Application of composite materials in axial magnetic field permanent magnet wind turbine
The radial magnetic field permanent magnet synchronous generator used in the low-speed direct-drive wind energy system is a flat large disk having a large inner diameter, a large rotor size and a moment of inertia. This is advantageous for suppressing fluctuations in the electromotive force caused by wind fluctuations, but it also imposes higher requirements on motor control. In addition, direct-drive permanent magnet synchronous generators are generally of higher quality and economical than conventional generators. In order to be more competitive in the business, it is necessary to optimize the cost, power density and efficiency of low-speed large-diameter generators.
It is well known that if the number of poles of the motor is sufficient and the ratio of the axial length to the outer diameter is small enough, the axial field motor has a greater advantage in torque and power density than the conventional radial field motor. The axial magnetic field permanent magnet motor also has the advantages of small moment of inertia and good heat dissipation condition of the stator winding, and can also be multi-air gap structure with multiple stators and multiple rotors to improve the output power. Therefore, the axial permanent magnet synchronous generator is suitable for the application of direct drive wind energy conversion.
The main drawback of axial flux machines is related to the manufacture of the stator core. The stator core is formed by winding a silicon steel sheet strip and then performing groove processing or winding a grooved silicon steel sheet strip. During the processing of the groove, a short circuit problem between the laminations is encountered, and when the lamination of the lamination is performed, there is a problem that the pre-perforated grooves are difficult to align. A core made of a pressed soft magnetic composite (hereinafter referred to as sMc) material provides a solution to the above problem.
Recently, improvements in the low frequency characteristics of sMc materials have led to widespread interest in motor design applications. The unique advantages of sMc materials and powder metallurgy extrusion processes are that it allows complex structures to be easily formed, overcoming some of the drawbacks of conventional slotted laminated stator core fabrication. In a silicon steel sheet laminated core motor, good magnetic properties are obtained in a planar magnetic circuit, which produces a two-dimensional magnetic circuit, which limits the design possibilities. Iron particles insulated in the sMc material can produce an isotropic magnetic property. Therefore, a three-dimensional magnetic circuit can be obtained in the design of the magnetic pole assembly, which provides a new design method for the motor designer.
