Axial-Flux Permanent-Magnet Generator Design for Hybrid Electric Propulsion Drone Applications

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.

Long endurance hybrid propulsion configuration for middle-large size compound-wing VTOL UAV

“…In a hybrid power unmanned aerial vehicle (UAV), the generator is responsible for converting mechanical energy into electrical energy, which is used to power the rotor during hover or charge the battery during horizontal flight, as shown in Figure 4. In this paper, a permanent magnet synchronous generator (PMSG) is selected with a rated power of 2 kW, considering the actual payload of the UAV to be 25 kg [9]. The working principle of a PMSG involves the rotor being equipped with permanent magnets that generate a constant magnetic field while rotating.…”

Design and Analysis of Coreless Axial Flux Permanent Magnet Machine with Novel Composite Structure Coils

“…Compared with the conventional radial flux permanent magnet (PM) machine, the axial flux permanent magnet (AFPM) machine can be used in some special applications such as electric vehicles [1], wind turbine systems [2], and unmanned aerial vehicles [3] due to its short axial size, compact structure, disk-shaped profile, and high efficiency. The AFPM machine has a variety of classical structures; wherein, the configuration with double rotors and a single stator is preferred chiefly [4,5], and the stator core is not necessarily required to form a closed magnetic circuit in the design.…”

“…The AFPM machine has a variety of classical structures; wherein, the configuration with double rotors and a single stator is preferred chiefly [4,5], and the stator core is not necessarily required to form a closed magnetic circuit in the design. By eliminating the iron core of the stator, the coreless AFPM machine has the following advantages [6][7][8]: (1) The quality and cost of the machine are reduced; (2) The loss of the stator core and the cogging torque of the machine are eliminated; (3) The inductance of windings is small, and the influence of the stator current on the air gap flux density is almost negligible; (4) The ability of overload is greatly improved; (5) The arrangement of coils is more flexible and not constrained by slots and teeth of the stator.…”

“…In general studies, this type of machine has lower air gap density and power density because the air gap length is limited by the axial length of the coreless stator (armature). Several authors have studied that the optimized shape, structure, and parameters of PMs [9][10][11] or the special arrangement of Halbach array PMs [1,3,9,[11][12][13] can be used to improve the amplitude and sinusoidal level of the air gap flux density. In [12], the hybrid PM array is proposed and applied in a multi-disc AFPM machine to form a series magnetic circuit to improve the air gap flux density and reduce the rotor mass.…”

“…The significant loss of the coreless AFPM machine is the DC copper loss and eddy current loss in windings, of which the former is generated when the stator current flows through the conductor, and the latter is generated because the coils are directly exposed to the air magnetic field [3,14], especially when operated at a high electric frequency. A number of works have been performed in recent years [15][16][17][18][19][20], that the trapezoidal coils or optimized trapezoidal coils are mostly used in the coreless stator [9,16], compared with the other special shapes such as the circular coils [10] and rhomboidal coils [15], to improve the winding factor The number of turns and width of the conductor can be synchronously optimized, and the structure of unequal width winding is proposed and applied in [16].…”