Final Report Summary - HPEM (Development of key technology components for high performance electric motors)
Executive Summary:
The aim of the HPEM project is the study, design and construction of ten motor and sensor prototype parts for particular actuators involving high performance specifications for aerospace applications.
In a first phase the preliminary design has been performed including the selection of appropriate materials, configurations and technologies enabling to meet the desirable requirements. During this phase particular Silicium Cobalt iron laminations (Vacoflux50 with width 0.35 mm) have been selected for the magnetic circuits providing high saturation magnetization and reduced losses. Furthermore two alternative motor configurations, involving axial and circumferential segmentations respectively, have been compared by performing design sensitivities through electromagnetic modeling by 2D finite element techniques in order to obtain the optimal values of the key geometrical and operating parameters and then the calculated electromagnetic performance and thermal characteristics have been assessed. The optimized configuration selected is the circumferentially segmented one, mainly due to its better thermal characteristics.
In a second phase the critical design has been performed, by selecting adequate insulating materials enabling temperature withstand up to 200 oC, implementing mica based components, windings composed of specially enamelled with aromatic Polyimide round copper wires, mica reinforced Nomex slot insulations and Samarium Cobalt alloy permanent magnets. Moreover, an appropriate resolver technology has been proposed presenting robust design and the increased thermal endurance for the the rotor speed and position sensing (Rotasyn RO2010-K-R004 type), which has demonstrated satisfactory performance under all the considered operating conditions for this application. It may be noted that at the validation stage of the constructed parts of the prototype, appropriate adaptations and reconstructions have been performed due to difficulties encountered both on procurement procedures and on the implementation of newly defined technologies, involving rotor parts with Halbach array reconstruction as well as copper density modification in slots of stator parts. The critical design stage, including the above mentioned adaptations with respect to the preliminary design outcomes and the successful acceptance tests of the two delivered actuators, has been finalised.
Finally the remaining eight motors have been extensively tested and after assessing their compliance with all characteristics of the defined operating conditions they have been delivered. Furthermore, in order to overcome some problems encountered after the mechanical assembly concerning the machine-converter coupling appropriate fitting and the harness of the mechanism driven by the delivered machines due to dynamic loading characteristics, specific corrective actions have been proposed.
Project Context and Objectives:
The HPEM project aims to develop a state of art electric motor and sensor actuation system, in order to suppress the whole hydraulic system in rotorcrafts. The project is divided into three phases that will lead to the achievement of the HPEM project objectives. The first phase dedicated to the motor and sensor preliminary design and initial hardware manufacturing is oriented to the better understanding of the specifications and the complex validation plan to ensure the best implementation of the new motor - sensor actuation system. The second phase concerning the motor and sensor critical design is the core development of the HPEM project and leads to the creation of the new electromagnetic-electronic part of the actuator. The third phase, actually underway involves the final hardware sets testing and manufacturing, aiming to validate both the new motor and sensor capabilities to perform the technological readiness level expected, as well as the remaining prototypes manufacturing..
WP1 (Motor and sensor preliminary design - initial hardware manufacturing) was oriented to the better understanding of the specifications and the complex validation plan to ensure the best implementation of the new motor - sensor actuation system. More particularly during the preliminary design the selection of appropriate materials, configurations and technologies enabling to meet the desirable requirements has been undertaken. That is particular Silicium Cobalt iron laminations (Vacoflux50 with width 0.35 mm) have been selected for the magnetic circuits providing high saturation magnetization and reduced losses. Furthermore, two alternative motor configurations, involving axial and circumferential segmentations respectively, have been compared by performing design sensitivities through electromagnetic modeling by 2D finite element techniques in order to obtain the optimal values of the key geometrical and operating parameters and then the calculated electromagnetic performance and thermal characteristics have been assessed. The optimized configuration selected is the circumferentially segmented one, mainly due to its better thermal characteristics. As a result of this first WP emerged the full specification for the two next WPs.
