Stator Winding Assembly Research Articles

Effectiveness of Thermal Interface Materials on Electrical Machines Thermal Performance With Heat Pipes

Thermal issue has always been a major concern in motor design. Heat pipes (HPs) have been applied in electrical machines with remarkable cooling effects reported. However, critical factors that affect HP thermal benefits have rarely been studied, such as limited contact area between HPs and heat sources, which may lead to high thermal resistance and degrade motor thermal performance. Due to limited thermal conductivities, conventional motor thermal interface materials (TIMs), such as epoxy resin, fail to maximize HP thermal benefits and minimize motor temperature rise. In this case, new TIMs with outstanding thermal properties that have not been used in electrical machines, such as thermal grease and adhesive, are potential candidates to address this issue, while their thermal impact is still unclear. This article conducts both experiments and thermal analyses to quantify the effects of TIM on motor cooling performance. Firstly, the thermal properties of ten typical TIMs in four categories are experimentally characterized. Then, the selected TIMs are applied to a stator-winding assembly with HP to evaluate their thermal impact on motor cooling performance under different cooling conditions. Finally, practical guidelines are given for TIM selection in electrical machines with HPs or other cooling media.

Heat Pipe Bending Effect on Cooling Effectiveness in Electrical Machines

Heat pipes (HPs) are being extensively explored in motor cooling scenarios for enhanced cooling capacity. HPs are commonly bent to adapt to the compact structure of electrical machines, whereas the bending effect on motor cooling effectiveness still requires further investigation. This article analytically and experimentally studies the effect of the bending process, including bending angle and bending radius, on HP thermal properties. Cooling density is defined and derived to analyze the tradeoff between HP thermal performance and additional volume due to HP installation. Practical guidelines for feasible HP bending solutions under different space constraints are provided to achieve a higher cooling density. Finally, the HP bending effect on motor cooling effectiveness under various cooling methods is quantitatively evaluated through a validated thermal model based on a stator-winding assembly. The bending process can degrade the HP equivalent thermal conductivity by up to 76%, thus leading to a temperature difference of 4.8K under liquid cooling conditions.

Experimental Investigation of Heat Pipe Inclination Angle Effect on Temperature Nonuniformity in Electrical Machines

Heat pipes (HPs) are gaining increasing popularity in the propulsion motors of transportation electrification due to their remarkable thermal properties. However, the inclination angle affects the HP thermal performance and, thus, results in temperature nonuniformity, which may generate unbalanced thermal stress on the motor. Such an issue has received less attention to date and requires corresponding solutions. This article performs an experimental investigation on motor temperature nonuniformity with HPs and further proposes an improved structure to address this problem. A specimen based on a stator-winding assembly with HPs is prepared and a dedicated experimental platform is established. Then, the temperature distribution across the specimen is studied, followed by an evaluation of the effects of current density and wind velocity. To compensate for the degradation of HP thermal performance, an improved structure with enlarged fins is proposed, and the equilibrium point is determined by fitting and comparing the obtained temperature data. Finally, the proposed structure is verified by the comparison between the original and improved specimens. The experimental results show that the non-uniform temperature distribution is significantly improved, with the temperature range and standard deviation reduced by 42% and 44.3%, respectively.

Heat pipe based thermal management of electrical machines – A feasibility study

In this paper the use of off-the-shelf heat pipes (HPs) are assessed for the thermal management of electrical machines. The stator-winding assembly has been selected to assess the suitability and effectiveness of cooling systems based upon HPs. The proposed approach targets the main heat source in electrical machines, which is generally associated with the winding subassembly. Two thermal management systems are investigated from a conceptual point of view. The first one uses HPs to improve heat removal for a machine with conventional cooling, e.g. a liquid or air-cooled housing. The second variant uses HPs as the main heat transfer route, e.g. a fully enclosed machine with no integrated, actively cooled housing. Both active- and end-winding regions are considered for direct heat removal from the winding body using HPs. The analysis of the electromagnetic and thermal compatibility of the proposed HP-based thermal management systems is via three-dimensional (3D) finite element analyses (FEAs). It is theoretically shown that the winding active region is better suited for effective HP-based thermal management, compared with the end-winding alternative. Also, the results suggest that proposed thermal management systems allow for a considerable improvement in heat removal from the machine body, up to 43% and 25% for the concepts one and two respectively (applied to the winding active region) respectively, as compared with a more conventional heat removal system. The overall performance gains of course depend upon the specific manufacture and assembly processes used in construction of the stator-winding. The initial results from tests on the hardware subassemblies confirm validity of the theoretical methods employed in this feasibility study.

