Comparison of designs of synchronous machines with integrated torque transformer for renewable energy

Abstract

Increasing the specific torque of electric machines is an urgent problem for a number of low-speed power electromechanical systems, one of such systems is a wind power plant. Determining the optimal design of a synchronous generator with a built-in torque transformer is important for the further development of wind power. The purpose of the research is to determine the optimal design of a generator with a built-in torque transformer for wind power plants, which is a solution to the problem of creating low-speed, high-torque and relatively compact electric generators, and will make it possible to abandon the gear drive. The paper examines two designs of a direct drive synchronous generator with a built-in torque transformer with two and three air gaps. The calculation is performed using the Comsol Multiphysics software based on the finite element method. The main criteria for comparison are the generator's output power, the maximum torque of the low-speed rotor connected to the wind turbine, the maximum torque per unit volume of the generator, and the maximum torque per unit mass of the permanent magnets. Based on the calculation results, it has been concluded that a synchronous generator with two air gaps has a higher torque per unit volume and torque per mass of permanent magnets, i. e. with the same power, the expenses on active materials will be lower. This type of generator has a higher output power compared to both the direct-drive synchronous generator and the synchronous generator with three air gaps, with the same dimensional parameters.