# Switched Reluctance Motor Design for a Light Sport Aircraft Application

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Benchmark Motor Specifications and Operational Requirements

## 3. Sizing and Design of LSA SRM

#### 3.1. Selection of the Core Material

^{®}has been investigated as the core material. Iron–cobalt vanadium alloys, such as HIPERCO

^{®}50 and HIPERCO

^{®}50A, have the highest magnetic saturation (2.4 Tesla) of all soft magnetic alloys [22]. Besides, they have low core loss that can contribute to improving the efficiency of an SRM.

^{®}50/50A. They both have high magnetic saturation level, but slightly different permeability. Figure 2 shows the static torque performance for the same geometry and the current-density levels applied to LSA SRM. The static torque performances are close at low current density where the magnetic field intensity is small. As the current density increases, HIPERCO

^{®}50A shows higher static torque in the entire electrical cycle. This helps improving the torque density of the LSA SRM design. Therefore, the HIPERCO

^{®}50A with a lamination thickness of 0.1524 mm from Carpenter Technology is selected as the core material.

#### 3.2. Electromagnetic Design with the Proposed Framework

#### 3.3. Static Design and Results

#### 3.4. Dynamic Design Process and Results

## 4. Coil Design

#### 4.1. Calculation of Coil Parameters

#### 4.2. Calculation of AC Copper Loss

#### 4.3. Coil Retention Design

#### 4.4. Experimental Verification of Coil Retention and Coil Fit

## 5. Rotor-Mass Reduction

^{®}50A material, the analyses were carried out for the rotor with and without the cutouts at the maximum operating speed of 4500 rpm. The maximum displacement with no cuts is 1.3 µm, and with the cutouts it was 1.9 µm. The maximum deviation is within the rotor airgap clearance, and this ensures that there would be no contact. The maximum stress experienced by the reduced-weight rotor was 17.84 MPa, which is well below the material’s yield strength of 212 MPa. From the following analysis, it can be concluded that the rotor-mass reduction would not compromise the mechanical operation of the motor at the maximum operational speed.

## 6. Final Design and Performance Results

## 7. Loss Calculation and Efficiency Analysis

^{®}50A core material [22]. The steady-state core loss equation is presented in (1), and the transient core loss equation is presented in (2). The function g($\alpha $) in (2) is defined as in (3),

^{®}50A alloy are presented in Table 6. The average error between calculated core losses from the defined model and core losses provided by in the material datasheet is less than 3%.

## 8. Thermal Analysis

^{®}818 is selected as the slot liner paper due to its higher voltage endurance compared to traditional options. The slot area is also filled with a low viscosity thermally conductive epoxy from Lord company. For thermal analysis, the conductivity characteristics of the materials and maximum operating temperatures are provided in Table 8.

## 9. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

^{®}50A material data. The authors would also like to thank Altair Engineering Inc. (Troy, MI, USA) for their support with Flux

^{TM}2022, Compose

^{TM}2022 and Activate

^{TM}2022 software, and MathWorks (Natick, MA, USA) for their support with MATLAB

^{®}2022A and Simulink

^{®}2022A software in this research.

