Research On The Squirrel-Cage Asynchronous Motor Fault Detection Device

The squirrel-cage asynchronous motor is used widely in the national production, because of its merits such as simple structure, low price, etc. If the motor went wrong, the national production and the people's normal life would be interrupted, and the economic loss even casualties would happen. Though the traditional relay protection can protect the motor from destruction, it can't prevent the motor failure from occurring. It has important meaning to do research on the motor fault detection technique and give the motor Condition Maintenance, because it can reduce the cost of maintenance and enhance the motor's operational reliability.In this paper, a squirrel-cage asynchronous motor fault detection device is designed, which is based on the platform of the dual-CPU of DSP-TMS320F2812 and ARM-S3C44B0X and their peripheral devices. By adopting the Motor Current Signature Analysis (MCSA) technique, the device provides on-line detection for the squirrel-cage asynchronous motor's faults such as stator winding fault, broken rotor bars, airgap eccentricity etc. The device also can detect the quality of the motor's power supply so as to avoid misjudging the motor fault because of the power supply fault's influence.During developing the squirrel-cage asynchronous motor fault detection device, the causation and characteristic of the squirrel-cage asynchronous motor's stypical fault are analyzed, and the fault detection principle and method are studied. Then, the the device's function is designed.From the motor fault detection principle and combining the signal processing technique, the motor fault detection algorithm and real time parameters measure algorithm are studied. The fault detection algorithm of broken rotor bars is studied especially. The potential sources of error when using Fourier transform to analyze the motor current spectrum such as spectral aliasing, frequency leaked, fence phenomenon, network frequency fluctuation, load fluctuation are analyzed, and the corresponding improvement of the errors are proposed and proved by the simulation of the Matlab software.The device's major structure is DSP plus DARAM plus ARM. By combining some peripheral resource, the whole hardware platform is builted. In order to achieve on-line fault detection, the split core type current transformer MG8 is adopted, which can acquire the motor's current easily. In consideration of the portable application, the device takes large capacity lithium battery as its power supply, and pay attention to the demand of low power dissipation when choosing chips.The menu display scheme of the liquid crystal is designed elaborately so that the device has a friendly man machine interaction. To fit the demand of serial communication of the device, the application layer protocol of RS-232 serial communication is established, and the serial communication software is designed. The DSP's program adopts the modular programming ideas. The ARM's program is based on the Embedded Operating System,μC/OS-II; a series of tasks are designed due to the device's function. The tasks are programmed respectively and scheduled by theμC/OS-II kernel.