Abstract
This paper presents the design of an axial-flux permanent-magnet (AFPM) generator used for hybrid electric propulsion drone applications. The design objectives of the AFPM generator are high power density, which is defined as output power per generator weight, and high efficiency. In order to satisfy the requirements for the target application and consider the practical problems in the manufacturing process, the structure of the AFPM generator comprising a double-rotor single-stator (DR-SS) was studied. In order to determine the rotor topology and stator winding specifications that had the greatest impact on performance in the DR-SS type design process, we selected three rotor models according to the arrangement of the magnetization direction and three stator models according to the coreless winding specifications. These models were first compared and analyzed. Then, a 3-D finite element method was performed to calculate the magnetic, mechanical, and thermal characteristics of the designed models. By consideration of the output power, efficiency, temperature, and mechanical stability, etc., a topology suitable for the design of generators for UAV systems was determined and manufactured. The reliability of the design result was confirmed through the test.
Highlights
In existing small electric drone systems, the battery is mainly used as a power source and the operation time is several tens of minutes, so it needs to be charged frequently
A hybrid electric propulsion system that combines a gasoline engine and a generator can dramatically increase flight time compared to a battery-only system
Since axial-flux permanent-magnet (AFPM) generators are known to have a high power density, which is defined as the ratio of output power to weight [1,2,3], the authors of this paper reviewed the development of an AFPM electric machine for 3 kW class drones
Summary
In existing small electric drone systems, the battery is mainly used as a power source and the operation time is several tens of minutes, so it needs to be charged frequently. “NS type” refers to north pole and south pole magnets facing each other at either side; the flux can travel straight through this stator without any circumferential flow [4] This type of DR-SS is more commonly known as a yokeless and segmented armature (YASA) motor or generator [5,6,7] and is often described as having a relatively high power density because it does not require a stator yoke. The maximum line voltage constant at no-load was limited to 11 mV/rpm or less in consideration of the AC/DC converter performance to be used for 48 V DC battery charging.
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