Descriptive brushless motor synchronous generator excitation system 1 Introduction Synchronous generator excitation system has important significance for the reliability of the generator and power system, it directly affects the performance reliability and technical requirements of the generator, so the study of the excitation system Has become an important lesson in motor development. The original direct use of DC generator to excitation, but with the continuous increase in the capacity of the motor, DC motor commutation has become a dilemma, and the need for carbon brushes and slip rings, the presence of carbon brush wear and carbon powder brush coil insulation and other Parts and components With the development of rotary rectifiers, the brushless excitation method has been increasingly perfected, which has promoted the development of brushless motors. At present, the industrialized developed countries have formed the trend of brushless motors.
2 Development of Synchronous Generator Excitation Mode Since the advent of synchronous generators, DC exciter has been used directly, which is divided into two types: coaxial DC exciter and different-axis DC exciter. DC exciter is essentially a DC generator. With the development of semiconductor technology, large-capacity motors have evolved into semiconductor excitation.
There are two types of excitation system: self-excited system and self-excited system. Commonly used excitation methods are self-resonant, some products of the company, compound excitation or voltage regulators. Phase compound excitation also has a reactive phase-shifted electromagnetic compound excitation and a reactive phase-shifted current compound excitation. Its excitation power is taken from the generator output or an additional winding on the stator winding of the generator. The generator of this principle is called a self-excited constant voltage generator.
Generally relying on their own remanence, sometimes in order to improve the reliability of the starting excitation, not only excitation measures are taken in the excitation circuit, but also a small permanent magnet is placed on the stator pole shoes of the AC exciter for excitation. According to the installation method of the rectifier, it can be divided into a static device and placed in a special cabinet. A slip ring is needed to introduce the DC power into the rotor winding of the generator. In essence, the AC exciter is used instead of the DC exciter, and the rectifier is used to replace the direction finder. The semiconductor rectifier device is mounted on the shaft of the main generator, fixed by a steel ring and screws, and rotates coaxially with the main generator, and the AC output from the excitation armature is rectified into a direct current by a rotary rectifier device, and then is transmitted to the main generator. The rotor winding is excited. Thus eliminating the carbon brush slip ring, it is called brushless excitation.
3 Design of Brushless Excitation System 3.1 AC exciter and rotary rectifier AC exciter and rotary rectifier are the key components for the evolution of synchronous motors from brush to brushless. The excitation system of the brushless synchronous generator produced by a certain factory will be described below. The AC exciter is essentially an alternator. Unlike the main generator, the AC exciter is pivoted. The field winding is fixed on the stator frame. The DC excitation is used to connect the exciter. The rotor is the armature. In order to increase the response speed of the excitation system, the frequency of the AC exciter is generally higher than that of the main generator and can be as high as several hundred. Therefore, the number of poles of the AC exciter is more than the number of poles of the main generator, but it is not necessarily a simple integer multiple. The purpose is to prevent generators from generating relative short circuits. The induced current in the rotor field coil flows through the pole tube that is conducting, causing damage to the pole tube. The rotating rectifier is composed of semiconductor rotating rectifier diode fast-fuse overvoltage protector and other components. The fast fuse is used as over-current or short-circuit protection in series with each branch of the polar tube. The surge suppressor or varistor is connected in parallel to the rotating rectifier device. Both sides of the DC side can absorb transient overvoltages for overvoltage protection. The rotating rectifier and the main generator rotor are also installed coaxially. The single phase of the rectifier circuit is the same as that of the AC exciter. It can be the full-bridge commutated or half-bridge commutative type 1 rotating rectifier with the AC side connected to the AC exciter. At the output side, the DC side of the output side is connected to the rotor field winding of the main generator through the shaft hole at the center of the shaft, and the motor technology 2001 supplies the main generator with excitation. Principle 2.
1 stator outlet terminal 2 main engine stator 3 main engine rotor 4 varistor 5 rotating rectifier 6, magnetic rotor 7 exciter stator 8 regulator connection terminal 1 series resistor 1 voltage drop compensation current transformer 1 rectifier transformer, static rectifier rotation Rectifier 3.2 Brushless Synchronous Generator Operation When the prime mover drags the main generator to rotate, the AC exciter enters the main generator rotor winding for excitation after being turned into a direct current by the rotating rectifier. At this time, only the excitation current of the AC exciter is adjusted. The excitation current of the main generator can be changed to control the output voltage of the main generator, and the main generator terminal can be stabilized by an automatic voltage regulator connected between the output of the main generator and the field winding of the AC exciter stator. Voltage. Brushless synchronous generator wiring principle.