WP 2 (Motor and sensor critical design) hosted the core development of the HPEM project and led to the creation of the new electromagnetic-electronic part of the actuator. In addition during the critical design adequate materials have been selected for the motor synthesis. That is insulating materials enabling temperature withstand up to 200 oC, implementing mica based components, windings composed of specially enamelled with aromatic Polyimide round copper wires, mica reinforced Nomex slot insulations and Samarium Cobalt alloy permanent magnets. Moreover, an appropriate resolver technology has been proposed presenting robust design and the increased thermal endurance for the the rotor speed and position sensing (Rotasyn RO2010-K-R004 type), which has demonstrated satisfactory performance under all the considered operating conditions for this application. It may be noted that at the validation stage of the constructed parts of the prototype, appropriate adaptations and reconstructions have been performed due to difficulties encountered both on procurement procedures and on the implementation of newly defined technologies, involving rotor parts with Halbach array reconstruction as well as copper density modificaton in slots of stator parts. The critical design stage, including the above mentioned adaptations with respect to the preliminary design outcomes and the successful acceptance tests of the two delivered actuators, has been finalised.
Consequently, the main conclusions drawn can be summarized as follows: the particular methodology developed for the comparative design optimization and the performance analysis of single layer and double layer permanent magnet actuators, employing different segmentation strategies has enabled successful definition of the motor configurations. The two distinct operating conditions foreseen have been integrated in the optimization routine via appropriate objective and constraint functions. The optimal winding configurations and their segmentation strategies have then been evaluated in terms of electromagnetic, fault tolerance and thermal behaviour. Electromagnetic field analysis resulted in higher efficiency of single layer configuration, while the double layer one involves advantages in torque and induced back-EMF quality, exhibiting lower harmonic distortion effects. Moreover, optimal latter topology presented lower braking torque and short circuit currents with respect to the single layer configuration due to its lower winding factor and higher inductances under fault conditions. On the other hand, single layer configuration offers greater thermal robustness.
Finally, through the combined analysis developed, the considered two configurations present complementary advantages, the former concerning efficiency and thermal behaviour and the latter concerning torque, EMF quality and fault tolerance characteristics. Thus, according to the deliverable findings, on a strict motor basis the single layer topology is favoured, that is why it has been adopted and validated by initial measurements on the two prototype actuators delivered.
WP3 (Final hardware set testing and manufacturing) validated the motor characteristics through test results on the manufactured prototypes for the HPEM project. The components have been manufactured and assembled in final machines that have been tested under no load, load and fault conditions. The final selected materials have been defined during the previous WPs. For the Permanents Magnets (PMs), the Recoma family of materials are selected, offering a combination of high magnetic output and excellent temperature stability.
Furthermore, a retaining sleeve comprised of filament wound carbon fiber has been constructed, protecting PMs from centrifugal forces, enhancing mechanical robustness of the rotor, especially at high speeds. The test are performed on a rig where the load made by means of an induction machine (20.000 rpm – 64 Nm) controlled by means an industrial drive. The two winding structures of the HPEM are connected to a six phase inverter used to feed the machine with the required electrical load. The final manufactured prototypes have been the subject of the following tests in order to validate the steady state performance of the actuators: no load tests, load tests, short circuit tests and inductance measurement tests. Through these extended experiments performed successfully, concerning the various operating modes of the remaining eight actuators, and the obtained good agreement with the respective simulation results, it was assessed that the designed fault tolerant FSCW PMSMs fulfil the required specifications and constitute a favourable option for the considered swashplate actuation system.
Project Results:
The analysis of the two initial design motor configurations involving axial and circumferential segmentations has been undertaken by performing design sensitivities through electromagnetic modeling by 2D finite element techniques in order to validate the optimal values of the key geometrical and operating parameters and then the calculated electromagnetic performance and thermal characteristics have been compared and assessed.
