Design of a 5 kW Tubular Permanent Magnet Linear Generator Khalid Mohamed Nor, Senior Member, IEEE, Wanizah Arof, and Wijono
ABSTRACT A tubular permanent magnet linear generator with the output power of 5 kW and output voltage of 200 V with minimum cogging force is designed, simulated and fabricated. Specific design criteria are employed to meet exclusive requirements rclated to its stator and translator. A simple model of the electromagnetic analysis of the cogging force and generated emf is presented. Finite elemcnt software is used to simulate the machine. The linear machine is developed based on the results of finite element simulation. A radially magnetized magnet is chosen to give a high performance and to solve the cogging force-voltage problem.
Keyword: Cogging Force, Finite Element Simulation, Linear Generator, Permanent Magnet Tubular Linear Generator.
optimization of models involves the permanent magnet, the coil and the stator dimension. A srnaller generator of 0.3 kW,200V was also designed and constructed [2]. The voltage induced in the coil is derived from the flux calculated with the finitc element method and the dynamic performance of the generator is examined using the electric circuit simulation software.
1. INTRODUCTION
Prospective applications of linear engine are for industrial, conmiercial and personal purposes especially where a stand alone power generation is needed. It is also vital when grid power utility is unavailable. It can also be used as an alternative power generator for hybrid vehicles.
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NASA Glenn Research Center, Cleveland, Ohio, the Department of Energy (DOE), and Stirling Energy Company [ 3 ] developed a lightweight and highly efficient linear generator driven by a stirling engine for space applications. The generator consists of a moving part and a stator where the coil is wound on its outer surface. A 3D parametric finite element method is used to simulate and evaluate the open circuit voltage and the flux density of the generator.
In this paper, design and simulation aspects of a tubular permanent magnet linear generator intended to be driven by a free-piston internal combustion engine are outlined. Specific design criteria are employed to meet exclusive requirements related to its stator and translator. In our previous design, axially magnetized permanent magnets are used as magnetic flux sources. Due to cogging force problem, a series of modifications and improvements have been made. In normal circuinstances, reduction in cogging force yields lower output voltage. However, in using radially magnetized permanent magnets, we hope to achieve low cogging force and high output voltage. Optimization is performed to maximize the flux density in the magnetic core and minimize the dimension while avoiding saturation. The tooth shoe is introduced to minimize the cogging force. Finite element software is used to siinulatc the machine
Blarigan [4] at Sandia National Laboratories, Livermore
designed and constructed an efficient linear generator, The generator is driven by a high speed hydrogen fuel free piston engine. This speed is achieved by increasing the compression ratio. With an oriented-grain silicon steel lamination stator, NdFeB radial magnetized permanent magnets and 25 coil slots, the generator produces 40 kW of output power, with an efficiency of 96%.
Cawthome [I] developed two models of 5 kW, 220V iron and air core tubular permanent magnet linear generators driven by a linear internal combustion engine. In the previous design, the generator and engine are designed independently with thc only link between the design of the two systems being the stroke length and the estimated speed of oscillation. The design method includes an optimization that maximizes the efficiency and minimizes the volume of the alternator while providing the desired output power and output voltage. The 2D parametric finite element method is used in generator parameters calculation. The
11. LINEAR GENERATOR DESIGN
The combustion engine has a single internal combustion chamber. It has stroke length of 76 inm, The generator is designed to have 4 winding slots. As the square wire is used, the slot fill factor is assumed to close to one, and the air gap in the winding slot is ignored in the simulation model. The generator is nominally designed to run at 3000 rpm.
The stator is constructed of non-oriented silicon steel
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