Influence of Single-Phase Voltage Loss and Load Carrying Mode on Mine Drainage Pump Motor in Vietnam

Mine drainage pump is the most important load in mining which requires high reliabilitywhen operating. Currently, the power supply of a mine drainage pump is connected to the same powerline with many nonlinear loads, and is equipped with power electronic converters, which makes thepower supply nonsinusoidal. During the working process of a mine drainage pump, the load-carryingfactor often changes, and many types of failures occur, among which single-phase voltage loss is themost common problem. In the case of a nonsinusoidal power supply, if a single-phase voltage lossoccurs in different load modes, it will greatly affect the working mode of the mine drainage pumpleading to influences on the working efficiency, the life of the pump, and sometimes it is necessary torecalculate the protection parameters. This paper studies the influence of single-phase voltage loss andload carrying mode on the working mode of mine drainage pump motor in case the of nonsinusoidalpower supply. Research results show that, in the case of nonsinusoidal power supplied with single-phasevoltage loss, copper losses in the rotor and stator circuits increase with increases in voltage totalharmonic distortion (THD) and load-carrying factor, 5th order reverse harmonic increases copper loss inasynchronous motor the most, and higher harmonic components have less effect on copper loss in themotor. At the same time, the speed ripple decreases with the increase of the motor load factor anddecreases in the presence of the 5th order negative sequence harmonic, and increases significantly in thepresence of the 7th order positive sequence harmonic. 5th order negative sequence harmonic increases,the torque ripple increases, while the 7th order positive sequence harmonic reduces the torque ripple inthe case of single-phase voltage loss. The results of the paper will help improve the operationalefficiency of the mine drainage pump in Vietnam's mines.

Verification of Possibility of Molten Steels Decopperization with ZnAl2O4

In the previous research works, ZnAl2O4 material was considered as one of the solutions for the decopperization process of molten steels; up to 33% of decopperization efficiency was reported by utilising the ZnAl2O4 filter. In order to verify the decopperization possibility of ZnAl2O4 materials, iron-based alloys with various copper and carbon contents were interacted with ZnAl2O4 substrates in a heating microscope under an argon gas atmosphere at 1600 °C. Fe-Cu alloys were found to react with the ZnAl2O4 substrate during the interaction process, and a reaction layer with a complex composition around the alloy droplet was formed; however, Cu was not detected in the reaction layer. Cu was later found diffused inside of the ZnAl2O4 substrates. Furthermore, the Cu-Zn compounds were detected when the copper content in Fe-Cu alloys was 10 wt% Cu. After interaction experiments, copper was decreased in all cases. Thereby, the copper evaporation and infiltration into the ZnAl2O4 substrate were considered as the reasons for copper loss. Moreover, oxygen dissolved in melt was found to have a great effect on the copper evaporation process.

Research on the influence of temperature on the performance of induction motor

Background: : Induction motor occupies a large proportion in various industries, and its number is increasing. Due to the environmental temperature or sealed working environment, heat generation is generally serious. The heat exchange with the outside environment does not take place smoothly and the motor temperature increases. The performance of the induction motors also significantly influenced by the temperature. Therefore, it is necessary to study the influence of temperature on the performance of induction motor. Objective: The influence of temperature on induction motor is analysed. The variation of performance parameters at different temperatures is obtained. Methods: Taking an 11 kW, 1500r/min induction motor as an example, a two-dimensional transient electromagnetic field model was established, and the correctness of the model was verified by experiments. The motor starting performance, various losses and efficiency under different temperatures were calculated. Results : As the stator and rotor resistance increases, the starting current decreases by 11.99% when the internal temperature rises from 25℃ to 150℃. When the internal temperature rises from 25℃ to 150℃, the stator copper loss increases by 32.83%, and the rotor copper loss increases by 28.79%. However, the core loss of the motor increases by 3W. and the motor efficiency decreases by 2.12%. Conclusion: When the temperature is different, the starting torque of the motor is almost unchanged, and the starting current decreases with the increase of temperature. The stator copper loss and rotor copper loss of the motor increase with the increase of temperature, while the core loss is almost unchanged. In addition, the efficiency of the motor gradually decreases with the increase of temperature.

Optimum Switching Angles Control of SRM for Electric Vehicle Applications

Switched Reluctance Motor (SRM) drive is being gradually used in industrial applications, including electric vehicles (EVs), due to several advantages over conventional motors. However, the nonlinear magnetic characteristics of the motor make its controller very complicated. This paper presents a simplified procedure to obtain the optimal switching angles under hysteresis current control SRM drive over a wide range of speeds. A multi-objective optimization technique is applied to determine the optimal switch on and switch off angles that achieve the optimum combination of maximum average torque with minimum torque ripple and copper loss. A searching algorithm is developed for each operating point to define the maximum average torque and the minimum torque ripple and copper losses, as they vary for different currents and motor speeds. Then the optimal values of switching angles are stored in the lookup tables to build a MATLAB model of the SRM drive system. Finally, simulation and experimental results are presented to show the validity and effectiveness of the proposed controller.