Thermal Design

Knowledge of the temperature distribution in an electric machine is extremely important for its design. This is especially the case when the machine is designed to operate at or near its thermal limits. To determine the temperature distribution in an electric machine, one must have a good estimate of the machine electrical (losses) properties of the cooling fluid and thermal characteristics of the magnetic, conductive, and insulating portions of the machines. First, the distribution of heat sources has to be found based upon the machine geometry and dissipated losses. Typical geometry in which the heat convection takes place in an electric machine is a heated tube through which a cooling fluid is flowing. The heat convection coefficient is dependent on the geometry of surface on which the heat is transferred between the solid medium and cooling fluid, on cooling medium thermal parameters and on its velocity.