The Research And Development Of A Communication-capable Motor Protector

The motor protector is the most widely used for motor protection. The formermotor protector can no longer meet the requirements of the people with the rapiddevelopment of electronic technology, computer technology and communicationtechnology. Simple operation, accurate protection and fully functions have become thebasic requirements of the motor protector. Networking, digital and structure ofstandardization has become developing direction in the future. The motor protectorbased on DeviceNet filedbus is proposed based on such background. In this thesis, theresearch is focus on following topics:Firstly, after introducing the current situation and the trend of the development ofmotor protector, the paper analyzed the limitation of the traditional motor protector,and designed a dual-CPU architecture motor protector based on the DeviceNetfiledbus.Secondly, the theory and technology of the development of the motor protector isdescribed, such as analyzing varieties of symmetrical and asymmetrical faults of motorby using the symmetrical components method, sampling for the electrical parameter,communicating with other filedbus devices based on the DeviceNet filedbus network.Thirdly, according to GB14048.4-2008and JB10736-2007-T standards, thetechnical indicators of motor protector are proposed. Besides, DeviceNetcommunication standard is given in accordance with GBT18858.3-2002part3.Theoverall design of motor protector is proposed based on the dual-CPU and DeviceNetfiledbus and the overall plant of the hardware circuit is explained. Then every moduleof circuit is discoursed in detail, such as the signal process circuit, DeviceNet interfacecircuit, the HMI (human machine interface) module circuit, the digital variable(input/output) module and serial communication modules. Then the overall schematicdiagram of the system is provided.Fourthly, after finishing the hardware design, the structured design method isapplied for programming for motor software. Each module is dependently programmedby function of the system from driver layer to application layer. Processing ofsampling, motor protection handler, HMI control program and DeviceNet filedbusmodule are designed, and the communication protocol between the dual-CPU for serialports is defined.Finally, the prototype is tested repeatedly, including the functional testing andconformance testing of the DeviceNet filedbus. The performance indicators are analyzed.The test shows that the motor protector achieves the designed indicators,which can meet the reliability and real-time of the fault protection system andcommunicate with other field devices.