Design sensitivities of magnetic field analysis for axial segmentation
Winding topology: Single Layer Concentrated winding
Table 1. Initial machine design characteristics
Number of slots N 12
Number of poles p 10
Airgap diameter D_ag 30 mm
Airgap Height H_ag 1.0 mm
Stator Inner Diameter D_si 31.0 mm
Stator Outer Diameter D_so 66.7 mm
Rotor Outer Diameter D_ro 29.0 mm
Magnet Height H_m 4.0 mm
Tooth Width T_w 3.8 mm
Back Iron Thickness T_bi 2.3 mm
Number of turns per phase N_ph 42
Active Length L 102 mm
Magnet Arch M_a 0.84
Slot opening S_o 2.0 mm
Tooth tip height H_tt 1.0 mm
Figure 1. Machine parameters definition
Permanent Magnet Material Considered: Samarium Cobalt 28
Table 2. Samarium Cobalt 28 characteristics
Remanence Flux Density (T) Br 1.05
Coercive Force (A/m) Hc 756000
Maximun working temperature (oC) T 350
Iron lamination Material considered: Vacoflux50 with lamination width 0.35 mm
Figure 2. Soft magnetic cobalt iron alloys B-H curves
Figure 3. Typical core losses for strips with a thickness of 0.35 mm for different frequencies
Figure 4. Motor concept for axial segmentation
Figure 5. Single layer winding structure for the initial HPEM configuration
Figure 6. Initial HPEM and final EMAS configurations
Copper fill factor determination
According to previous project findings, a relatively low copper fill factor has been finally achieved in stator slots (approximately 0.3 in constructed prototypes) due to small machine dimensions. An important parameter influencing copper fill factor is the slot opening (D_so), in conjunction with the implemented slot insulation (2 x 0.25 mm). In a first step an investigation of the main operating characteristics for two different D_so values has been performed, the initial one of 2 mm and a greater one of 3 mm facilitating greater copper fill factor, respectively. The obtained simulation results, tabulated in table 3 illustrate that the main operating characteristics are similar, therefore D_so = 3 mm is proposed, in order to achieve higher copper fill factors in stator slots. Thus a fill factor = 0.5 is expected to be achieved.
Table 3. Operating characteristics for two types of slot openings
Considered Slot opening (mm) D_so 2 3
Mean Torque (Nm) Tmean 4.87 4.74
Torque ripple (%) Tripple 0.97 1.44
EMF fundamental (V) EMF 7.61 7
Total Harmonic Distortion (%) THD 4.43 3.06
Current density (A/mm2) J 8 8
Copper losses (W) Pcopper 111.2 112.21
Iron losses (W) PFE 1.23 1.07
Maximum flux density in stator yoke (T) Byoke 2.03 1.92
Maximum flux density in tooth (T) Btooth 1.52 1.38
In a second step, a sensitivity analysis for the tooth width and back iron thickness, for J=8 A/mm2 and for two different speeds, 750 and 5000 rpm, respectively, has been performed. The simulation results obtained by using a parametric 2D finite element modeling, are tabulated in table 4. These results show that the core losses are higher at 5000 rpm, involving a fundamental frequency of 400 Hz. Core losses are calculated by using provided curves for Vacoflux50 material shown in Fig. 2. The mean torque, as well as the total losses, for the two different speeds considered, 750 and 5000 rpm, are shown in Figs. 7-9, respectively. These figures illustrate that a global optimal compromise for back iron thickness and tooth width is obtained for T_bi=2.4mm and T_w=3.5mm respectively, involving maximum performance (mean torque) to power losses ratio.
