Permanent magnet generator is a power generation device that converts mechanical energy from thermal energy into electrical energy.It was first developed by France.
TodayDC motorThe excitation method of using DC current to generate the main pole magnetic field is called current excitation;If permanent magnet is used instead of current excitation to generate main pole magnetic field, such motor is calledPermanent magnet motor。
Permanent magnet generator has the advantages of small size, low loss, high efficiency, and so on. Today, energy conservation and environmental protection are increasingly valued, so it is necessary to study it.[1]Brushless can be achieved in many cases, so it is mostly small andMicromotorUsed.When variable frequency power supply is used for power supply, permanent magnet motor can also be used for speed regulating drive system.With the continuous improvement and perfection of the performance of permanent magnet materials, permanent magnet motors have been widely used in household appliances, medical devices, automobiles, aviation, national defense and other fields.
Permanent magnet generator asVehicle motorIt has the advantages of high efficiency, energy saving, low carbon, large power and small size, but its output voltage is not easy to adjust, high-frequency iron loss is large, motor temperature is high, and starting torque is large.[2]The disadvantage of the permanent magnet motor is that if it is used improperly, it may produce irreversible demagnetization under the action of armature reaction generated by impulse current or severe mechanical vibration when working at an excessively high or low temperature, which may degrade the performance of the motor or even make it unusable.Therefore, special attention should be paid when using permanent magnet motors.[3]
development history
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In 1832, French young electrical engineer Pike Xi successfully trial produced the world's first manual permanent magnet rotatingalternator。
In this generator, Pikshi installed an originalcommutator, so that the alternating current generated in the generator can be changed into the direct current needed by the industrial production at that time. However, the permanent magnet generator of Pichy has two obvious shortcomings.First, its equipment is bulky, and it is difficult to increase power by increasing speed. Second, its prime power is human power, which is also difficult to obtain high-power current by increasing speed.
While Pikeshi improved his permanent magnet generator, others also studied it and made some important inventions.Between 1833 and 1835, Sasston, Clark and others successively invented the rotating coilarmature, static magnet structure and other new devices. The introduction of these new devices has greatly reduced the operating part of the generator, thus increasing the speed of the generator.
Since then, people have also carried out reform on the original power device of the generator, changing the handle handle to the rotating shaft, and changing the hand cranking to the steam engine driving. In this way, the speed has been greatly improved, and the electricity generated has also been greatly increased.
On the basis of the above two innovations, people have also carried out other innovations.By about 1844, in France, Germany, Britain and other countries, there had been huge and clumsy generators to provide new power for electrolysis and new power for machines through the original motors.
The birth of the permanent magnet generator is the first time that the mechanical energy transformed from heat energy is transformed into electrical energy, so that human beings can obtain a new energy with broad prospects after heat energy.
Structural design
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Permanent magnet generator andExcitation generatorThe biggest difference is that its exciting magnetic field is generated by permanent magnets.The permanent magnet is both the magnetic source and the component of the magnetic circuit in the motor.The magnetic properties of the permanent magnet are not only related to the manufacturing process of the manufacturer, but also related to the shape and size of the permanent magnet, the capacity of the magnetizer and the magnetizing method. The specific performance data are very discrete.Moreover, the magnetic flux and magnetomotive force provided by the permanent magnet in the motor also change with the material performance, size of the rest of the magnetic circuit and the operating state of the motor.In addition, the magnetic circuit structure of the permanent magnet generator is diverse, the magnetic leakage circuit is very complex and the leakage flux accounts for a large proportion,Ferromagnetic materialSome of them are easy to be saturated, and the permeance is nonlinear.All these increase the complexity of electromagnetic calculation of permanent magnet generator, and make the accuracy of calculation results lower than that of electric excitation generator.Therefore, it is necessary to establish a new design concept, re analyze and improve the magnetic circuit structure and control system;Modern design methods must be applied to study new analysis and calculation methods to improve the accuracy of design and calculation;Advanced test methods and manufacturing processes must be studied and adopted.
Control problems
The permanent magnet generator 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 limits the application range of permanent magnet generator.However, with MOSFET, IGBTT, etcPower electronic devicesWith the rapid development of control technology, permanent magnet generator does not need magnetic field control in application, but only carries out motor output control.The design requires the combination of Nd-Fe-B materials, power electronic devices and microcomputer control to enable the permanent magnet generator to operate under new conditions.
