An induction motor constant unit power factor operation strategy
Building a well-off society in an all-round way: the historical responsibility of Chinese science and technology workers A constant power factor operation strategy for induction motors Zhang Qingxin, Wang Fengxiang, Li Wenjun In recent years, new active compensation technologies for power electronics research have been developed, and active power filters have been implemented. Harmonic pollution caused by linear power devices is suppressed; unity power factor rectifiers minimize the harmonics generated by AC-DC rectifiers. Based on active compensation technology, this paper proposes a constant unit power factor operation strategy of induction motor, that is, the use of active compensation technology developed in power electronics field in recent years. It is used in induction motor to realize induction motor in any working condition. Constant unit power factor operation under conditions. The operation strategy mainly adopts the method of controlling the current on the grid side. That is, regardless of the load characteristics, the active filter forces the grid-side current to be sinusoidal and in phase with the voltage. The traditional compensation method based on instantaneous reactive power theory is to control the output current of the inverter, so it is indispensable to detect the load current; while the method of controlling the current on the grid side does not need to detect the load current, and reduces the system to the current sensor. The need for such an operation strategy is that the amplitude of the network measurement current is determined by the power balance between the grid, the inverter and the motor. The capacitor on the DC side is used to store the active power, and there is no merit without considering the system loss. Power flows through the inverter, so the average voltage across the capacitor is a constant value. When there is a power imbalance, the difference in power between the grid and the motor is injected into the storage capacitor through the inverter. If the utility power provided by the grid is less than the demand of the motor, the average voltage of the capacitor decreases, the amplitude of the grid-side current increases, and the output power of the grid increases; if the active power provided by the grid exceeds the demand of the motor, the average voltage of the capacitor increases. The amplitude of the current on the grid side is reduced. Therefore, the average voltage of the capacitor provides information on the active power flow. The amplitude control of the grid-side current can be achieved through the adjustment of the capacitor voltage. In this way, the use of active compensation technology in the induction motor can realize the operation of the induction motor at a constant unit power factor, which reduces the amplitude of the grid-side current and achieves the purpose of energy saving.
The college is engaged in teaching and research work, lecturer, and studying for a doctorate at Shenyang University of Technology. He is mainly engaged in the research of electronic motors and their control systems. He has published more than ten papers in academic journals.
Power frequency test transformer computer control system Zhang Chao Li Wei At this stage, the voltage insulation theory is not very perfect, using existing theory for high voltage electrical equipment insulation design sometimes can not meet technical requirements, so the insulation of high voltage electrical equipment in the product set, factory and During the operation, strict insulation capability tests should be conducted to ensure that the insulation of high-voltage electrical equipment can be safely and reliably operated in the field.
This paper introduces a computer control system for power frequency test transformers that uses industrial computers as the center to control, protect and measure, record, and output power frequency test transformers. The system has all the functions of the traditional industrial frequency pressure test. Through the digital control, it can be set randomly to test the time of rising and dropping. There are several ways to choose the test parameters and test procedures. The system also uses a computer to perform real-time monitoring of power frequency high-voltage tests. Once a failure occurs, an automatic alarm is issued and corresponding protection is performed in time to avoid damage to the test equipment or the test product. This ensures the safety of personnel and the peak voltage of the system. The measurement uses a computer point-by-point sampling method to obtain peaks by software, and gives theoretical error analysis and test results. When the discharge occurs during the test, the design of the measurement program allows the measurement speed to reach a sufficiently fast tracking level, thus ensuring the accuracy of the discharge voltage measurement. This program also has a number of functions such as determining over-limit, breakdown, timing, and digital filtering. The system's anti-interference has also been carefully designed, using shielding techniques, anti-interference power supply, optical isolation and other measures, so that the computer device can still operate normally under high voltage discharge. The system also retains the traditional manual console for the operation or emergency treatment of the high-frequency test of the power frequency when the computer fails or some special occasions.
College of Electrical Engineering; Research on the design and test method of the test power supply for electric kV shunt reactors Zeng Linsuo Liu Zhuo This paper presents the problems in the manufacture of mid-test power supplies and test methods for 500kV shunt reactors for practical problems in Shenchuang Corporation's production practice. The design and research, combined with the company's existing site and equipment, carried out detailed analysis, a large number of comparisons, calculations, and obtained a technically feasible and economically optimal solution. Through creative design work, we designed and built the first large-scale high-voltage capacitor tower with multiple voltage switching and wiring methods in China to satisfy the requirements of current temperature rise, magnetization characteristics, induction and other tests of 500kV shunt reactors. It can meet the needs of the three-phase power transformers for 500 kV and 840 MVA three-phase power transformers in the near future. It can also meet the test requirements for the converter transformers in the *500 kV DC transmission line.
The test of this new product is the first time for a rebuilt company. This paper theoretically analyzes and calculates the test method. And in the actual use, achieved satisfactory results.
In addition, this article also introduced another extension of the capacitor tower using the test capability of a one-on-one plant.
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