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As main power equipment in modern industry, three-phase squirrel-cage motor has been used more and more extensively. If there is some part of motor goes wrong, it may cause production delay which brings about economic losses. What’s more severe, it may result in serious casualty damage. Therefore, the operating condition online monitoring and the corresponding fault diagnosis of motor seems very important.In this paper, an online monitoring and fault diagnosis for motors system based on SCADA is been presented. Besides, in the way of block design, three parts of SCADA system which named RTU system, communication system and centralized surveillance system is been accomplished.First of all, according to the field operational aspect, it shows the main faults of three-phase squirrel-cage motor, such as broken rotor bar fault, stator winding inter-turn short circuit fault, stator winding open circuit fault, stator winding ground fault, power under-voltage, power over-voltage and lack of power phase. Then the forming mechanism of these faults is analyzed in detail. Based on which, the paper elaborates on the fault characteristics and the way of extracting of effective fault characteristic value. Which means, the detection method is been given.Secondly, in basis of motor Multi-Loop analysis method, the mathematical models of motor which is fault-free and which has broken rotor bar fault are established. Then in the platform of MATLAB, the two states of motor are simulated. The result shows that the method of detecting broken rotor bar fault is correct. Thirdly, hardware and software design of RTU system and communication system is completed, the core of which is MCU MC9S12DG128. In the part of hardware design, main function of every block circuit is presented, the circuit diagram is showed and circuit is analyzed too. Otherwise, some circuit is simulated as needed and proves the role of these circuits. The communication with supervisory computer is based on RS485 bus. In the part of software design, the algorithm program and systemic function program are finished in type of modular programming. Then Modbus-RTU communication protocol is employed to realize the serial communication with supervisory computer.At last, software program of SCADA supervisory computer is been designed. In which Visual Basic 6.0 and industrial control configuration software Kingview are combined to realize the function. In this mean, VB is used to communicate with MCU and to manipulate the field data. And also Kingview is employed to realize displaying technologic flow, alarming, historical curve, report forms and database.
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