Figure 7. Mean Torque versus back iron thickness and tooth width
Figure 8. Total power losses versus back iron thickness and tooth width for n=750rpm
Figure 9. Total power losses versus back iron thickness and tooth width for n=5000rpm
Table 4. Main operating characteristics for J=8A/mm2 and different T_w, T_bi values
T_w (mm) T_bi (mm) Tmean (Nm) Tripple (%) EMF (V) THD (%) Pcu (W) PFE (W) Btooth (T) Byoke(T)
750 (rpm) 5000
(rpm) 750 (rpm) 5000
(rpm)
3.3 2.8 4.75 1.53 6.52 45.79 3.05 124.98 0.98 15.95 1.55 1.55
2.7 4.79 1.27 6.56 46.03 3.03 126.27 0.996 16.31 1.56 1.61
2.6 4.84 1.26 6.59 46.28 3.06 127.56 1.013 16.7 1.57 1.69
2.5 4.89 1.26 6.62 46.53 3.09 128.85 1.031 17.1 1.59 1.76
2.4 4.94 1.25 6.66 46.77 3.14 130.16 1.05 17.52 1.59 1.85
2.3 4.98 1.31 6.69 47.02 3.16 131.46 1.069 17.94 1.6 1.94
2.2 5.03 1.32 6.73 47.24 3.27 132.78 1.088 18.38 1.61 2.03
3.4 2.8 4.7 1.38 6.57 45.68 3.01 123.57 0.981 15.6 1.52 1.54
2.7 4.75 1.37 6.61 45.93 3.03 124.85 0.997 15.96 1.52 1.61
2.6 4.79 1.36 6.64 46.18 3.04 126.13 1.013 16.34 1.53 1.68
2.5 4.84 1.37 6.67 46.42 3.06 127.41 1.031 16.73 1.54 1.76
2.4 4.89 1.36 6.71 46.66 3.09 128.71 1.05 17.13 1.55 1.84
2.3 4.93 1.33 6.75 46.91 3.15 130 1.068 17.56 1.56 1.93
2.2 4.98 1.34 6.78 47.14 3.24 131.31 1.088 18 1.57 2.03
3.5 2.8 4.65 1.36 6.63 45.57 2.99 122.16 0.982 15.27 1.47 1.54
2.7 4.7 1.35 6.66 45.81 2.99 123.43 0.998 15.62 1.48 1.61
2.6 4.75 1.34 6.7 46.06 3.02 124.7 1.015 15.99 1.49 1.68
2.5 4.79 1.33 6.73 46.29 3.03 125.97 1.033 16.37 1.5 1.76
2.4 4.84 1.37 6.77 46.54 3.06 127.26 1.052 16.78 1.5 1.84
2.3 4.89 1.33 6.8 46.78 3.11 128.55 1.071 17.2 1.51 1.93
2.2 4.93 1.34 6.84 47.01 3.18 129.84 1.091 17.63 1.52 2.02
3.6 2.8 4.61 1.27 6.68 45.47 2.98 120.76 0.985 14.96 1.43 1.54
2.7 4.65 1.26 6.72 45.71 2.98 122.01 1.001 15.3 1.44 1.6
2.6 4.7 1.26 6.75 45.95 2.98 123.27 1.018 15.67 1.45 1.68
2.5 4.75 1.24 6.79 46.2 3.02 124.54 1.036 16.05 1.44 1.75
2.4 4.79 1.3 6.82 46.44 3.04 125.81 1.054 16.44 1.46 1.84
2.3 4.84 1.42 6.86 46.68 3.1 127.09 1.074 16.86 1.47 1.93
2.2 4.88 1.43 6.89 46.92 3.18 128.38 1.094 17.3 1.48 2.02
3.7 2.8 4.56 1.28 6.73 45.37 2.97 119.35 0.986 14.65 1.38 1.53
2.7 4.61 1.27 6.77 45.61 2.97 120.6 1.002 15 1.39 1.6
2.6 4.65 1.27 6.81 45.86 2.97 121.85 1.02 15.36 1.4 1.67
2.5 4.7 1.25 6.84 46.1 2.99 123.11 1.038 15.73 1.41 1.75
2.4 4.75 1.25 6.88 46.34 3.04 124.37 1.056 16.12 1.41 1.83
2.3 4.79 1.43 6.92 46.58 3.08 125.64 1.076 16.53 1.43 1.92
2.2 4.84 1.45 6.95 46.81 3.16 126.91 1.097 16.95 1.43 2.02
3.8 2.8 4.51 1.48 6.78 45.25 2.95 117.95 0.987 14.34 1.34 1.53
2.7 4.56 1.47 6.82 45.48 2.96 119.19 1.004 14.68 1.36 1.6
2.6 4.6 1.46 6.86 45.73 2.95 120.43 1.021 15.03 1.36 1.67
2.5 4.65 1.45 6.89 45.97 2.95 121.67 1.038 15.39 1.37 1.75
2.4 4.7 1.45 6.93 46.2 3.02 122.93 1.057 15.78 1.38 1.83
2.3 4.74 1.44 6.97 46.43 3.06 124.19 1.077 16.18 1.38 1.92
2.2 4.79 1.49 7 46.67 3.15 125.45 1.098 16.61 1.39 2.01
3.9 2.8 4.47 1.28 6.85 45.15 2.91 116.55 0.991 14.06 1.31 1.53
2.7 4.51 1.27 6.88 45.38 2.93 117.78 1.008 14.39 1.32 1.59
2.6 4.56 1.26 6.92 45.63 2.92 119.01 1.024 14.74 1.32 1.67
