature environment(30～305℃)and isolates the high and low temperature circuits to ensure the stability of the test.The temperature control program was designed to realize the intelligent control of the temperature in the furnace;the overall software part of the system uses C++11 multi-threaded programming to keep the temperature and voltage data reading synchronized,to ensure the immediacy and accuracy of the data,and to control each module to complete the test of the PTCR voltage effect at different temperatures.After completing the construction and debugging of the system,I set multiple tests of PTCR sampled and recorded the temperature-resistance curves under different high voltage,then fitted the voltage effect curve after processing the data.Through comparative analysis and calculation of the voltage effect coefficient,the results obtained are basically in line with our expected results.then a detailed error analysis was carried out for the unevenness of the voltage curve,and we successfully gave out some improvements.The test system designed in this research can basically realize the zero-power voltage effect test of PTC thermistor under high voltage intensity,which provides a strong theoretical basis for studying the voltage effect of high withstand voltage PTC thermistor. |
