Classification of Generators

The common classification of generators is wind generators, high-speed synchronous generators, low-speed synchronous generators, permanent magnet synchronous wind generators, alternators, diesel generators, etc.

Wind Turbines

As a new type of power generation system with low price, reliable operation,and no greenhouse gas emission, the installed capacity of wind power generation system is being increasingly widely used in the world with an annual growth rate of more than 30% and has formed an annual output value of more than 50%. billion dodollarslobal industry. However, the small-scale wind power generation system used for independent power supply in remote areas still needs to overcome many technical difficulties before it can be widely used. With my country's increasing investment in "agriculture, rural areas and farmers" and the sustained and rapid economic development, the majority of farmers, herdsmen n d fishermen have adopted small wind power generation systems to provide local loads to improve their living environment, improve their quality of life, and solve the urgent requirements of domestic electricity consumption. Electricity can not only reduce one-time huge investment, but also eliminate greenhouse gas emissions from thermal power generation systems, improve the environment and energy structure in rural areas, and be beneficial to sustainable development.
Wind turbines convert wind energy into mechanical work and drive the generator to run to generate electricity. Broadly speaking, it is a thermal energy utilization engine with the sun as the heat source and the atmosphere as the working medium. Wind power uses natural energy. Much better than diesel power generation. However, if it is used in an emergency, it is still not as good as a diesel generator. Wind power cannot be regarded as a backup power source, but it can be used for a long time.

High-speed synchronous generator

Because most generators are coaxially linked with the prime mover, thermal power plants use high-speed steam turbines as prime movers, so turbo-generators usually use high-speed 2-pole motors with a speed of 3000 rpm (at a grid frequency of 60 Hz). 3600 rpm). Nuclear power plants mostly use 4-pole motors with a speed of 1500 rpm (when the grid frequency is 60 Hz, it is 1800 rpm). To meet the high-speed and high-power requirements, the high-speed synchronous generator adopts a hidden-pole rotor in the structure, and secondly, a special cooling system is set up.
Concealed-pole rotor: The outer surface is cylindrical, the surface of the cylinder is slotted to place the DC excitation winding, and it is fastened with metal slot wedges so that the motor has a uniform air gap. Due to the huge centrifugal force during high-speed rotation, the rotor is required to have high mechanical strength. Concealed pole rotors are generally forged from high-strength alloy steel in one piece, and the slot shape is generally open so that the excitation winding can be installed. About 1/3 of each pole pitch is not slotted, forming large teeth; the rest of the teeth are narrower, called small teeth. The center of the large tooth is the center of the rotor pole. Sometimes the large teeth also open some smaller ventilation slots, but the windings are not embedded; sometimes a narrow and shallow small slot is milled at the bottom of the embedding slot as a ventilation slot. The hidden pole rotor is also equipped with metal guard rings and center rings at both ends of the rotor body in the axial direction. The retaining ring is a thick-walled cylinder made of high-strength alloy to protect the end of the excitation winding from being thrown out by huge centrifugal force; the center ring is used to prevent the axial movement of the winding end and support the retaining ring. In addition, to pass the excitation current into the excitation winding, a collector ring and a brush are also installed on the motor shaft.

Cooling system: Since the energy loss in the motor is proportional to the volume of the motor, its magnitude is proportional to the cube of the motor's linear scale, and the magnitude of the motor's heat dissipation surface is only the quadratic of the motor's linear scale. Therefore, when the size of the motor increases (limited by materials, increasing the capacity of the motor must increase its size), the heat that the motor needs to dissipate per unit surface will increase, and the temperature rise of the motor will increase. In a high-speed turbo-generator, the centrifugal force will cause huge tangential stress on the rotor surface and the surface of the rotor center hole, and the larger the rotor diameter, the greater the stress. Therefore, within the allowable stress limit of the forging material, the diameter of the rotor body of the 2-pole turbo-generator cannot exceed 1250 mm. Large-scale turbo-generators need to increase the single-unit capacity only by increasing the length of the rotor body (that is, using a slender rotor) and increasing the electromagnetic load. The rotor length can reach 8 meters, which is close to the limit. To continue to increase the capacity of a single machine, we can only increase the electromagnetic load of the motor. This makes the heating and cooling problems of large turbo-generators particularly prominent. For turbo-generators below 50,000 kilowatts, closed-circuit air cooling systems are mostly used, and engine fan parts in the motor are used to blow heat-generating components to cool down. For generators with a capacity of 50,000 to 600,000 kilowatts, hydrogen cooling is widely used. The heat dissipation performance of hydrogen (purity 99%) is better than that of air. Using it to replace air not only has a good heat dissipation effect but also greatly reduces the ventilation friction loss of the motor, thereby significantly improving the efficiency of the generator. However, the use of hydrogen cooling must have explosion-proof and leak-proof measures, which makes the motor structure more complicated, and also increases the consumption and cost of electrode materials. In addition, liquid medium cooling can also be used, for example, the relative cooling capacity of water is 50 times that of air, taking away the same heat, and the flow rate of water required is much smaller than that of air. Therefore, a part of the hollow wire is used in the coil, and the wire is cooled by water, which can greatly reduce the temperature rise of the motor, delay the aging of the insulation, and increase the life of the motor.