2.5 4.6 1.21 6.96 45.87 2.95 120.24 1.043 15.11 1.33 1.74
2.4 4.65 1.21 6.99 46.11 2.98 121.49 1.063 15.49 1.33 1.82
2.3 4.69 1.31 7.03 46.34 3.04 122.74 1.083 15.88 1.34 1.91
2.2 4.74 1.31 7.07 46.57 3.12 123.99 1.103 16.3 1.35 2.01
In a third step, a sensitivity analysis concerning the mean airgap diameter is implemented, considering the fact that by increasing the air gap diameter the torque is increased due to D2L considerations while the armature magnetomotive force is decreased. The simulation results for J=8A/mm2 for three mean airgap diameters are illustrated in table 5, while the respective calculated torque, as well as the power losses versus airgap diameter are shown in Fig. 10. This figure illustrates that higher airgap diameters are favoured, that is why a relatively small increase to D_ag=31mm is proposed, under the reserve that rotor inertial constraints are not violated.
Potential Impact:
The use of electrically powered actuators integrating speed and position sensors is expected to enable to save weight, and to increase engine monitoring and diagnostics. Moreover, HPEM project findings will allow to reduce the size of components of generation equipment as well as to achieve significant reduction in maintenance. Another aspect of HPEM developments is increased reliability because safety has a great impact in aeronautic transports.
The main objective of the dissemination plan was to guarantee proper diffusion of knowledge and project results. The dissemination process was handled so as to spread information among all potentially concerned stakeholders and all levels of policy-makers: such as aeronautics supply industry, Safety and certification bodies, Standardization bodies, Engineering Organizations, European and national policy makers, Universities, Schools and European citizens. The activities that disseminated HPEM results are as follows:
• Presentations in International Conferences and Workshops.
▪ A. Sarigiannidis and A. Kladas, “Switching frequency impact on Permanent Magnet Actuators for Aerospace Applications,” The 16th Biennial IEEE Conference on Electromagnetic Field Computation, Annecy, France, 25-28 May 2014.
▪ T. Kefalas, A. Kladas, “3D FEM and Lumped-Parameter Network Transient Thermal Analysis of Induction and Permanent Magnet Motors for Aerospace Applications,” Ninth Japanese-Mediterranean Workshop on Applied Electromagnetic Engineering for Magnetic, Super-conducting, Multifunctional and Nanomaterials (JAPMED’9), Sofia, Bulgaria, 5-8 July 2015.
▪ K. Anagnostopoulos, M. Beniakar, A. Sarigiannidis and A. Kladas, “Investigation of alternative actuator configurations for aerospace applications,” European Conference on More Electric Aircraft –MEA 2015, Toulouse, France, 4-5 February 2015.
• Graduate students training involved in the project
PhD students M. Beniakar and A. Sarigiannidis, that are with the Department of Electrical and Computer Engineering, Laboratory of Electrical Machines and Power Electronics, National Technical University of Athens, were involved to the developmental activities of the project.
