Motor Restarting System Design Based On Peak Voltage Method

The voltage sags often occur in continuous oil industry production, which may cause that the working motors stop running unexpectedly. Once the motor stops running, the continuity of the production sequence will be destroyed to cause the stagnation of production, there is a need to re-start the motor to process again and recover the motor back to its original running status so that the production can be resumed. Adding A/D module to PLC to test the effective value to determine whether the motor can be restated is the conventional means, which has defects such as low reliability, high cost, and low efficiency and so on. Thus, based on the analysis of the existing technology of motor restarting, a controllable motor restart system is designed with the external MCU attached to the control core of PLD to reduce the cost, by measuring the three-phase peak voltage of the module to improve the efficiency.The system of motor restarting based on the method of peak voltage can be computed by the adoption of the method of peak voltage through the external detection module of PLC to measure the magnitude of three-phase peak voltage, and then the measured value will be compared with the minimum peak voltage of the set normal operation of the motor, in order to obtain the logical values. Peak voltage method is to collect the instantaneous voltage value during a certain period and then the bubbling method is adopted to obtain the peak voltage of the period. In the process, the peak voltage through A/D conversion is displayed on the PC through serial port and verified the accuracy of the logical values. After the logical value is tested, it is sent to the control system PLC by connection to photoelectric coupler as a judgment whether motor can be restarted. This process focuses on the various conditions of motor restart, and the interlock programming is carried out on the motor restart. Finally, the monitor screen is constructed by using Kingview to validate the restart process.Experiments show that the system is highly accurate and it can meet the demand of industrial production. Meanwhile the development cost is relatively low and it can be widely used in a variety of industries with high power quality requirements.