Friends, today in this article we will learn about vertical axis direct drive wind power plant. I am going to give information about all this in a very good way. So let’s start.
Vertical axis direct drive wind power plant – The rotor speed of wind turbines is always low, small power size wind turbines turn a few hundred rpm at most, some higher rpm are for medium and megawatt power size wind turbines which require a speed increasing gearbox to take the generator speed up to the rated speed. Figure 1 shows the structure of a horizontal axis wind turbine inside a speed increasing gearbox.
The efficiency of wind turbine is low due to the use of speed-increasing gearbox. Gearbox is a quick device especially for high-speed turbine and it is difficult to maintain the gearbox in the nacelle of wind turbine. Replacing gearbox regularly is a very expensive job. It is possible to make direct driving generator through rotor system without gearbox, but low-speed alternator must be used in wind turbine, which is called direct driving wind turbine. Wind turbine technology has been developing from small power-size to huge power-size in recent years. 5MW permanent magnet direct drive wind turbine has been developed in China with independent intellectual property rights. It should be known that the largest wind turbine in foreign countries has reached 7MW, which is a direct-drive wind turbine.
The multi-pole structure is for low speed generators, so the hydraulic turbine generators are multi-pole. At present, the direct driving wind turbine is mainly made of multi-pole type with outer rotor structure and inner rotor structure, but it needs to be a little lighter in structure.
Permanent magnet technology with high magnetic energy has developed rapidly. In particular, the rare earth permanent magnet NdFeB (neodymium iron boron) is widely used in direct drive generators. Simple structure and high efficiency are achieved in direct drive generators with permanent magnet technology. Permanent magnet direct drive wind turbines have both main shaft structure and disc structure. The axial structure has radial air gap flux in the direction of axial magnetic field. Which is divided into inner rotor and outer rotor. The magnetic field direction of disc structure is in line with the axial air-gap flux, which is divided into intermediate rotor, intermediate stator and multi-disk. In recent years, new types of dual main pole generators and switched reluctance generators are also being applied in permanent magnet direct drive generators. Thin disc multi-pole permanent magnet generator It is made thin due to the low windage resistance demand of vertical axis wind turbine. This generator has axial alignment of disc stator and disc rotor. The structure of a thin disc multipole generator is described below. The panel in Figure 2 is a stator core with uniformly arranged grooves on its surface.
The rotor of a disk generator is composed of many permanent magnetic poles, these poles are arranged in a circle and both north and south magnetic poles are arranged alternately. The permanent magnetic poles require a magnetic yoke as a magnetic force line path to fix the magnetic poles on the disk surface of the rotor magnetic yoke, which is the upper terminal cover of the generator.
The upper casing centre is equipped with two upper and lower bearings to enable the rotor to rotate continuously on the main shaft.
When the rotor is inserted into the main shaft of the stator, there is a small gap between them. The rotor can rotate freely around the main shaft and thus a thin disc generator model is prepared.
The axial magnetic field of the disc generator through the coil is parallel to the main shaft. When the rotor rotates, the coil wire cuts the magnetic field line to generate electromotive force.
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