Abstract
The slot thermal condition is critical for thermal management of high-performance electrical machines, due to the high heat losses and poor heat transfer ability within the slot. With a part of the back iron projected radially downward into the slot, back-iron extension (BIE) shortens the heat dissipation path from the slot coil to the back iron and was proved to be an effective thermal improvement technique. The relationship between BIE thermal benefits and various electrical machines’ parameters remains to be investigated. Based on an existing concentrated-wound machine, the relationship between the equivalent slot thermal conductivity (ESTC) and the BIE effectiveness is researched in this article. Utilizing a developed 3-D thermal model, the ESTC effects on the temperature reduction with BIE are indicated with simulation results and verified with experimental tests. BIE is reported to provide temperature reductions ranging from 48 °C down to 18 °C across the plausible range of ESTC values considered. Guidelines are given in the final part to suggest the situations under which BIE is more effective.
Highlights
INTRODUCTIONFOR electrical machines with ever higher power densities (kW/L, kW/kg), and improved cost performance ($/kW) developed for transport
FOR electrical machines with ever higher power densities, and improved cost performance ($/kW) developed for transportManuscript received January 28, 2021; revised April 19, 2021; accepted May 18, 2021
Due to the random placement of the winding in the manufacturing process, and large number of conductors, the equivalent slot thermal conductivity (ESTC) is used to capture the thermal behavior of the mishmash of slot components [14], which consist of copper, enamel, impregnation resin, and air-bubbles: in general the higher the ESTC, the better the slot thermal condition is
Summary
FOR electrical machines with ever higher power densities (kW/L, kW/kg), and improved cost performance ($/kW) developed for transport. For machines with different ESTC values which correspond to various slot compositions, the temperature reduction with back-iron extension is quantified and compared based on both the developed 3D thermal model as well as through experimental measurements. Description of sufficiently detailed analytical and experimental methods which readers can reproduce for their case-investigations These include 3D thermal models, an improved ESTC calculation method which accounts for air bubbles and various impregnation resin materials, together with instrumented motorette setups for practical verification. The organization of the paper is as follows: Section II describes the thermal model based on which the research is conducted, together with the technique used to investigate the relationship between the BIE thermal effectiveness and ESTC
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