Low-speed synchronous generator

Most are driven by lower-speed hydro turbines or diesel engines. The number of magnetic poles of the motor ranges from 4 poles to 60 poles, or even more. The corresponding speed is 1500-100 rpm and below. Due to the low rotational speed, salient-pole rotors with lower requirements on materials and manufacturing processes are generally used.
Each magnetic pole of the salient-pole rotor is often made of 1-2 mm thick steel plates, which are assembled into a whole with rivets, and the magnetic poles are covered with excitation windings. The field winding is usually made of flat copper wire. The pole piece of the magnetic pole is also often equipped with a damping winding. It is a short circuit formed by the bare copper strip in the damping groove of the pole shoe and the copper ring welded at both ends. The magnetic poles are fixed on the rotor yoke, which is made of cast steel. Salient-pole rotors can be divided into horizontal and vertical types. Most synchronous motors, synchronous controllers, and generators are driven by internal combustion engines or impact turbines use horizontal structures; low-speed, large-capacity hydro-generators use vertical structures.
The rotor of the horizontal synchronous motor is mainly composed of the main magnetic pole, the yoke, the excitation winding, the collector ring, and the rotating shaft. Its stator structure is similar to that of an asynchronous motor. The vertical structure must use the thrust bearing to bear the gravity of the rotating part of the unit and the downward pressure of the water. In large-capacity hydro-generators, this force can be as high as 40 to 50 meganewtons (equivalent to the gravity of 4,000 to 5,000 tons of objects), so the structure of this kind of thrust bearing is complex, and the processing technology and installation requirements are very high. According to the placement position of the thrust bearing, vertical hydro-generators are divided into two types: suspension type and umbrella type. The suspended thrust bearing is placed on the upper or middle part of the upper frame. When the rotation speed is high and the ratio of the rotor diameter to the core length is small, the mechanical operation is more stable. The umbrella-type thrust bearing is placed on the lower frame of the lower part of the rotor or the top cover of the turbine. The load-bearing frame is a lower frame with a smaller size, which saves a lot of steel and reduces the height of the generator and plant from the base of the frame.

Permanent magnet synchronous wind turbine

Permanent magnet synchronous wind turbine has become another important wind turbine type after DFIG due to its advantages of small mechanical loss, high operating efficiency, and low maintenance cost, and has gradually begun to be put into use. The basic structure of a permanent magnet synchronous wind power generation system is mainly composed of a wind turbine, permanent magnet synchronous engine, frequency converter, and transformer.
The basic principle of permanent magnet synchronous wind power generation is to use the wind to drive the blades of the wind turbine to rotate, and to drive the rotor of the permanent magnet synchronous generator to rotate to achieve power generation. The permanent magnet synchronous wind power generation system is similar to the cage variable speed constant frequency wind power generation system, but the generator used is a permanent magnet generator, and the rotor is a permanent magnet structure, which does not require external excitation power, which improves the efficiency. Its variable frequency constant speed control is realized in the stator loop, and the variable frequency alternating current of the permanent magnet synchronous generator is converted into the alternating current of the same frequency of the power grid through the frequency converter, to realize the grid connection of wind power generation. The rated capacity is the same.
In the past few decades, permanent magnet synchronous generators have become increasingly attractive due to improvements in the performance of permanent magnet materials and power electronics. The wind power generation system using a permanent magnet synchronous generator has the following characteristics:
1. The permanent magnet synchronous generator system does not need an excitation device, and has the advantages of light weightlightweightiency, high power factor, and good reliability;
2. The variable speed operation range is wide, which can be super-synchronous or sub-synchronous;
3. The rotor has no excitation winding, the magnetic pole structure is simple, the inverter capacity is small, and it can be made into a multi-pole motor;
4. The synchronous speed is reduced, so that the wind turbine and the permanent magnet generator can be directly coupled, eliminating the need for the gear speed increase box in the wind power generation system, reducing the maintenance work of the generator, and reducing the noise, so that the direct drive permanent magnet wind power can be generated. machine system.
Applications:
1. In areas where power facilities are scarce, transportation is inconvenient, and conventional fuels are lacking, but wind resources are abundant, some power consumption problems can be solved, such as providing power for highway lighting equipment;
2. In wind farms with relatively small single-unit capacity, the permanent magnet synchronous power generation system can efficiently connect to the grid for power generation;
3. Provide AC or DC power for remote and light-loaded users in rural areas, pastoral areas, border guard posts, meteorological stations, etc.In daily life, when the alternator is used to supply electrical equipment, it often happens that the electrical equipment cannot work normally. That is, the AC-regulated power supply is commonly used in daily life, the AC-regulated power supply can stabilize the output voltage accuracy of the generator to the range allowed by the normal operation of the electrical equipment.
Alternator Construction
The construction of the alternator is slightly more complicated. But whether it is single-phase or three-phase, it is composed of the following main parts:
(1) Excitation part: including the exciter and the magnetic field part.
⑵ armature part.
(3) Chassis part: including the iron frame and machine base of the equipment and spare parts.