Irreversible demagnetization
If the design and use are improper, the permanent magnet generator will be subject to high temperature（NdFeB When the permanent magnet is too low (ferrite permanent magnet), irreversible demagnetization, or loss of excitation, may occur under the action of armature reaction generated by impulse current, or during severe mechanical vibration, which will reduce the performance of the motor or even make it unusable.Therefore, it is necessary not only to research and develop methods and devices suitable for motor manufacturers to check the thermal stability of permanent magnet materials, but also to analyze the anti demagnetization ability of various structural forms, so as to take corresponding measures during design and manufacturing to ensure that permanent magnet generators will not lose excitation.
Cost issues
becauseRare earth permanent magnetic materialsThe current price is relatively expensive. The cost of rare earth permanent magnet generator is generally higher than that of electric excitation generator, but this will be better compensated in the high performance and operation of the motor.In the future design, the performance and price will be compared according to the specific use occasions and requirements, and the structural innovation and design optimization will be carried out to reduce the manufacturing cost.There is no denying that the cost price of the product under development is slightly higher than that of the current GM generator, but we believe that with the further perfection of the product, the cost problem will be well solved.The head of the technology department of DELPHI (Delphi) in the United States believes that "customers pay attention to the cost per kilowatt." This statement fully shows that the market prospect of AC permanent magnet generators will not be troubled by the cost problem.
Characteristics of permanent magnet rotor
Structure 1: parallel magnetic field structure;It is cast and pressed, embedded with permanent magnets, with large energy, light weight, small size, solid and reliable overall structure, and the maximum operating speed is more than 15000 rpm.Patent number;ZL96 2 47776.1 Structure 2: series magnetic field structure;The rotor is of steel structure, and permanent magnets are embedded on the surface in order. The rotor surface has strong magnetic flux, light weight, small size, solid and reliable overall structure, and the maximum operating speed is more than 15000 rpm.Patent No.: ZL98 2 33864.3 Whole machine voltage stabilizing system Features: semi controlled bridge rectifier circuit is composed of silicon controlled rectifier and diode.The voltage stabilizing system is a chopping modulation type voltage stabilizing device, with a voltage stabilizing accuracy of plus or minus 0.1v, so the generator has the characteristics of being able to withstand large current instantly, reliable and durable in operation, and can directly use the reverse voltage of AC generated by the generator to turn off the thyristor itself, so there is no need to add a turn off circuit, making the circuit structure simple and reliable.
advantage
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1: Simple structure and high reliability.The permanent-magnet generator eliminates the excitation winding, carbon brush and slip ring structure of the excitation generator. The overall structure is simple, avoiding the excitation winding from being easily burned and broken, and the carbon brush and slip ring structure. The overall structure is simple, avoiding the excitation winding of the excitation generator from being easily burned and broken, and the carbon brush and slip ring from being easily worn. The reliability is greatly improved.
2: Small size, light weight and high specific power.The adoption of permanent magnet rotor structure makes the internal structure design of the generator very compact, and greatly reduces the volume and weight.The simplification of the permanent magnet rotor structure also reduces the rotor moment of inertia, increases the practical speed, and reaches a high specific power (that is, the ratio of power to volume).
3: Good power generation performance at medium and low speeds.Under the same power level, when idling, the output power of the permanent magnet generator is twice as high as that of the excitation generator, that is, the excitation generator of the actual equal power level of the permanent magnet generator.
4: It can significantly extend battery life and reduce battery maintenance.The main reason is that the permanent magnet generator adopts the switch type rectifier voltage stabilizing mode, which has high voltage stabilizing precision and good charging effect.The battery life reduction caused by overcurrent charging is avoided.The starting rectifier output of the permanent magnet generator uses small current pulse charging for the battery. The same charging current has better charging effect, thus extending the service life of the battery.
5: 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 losses caused by friction between carbon brushes and slip rings, which greatly improves the efficiency of the permanent magnet generator.The average efficiency of ordinary excitation generator is only 45% to 55% in the speed range from 1500 rpm to 6000 rpm, while that of permanent magnet generator can be as high as 75% to 80%.
6: It is unnecessary to apply self starting voltage regulatorExcitation power supply。The generator can generate electricity as soon as it rotates.When the battery is damaged, the vehicle charging system can still work normally as long as the engine is running.If the car does not have a battery, the ignition operation can also be realized by turning the handle or sliding the car.
7: It is especially suitable for working in humid or dusty environment.
8: Radio interference.The permanent magnet generator has the structure of no carbon brush and no slip ring, which eliminates the radio interference caused by the friction between the carbon brush and the slip ring;The electric spark is eliminated, which is especially suitable for working in the environment with high explosive risk, and also reduces the requirements of the generator on the ambient temperature.