## Conflicts of Interest

## References

- Overton, J. Fact Sheet|The Growth in Greenhouse Gas Emissions from Commercial Aviation|White Papers|EESI. Available online: https://www.eesi.org/papers/view/fact-sheet-the-growth-in-greenhouse-gas-emissions-from-commercial-aviation (accessed on 29 January 2023).
- Regulatory Brief-General Aviation and Greenhouse Gas Emission–AOPA. Available online: https://www.aopa.org/advocacy/advocacy-briefs/regulatory-brief-general-aviation-and-greenhouse-gas-emission (accessed on 29 January 2023).
- Thanikasalam, K.; Rahmat, M.; Fahmi, A.G.M.; Zulkifli, A.M.; Shawal, N.N.; Ilanchelvi, K.; Ananth, M.; Elayarasan, R. Emissions of piston engine aircraft using aviation gasoline (avgas) and motor gasoline (mogas) as fuel A review. IOP Conf. Ser. Mater. Sci. Eng.
**2018**, 370, 012012. [Google Scholar] [CrossRef] - PowerON and TTC Agree to Drive Transit Electrification. Available online: https://www.opg.com/media_releases/poweron-and-ttc-agree-to-drive-transit-electrification/ (accessed on 29 January 2023).
- Bye, G. Sun Flyer. Available online: https://nbaa.org/wp-content/uploads/events/Sun-Flyer-PP_NBAA-template.pdf (accessed on 29 January 2023).
- Guo, H.; Xu, J.; Kuang, X. A novel fault tolerant permanent magnet synchronous motor with improved optimal torque control for aerospace application. Chin. J. Aeronaut.
**2015**, 28, 535–544. [Google Scholar] [CrossRef] [Green Version] - Bilgin, B.; Jiang, J.; Emadi, A. Switched Reluctance Motor Drives-Fundamentals to Applications, 1st ed.; CRC Press: Boca Raton, FL, USA, 2018. [Google Scholar]
- Nansai, K.; Nakajima, K.; Kagawa, S.; Kondo, Y.; Shigetomi, Y.; Suh, S. Global Mining Risk Footprint of Critical Metals Necessary for Low-Carbon Technologies: The Case of Neodymium, Cobalt, and Platinum in Japan. Environ. Sci. Technol.
**2015**, 49, 2022–2031. [Google Scholar] [CrossRef] [PubMed] - Rare Earth Elements: A Review of Production, Processing, Recycling, and Associated Environmental Issues. Available online: https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=251706&Lab=NRMRL (accessed on 29 January 2023).
- Tursini, M.; Villani, M.; Fabri, G.; Di Leonardo, L. A switched-reluctance motor for aerospace application: Design, analysis and results. Electr. Power Syst. Res.
**2017**, 142, 74–83. [Google Scholar] [CrossRef] - Castellini, L.; Lucidi, S.; Villani, M. Design optimization of switched reluctance motor for aerospace application. In Proceedings of the 2015 IEEE International Electric Machines Drives Conference (IEMDC), Nagercoil, India, 10–12 April 2015; pp. 1678–1682. [Google Scholar] [CrossRef]
- Nøland, J.K.; Leandro, M.; Suul, J.A.; Molinas, M. High-power machines and starter-generator topologies for more electric aircraft: A technology outlook. IEEE Access
**2020**, 8, 130104–130123. [Google Scholar] [CrossRef] - Sedky, M.M.; Abdel-Azim, W.E.; Abdel-Khalik, A.S.; Massoud, A.M. Integrated Switched Reluctance Starter/Generator for Aerospace Applications: Particle Swarm Optimization for Constant Current and Constant Voltage Control Designs. Appl. Sci.
**2022**, 12, 7583. [Google Scholar] [CrossRef] - Wiegand, C.; Bullick, B.; Catt, J.; Hamstra, J.; Walker, G.; Wruth, S. F-35 Air Vehicle Technology Overview. In Proceedings of the 2018 Aviation Technology, Integration, and Operations Conference, Atlanta, Georgia, 25–29 June 2018. [Google Scholar] [CrossRef]
- Watthewaduge, G.; Bilgin, B. Sizing of the Motor Geometry for an Electric Aircraft Propulsion Switched Reluctance Machine Using a Reluctance Mesh-Based Magnetic Equivalent Circuit. Machines
