A Thermal Modeling Approach and Experimental Validation for an Oil Spray-Cooled Hairpin Winding Machine

Abstract

While the electromagnetic aspects of hairpin windings are actively being investigated and discussed in recent literature, including the design rules together with the loss calculation and reduction techniques, the thermal performance and modeling aspects have received less attention to date. In hairpin windings, the conductors (pins) are comparatively larger and arranged as separate components in parallel within the slot. In contrast, conductors randomly overlap and contact each other for traditional random windings. The differences in the aforementioned winding physical characteristics result into a different methodology to develop the thermal network. This paper presents a 3D Lumped Parameter Thermal Network (LPTN) approach for an oil-spray cooled hairpin winding, which includes the slot thermal model configuration, the end-winding connections, together with different methodologies of analyzing the end-winding sprayed-oil characteristics. The aforesaid thermal model captures unique features related to the winding technology and cooling mechanism, such as the non-uniform endwinding temperature caused by the uneven oil spray cooling effects. Finally, taking an existing propulsion drive hairpin stator and a bespoke-designed test setup, the presented steady state thermal modelling approach is experimentally validated covering various experimental tests, including different spray conditions.

Analysis of Interior Permanent Magnet Synchronous Motor according to Winding Method

“…The key content in [10][11][12][13][14][15] is research on optimizing the cooling method for high efficiency. It is mentioned that it is necessary to improve the thermal characteristics because the characteristics deteriorate as the high-temperature characteristics of the PM motor continue to be maintained.…”

“…In the case of oil cooling, it is used when it is 20 A/mm 2 or more. In the case of hairpin winding, use the oil cooling type with a current density of 20 A/mm 2 or more [13][14][15].…”

A Comprehensive Design Guideline of Hairpin Windings for High Power Density Electric Vehicle Traction Motors

“…Research activities on hairpin windings in recent years have mainly focused on electromagnetic design [15][16][17], AC losses [18][19][20], thermal management [21][22][23], insulation properties [24,25] as well as manufacturing process [26][27][28]. Quantitative performance comparisons were made in [10,15] which highlighted the advantages of hairpin windings over random windings.…”

Advances in Thermal Management Technologies of Electrical Machines

“…Compared with water jacket cooling, oil spray cooling can almost double the current density and power of electrical machines [43]. A 3-D lumped parameter thermal network (LPTN) of the oil spray cooled hairpin windings was proposed in [44], which considered the slot configuration, winding connection, and sprayed oil characteristics. This LPTN had been validated through experimental investigations and can be used as a good reference for electrical machine researchers to investigate the thermal performance of such windings.…”