The intellectual property monitoring and patent survey is an indispensable prerequisite to ensure that the research and developments are driven properly. It consists in a continuous identification, monitoring and qualification of tangible and intangible results that should be either kept confidential, legally protected, disseminated or transferred to third parties. Dissemination and exploitation of the results is ensured by the Coordinator. They ensured that the issues related to Intellectual Property Rights were properly assessed and managed. The IPR management shall cover milestones and deliverables of the HPEM project to identify any commercial potential of generated knowledge and information.
List of Websites:
No website
The aim of the HPEM project is the study, design and construction of ten motor and sensor prototype parts for particular actuators involving high performance specifications for aerospace applications.
In a first phase the preliminary design has been performed including the selection of appropriate materials, configurations and technologies enabling to meet the desirable requirements. During this phase particular Silicium Cobalt iron laminations (Vacoflux50 with width 0.35 mm) have been selected for the magnetic circuits providing high saturation magnetization and reduced losses. Furthermore two alternative motor configurations, involving axial and circumferential segmentations respectively, have been compared by performing design sensitivities through electromagnetic modeling by 2D finite element techniques in order to obtain the optimal values of the key geometrical and operating parameters and then the calculated electromagnetic performance and thermal characteristics have been assessed. The optimized configuration selected is the circumferentially segmented one, mainly due to its better thermal characteristics.
In a second phase the critical design has been performed, by selecting adequate insulating materials enabling temperature withstand up to 200 oC, implementing mica based components, windings composed of specially enamelled with aromatic Polyimide round copper wires, mica reinforced Nomex slot insulations and Samarium Cobalt alloy permanent magnets. Moreover, an appropriate resolver technology has been proposed presenting robust design and the increased thermal endurance for the the rotor speed and position sensing (Rotasyn RO2010-K-R004 type), which has demonstrated satisfactory performance under all the considered operating conditions for this application. It may be noted that at the validation stage of the constructed parts of the prototype, appropriate adaptations and reconstructions have been performed due to difficulties encountered both on procurement procedures and on the implementation of newly defined technologies, involving rotor parts with Halbach array reconstruction as well as copper density modification in slots of stator parts. The critical design stage, including the above mentioned adaptations with respect to the preliminary design outcomes and the successful acceptance tests of the two delivered actuators, has been finalised.
Finally the remaining eight motors have been extensively tested and after assessing their compliance with all characteristics of the defined operating conditions they have been delivered. Furthermore, in order to overcome some problems encountered after the mechanical assembly concerning the machine-converter coupling appropriate fitting and the harness of the mechanism driven by the delivered machines due to dynamic loading characteristics, specific corrective actions have been proposed.
Project Context and Objectives:
The HPEM project aims to develop a state of art electric motor and sensor actuation system, in order to suppress the whole hydraulic system in rotorcrafts. The project is divided into three phases that will lead to the achievement of the HPEM project objectives. The first phase dedicated to the motor and sensor preliminary design and initial hardware manufacturing is oriented to the better understanding of the specifications and the complex validation plan to ensure the best implementation of the new motor - sensor actuation system. The second phase concerning the motor and sensor critical design is the core development of the HPEM project and leads to the creation of the new electromagnetic-electronic part of the actuator. The third phase, actually underway involves the final hardware sets testing and manufacturing, aiming to validate both the new motor and sensor capabilities to perform the technological readiness level expected, as well as the remaining prototypes manufacturing..
WP1 (Motor and sensor preliminary design - initial hardware manufacturing) was oriented to the better understanding of the specifications and the complex validation plan to ensure the best implementation of the new motor - sensor actuation system. More particularly during the preliminary design the selection of appropriate materials, configurations and technologies enabling to meet the desirable requirements has been undertaken. That is particular Silicium Cobalt iron laminations (Vacoflux50 with width 0.35 mm) have been selected for the magnetic circuits providing high saturation magnetization and reduced losses. Furthermore, two alternative motor configurations, involving axial and circumferential segmentations respectively, have been compared by performing design sensitivities through electromagnetic modeling by 2D finite element techniques in order to obtain the optimal values of the key geometrical and operating parameters and then the calculated electromagnetic performance and thermal characteristics have been assessed. The optimized configuration selected is the circumferentially segmented one, mainly due to its better thermal characteristics. As a result of this first WP emerged the full specification for the two next WPs.