**2023**, 11, 59. [Google Scholar] [CrossRef] - Filipenko, M. Electric and Hybrid-Electric Aircraft: A Pragmatic View. Available online: https://indico.cern.ch/event/760666/contributions/3481376/attachments/1888359/3113576/20190708_CECICMC_2019_plenary_talk_filipenko_pub.pdf (accessed on 29 January 2023).
- Pipistrel Aircraft E-811 EASA TC–Pipistrel Aircraft. Available online: https://www.pipistrel-aircraft.com/products/other-products/e-811/ (accessed on 29 January 2023).
- MagniX Co. Products. Available online: https://www.magnix.aero/services (accessed on 29 January 2023).
- Anton, F.; Otto, O.; Hetz, J.; Olbrechts, T. Presentation on Behalf of Siemens eAircraft Siemens eAircraft Siemens Next47 Siemens Digital Factory PLM Software Simulation & Testing Solutions. Available online: https://www.ie-net.be/sites/default/files/Siemens%20eAircraft%20-%20Disrupting%20Aircraft%20Propulsion%20-%20OO%20JH%20THO%20-%2020180427.cleaned.pdf (accessed on 29 January 2023).
- eFlyer Begins Flight Tests with Production Motor. Available online: https://flyer.co.uk/eflyer-begins-flight-tests-siemens-production-motor/ (accessed on 29 January 2023).
- Cervinka, D.; Knobloch, J.; Prochazka, P.; Kadlec, J.; Cipin, R.; Pazdera, I. Electric powered airplane VUT 051 RAY. In Proceedings of the 16th International Conference on Mechatronics-Mechatronika 2014, Brno, Czech Republic, 3–5 December 2014; pp. 6–10. [Google Scholar] [CrossRef]
- HIPERCO® 50A Datasheet. Carpenter. 2020. Available online: https://www.carpentertechnology.com/alloy-finder/hiperco-50a (accessed on 29 January 2023).
- Abdollahi, M.E.; Vaks, N.; Bilgin, B. A Multi-objective Optimization Framework for the Design of a High Power-Density Switched Reluctance Motor. In Proceedings of the 2022 IEEE Transportation Electrification Conference Expo (ITEC), Anaheim, CA, USA, 15–17 June 2022; pp. 67–73. [Google Scholar] [CrossRef]
- Jiang, J.W.; Bilgin, B.; Sathyan, A.; Dadkhah, H.; Emadi, A. Analysis of unbalanced magnetic pull in eccentric interior permanent magnet machines with series and parallel windings. IET Electr. Power Appl.
**2016**, 10, 526–538. [Google Scholar] [CrossRef] - Kasprzak, M. 6/14 Switched Reluctance Machine Design for Household HVAC System Applications. Ph.D. Thesis, Department of Mechanical Engineering, McMaster University, Hamilton, ON, Canada, 2017. Available online: http://hdl.handle.net/11375/20877 (accessed on 29 January 2023).
- Altair FluxTM 2019.1 User Guide. Available online: https://altair.com/ (accessed on 29 January 2023).
- ANSI/NEMA MW 1000-2018; American National Standard for Magnet Wire. NEMA: Rosslyn, VA, USA, 2018.
- Ghose, S.; Watson, K.; Delozier, D.; Working, D.; Connell, J.; Smith, J.; Sun, Y.; Lin, Y. Thermal Conductivity of Polyimide/Carbon Nanofiller Blends. Available online: https://ntrs.nasa.gov/api/citations/20080013603/downloads/20080013603.pdf (accessed on 29 January 2023).
- Startseite|KHP Kunststofftechnik. Available online: https://www.khp-kunststoffe.de/ (accessed on 29 January 2023).
- CoolTherm® EP-2000 Thermally Conductive Epoxy Encapsulant. Parker Lord. 2021. Available online: https://ph.parker.com/us/en/cooltherm-ep-2000-thermally-conductive-epoxy-encapsulant (accessed on 29 January 2023).
- DuraForm® PA plastic. 3D Systems Corp. 2017. Available online: https://www.3dsystems.com/sites/default/files/2017-03/3D-Systems_DuraForm_PA_DATASHEET_USEN_2017.03.22_a_WEB.pdf (accessed on 29 January 2023).
- DuPont™ Nomex® 818 Datasheet. DuPont. 2016. Available online: https://www.dupont.com/content/dam/dupont/amer/us/en/safety/public/documents/en/DPT16_21668_Nomex_818_Tech_Data_Sheet_me02_REFERENCE.pdf (accessed on 29 January 2023).
- Staton, D. Thermal analysis of traction motors. In Proceedings of the 2014 IEEE Transportation Electrification Conference and Expo (ITEC), Dearborn, MI, USA, 15–18 June 2014; pp. 1–139. [Google Scholar] [CrossRef]

