[Permanent magnet generator] What is the principle of permanent magnet generator, the principle of permanent magnet generator, the advantages of permanent magnet generator
The advantages of permanent magnet generator
1. Simple structure and high reliability. The permanent magnet generator eliminates the excitation winding, carbon brush and slip ring structure of the excitation generator, and the whole machine has a simple structure, which avoids the easy burning and disconnection of the excitation winding, carbon brush and slip ring structure, and the whole machine has a simple structure. It avoids failures such as easy burning and disconnection of the excitation winding of the excitation generator, and easy wear and tear of the carbon brush and slip ring, and the reliability is greatly improved.
2. It can significantly prolong battery life and reduce battery maintenance work. The main reason is that the permanent magnet generator adopts a switching rectification and voltage regulation method, which has high voltage regulation accuracy and good charging effect. The shortening of battery life caused by overcurrent charging is avoided. The head-type rectifier output of the permanent magnet generator uses a small current pulse to charge the battery, and the charging effect is better with the same charging current, thereby prolonging the service life of the battery.
3. High efficiency. Permanent magnet generator is an energy-saving product. The permanent magnet rotor structure eliminates the excitation power required to generate the rotor magnetic field and the mechanical loss of friction between carbon brushes and slip rings, which greatly improves the efficiency of the permanent magnet generator. The average efficiency of ordinary excitation generators is only 45% to 55% in the speed range between 1500 rpm and 6000 rpm, while the permanent magnet generator can be as high as 75% to 80%.
4. The self-starting voltage stabilizer is used without external excitation power supply. The generator can generate electricity as long as it rotates. When the battery is damaged, the car charging system can still work as long as the engine is running. If the car does not have a battery, as long as the handle is turned or the car is rolled, the ignition operation can also be realized.
Three major problems of permanent magnet generators
1. Control problems
After the permanent magnet generator is made, it can maintain its magnetic field without external energy, but it also makes it extremely difficult to adjust and control its magnetic field from the outside. These limit the application range of permanent magnet generators. However, with the rapid development of the control technology of power electronic devices such as MOSFET and IGBTT, the permanent magnet generator does not need magnetic field control and only performs motor output control in application. The design requires the combination of three new technologies of NdFeB material, power electronic devices and microcomputer control, so that the permanent magnet generator can operate under brand-new conditions.
2. The problem of irreversible demagnetization
If the design and use are not appropriate, the permanent magnet generator will have a high temperature (NdFeB permanent magnet) or low temperature. (ferrite permanent magnet), irreversible demagnetization, or demagnetization, may occur under the action of the armature reaction generated by the inrush current or during severe mechanical vibration, which will reduce the performance of the motor and even make it unusable. Therefore, it is necessary to research and develop methods and devices for checking the thermal stability of permanent magnet materials suitable for motor manufacturers, and to analyze the demagnetization resistance of various structural forms, so as to adopt corresponding measures during design and manufacture to ensure permanent magnetism. Magnetic generators do not lose their magnetism.
3. Cost issue
Since the current price of rare earth permanent magnet materials is still relatively expensive, the cost of rare earth permanent magnet generators is generally higher than that of electric excitation power generation. The machine is high, but this achievement will be better compensated in the high performance and operation of the motor. In the future design, according to the specific use occasions and requirements, the performance and price will be compared, and the structure innovation and design optimization will be carried out to reduce the manufacturing cost. It is undeniable that the cost price of the product under development is slightly higher than the current general generator, but we believe that with the further perfection of the product, the cost problem will be well resolved.
Permanent magnet generator structure
The biggest difference between permanent magnet generator and excitation generator is that its excitation magnetic field is generated by permanent magnets. Permanent magnets are both a magnetic source and an integral part of the magnetic circuit in the motor.
The magnetic properties of permanent magnets are related to the manufacturing process of the factory, the shape and size of the permanent magnets, the capacity of the magnetizer and the magnetization method, and the specific performance data are very discrete. Moreover, the magnetic flux and magnetomotive force that permanent magnets can provide in the motor also vary with the material properties, dimensions and motor operating conditions of the rest of the magnetic circuit.
The magnetic circuit structure of the permanent magnet generator is various, the leakage magnetic circuit is very complex and the leakage magnetic flux accounts for a large proportion, the ferromagnetic material part is relatively easy to saturate, and the permeance is nonlinear. These all increase the complexity of the electromagnetic calculation of the permanent magnet generator, so that the accuracy of the calculation results is lower than that of the electric excitation generator.
Principle of permanent magnet generator
Like the alternator, it uses the principle of electromagnetic induction to induce electric potential by cutting the magnetic lines of force with wires, and converts the mechanical energy of the prime mover into Power output. It consists of stator and rotor. The stator is the armature that generates electricity, and the rotor is the magnetic pole. The stator is composed of armature core, three-phase windings evenly distributed, frame and end cover.
The rotor is usually of the hidden pole type and consists of the field winding, iron core and shaft, guard ring, center ring, etc. The excitation winding of the rotor is fed with a DC current to generate a nearly sinusoidal distributed magnetic field (called the rotor magnetic field), and its effective excitation magnetic flux intersects with the stationary armature winding. When the rotor rotates, the magnetic field of the rotor rotates along with it, and the magnetic field line cuts each phase winding of the stator sequentially, and a three-phase alternating current potential is induced in the three-phase stator winding.
When the generator runs with a symmetrical load, the three-phase armature currents combine to produce a rotating magnetic field with synchronous speed. The interaction between the stator magnetic field and the rotor magnetic field produces braking torque. From the steam/water/gas turbine, the input mechanical torque overcomes the braking torque to do work.
