Synchronous generators are divided into 3 kinds of turbo-generators, hydro-generators and diesel generators according to the original motive. The common denominator in their structure is that except for a small motor useful permanent magnet to produce magnetic fields, the general magnetic field is produced by the DC excitation coil, and the excitation coil is placed on the rotor, the armature winding on the stator. Because the excitation coil voltage is low, the power is small, but also only two of the outlet head, easy through the slip ring leads; the armature winding voltage is higher, the power is large, multi-phase winding, 3 or 4 leads to the stator, it is more convenient to put on. The armature (stator) core of the generator is stacked with silicon steel sheets to reduce iron consumption. The rotor core can be made of the whole steel block because of the flux unchanged. In the large motor, because the rotor is subjected to strong centrifugal force, the material of the rotor must be manufactured with high quality steel.
Because of the different energy forms, different generators can be made.
With water conservancy resources and hydraulic turbines, the hydro-generators can be made, and the hydro generators with different capacity and rotational speeds can be made because of the difference of reservoir capacity and head drop.
The use of coal, oil and other resources, and boiler, turbo-steam engine, can be made into turbo-generators, the generator is a high speed motor (3000rpm).
In addition, there are various types of generators that utilize energy, such as wind power, atomic energy, geothermal and tidal waves.
In addition, the generator working principle is divided into DC generators, asynchronous generators and synchronous generators. The large generators currently used are synchronous generators.
Water conservancy generators are the power machinery that converts the kinetic energy and gravitational potential energy to the mechanical work. The Three Gorges in China is a good example. In the power generation, it is best to count nuclear power, but the relative nuclear pollution is larger. So China is now widely used in coal generation. At present, China's coal resources are tight, coal prices have been rising, which is why there is now the emergence of the main reason for the shortage of electricity.
Because of the different natural conditions of hydropower station, the capacity and rotational speed of hydrogenerator unit varies greatly. Usually small hydro-generator and impact turbine-driven high speed hydro-generator adopts horizontal structure, while large and medium-sized generation-speed generators adopt vertical structure (see chart). Since the hydropower station is mostly located in the far away from the city, it usually needs to be powered by a longer power transmission line, so the power system has higher requirements for the running stability of Hydrogenerator: The motor parameters need to be carefully chosen; Therefore, the type of hydrogenerator is different from turbo-generator, its rotor diameter is large and short length. Hydro-Generator set start-up, grid-connected to a shorter time, the operation of flexible scheduling, in addition to general electricity, it is particularly suitable for the surge unit and accident standby unit. The maximum capacity of hydro-generator sets has reached 700,000-kilowatt.