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Hydro generator

key word:Heat exchange element


Product description

1. Breif and structure of the hydro generator 

Hydro generator refers to the generator that takes the water turbine as the prime mover to convert water energy into electric energy. When the water flows through the turbine, the water energy is converted into mechanical energy, and the rotating shaft of the turbine drives the rotor of the generator to convert the mechanical energy into electrical energy for output. Hydro generator is the main power equipment of hydropower station to produce electric energy.

Hydro generators can be divided into synchronous hydro generators and asynchronous hydro generators. In small and medium-sized hydropower stations, synchronous hydro generators are basically used, and only small micro hydropower stations use asynchronous hydro generators. Hydro generators are usually synchronous generators.

Hydro generators can be divided into vertical and horizontal types according to the axis position. Large and medium-sized units generally adopt vertical layout, and horizontal layout is usually used for small units and tubular units. According to the support mode of guide bearing, vertical hydro generator is divided into suspension type and umbrella type.

The speed of water turbines is relatively low, especially the vertical water turbine. In order to generate 50Hz AC, the water turbine generator adopts multi pair magnetic pole structure. For the water turbine generator with 120 revolutions per minute, 25 pairs of magnetic poles are required. Since it is difficult to see the structure of too many magnetic poles, the following is a model of a hydraulic turbine generator with 12 pairs of magnetic poles.

The rotor of hydro generator adopts salient pole structure. Figure 1 shows the yoke and magnetic pole of the generator. The magnetic pole is installed on the yoke. The yoke is the path of the magnetic field line of the magnetic pole. The generator model has 24 magnetic poles between North and south, and each magnetic pole is wound with an excitation coil. The excitation power is provided by the excitation generator installed at the end of the main shaft or by the external thyristor excitation system (power is supplied to the excitation coil by the collector ring).

 

Figure 1 - Rotor of hydro generator has multiple pairs of magnetic poles

 

 

The magnetic 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 collector ring is installed at the upper end of the main shaft. The lower end of the shaft is provided with a flange connecting the water turbine, as shown in Figure 2.

 

Figure 2 - hydro generator rotor

 

The generator stator core is made of silicon steel sheets with good magnetic conductivity. Many slots are evenly distributed in the inner circle of the core to embed the stator coil, as shown in Figure 3.

 

Figure 3 - stator core of hydro generator

 

 

The stator coil is embedded in the stator slot to form a three-phase winding. Each phase winding is composed of multiple coils and arranged according to certain rules, as shown in Figure 4.

 

Figure 4 - stator winding of hydro generator

 

The water turbine generator is installed on the concrete cast turbine pier, on which the base is installed. The base is not only the installation base of the stator core, but also the shell of the water turbine generator. The heat dissipation device is installed on the base shell to reduce the temperature of the generator cooling air; the lower frame is also installed on the turbine pier, and the lower frame is equipped with thrust bearing to install the generator rotor. The thrust bearing can bear rotating speed The weight, vibration, impact and other forces of the sub. see Fig. 5.

Figure 5 - Turbine pier, base and lower frame of hydro generator

 

 

 

Install the stator core and stator coil on the base, as shown in Figure 6.

Figure 6 - stator of hydro generator

 

 

The rotor is inserted in the middle of the stator and has a small gap with the stator. The rotor is supported by the thrust bearing of the lower frame and can rotate freely, as shown in Figure 7.

Figure 7 - stator and rotor installed on the base

 

 

Install the upper frame. A guide bearing is installed in the center of the upper frame to prevent the main shaft of the generator from shaking and make it stably in the center position, as shown in Figure 8.

Figure 8 - turbine generator uncovered floor

 

 

 

After laying the upper platform floor and installing the brush device or excitation motor, a hydro generator model is installed, as shown in Figure 9.

Figure 9 - turbine generator model

 

The above hydro generator model has 12 pairs of magnetic poles, and a rotation of the rotor will induce 12 cycles of three-phase AC electromotive force. When the rotor speed is 250 rpm, the frequency of the generated AC is 50 Hz.

 

2. Relationship between rated speed and magnetic pole logarithm of hydro generator

The frequency of electromotive force generated by hydro generator meets f = Pn / 60 (Hz), where p is the number of generator poles and N is the rotor speed. In China, f = 50 Hz, so the relationship between speed and number of poles is: n = 3000 / P. that is, if P = 1, the generator speed is 3000 r/min (steam turbine is usually a pair of synchronous generators) ; if P = 2, the generator speed is 1500 r /min; if P = 3, the generator speed is 1000r / min; and so on. The rated speed of hydro generator takes precedence over the following speed (r / min) Middle selection: 1500, 1000, 750, 600, 500, 428.6, 375, 333.3, 300, 250, 214.3, 200, 187.5, 166.7, 150, 142.9, 136.4, 125, 115.4, 107.1, 100, 93.8, 88.2, 83.3, 75, 71.4, 68.2, 62.5, 60.