length of the shell to a minimum, a square-ended shell can be used. However, unless the end of the shell is made extra thick, it would have a relatively low pressure capability. Therefore, an end shape which is elliptical or spherical is used to obtain higher pressure capability (Figure 12).

Examples of how allowable shell pressure varies with the shape of the end plate are shown in Table 4.

The classes of materials used for containment shells (Figure 11) include metals, polymers, and ceramics. The characteristics of containment shells of various materials are shown in Table 5. The main advantage of polymer or ceramic shells is that there are no eddy current losses. Therefore, cooling of the magnets is not required.

Eddy Currents Metallic or metallic-lined shells will produce eddy currents. Depending on the thickness of the shell, the eddy current losses (PL) can amount to as much as 20% of the total power.

where K = a constant, depending on the design T = thickness of the shell

L = length of magnets (times the core of magnets) N = speed, rpm

Bg = flux density of the magnets D = mean diameter M = number of sets of magnets

R = electrical resistivity, microhms per cm3 (electrical resistivity for various shell materials is given in Table 6)

TABLE 5 Characteristics of containment shells of various materials
Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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