**Figure 2.**Comparison of static torque production with HIPERCO

^{®}50 and HIPERCO

^{®}50A for the dimensional constraints and current density levels of LSA SRM: (

**a**) J = 5 A/mm

^{2}, (

**b**) J = 15 A/mm

^{2}, and (

**c**) J = 25 A/mm

^{2}.

**Figure 3.**Proposed multi-objective optimization framework [23].

**Figure 4.**Block diagram of the static design: fit models and global optimizations used for two different current ratings [23].

**Figure 5.**Illustration of static design results with respect to the three geometry parameters with highest correlation to average torque.

**Figure 6.**Block diagram of the dynamic optimization stage [23].

**Figure 11.**Coil retention with grooves and slot wedge, and the geometry parameters of the slot wedge.

**Figure 13.**Experimental verification of coil fit, fill factor, and slot retention with 3D printed stator core for optimized dimensions: (

**a**) front view and (

**b**) top view.

**Figure 16.**Static torque for half of an electrical cycle with 195 A current reference before and after rotor cutouts.

**Figure 24.**Comparison of torque production with three-dimensional and two-dimensional FEA at 2600 RPM with conduction angle −47.9° and 125°, and reference current of 200 A.

**Figure 25.**Torque speed characteristics of the designed motor with optimized turn-on and turn-off angles.

**Figure 26.**Steady-state thermal FEA result for LSA SRM at the base speed and maximum continuous power.

**Table 1.**Specification of SP70d PMSM [19].

Parameter | Value |
---|---|

Continuous power | 70 kW |

Continues speed | 2600 rpm |

Continuous torque @ 2600 rpm | 260 Nm |

DC-link voltage | 450 V |

Mass | 26 kg |

Cooling system | Water/Glycol |

Max efficiency | 95% |

Estimated motor diameter | ~300 mm |

Estimated stack length | 50 to 100 mm |

Shaft diameter | 50 mm |

**Table 2.**The improvements of the motor performance after five iterations in the dynamic design process for the selected design.

Parameter | Initial Iteration | Final Iteration |
---|---|---|

Stator pole arc angle, βs | 13.25° | 13.153° |

Rotor pole arc angle, βr | 12.65° | 12.74° |

Turn on angle | −54.65° | −47.9° |

Turn off angle | 122.93° | 125° |

Average torque | 258.56 N.m | 267.8 N.m |

Torque ripple (%) | 18.04 | 19.48 |

Radial force objective | 245.45 | 241.52 |

Winding Pattern | Number of Turns per Coil | Magnetic Wire American WIRE Gauge (AWG) | Number of Strands | Copper Fill Factor [%] | Current Density (@120 A) [A/mm^{2}] | Phase Resistance (@25 °C) [mΩ] |
---|---|---|---|---|---|---|

