Determination of heat transfer coefficient of finned housing of a TEFC variable speed motor
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ORIGINAL PAPER
Determination of heat transfer coefficient of finned housing of a TEFC variable speed motor Payam Shams Ghahfarokhi1,2 Bilal Asad2
· Ants Kallaste2 · Andrejs Podgornovs1 · Anouar Belahcen2,3 · Toomas Vaimann2 ·
Received: 24 February 2020 / Accepted: 20 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This paper proposes the analytical calculation of the heat transfer coefficient from the housing of a totally enclosed fan cooled (TEFC) machine during the active cooling. A particular focus is on the calculation of the heat transfer coefficient from the machine’s housing for different fan rotational speeds. The paper describes the challenges and provides solutions to dominate them during the analytical calculation of the heat transfer coefficient a TEFC electrical machine. Finally, the proposed method is validated experimentally on a totally enclosed fan cooled synchronous reluctance motor, and good correspondence between the analytical and experimental results is obtained. Keywords AC machines · Convection coefficient · Forced cooling · Synchronous reluctance motor · Thermal analysis · Totally enclosed fan cooled (TEFC)
1 Introduction The electrical machine encounters several thermal restrictions. These thermal drawbacks are adjusted by selecting an appropriate cooling method. Different applications of electrical machines require different cooling methods. The proper cooling method of an electrical machine is selected according to several different parameters, e.g., machine application, machine topology, machine current density, speed, the operational environment, cost, and machine size [1, 2]. The conventional cooling system implemented in industrial electrical motors is a totally enclosed fan cooled (TEFC). In this cooling system, the external fan is attached to the non-driven part of the machine to blow the fluid toward the semi-open fin channels (Fig. 1) [5]. In this approach, the fin channels over the housing are essential [1].
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Payam Shams Ghahfarokhi payam.shams@taltech.ee
1
Department of Electrical Machines and Devices, Riga Technical University, Ka¸lk¸ u iela 1, Riga, Latvia
2
Department of Electrical Power Engineering and Mechatronics, Tallinn University of Technology, Ehitajate tee 5, Tallinn, Estonia
3
Department of Electrical Engineering and Automation, Aalto University, Espoo, Finland
One of the most critical parts of the thermal analysis of TEFC machines is determining the heat transfer from the machine housing to the ambient. The TEFC machine is cooled by passing the coolant over spacing among the semiopen fins of the housing. In comparison with some other active cooling systems, such as the liquid cooling systems, in which the coolant flow rate is predicted with reasonable accuracy, the estimation of the airflow velocity from the housing of a TEFC machine is a challenging task [6]. There are several reasons to describe this statement. The distribution of the airflow produced by the fan is not uniform in every fin channel [6, 7]. Accordin
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