| As one of main power equipments in the industrial production processing, due to complex work environment coupled with unstable power supply, leading to the motor’s insulation ability weakened and even motors were burned. So the embedded motor protector become more and more important particularly, which be able to protect it timely and effectively when the faults happened such as frequent starting, overload and fault.Firstly in the thesis, making a deep thought of traditional overload protection models in theory, it establishes a heat overload protection model. To simulate the faults by using MATLAB software and give the related fault protection measures. As to the saturation condition of transformers, which causes the secondary current waveform distored, it makes use of the least square method to make a related compensation. And in view of the error influence of transformer measurement precision at different temperature, then proposing the Lagrange interpolation for related compensation.Secondly introducing two parts of hardware and software. Selecting PIC18f4620 and setting up the peripheral circuits around it. Peripheral circuit adopts modular design idea:signal acquisition circuit, power supply circuit, human-computer interaction, executing output module and the RS-485 Bus communication module and making the detailed introduction for each part. Then the software programming could be divided into different functions: system initialization, current signal acquisition and data processing module, human-computer interaction and communication and performed in this paper.The final contents of the thesis are related experiments which including two parts of the motor overload operating and the current transformer temperature experiment. And designing a kind of digital filter to remove the high frequency harmonic and noise influence. Meanwhile making related temperature error compensation based on Lagrange interpolation, which improving the accuracy and reliability of embedded protector. |
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