Motor technology 200123.3 Failure analysis and preventive measures of the excitation system The rotating rectifier not only operates at high speed and high temperature, but also has parts with high failure rate of the vibration machine, because when the motor is subjected to external disturbances, despite the stator rotating magnetic field and rotor winding generated by the load current There is no relative motion, but with the abrupt change of the stator magnetic field amplitude, the transformer potential will be induced in the rotor winding; and when the motor load is asymmetric, a negative sequence current will flow in the stator winding. This negative sequence current generates The negative sequence magnetic field of the rotor has twice the relative speed of the synchronous speed, will induce the rotating potential in the rotor field winding; the out-of-phase closing often occurs after the synchronization equipment is overhauled, due to the wrong connection of the voltage transformer phase, when the generator When the phase angle between the voltage and the system voltage is 60 degrees, the rotor voltage will be very high. In the process of asymmetrical short-circuit or grid-connected misoperation, the above-mentioned rotation potential and transformer potential may be generated at the same time. These two transient potentials are added to the potential of the rotating commutator by the AC excitation armature, and then transferred to the main generator. The currents in the subfield windings are superposed. Note that the rotor field windings are inductive components. Together, they act on the rotating rectifiers, allowing large currents to flow through the current-carrying tubes, and may also endure the blocked polar tubes. A very high reverse voltage will damage the pole tube. This phenomenon is even more pronounced in salient-pole synchronous generators with poor air gap damping or without damping. If the number of pairs of poles of the AC exciter is an integral multiple of the number of pole pairs of the main generator, when the generator is short-circuited symmetrically, the induced current in the rotor coil will flow through the pole tube that is conducting, causing the pole tube to be damaged.
Based on the above analysis, appropriate measures must be taken to prevent the possible occurrence of faults with damper windings on the pole faces of the rotor. In order to improve the dynamic performance; the number of poles of the AC exciter and the overcurrent protection of the main generator; there is a large margin when selecting the rated capacity of the rotator. Therefore, the rotating rectifying device is tested in the installation method of insulation and strict high-speed vibration and other high-temperature tests, so that it has a very high reliability, the output side of the rectifier bridge is equipped with a varistor to prevent damage to the rectifier when the generator field winding overvoltage The pole tube, while the fuse is connected as an over-current or short-circuit protection in series with each branch of the pole tube. When the million rectifier fails, the fast fuse in series with it can ensure that it is automatically disconnected, thus preventing the exciter head from bending. Design of Plug-in Rotor Coil Dalian Bodun Electric Co., Ltd. 1 16023 Wang Xiaowei Wu Zuocheng Li Long Stone coils are often hand-crafted. If the cross-section of the flat copper wire is large, the end of the coil has great difficulty in shaping or even does not work. Based on the practical experience, this paper introduces the structure of the head-bend insert rotor winding and its calculation process. This method can reduce the difficulty of manual operation of the rotor coil and solve the key issues of the rotor offline of the medium-sized wound rotor motor.
Descriptors Asynchronous Motor Rotor Coil Winding Rotor Coil 1 Introduction For a long time, the rotors of a large number of models of large metallurgy wound rotor motors usually use single-turn flat copper wire wave winding structure. The flat copper wire is made up and down the half coil. The two coil sides are formed by the upper and lower half coils. This type of rotor coil is often bent first at the end of the tire, and the other end is made straight. After the rotor core is inserted, it is manually bent. This kind of technology can still be used in motors whose center height is less than 400. If it is used in larger models, it will be very difficult to operate due to the rough copper wire, and the end insulation will be easily damaged. For this reason, we do not need to bend the straight end of the traditional line. This method was adopted in the design of medium-sized wound rotor motor 2560 River 10 and received very good results.
The structure and calculation of the 2 coils are based on the known data of the entire coil. The outer diameter of the rotor, the number of 2 poles, the length of the iron core, the number of rotor slots, the pitch of the coil pitch gauge, and the parent insulation specification and connection method.
The mechanical angle of the slot where the two coil sides cross The distance between the adjacent two coils of the hypotenuse The distance between the lines of the two adjacent spirals of the brother. 3.0. The arc length of the ray at the end of the upper coil is so good that the name is lucky. Fortunately, the fate of the fate contends that the dispute is caused by a serious local overheated overheating; the design capacity of the rectifier bridge and the exciter should take into account that the generator can still provide field current even when the rectifier is disconnected. The generator can still be operated with light and light loads without the phenomenon of fault expansion. If appropriate fault monitoring devices are provided in the control system, it is possible to stop and troubleshoot at the most appropriate time.
4 Conclusions Effectively prevent over-voltage over-current impact on the pole tube. Install the rotating rectifier and AC exciter outside the non-drive end. Punctured from the center of the shaft, the DC power rectified by the rotating rectifier is passed through the shaft hole through the wire to the rotor winding of the main generator. This increases the trouble of replacing the bearing, but it can bring convenience to the maintenance of the rotating rectifier. This makes it easier to replace the pole fuses and improve the reliability of operation.
Deng Qiuling female lecturer motor technology 20012 in 1966
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