Asynchronous generator

Asynchronous generators are also called "induction generators". An alternator that uses the air gap between the stator and the rotor to interact with the rotating magnetic field and the induced current in the rotor winding. The rotation of the rotor is the same as that of the rotating magnetic field, but the speed is slightly higher than the synchronous speed of the rotating magnetic field. Often used as a small power hydro-generator.
The AC excitation generator has a flexible operation mode due to the use of AC voltage excitation on the rotor side. It has a traditional way of solving problems such as continuous power frequency overvoltage in power stations, variable speed constant frequency power generation, and speed regulation of motor-generator units in pumped storage power stations. Synchronous generator incomparable superiority. There are three main operating modes of AC excitation generators:
1) Running in variable speed constant frequency mode;
2) It operates in the mode of large-scale adjustment of reactive power;
3) Operates in power-electric mode.
With the increase of the transmission voltage of the power system and the growth of the line, when the transmission power of the line is lower than the natural power, there will be continuous power frequency overvoltage in the line and power station. To improve the operating characteristics of the system, many technologically advanced countries, At the beginning of the 6th "century A", the application of asynchronous generators in large power systems were studied, and it was believed that the use of asynchronous generators in large systems could improve the stability, reliability and economical operation of the system.

Tachogenerator

A tachogenerator is a micro-generator that measures the rotational speed. It converts the input mechanical rotational speed into a voltage signal output and requires the output voltage signal to be proportional to the rotational speed.
Classification of tacho generators: tacho generators are divided into two categories: DC tacho generators and AC tacho generators.
DC tachogenerator: The DC tachogenerator is essentially a miniature DC generator, which is divided into electromagnetic type and permanent magnet type according to the excitation method of the stator poles. The working principle of the DC tachogenerator is the same as that of the general DC generator.
AC tachogenerator: The rotor structure of the AC asynchronous tachogenerator has cage type and cup type. In the control system, hollow cup rotor asynchronous tachometer generators are often used. There are two windings on the stator of the hollow cup rotor asynchronous tachometer generator which are separated by a 90° electrical angle in space, one is the excitation winding and the other is the output winding.
The main errors of AC asynchronous tachogenerator are:
Non-linear error: the non-linear error of the tachogenerator due to the change of the direct-axis magnetic flux;
Residual voltage: In actual operation, when the rotor is stationary, the tacho generator outputs a small voltage;
Phase error: Due to the leakage reactance of the excitation winding and the leakage reactance of the hollow cup rotor, the phase of the output voltage and the excitation voltage are different.
AC synchronous tacho generators are divided into permanent magnet type, induction type, and pulse type.

Diesel generators

A diesel generator set is a kind of independent power generation equipment, which refers to a powerful machine that uses diesel as fuel, uses a diesel engine as a prime mover, and uses a crankshaft to drive a generator to generate electricity. The whole set is generally composed of a diesel engine, generator, control box, fuel tank, battery for starting and control, protection device, emergency cabinet, and other components. The whole can be fixed on the foundation, used for positioning, or mounted on a trailer for mobile use. The diesel generator set is a non-continuous operation of power generation equipment. If it runs continuously for more than 12 hours, its output power will be about 90% lower than the rated power.

Our website also provides camshaft 059109101, you can buy a variety of spare parts for excavators, and aerial platforms on our website.