Article
Electromagnetic Field Analysis and Design of a Hermetic
Interior Permanent Magnet Synchronous Motor with
Helical-Grooved Self-Cooling Case for Unmanned
Aerial Vehicles
Hae-Sol Lee
1,2
, Myeong-Hwan Hwang
1
and Hyun-Rok Cha
1,
*
Citation: Lee, H.-S.; Hwang, M.-H.;
Cha, H.-R. Electromagnetic Field
Analysis and Design of a Hermetic
Interior Permanent Magnet
Synchronous Motor with
Helical-Grooved Self-Cooling Case
for Unmanned Aerial Vehicles. Appl.
Sci. 2021, 11, 4856. https://doi.org/
10.3390/app11114856
Academic Editor:
George Nikolakopoulos
Received: 2 May 2021
Accepted: 19 May 2021
Published: 25 May 2021
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1
EV Components & Materials R&D Group, Korea Institute of Industrial Technology,
6 Cheomdan-gwagiro 208 beon-gil, Buk-gu, Gwangju 61012, Korea; eddylee0319@gmail.com (H.-S.L.);
han9215@kitech.re.kr (M.-H.H.)
2
Robotics and Virtual Engineering, Korea University of Science and Technology, Daejeon 34113, Korea
* Correspondence: hrcha@kitech.re.kr; Tel.: +82-62-600-6212
Abstract:
As unmanned aerial vehicles expand their utilization and coverage, research is in progress
to develop low-weight and high-performance motors to efficiently carry out various missions. An
electromagnetic field interior permanent magnet (IPM) motor was designed and analyzed in this
study that improved the flight performance and flight duration of an unmanned aerial vehicle
(UAV). The output power and efficiency of a conventional commercial UAV motor were improved by
designing an IPM motor of the same size, providing high power output and high-speed operation by
securing high power density, wide speed range, and mechanical stiffness. The cooling performance
and efficiency of the drive motor were improved without requiring a separate power source for
cooling by introducing the helical-grooved self-cooling case, which has a low heat generation struc-
ture. Furthermore, the motor is oil-cooled through rotating power without a separate power source,
reducing the weight of the UAV. The heat dissipation characteristics were verified by fabricating a
prototype and taking actual measurements to verify the validity of the heat dissipation characteristics.
The results of this study are expected to improve the flight duration and performance of UAVs and
contribute to the efficiency of the design of a UAV drive motor.
Keywords:
interior permanent magnet; unmanned aerial vehicle; finite element method; drive motor
efficiency; heat dissipation characteristics
1. Introduction
Unmanned aerial vehicles (UAVs) are increasingly being used for civilian purposes
such as logistics, transportation, traffic relations, and security. Recently, their application
range has been expanding; UAVs, initially operated only for military uses, have started to
be used for various purposes such as aerial photography and pesticide application. The
application range of UAVs will expand because they do not entail inherent safety risks
and high expenses compared to a much larger, manned aircraft. In recent years, China has
emerged as a leader in the commercial UAV market, along with technology powerhouses
such as the United States and Europe [1–3].
The technology for creating a UAV motor with high power output and high efficiency
has emerged to enlarge the size of the UAV platform, because the weight of the UAV
increases owing to the use of various functions of the UAV platform. Therefore, most
UAV motors adopt permanent-magnet synchronous motors, in which surface permanent
magnet motors are most commonly used. Electric motors for operating UAVs significantly
affect flight performance. The flight distance, efficiency, torque, vibration, maximum speed,
and acceleration forces are determined or changed depending on the drive motor.
Appl. Sci. 2021, 11, 4856. https://doi.org/10.3390/app11114856 https://www.mdpi.com/journal/applsci
