"High cooling rotor construction" reduces wind turbine weight by approximately 30%
Hitachi, Ltd. has developed a compact and lightweight technology for permanent magnet generators for 2000kW wind power generation. This time, a high-cooling rotor structure was developed, and a cooling ventilating groove was reserved on the rotor of the generator to efficiently cool the permanent magnets provided in the rotor. Generator design techniques have also been developed to optimize the size of the magnet arrangement and cooling vents using electromagnetic field analysis, stress analysis and thermal fluid analysis to ensure a balance between electrical and mechanical strength. As the output power of the permanent magnet generator increases, the diameter of the rotor also increases, resulting in an increase in centrifugal force. Therefore, there is a need to ensure a design in which electrical characteristics are balanced with mechanical strength. By increasing the cooling performance, a higher density package can be realized, resulting in a smaller size and lighter weight.
Hitachi, Ltd. used this technology to produce a 2000kW class permanent magnet generator. Compared with the company's wound-type induction generators for wind power generation (2000kW class), the power generation efficiency (97% or more) is the same, but the weight is reduced by about 30%. Wind turbines now mainly use wound-type induction generators.
The high-cooling rotor structure is a structure in which a cooling ventilating groove is provided between the magnetic poles of the N-pole and the S-pole of the permanent magnet to increase the amount of cooling air. Since the cooling air can be appropriately sent into the inside of the generator, the permanent magnets disposed in the rotor can be efficiently cooled. In addition, the ventilation groove can reduce the magnetic lines of force for increasing the heat generation of the permanent magnet (loss of the magnet), and is more advantageous for achieving small size, light weight, and high efficiency of the generator.