Comparison of structural characteristics
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1: Permanent magnet generator: simple structure, large rotor magnetic field, no excitation winding, no carbon brush, no slip ring, large air gap, no contact, the only wearing part of the whole machine is the bearing.The reliability of the product is improved, no external regulator is needed, and the spacing of the magnet material is optimized to reduce the magnetic leakage, so that the generator has good idle speed performance and sufficient output circuit.
Excitation generator: poor idle power generation performance, easy to discharge the battery;The efficiency of the generator is only 40% - 50% when the rotating speed is 1500-6000 rpm/partition. The efficiency is low. Because there is an excitation coil in the rotor, the temperature of the whole machine rises;The excitation generator is also prone to carbon brush, slip ring damage and other problems.
2: Performance comparison.(Take 28V, 36A, 1000W generators as examples)
28V, 36A, 1000W generator
Current (A)
Full load speed (r/min)
Average efficiency (1500-6000r/min)
Regulating voltage (V)
Load characteristics (V)
Speed characteristic (V)
Excitation type
nine
three thousand and five hundred
zero point four five
28±0.3
|△U|≤0.8
|△U|≤0.5
Permanent magnet type
eighteen
two thousand and eight hundred
zero point eight
28±0.2
|△U|≤0.3
|△U|≤0.2
3: Volume temperature rise comparison.The following table:
Outer diameter (mm)
Length (mm)
Temperature rise (K)
Weight (kg)
Excitation type
Φ142
one hundred and eighty
seventy-five
six point five
Permanent magnet type
Φ128
one hundred and sixty-five
fifty
four
From the analysis of the above performance, structure, volume and other comparative situations, the permanent magnet generator is simpler in structure, smaller in volume, lighter in weight, superior in performance, and sufficient in power generation at low speed than the excitation generator.The volume and weight of JFYJ permanent magnet generator (3000W) and ordinary excitation generator (3000W) are compared as follows:
3000W
Outer diameter (mm)
Length (mm)
Weight (kg)
JFYJ permanent magnet generator
Φ171
two hundred and sixty-five
twelve
Common excitation generator
Φ200
three hundred and ten
twenty-four
prospect
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Permanent magnet generator
It has been greatly utilized in industrial and agricultural production, daily life, national defense science and technology, and has a great trend of development and expansion.[4]High power generators are often used in luxury and ultra luxury air-conditioned vehicles. When idling, the power consumption is large, and the excitation generator can only meet this requirement by increasing the speed ratio of the driving wheel to the generator pulley. The excellent medium and low speed power generation performance of the permanent magnet generator can just solve this technical problem
The vehicle air conditioner is installed on the side of the vehicle, which is close to the ground. During driving, dust and sundries are easy to enter the generator body, which is easy to increase the contact between the carbon brush of the excitation generator and the slip ring, thus affecting the normal operation of the generator;The permanent magnet generator has no slip ring, no carbon brush, and large air gap between stator and rotor, which is particularly suitable for working in this harsh working environment
The new generation of maintenance free battery has higher and higher accuracy of charging voltage. The excellent power generation performance of permanent magnet generator and high-precision voltage stabilization technology are effective ways to solve the battery power loss and extend the battery life
rare earthNdFeB Charm.The "crown of rare earth" neodymium iron boron, a unique rare material, will become the 21st century due to its powerful magnetic carrying functionindustrial revolutionMy darling.The motor industrial revolution triggered by it has become a high concern of motor experts and automotive experts all over the world.According to experts in the industry, the motor in the 21st century will be a permanent magnet world.As a country of rare earth, China's reserves account for 80% of the world's total, but the utilization and development of rare earth is not ideal. On the contrary, some developed countries have fully recognized the potential value of rare earth and are making in-depth research.China should develop its unique rare earth resources as South Africans exploit diamonds and Middle Easters exploit oil, and give full play to this resource advantage.At present, we have found a breakthrough in the deep development and utilization of rare earth in wind power projects.
Machine room size
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The description of the size of the generator room is very important, which provides direct technical parameters for the manufacturer who purchases the generator, and also provides enough parameters and digital basis for the designer of the machine room.However, there are several problems to be noted: First, the generator should be placed in a certain ventilated space, that is, the length, width and height should be more than a certain position, for example, there should be space for maintenance and inspection.2、 The part of the generator extending out of the smoke pipe shall have a position that can reach the specified installation part.3、 Is it easy to install the exterior wall at the wind guide position?Whether there is enough space for placing
Basic knowledge
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Composition of generator;There are three major parts: engine, electric ball and controller.It is a four stroke.yeswaterCold,Air-cooled, oil cooling.
maintain
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There are many common faults of the generator, which are mainly caused by poor maintenance or untimely maintenance.The engine is no different from the car. You should develop good maintenance habits.Timely and according to the standard, treat the generator like your own car, so you can adjust before rain
