6 The shaft-generator system with slip induction motor Nie Yansheng Liaoning Institute of Marine Engineering, Liaoning Maritime University, 6,26 machine system, and the structure of the system features and working principles are briefly analyzed. It is pointed out that the advanced circuit forms and control methods used in such systems increase the difficulty of management and maintenance. When such systems are used, comprehensive consideration should be given to energy efficiency and the difficulty of management and maintenance.

From the perspective of energy conservation, the use of a shaft generator system is a viable option. In the large-scale low-speed diesel engine directly driven by a fixed-slurry ship, the shaft-generator system is widely used today.

Here, the shaft generator is installed between the host flywheel and the propeller shaft. The alternator emits alternating current with frequency varying with the rotation speed of the main engine. After rectification and inversion, the magnetic field oriented control pulse width modulation type inverter is converted to meet the required alternating current. The output voltage of the system is regulated by the regulator of the sync compensator. At the same time, the synchronous compensator also provides reactive power and short-circuit current for the system. The excitation current of the shaft generator is provided by the thyristor for excitation. Changing the control angle of the rectifying device to control the excitation current of the shaft generator, adjusting the output power of the system uses a brushless excited synchronous generator. The relevant information shows that in the field of system output power greater than 12001, this type of shaft generator system will still dominate the world shaft generator market. However, this type is best when the rated output power of the system is around 500 kW. The study found that the loss caused by the synchronous compensator is relatively large. In addition, because the static frequency conversion device is in the main power supply circuit, the cost and volume are relatively large. For this reason, Siemens has developed a shaft-generator system using a slip induction motor, referred to as the shaft-induction generator system 81. For example, the mouth, 6,131. This type of shaft-generator system positioning In the application of 10O0kW to 500kW. Its purpose is to reduce costs and improve efficiency.

Structure characteristics and working principle of 2-axis induction generator system Structure of the shaft induction generator system Box 2.

Diesel engines need to drive the generator through a gear train. The reason for this is that the induction motor requires a smaller air gap, and the structural characteristics of the rotor core also determine the use of this method. In this way, conventional machines can be used to reduce costs and maintenance costs. The converter device and the system reactor are on the excitation circuit of the generator instead of the main power supply circuit, and their capacity and volume are significantly reduced.

The converter of the converter adopts advanced pulse width modulation, which replaces ordinary thyristors.

The gate can turn off the thyristor, which has the function of an ordinary thyristor, that is, applying a gate current pulse with a very short duration can make the D, trigger conduction, and once it is turned on, even if no gate current exists, it can maintain its Conduction state. However, unlike ordinary thyristors, a negative gate anode voltage can be applied to make 1 turn off. That is, a large negative current flows through the gate when it is turned off. During the off-time, this negative gate current must last for a few microseconds but it must have a large amplitude. In the actual circuit, it plays the role of a controllable switch. In the inductive circuit, in order to reduce, in the shutdown, one of the mountains on the anode must be provided with a buffer absorption circuit at both ends of 0, so that when D is turned off, the sine 1 is reduced as much as possible. The low-bus-side converter circuit is a two-phase full-control bridge. An anti-parallel connection method is used between them to ensure that the shuffling capacitor can replace the conventional smoothing reactor. On the motor side, in addition to the pulse width modulation type inverter, a group feedback transistor is added. Its function is to feedback the lagging current to the filter capacitor and improve the stability of the commutation work of the inverter. The outstanding feature of the system is that the synchronous compensator is cancelled, so that the loss of the entire system can be reduced.

From the superposition principle and the physical properties of the induction motor, the relationship can be drawn where the voltage frequency unit of the 5 stator windings is the frequency division; the voltage frequency of the Fn rotor winding. The stator winding voltage frequency is the same as the grid voltage frequency, usually 601 or 502. The rotation speed of the rotor of the rotor, 1 changes with the change of the host speed, so to make 5 remain unchanged, only at 0! Change ç›±, adjust the voltage frequency Fn of the rotor winding accordingly. The lexical regularity satisfies the equation Fn = Fsp. Fm. In practice, the adjustment is realized through the pulse width modulation inverter.

