Influence of secondary insulation on the possible electrical stress of a PMSM with natural air cooling

Abstract:
The power density of electric machines is basically limited by the permissible electrical, magnetic and mechanical stresses. The limits result essentially from the materials being used, the manufacturing processes and the ambient conditions. In this paper, the feasible electrical stress in the form of the product of current density and electric loading for a permanent-magnet excited synchronous machine is investigated in more detail. Based on thermal experiments on air-cooled test motors of small power, the dissipated power losses and the temperatures at the components of the PMSM were measured. Both established winding insulations and alternative materials with higher thermal conductivity were tested in practice. Based on the extensive temperature measurements, a thermal network model was also parameterized. With the validated model, further design variants for the insulation and manufacturing influences are evaluated. With this data as a basis, the potential for performance improvement is predictable. However, the measures can also be used to reduce the winding temperature and increase the motor efficiency.