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The magnetic properties of 3 p/, grain-oriented silicon iron were measured when the material was subjected to tensile and compressive stress. The effect of tensile stress up to 120 MN m-2 applied along the rolling direction was to increase the magnetizing force and decrease the losses. An explanation for the rise in magnetizing current is based on the theories of Nee1 who suggested that the largest contribution to the coercive force in iron arises from the inclusions and not from stress gradients.Compressive stress up to 50 MN m-2 caused both the magnetizing force and losses to rise. Surface domains oriented along the [Ool] direction have been observed to take up positions perpendicular to the rolling direction when the stress was approximately 5 MN m-2 and a clearly defined pattern re-appeared which corresponded to domains oriented in the [OlO] and [loo] directions. The magnetization loops indicated that after a critical magnetizing force had been reached, magnetization became relatively easy. This suggests that walls were being reformed in the [OOl] direction and subsequently moved enabling the anisotropy energy barrier to be overcome by changes taking place consecutively in adjacent regions of the material.

This paper concentrates on the development and analysis of a new generic steady state thermal model for mapping the heat transfer throughout a permanent magnet synchronous motor by considering its individual components as elements of an overall thermal equivalent circuit. This model includes (a) conduction resistances for the stator laminations and housing, conduction resistances between the copper winding and the stator teeth and yoke, between the housing and the stator, and between the housing and the flange, (b) heat flow in the air-gap for vortex and turbulent flow, (c) natural convection and forced cooling for the housing surface and the mounting flange surface, and (d) radiation resistance for the housing surface and mounting flange. The results obtained from the model are compared with corresponding experimental tests for the stall and rated performance with natural and forced cooling for two different motors, one with a rated speed of 1500 r/min and 130 Nm stall torque having 30 slots and 10 poles, and the other with a rated speed of 3000 r/min, and 15 Nm stall torque having 18 slots and 6 poles. The results achieved demonstrate a good correlation between the experimental results and the theoretical results obtained from the thermal model. The main heat paths and thermal resistances of the motor are: • Convection heat transfer and resistance between the motor housing and the ambient environment • Radiation heat transfer and resistance from the housing • Convection heat transfer and resistance between the motor heat sink plate and the ambient environment • Radiation heat transfer and resistance from the motor heat sink plate • Convection heat transfer and resistance between encoder housing and the ambient environment • Radiation heat transfer and resistance from the encoder housing • Contact resistance between the motor housing and the stator laminations • Contact resistance between the winding and the stator laminations which includes the effect of impregnation and nomax insulation between the winding and stator laminations.• Other conduction resistances such as axial conduction resistances of the motor housing.