Generator encyclopedia

Generator encyclopedia
The mechanical energy into electrical energy motor. Usually by steam turbine, turbine or internal combustion engine. Also useful for small windmill generator or other mechanical or belt driven by the gear.
DC generator is divided into two major categories of generators and alternators. The latter can be divided into two kinds of synchronous generators and asynchronous generators. Modern power stations are the most commonly used in synchronous generators. This generator is characterized by the direct current excitation, both to provide active power, reactive power can also be provided to meet the needs of a variety of loads. Since there is no independent induction generator field winding, and its simple structure, convenient operation, but can not provide reactive power to the load, but also to learn from the access network behind the magnetizing current. Therefore, induction generator must be run in parallel with other synchronous motor, or capacitor and then a considerable number. This limits the application of induction generators, used in only a small automation more hydropower. City trams, electrolysis, electrochemical DC power supply used in industry, in the 20th century, more than 50 years before the DC generator. But the DC generator with commutator, complex structure, making time-consuming, expensive, and failure-prone, difficult to maintain, is not as efficient alternator. Therefore, since the advent of high-power controlled rectifier, a semiconductor rectifier using AC power obtained by the direct current trend to replace the DC generator.
Synchronous generator used by the different prime mover into turbine generator, turbine and diesel generator three kinds. Their structure in common is useful in addition to a small permanent magnet motor produces a magnetic field outside the normal magnetic field excitation by direct current through the coil and excitation coil on the rotor, the armature windings on the stator. Because the excitation coil voltage is low, less power, but only two outlet headers and easily through the slip ring leads; the armature winding voltage high power and large, multi-purpose three-phase winding, there are three or four leads to the head , on the stator is relatively easy. Generator armature (stator) with a silicon core quartet built, in order to reduce iron loss. As the rotor core flux through the same, you can use the whole block is made of steel. In large motors, due to the rotor under strong centrifugal force, making the rotor material must be of high quality steel.
Turbine and steam turbine generator package. In order to obtain high efficiency, generally made of high-speed turbine, usually 3000 r / min (frequency 50 Hz) or 3600 r / min (frequency 60 Hz). Nuclear power plant in the turbine speed is low, but also 1500 rev / min or more. High-speed turbo-generator in order to reduce the centrifugal force generated due to mechanical stress and reduce wind abrasion, generally do relatively small rotor diameter, length is relatively large, that is, using thin rotor. Especially in the 3000 r / min or more of the large-capacity high-speed unit, because the relationship between the strength of the material, the rotor diameter are strictly limited, usually not more than 1.2 meters. The body length of the rotor critical speed has been limited. When the body length of more than 6 times the diameter, the rotor of the second critical speed will be close to the motor running speed, running a large vibration may occur. Therefore, the size of large high-speed turbo-generator rotor is severely restricted. About 100,000 kilowatts of its air-cooled motor rotor size has reached the limits of size, again increasing the motor capacity, only the electromagnetic load by increasing the motor to achieve. So we must strengthen the motor cooling. Therefore, 5 to 10 million kilowatts of turbo-generator with a cooling effect are good hydrogen-cooled or water-cooled technology. Since the 1970s, steam has reached the maximum capacity of 130 to 150 million kilowatts. Since 1986, the high critical temperature superconducting materials research has made a major breakthrough. Superconducting technology is expected to be applied in the turbine, the turbine-generator which will generate a new history leap.
Turbine driven by the turbine generator. Because the different natural conditions hydropower, hydro-generating unit’s capacity and speed vary widely. Typically small hydro and turbine-driven high-speed impact hydro and more horizontal structure, and large and medium-speed generator-generation multi-use vertical structure. As the station away from the city in most places, it usually takes longer to load power transmission lines, therefore, the operation of hydro electric power system to a higher stability of the proposed requirements: motor parameters need to be carefully selected; of moment of inertia of the rotor requires large. Therefore, the appearance and hydro turbine-generator is different from its rotor diameter and short length. Hydro-generating unit start, and net takes less time to run the scheduling flexibility, in addition to its general power outside, particularly suitable as a peaking unit and standby unit accidents. Hydro-generating unit’s maximum capacity has reached 70 million kilowatts.
Diesel generator driven by the internal combustion engine generators. It starts fast, easy to operate. However, the higher cost of power generation internal combustion engine, so the main diesel generator sets for emergency standby power, or in mobile power stations and some large regional power grid has not reached the use of diesel generator speed is usually 1000 r / min below the capacity of a few kW to between one thousand kilowatts, 200 kilowatts in particular the following units used more often. It is made relatively simple. Engine output shaft torque cyclical fluctuation, so the generator is in severe vibration conditions. Therefore, the structural components of diesel generators, especially shaft have sufficient strength and rigidity to prevent breakage due to vibration of these parts. In addition, to prevent the generator torque ripple caused by non-uniform angular velocity, resulting in voltage fluctuations caused by flashing lights, diesel generator rotor also requires a greater moment of inertia, and should make the shaft torsional vibration frequency and the inherent Engine torque ripple in either the frequency of the alternating component of more than 20% difference in order to avoid resonance, resulting in broken shaft accident.