Deok-je Bang

Structural Flexibility: A Solution for Weight Reduction of Large Direct-Drive Wind-Turbine Generators

This paper looks into a new concept for reducing the structural weight of large direct-drive generators used in wind turbines. The concept uses magnetic bearings to position the rotor of the generator. The use of magnetic bearings allows structural flexibility in the generator. The weight of the rotor using the new concept is compared to the weight of a rotor designed with conventional methods. For a 5-MW generator, the result is that the structural weight of the rotor reduces by 45%.

Comparative design of radial and transverse flux PM generators for direct-drive wind turbines

The aim of this paper is to assess the radial flux permanent magnet (RFPM) and transverse flux permanent magnet (TFPM) generators for large direct-drive wind turbines. For the assessment, the electromagnetic design of RFPM and TFPM generators is done. The analytical design result of a TFPM generator is compared with the experimental result. A RFPM machine concept and four different TFPM machine concepts are designed electromagnetically for 5 MW direct-drive wind turbines. These machines are assessed with criteria such as the cost, the mass, the copper loss, the power/mass ratio, the power/cost ratio, the cost/mass ratio and the mass/torque ratio.

Design of a Lightweight Transverse Flux Permanent Magnet Machine for Direct-Drive Wind Turbines

The aim of this paper is to design a lightweight transverse flux permanent magnet (TFPM) machine for large scale direct-drive wind turbines. The requirements for suitable generator systems for wind turbines are discussed. Analytical modeling of TFPM machines is discussed by considering the machine parameters and the magnetic circuit. The proposed analytical model is verified by comparing it to results of finite element analysis and experiments. A new lightweight TFPM machine is designed for a 10 MW direct-drive wind turbine and it is compared to the RFPM machine.

Ring-shaped transverse flux PM generator for large direct-drive wind turbines

A ring-shaped transverse flux permanent magnet (TFPM) generator with double-sided axial flux configuration is proposed in this paper. The ring-shaped TFPM generator does not use a shaft and arms to transfer the torque and to support both the rotor and the stator. The active part of the proposed generator consists of multiple-segment structure. This new generator configuration can remarkably reduce the mass, and can make the construction easy in manufacturing and handling. Analytical design model is developed for the TFPM generator. The analytical model is verified by the experimental analysis of the downscaled generator. The design results of 5 MW ring-shaped TFPM generators are compared with two different generators, namely a conventional radial flux PM generator and a single-sided air gap TFPM generator.

Promising Direct-Drive Generator System for Large Wind Turbines

Abstract The aim of this paper is to review direct-drive generators and to propose promising direct-drive generator concepts for large wind turbines. Different large direct-drive generators are compared based on the mass and the torque rating. Features of different PM machines are investigated to find a suitable machine type for direct-drive. Some promising solutions are proposed for both electromagnetic and mechanical design.

A new concept for weight reduction of large direct drive machines

This paper looks into a new concept for reducing the structural weight of large direct drive generators used in wind turbines. The concept uses magnetic bearings to position the rotor of the machine. The weight of the rotor using the new concept is compared to a rotor designed with conventional methods. The comparison of a 5 MW generator rotor structural material shows about 45% reduction of weight of the rotor.

Structural mass minimization of large direct-drive wind generators using a buoyant rotor structure

The aim of this paper is to minimize the structural mass of large direct-drive wind generators using a ring-shaped buoyant rotor structure. A surface mounted permanent-magnet machine configuration is chosen for the proposed generator. The active mass of the generator is estimated by an electromagnetic design. Structural deformation equations for the proposed generator are derived, and the structural dimensions of the generator are initially determined from the equations. Using a three-dimensional finite element analysis, the structural dimensions are modified and the structural mass is estimated. The total mass of the proposed generator estimated by the design and the analysis is 89, 195 and 430 tonnes for 5, 10 and 20 MW wind turbines. The results indicate that the proposed generator is lighter than conventional direct-drive generators, and becomes lighter than the geared generator in scaling up larger than 9 MW.

Human powered axial flux permanent magnet machines: Review and comparison

This paper presents a review of concepts for harvesting power from human movement and comparison of three axial flux permanent magnet machine (AFPM) designs. Some schemes for human power generating systems have been presented and compared in order to choose the most suitable configuration for our application. From the concepts evaluated, choices were made based on project specifications in the design of three axial flux permanent magnet (AFPM) machines with an output of 60W at a rotational speed of 3000 rpm. Comparison of the three AFPM generators: singled-sided with distributed winding, single-sided with concentrated windings, and double-sided (TORUS) with air gap winding show that the AFPM with concentrated windings and the TORUS are attractive having low mass and low losses.

Air gap control of multi-phase transverse flux permanent magnet linear synchronous motor by using independent vector control

This paper presents an air gap control method of a multi-phase transverse flux permanent magnet linear synchronous motor (MP-TFPMLSM) based on independent vector control. Especially, the MP-TFPMLSM is composed of symmetrical multi-phase and multiple-module structures, which are basically three-phase configurations. Hence, in this paper, a d-axis current control applying the d-q transformation and the independent vector control are proposed for the air gap control between two symmetric stators and mover of the MP-TFPMLSM. The control performance and characteristics of the MP-TFPMLSM, which is based on two basic three-phase structures of the air gap control and the position control of multi-phase linear machines using a concept of vector control are analyzed. As a result, the air gap control by using the independent vector control is a suitable method to efficiently control the interaction between stator and mover of the MP-TFPMLSM. The proposed method is easily implemented and has less computation time to design controllers for operating the multi-phase machines. The effectiveness of the proposed independent vector control algorithm is verified through several experimental results.

Vector control of multiple-module transverse flux PM generator for large-scale direct-drive wind turbines

This paper proposes an efficient current control algorithm and a suitable power conversion system of a multiple-module transverse flux permanent magnet generator (MM-TFPMG) for large-scale direct-drive wind turbines. The MM-TFPMG is composed of multiple-module structures based on an independent three-phase configuration. In this paper, the single-phase current control applying the d-q transformation and the independent three-phase dqn-axes current control are proposed for the generator-side control of the MM-TFPMG. The control performance and characteristics of the single-phase dq-axes current control with a variable cutoff frequency and the independent three-phase dqn-axes current control using a concept of vector control are analyzed. As a result, the independent three-phase dqn-axes current control by using the vector control is an appropriate method to efficiently control the generator-side of the MM-TFPMG. The proposed algorithm is easily implemented and has less computation resource. Moreover, the control performance is better than the independent single-phase dq-axes current control despite the change of wind speed. The validity and usefulness of the proposed independent three-phase dqn-axes current control algorithm are verified and compared through several experimental results.