| The material characteristics of electrical equipment such as motors and transformers are affected by the interaction of complex physical factors such as electricity,magnetism,fluid,heat and stress during the actual operation.This kind of coupling effect of multiple physical fields makes it very difficult to accurately analyze its operation performance.Electrical steel sheet is widely used in the iron core of these electrical equipment,and its electromagnetic characteristics are affected by physical factors of temperature and stress.In addition,complex magnetization factors such as rotating magnetization and harmonic wave also have a significant impact on the material properties of electrical steel sheet.Therefore,in order to accurately analyze and calculate the performance of electrical equipment,it is necessary to measure the material characteristics of electrical steel sheet.The measurement of the complex magnetic characteristics of electrical steel sheets under the combined factors of temperature and stress needs to consider parameters such as temperature,stress vector,axial ratio,magnetization angle,frequency and harmonics.These parameters themselves have a wide range of values and are combined with each other to test the work.As many as hundreds of cases,the workload of the entire measurement will be very huge,so it is necessary to develop an automatic measurement system.This paper mainly completes the design of an automatic measurement system for complex magnetic properties of electrical steel sheets and a program for measuring complex magnetic properties based on the LabVIEW platform.The hardware part of the measurement system is designed with STM32 as the core.temperature automatic loading module,including the host computer,STM32 core board,temperature controller,thermistor and so on.The temperature is automatically loaded by the host computer and MCU through serial port communication.The MCU transmits the temperature command to the temperature controller through the RS485 interface.The temperature of the sample is detected by the thermistor and the detected signal is fed back to the temperature controller.The temperature controller adjusts the feedback temperature signal and controls the ceramic heating plate to heat the electric steel sample.The stress automatic loading module mainly includes the host computer,STM32 core board,L298 N motor drive board and force sensor.The stress automatic loading control is sent by the host computer to the MCU through the serial port.The MCU compares the error and outputs the corresponding pulse to drive the motor.The stress vector of the sample is loaded by the linear motor and the real-time stress value is obtained by the force sensor and fed back to the MCU complete automatic control.The part of software is based on the LabVIEW platform,a non-sinusoidal excitation program for complex magnetic characteristics of electrical steel sheets is designed and the waveform feedback control method is improved,and then the magnetic characteristics under different frequencies and different harmonic excitations are measured,including different Axial ratio,magnetization angle and amplitude of magnetic flux density.The temperature varies from room temperature to 180℃,and the stress varies from-15 MPa to + 15 MPa.Finally,from the measurement results,the variation law of complex vector magnetic properties of electrical steel sheet under temperature stress coupling is summarized. |
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