WP 2 (Motor and sensor critical design) hosted the core development of the HPEM project and led to the creation of the new electromagnetic-electronic part of the actuator. In addition during the critical design adequate materials have been selected for the motor synthesis. That is insulating materials enabling temperature withstand up to 200 oC, implementing mica based components, windings composed of specially enamelled with aromatic Polyimide round copper wires, mica reinforced Nomex slot insulations and Samarium Cobalt alloy permanent magnets. Moreover, an appropriate resolver technology has been proposed presenting robust design and the increased thermal endurance for the the rotor speed and position sensing (Rotasyn RO2010-K-R004 type), which has demonstrated satisfactory performance under all the considered operating conditions for this application. It may be noted that at the validation stage of the constructed parts of the prototype, appropriate adaptations and reconstructions have been performed due to difficulties encountered both on procurement procedures and on the implementation of newly defined technologies, involving rotor parts with Halbach array reconstruction as well as copper density modificaton in slots of stator parts. The critical design stage, including the above mentioned adaptations with respect to the preliminary design outcomes and the successful acceptance tests of the two delivered actuators, has been finalised.
Consequently, the main conclusions drawn can be summarized as follows: the particular methodology developed for the comparative design optimization and the performance analysis of single layer and double layer permanent magnet actuators, employing different segmentation strategies has enabled successful definition of the motor configurations. The two distinct operating conditions foreseen have been integrated in the optimization routine via appropriate objective and constraint functions. The optimal winding configurations and their segmentation strategies have then been evaluated in terms of electromagnetic, fault tolerance and thermal behaviour. Electromagnetic field analysis resulted in higher efficiency of single layer configuration, while the double layer one involves advantages in torque and induced back-EMF quality, exhibiting lower harmonic distortion effects. Moreover, optimal latter topology presented lower braking torque and short circuit currents with respect to the single layer configuration due to its lower winding factor and higher inductances under fault conditions. On the other hand, single layer configuration offers greater thermal robustness.
Finally, through the combined analysis developed, the considered two configurations present complementary advantages, the former concerning efficiency and thermal behaviour and the latter concerning torque, EMF quality and fault tolerance characteristics. Thus, according to the deliverable findings, on a strict motor basis the single layer topology is favoured, that is why it has been adopted and validated by initial measurements on the two prototype actuators delivered.
WP3 (Final hardware set testing and manufacturing) validated the motor characteristics through test results on the manufactured prototypes for the HPEM project. The components have been manufactured and assembled in final machines that have been tested under no load, load and fault conditions. The final selected materials have been defined during the previous WPs. For the Permanents Magnets (PMs), the Recoma family of materials are selected, offering a combination of high magnetic output and excellent temperature stability.
Furthermore, a retaining sleeve comprised of filament wound carbon fiber has been constructed, protecting PMs from centrifugal forces, enhancing mechanical robustness of the rotor, especially at high speeds. The test are performed on a rig where the load made by means of an induction machine (20.000 rpm – 64 Nm) controlled by means an industrial drive. The two winding structures of the HPEM are connected to a six phase inverter used to feed the machine with the required electrical load. The final manufactured prototypes have been the subject of the following tests in order to validate the steady state performance of the actuators: no load tests, load tests, short circuit tests and inductance measurement tests. Through these extended experiments performed successfully, concerning the various operating modes of the remaining eight actuators, and the obtained good agreement with the respective simulation results, it was assessed that the designed fault tolerant FSCW PMSMs fulfil the required specifications and constitute a favourable option for the considered swashplate actuation system.
Project Results:
The analysis of the two initial design motor configurations involving axial and circumferential segmentations has been undertaken by performing design sensitivities through electromagnetic modeling by 2D finite element techniques in order to validate the optimal values of the key geometrical and operating parameters and then the calculated electromagnetic performance and thermal characteristics have been compared and assessed.