Pulse width modulation type inverter is a kind of on-off type inverter. Since its DC side can be considered as a DC voltage source, it is a kind of voltage source inverter. There are many methods of pulse width modulation. In the inverter circuit, pulse width modulation such as pulse width modulation and sine pulse width modulation is used to divide the square wave control of the voltage source inverter 180 into thousands of pulses. The control signal is generated by comparing an isosceles wave called a carrier with a tunable DC voltage. The output voltage and current waveforms are non-sinusoidal and have many sub-harmonic components. The difference between sinusoidal pulse width modulation and equal pulse width modulation is that the pulse width changes according to a sine law. The carrier signal is still an angular wave and the reference signal is a sine wave. This output voltage will also change according to sine law. In this case, the lowest harmonic contained in the output voltage is twice the pulse frequency, which greatly reduces the harmonic content of the output voltage. The sinusoidal pulse width modulation type inverter is used in the shaft induction generator system.

To realize the sinusoidal pulse width modulation, the time coordinates of all the intersections of the reference signal sine wave and the carrier angle wave must be calculated in real time. According to the calculation result, the on and off actions of the 0 elements in the inverter circuit are issued in an orderly manner. instruction. Therefore, in the sinusoidal pulse width modulation, the control part is composed of Siemens' control system 51 and 5,0 turn. The sequence and logic control functions are implemented through the 5550 programmable controller.

From the control point of view, the induction motor is a multi-variable and coupled nonlinear object. For this purpose, vector control technology is used. Vector control plays a significant role in decoupling and linearization. The basic idea of ​​vector control is to decompose the stator current of the motor along the axis of the motor flux into two components, the parallel component and the vertical component. The component parallel to the magnetic flux axis is the magnetic field current component of the motor, which is used to generate the magnetic field of the motor. It is divided into two types perpendicular to the magnetic flux axis, and the magnetic field orientation control is the magnetic pole position orientation control of the rotor. The field oriented control is used in this system. The so-called magnetic field orientation control is to take the real axis of the rotating coordinate system on the magnetic field axis and rotate synchronously with the magnetic field. If the rotor magnetic field axis is taken as the real axis, it is called the rotor magnetic field orientation control; if the stator magnetic field axis is taken as the real axis, it is called the stator magnetic field orientation control. This control idea was first put forward by Siemens engineers in 1971, and it has been widely used in AC frequency control.

3 Conclusion According to the above, we can easily find that the shaft generator system developed by Siemens adopts the advanced technology and results obtained in the research of AC speed control system. It is a computer control and control system of modern AC variable speed control. The perfect combination of advanced achievements in power electronics. Its advanced nature is unquestionable. The technologies and components used are all verified in the land-based control system. Therefore, there is no great technical problem in estimating the reliability of the actual ship. The more prominent question is how to maintain and manage this advanced system. Although Siemens researched and developed this kind of system from the perspective of energy saving, as a ship owner, the adoption of such a shaft generator system is likely to result It is difficult for the plumbing personnel to effectively maintain and manage them, resulting in increased maintenance costs that exceed the benefits of energy savings. In other words, it is more than worth it. The emergence of such a system is not only a challenge for personnel in charge of the cycle, but it is also a challenge for personnel engaged in the training of crews and navigation. The renewal of knowledge and the broadening of knowledge are not only the questions faced by the ship management personnel. The crew inverter is still in the state where the trigger pulse is blocked and the inverter cannot work. When the shaft generator system is stopped, 027 = the start of the 037 shaft generator system, the control program cannot start by the start program. Only 0矣6, when there is 037=0, the program can proceed and complete the startup process. This ensures that the inverter will not fail due to an excessively large inverter angle during operation of the inverter.

Adjust 1 to move the position of square wave 025 and adjust the lower limit of the output of the variable angle adjuster. Adjust Huang Jun. Semiconductor converter technology. The Machinery Industry Press, who took the first page of training and maritime higher education in 1984, must also face this question, and demand more and more urgent.

1 Xu Yingen. AC speed control system and its application. Textile industry out of 2 Nie Yansheng. A microcomputer controlled shaft generator system. world

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