Thermal analysis of direct air-cooled PM machine for UAV propulsion

This paper presents findings from a combined theoretical and computational thermal analysis of alternative heat removal concepts for an open-frame PM machine. The analysed machine design has been developed for propulsion of an unmanned aerial vehicle (UAV), which operates in a regime characterised by a high torque overload (×2.5) at take-off and a high efficiency (+95%) at high-altitude cruise operation. The thermal management of such a machine has a significant impact when balancing the design for a lightweight/compact solution. Here, direct air-cooling of the machine is analysed by focussing on the winding body that is the dominant heat source during the UAV's take-off phase. As the airflow into the machine body is generated by the forward motion of the UAV, a careful consideration needs to be taken when guiding the air through the machine body. In this analysis, alternative airflow channelling via the stator-winding assembly is investigated. The results suggest that the proposed motor design with reduced conductor slot utilisation and stator bore airflow guiding feature allows for achieving the required convection heat transfer coefficient (75W/m2K at 1m/s), which is 150% improvement as compared with a more conventional design with a good conductor slot utilisation. However, the reduced conductor volume needs to be compensated for by appropriately adjusting the machine outer diameter and profile during the initial design sizing exercise.

Разработка ветроэнергетической установки для размещения на дымовые трубы энергообъектов морской инфраструктуры

The article focuses on implementation and operation of the wind power plant of the original design for mounting on the chimneys of seaport power facilities. The worked out wind power unit makes it possible to use secondary thermal energy (heat from the exhaust gases of a boiler house, a mini-thermal power plant based on gas reciprocating plants, etc.) to generate electricity in an amount sufficient to satisfy or partially compensate the needs of the power facility. The aspect of the wind power plant design and the concept of energy generation have been worked out. The hot surface area of the stack serves as the source of energy for upward air flows in the developed original design of the wind power plant. The wind power plant placed on top of the stack is an additional environmentally friendly way of using the potential of renewable energy sources for electric power generation. This method differs from the existing ones in that the pipe is used not as a high support where higher wind speeds prevail, but as a source of thermal energy from secondary energy resources (flue gases of the fuel plant). Wind power plant design includes chimney, generator rotor, permanent rotor magnet, thrust collar for stator winding assembly, thrust collar for bearing assembly, brake drum, brake shoe, brake drive lever, rotor brake drive cable, brake handle and other elements. The introduction of such power units will partially or fully compensate for the own needs of the power facilities that generate thermal and electric energy for the reliable and uninterrupted operation of port services

A Feasibility Study of Additively Manufactured Heat Guides for Enhanced Heat Transfer in Electrical Machines

This article investigates a new heat extraction approach for application to high-specific-output electrical machines. The proposed technique employs thermally conductive heat guides (HGs) to provide supplementary heat evacuation paths for the machine regions, which are particularly susceptible to high power loss. Here, the research focus has been placed on the stator–winding assembly. The HGs investigated in this article rely solely on conductive heat transfer, in contrast to the solutions involving working fluid phase change, e.g., heat pipes. It is intended for the HGs to be an integral part of the stator–winding assembly, for e.g., HGs incorporated in the winding active and/or end region. Such arrangement, however, imposes several design challenges. These are related to the HGs being a source of additional power loss due to the machine's magnetic flux leakage. The objective of this study is to evaluate a concept of HGs, which are immune to the external magnetic field with good heat transfer capability. To facilitate that, a combination of detailed multiphysic design optimization and modern additive manufacturing (i.e., selective laser melting method) has been employed here. The theoretical analysis has been supplemented with an experimental work. A number of stator–winding hardware exemplars (motorettes) incorporating alternative HG designs have been fabricated and tested. This article provides a new set of experimental data in support of the authors’ initial work on HGs’ thermal behavior. The new research findings show that the optimized HGs allow for up to 85% improvement in dissipative heat transfer from the winding body and insignificant additional power loss, for the analyzed stator–winding assembly.

Reduction of Winding AC Losses by Accurate Conductor Placement in High Frequency Electrical Machines

In the design of electrical machines, the increase in power density has become one of the main research themes. With most of the power loss in high power density electrical machines often being generated in the stator winding assembly, it is necessary to reduce these losses. The effects of strands and bundle positions in the slot on the ac losses in the winding are often overlooked. Taking as a case-study an existing high-frequency machine, this article analyzes and provides an in-depth insight into such effects. Exploiting the rapid advancements in precision three-dimensional printing, it is found and experimentally verified that by controlling the position of the conductors within the top of the slot the ac losses can be markedly reduced.

Robotized stator cable winding

Automated stator winding assembly has been available for small and medium sized conventional electric machines for a long time. Cable winding is an alternative technology developed for medium and l ...