6 coils in series | 14 | 9 | 1 | 53.36 | 18.10 | 53.31 |

12 | 2 | 53.23 | 18.14 | 53.43 | ||

14 | 3 | 50.25 | 19.21 | 56.64 | ||

15 | 4 | 53.17 | 18.16 | 53.57 | ||

16 | 5 | 52.61 | 18.35 | 54.05 | ||

2-parallel, 3-series | 28 | 12 | 1 | 53.23 | 18.14 | 53.43 |

15 | 2 | 53.17 | 18.16 | 53.57 | ||

17 | 3 | 50.20 | 19.23 | 56.80 | ||

3-parallel, 2-series | 42 | 14 | 1 | 50.25 | 19.21 | 56.64 |

17 | 2 | 50.20 | 19.23 | 56.80 | ||

6 coils in parallel * | 83 | 17 | 1 | 49.60 | 19.23 | 56.12 |

20 | 2 | 49.50 | 19.27 | 56.25 |

Parameter | Option 1 | Option 2 |
---|---|---|

Pattern | 6 P | 6 P |

American wire gauge (AWG) | 17 | 20 |

Number of turns | 83 | 83 |

Number of strands | 1 | 2 |

Wire fill factor | 0.59 | 0.59 |

Current density (120 A) | 19.23 A/mm^{2} | 19.27 A/mm^{2} |

Phase resistance @ 25 °C | 56.12 mΩ | 56.25 mΩ |

Phase resistance with end turn @ 200 °C | 111.2254 mΩ | 111.4831 |

Parameter | Value |
---|---|

Number of stator poles | 18 |

Airgap length | 0.4 mm |

Stator outside diameter | 280 mm |

Stator pole arc angle | 13.15° |

Stack length | 100 mm |

Wire gauge | 17 AWG |

Current density (RMS) | 19.23 A/mm^{2} |

Phase resistance @ 200 °C | 111.22 mΩ |

Number of rotor poles | 12 |

Shaft diameter | 50 mm |

Rotor pole arc angle | 12.74° |

Wire fill factor | 59% |

Number of turns | 83 |

Number of strands | 1 |

Phase winding configuration | 6 Parallel |

Exponents | Value | Coefficients | Value |
---|---|---|---|

α_{1} | 1.61939 | k_{1} | 54.56280 |

α_{2} | 2.113459 | k_{2} | 0.0350734 |

α_{3} | 1.386721 | k_{3} | 6.527015 |

**Table 7.**Calculated Losses and Efficiency for Nominal Current Reference and Conduction Angles of −47.9° To 125°.

Parameter | Value |
---|---|

Average core loss in the rotor | 287.65 W |

Average core loss in the stator | 337.52 W |

Copper loss (including AC copper loss) | 3307.75 W |

Efficiency | 94.8% |

Application | Material | Thermal Cond. [W/m∙K] | Max Temp. [°C] |
---|---|---|---|

Stator/Rotor Laminations | HIPERCO^{®} 50A [22] | 29.83 | 704 * |

Conductors | Copper | 394.0 | 1080 |

Magnetic Wire | Polyimide [28,29] | 0.26 | 240 |

Impregnation Material | Lord CoolTherm^{®} EP-2000 [30] | 1.9 | 204 |

Coil retention | DuraForm^{®} PA plastic [31] | 0.7 | 180 |

Liner | Nomex 818 [32] | More than 0.1 | 250 |

Cooling jacket | Aluminum | 247 | 660 |

Air | Air | 0.024 | -- |

Moving air | Air | 0.24 | -- |

Cooling Type | Heat Transfer Coefficient Applied [W/(m^{2}∙K)] |
---|---|

Air flow by salient rotor poles | 150 |

Liquid cooled | 6000 |

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Abdollahi, M.E.; Zahid, A.; Vaks, N.; Bilgin, B.
Switched Reluctance Motor Design for a Light Sport Aircraft Application. *Machines* **2023**, *11*, 362.
https://doi.org/10.3390/machines11030362

**AMA Style**

Abdollahi ME, Zahid A, Vaks N, Bilgin B.
Switched Reluctance Motor Design for a Light Sport Aircraft Application. *Machines*. 2023; 11(3):362.
https://doi.org/10.3390/machines11030362

**Chicago/Turabian Style**

Abdollahi, Mohammad Ehsan, Ahsan Zahid, Nir Vaks, and Berker Bilgin.
2023. "Switched Reluctance Motor Design for a Light Sport Aircraft Application" *Machines* 11, no. 3: 362.
https://doi.org/10.3390/machines11030362