Power Losses and Heat Extraction in a Stator with Directly Air-Cooled Laminated Windings

This paper explores and assesses power loss generation and heat extraction in a stator with directly air-cooled laminated winding. An electrical machine winding made of an electric conducting sheet, which have slotted structure for accommodating a magnetic core, is denoted a laminated winding. A space is introduced between the conducting sheets so that the heating power is removed right where it is created. Explicit to the laminated windings, the conductors with smallest cross section and highest dc resistance have also limited cooling. Since these conductors are closest to the air-gap they become subject to induced power losses. An electrical machine with folded air-cooled laminated winding is built and evaluated. The paper demonstrates on how the thermal management of the stator segments is evaluated and adjusted during the manufacturing process. The power loss estimation of the prototype machine reveals significant discrepancy between the measurements and the calculation of known power losses at no load condition compared to short-circuit conditions. Conjugate heat transfer models are developed to evaluate the coolant flow distribution and heat dissipation in the direct air-cooled laminated windings.