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The Structure And Understanding Of Hydroelectric Generator

October 28, 2020

Hydro generator refers to a generator that uses water turbine as the prime mover to convert water energy into electrical energy. When the water flows through the turbine, it converts the water energy into mechanical energy, and the rotating shaft of the hydraulic turbine drives the rotor of the generator to convert the mechanical energy into electrical energy for output. Hydro generator is the main power equipment for producing electric energy in hydro power station.

Hydro generator can be divided into synchronous hydroelectric generator and asynchronous hydroelectric generator. In our country's small and medium-sized power stations, basically synchronous hydroelectric generators are used, and only small micro hydroelectric power stations use asynchronous hydroelectric generators. The hydroelectric generators usually mentioned are synchronous generators.

 Hydraulic generators can be divided into vertical and horizontal according to the axis position. Large and medium-sized units generally adopt vertical layout, while horizontal layout is usually used for small and tubular units. Vertical hydro-generators are divided into two types: suspension type and umbrella type according to the guide bearing support mode.

 The rotation speed of hydraulic turbines is relatively low, especially for vertical turbines. In order to generate 50Hz alternating current, the turbine generator adopts a structure of multiple magnetic poles. For a turbine generator with 120 revolutions per minute, 25 pairs of magnetic poles are required. Because it is difficult to see the structure with too many magnetic poles, this article shows a model of a hydraulic turbine generator with 12 pairs of magnetic poles.

The rotor of the water turbine generator adopts a salient pole structure. The magnetic poles are installed on the yoke. The yoke is the path of the magnetic field lines. The generator model has 24 magnetic poles in the north and south Excitation coils are wound on each magnetic pole, and the excitation power is provided by an excitation generator installed at the end of the main shaft, or by an external thyristor excitation system (power is supplied to the excitation coil by the slip ring).

  The rotor of the hydroelectric generator has multiple pairs of magnetic poles. The yoke is installed on the rotor support, the generator main shaft is installed in the center of the rotor support, and the excitation generator or the collector ring is installed on the upper end of the main shaft. There is a flange connected to the turbine at the lower end of the shaft.

  Hydraulic generator rotor: The stator core of the generator is made of silicon steel sheets with good magnetic conductivity. There are many slots evenly distributed in the inner circle of the iron core to embed the stator coil.

   Hydro generator stator iron core: The stator coil is embedded in the stator slot to form a three-phase winding. Each phase winding is composed of multiple coils, arranged according to a certain rule.

Hydro generator stator winding: The hydro generator is installed on the pier poured by concrete, and the base is installed on the pier. The base is the installation base of the stator core and the shell of the hydro generator. The base shell is equipped with a heat dissipation device to reduce the temperature of the cooling air of the generator; a lower frame is also installed on the pier, and the lower frame has a thrust bearing to install the generator rotor. The thrust bearing can bear the weight of the rotor and vibration and impact Equal strength.

  The rotor of the hydroelectric generator is inserted in the middle of the stator, and there is a small gap with the stator. The rotor is supported by the thrust bearing of the lower frame and can rotate freely.

  The stator and rotor are installed on the base. Install the upper frame. The center of the upper frame is equipped with a guide bearing to prevent the generator main shaft from shaking and make it stable in the center position.

  The uncovered floor of the turbine generator is laid on the upper platform floor, the brush device or the excitation motor is installed, and a turbine generator model is installed.

  The hydro-turbine generator model, for example, the hydro-generator model has 12 pairs of magnetic poles, and one rotation of the rotor will induce 12 cycles of three-phase AC electromotive force. When the rotor speed is 250 revolutions per minute, the frequency of the alternating current is 50 Hz. (The relationship between the rated speed of the turbine generator and the number of pole pairs).

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  The frequency of the electromotive force emitted by the hydroelectric generator satisfies f = Pn/60 (Hz), where P is the number of generator pole pairs and n is the rotor speed. In our country, f=50 Hz, so the relationship between the speed and the number of magnetic pole pairs is: n=3000/P. That is, if P=1, the generator speed is 3000r/min (the steam turbine is usually a pair of synchronous generators); if P=2, the generator speed is 1500r/min; if P=3, the generator The speed is 1000r/min; and so on.

  In the small hydro power industry, the more common rated speeds of hydroelectric generators are 600, 750 and 1000.