DESIGN AND SIMULATION OF A 3 PHASE PM AXIAL FLUX GENERATOR FOR WIND TURBINE

Renewable energy, known also as green or clean energy, is derived from natural processes that are regenerative over short periods of time and cannot be depleted. The most common renewable energy resources are biomass, geothermal, hydropower, solar, and wind. Essentially, the production of any clean energy does not result in the creation of environmental debt. Additionally, the technologies used in producing this energy pollute less or do not pollute at all while they also do not utilize resources that cannot easily be renewed.

What role does renewable energy play in the United States?
Until the mid-1800s, Wood was the main source of energy that covers all the US needs for heating, cooking and light. After the industrial revolution, the transition of new manufacturing processes has come with new energy sources.

Figure 1 shows the evolution of the energy consumption by major sources in the US starting from 1700 until now [1]. From Figure 2, renewable energy produced about 11 quadrillion British thermal units (Btu) which is equivalent to 11% of total US energy demands. About 57% of U.S. renewable energy consumption was by the electric power sector, and about 17% of U.S. electricity generation was from renewable energy sources [1]. Wind energy constitutes more than a quarter of the total renewable energy. The wind is a clean, free, and readily available renewable energy source. Each day, around the world, wind turbines are capturing the wind power and converting it to electricity. This source of power generation plays an increasingly important role in the way we power our world. These wind turbines use several types of electrical generators such as 3 phase axial flux machine.

Figure 1 - Evolution of the energy consumption in the US

Figure 2 - US energy consumption

In this article, a 3 phase PM axial flux machine is analyzed. This type of machines may have core or be coreless and they are used due to many reasons such as being highly efficient, economic, compact size and light weight, etc. The proposed model is shown in Figure 3. It is built using SOLIDWORKS CAD. The stator is made of 9 stranded coils forming the 3 winding phases.

Figure 3 - CAD model of the axial flux generator

Figure 4 shows the magnetic flux density while Figure 5 contains a plot of the field intensity of the analyzed model. The rotor speed is constant at the value of 1200 rpm (Figure 6). Figure 7 demonstrates the induced voltage at each phase versus time. The computed signal has a sinusoidal shape. The induced voltage curves have a maximum value of 37V. The signal frequency is calculated using the time period of one phase. The period extracted from Figure 7 is 0.008333s which leads to a frequency of 120Hz. The static inductance is 0.146 H. Dynamic inductances of each phase are plotted in Figure 8.

Figure 4 - Magnetic flux density	Figure 5 - Magnetic field Intensity
Figure 6 - Angular speed	Figure 7 - Induced voltages

Figure 8 - Dynamic inductances