The rotational speed of hydraulic turbines is relatively low, especially for vertical hydraulic turbines. In order to generate 50Hz alternating current, the hydraulic turbine generator adopts a structure of multiple pairs of magnetic poles. For a hydraulic turbine generator with 120 revolutions per minute, 25 pairs of magnetic poles are required. Since it is difficult to see the structure with too many magnetic poles, this courseware introduces a model of a hydro-turbine generator with 12 pairs of magnetic poles.
The rotor of the hydro-generator adopts a salient pole structure. Figure 1 shows the yoke and the magnetic pole of the generator. The magnetic pole is installed on the magnetic yoke. The magnetic yoke is the path of the magnetic field line of the magnetic pole. Each pole is wound with an excitation coil, and the excitation power is provided by the excitation generator installed at the end of the main shaft, or provided by an external thyristor excitation system (supplied by the collector ring to the excitation coil).
The yoke is installed on the rotor bracket, the generator main shaft is installed in the center of the rotor bracket, and the excitation generator or the collector ring is installed on the upper end of the main shaft.
The stator iron 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, which are used to embed the stator coils.
The stator coils are embedded in the stator slots to form three-phase windings, each phase winding is composed of multiple coils and arranged according to certain rules.
The hydro-generator is installed on the machine pier made of concrete, and the machine base is installed on the machine pier. The machine base is the installation base of the stator iron core and the shell of the hydro-generator. 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 withstand the weight of the rotor, vibration, impact and other forces.
Install the stator iron core and stator coil on the frame, the rotor 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. Install the upper frame, and the center of the upper frame is installed with a The guide bearing prevents the main shaft of the generator from shaking and keeps it stably in the center position. Lay the upper platform floor, install the brush device or the excitation motor, and a hydro-generator model is installed.
One rotation of the rotor of the hydro-generator model will induce 12 cycles of three-phase AC electromotive force. When the rotor rotates at 250 revolutions per minute, the frequency of the alternating current is 50 Hz.
Post time: Feb-21-2022