Design sensitivities of magnetic field analysis for axial segmentation
Winding topology: Single Layer Concentrated winding
Table 1. Initial machine design characteristics
Number of slots N 12
Number of poles p 10
Airgap diameter D_ag 30 mm
Airgap Height H_ag 1.0 mm
Stator Inner Diameter D_si 31.0 mm
Stator Outer Diameter D_so 66.7 mm
Rotor Outer Diameter D_ro 29.0 mm
Magnet Height H_m 4.0 mm
Tooth Width T_w 3.8 mm
Back Iron Thickness T_bi 2.3 mm
Number of turns per phase N_ph 42
Active Length L 102 mm
Magnet Arch M_a 0.84
Slot opening S_o 2.0 mm
Tooth tip height H_tt 1.0 mm
Figure 1. Machine parameters definition
Permanent Magnet Material Considered: Samarium Cobalt 28
Table 2. Samarium Cobalt 28 characteristics
Remanence Flux Density (T) Br 1.05
Coercive Force (A/m) Hc 756000
Maximun working temperature (oC) T 350
Iron lamination Material considered: Vacoflux50 with lamination width 0.35 mm
Figure 2. Soft magnetic cobalt iron alloys B-H curves
Figure 3. Typical core losses for strips with a thickness of 0.35 mm for different frequencies
Figure 4. Motor concept for axial segmentation
Figure 5. Single layer winding structure for the initial HPEM configuration
Figure 6. Initial HPEM and final EMAS configurations
Copper fill factor determination
According to previous project findings, a relatively low copper fill factor has been finally achieved in stator slots (approximately 0.3 in constructed prototypes) due to small machine dimensions. An important parameter influencing copper fill factor is the slot opening (D_so), in conjunction with the implemented slot insulation (2 x 0.25 mm). In a first step an investigation of the main operating characteristics for two different D_so values has been performed, the initial one of 2 mm and a greater one of 3 mm facilitating greater copper fill factor, respectively. The obtained simulation results, tabulated in table 3 illustrate that the main operating characteristics are similar, therefore D_so = 3 mm is proposed, in order to achieve higher copper fill factors in stator slots. Thus a fill factor = 0.5 is expected to be achieved.
Table 3. Operating characteristics for two types of slot openings
Considered Slot opening (mm) D_so 2 3
Mean Torque (Nm) Tmean 4.87 4.74
Torque ripple (%) Tripple 0.97 1.44
EMF fundamental (V) EMF 7.61 7
Total Harmonic Distortion (%) THD 4.43 3.06
Current density (A/mm2) J 8 8
Copper losses (W) Pcopper 111.2 112.21
Iron losses (W) PFE 1.23 1.07
Maximum flux density in stator yoke (T) Byoke 2.03 1.92
Maximum flux density in tooth (T) Btooth 1.52 1.38
In a second step, a sensitivity analysis for the tooth width and back iron thickness, for J=8 A/mm2 and for two different speeds, 750 and 5000 rpm, respectively, has been performed. The simulation results obtained by using a parametric 2D finite element modeling, are tabulated in table 4. These results show that the core losses are higher at 5000 rpm, involving a fundamental frequency of 400 Hz. Core losses are calculated by using provided curves for Vacoflux50 material shown in Fig. 2. The mean torque, as well as the total losses, for the two different speeds considered, 750 and 5000 rpm, are shown in Figs. 7-9, respectively. These figures illustrate that a global optimal compromise for back iron thickness and tooth width is obtained for T_bi=2.4mm and T_w=3.5mm respectively, involving maximum performance (mean torque) to power losses ratio.
Figure 7. Mean Torque versus back iron thickness and tooth width
Figure 8. Total power losses versus back iron thickness and tooth width for n=750rpm
Figure 9. Total power losses versus back iron thickness and tooth width for n=5000rpm
Table 4. Main operating characteristics for J=8A/mm2 and different T_w, T_bi values
T_w (mm) T_bi (mm) Tmean (Nm) Tripple (%) EMF (V) THD (%) Pcu (W) PFE (W) Btooth (T) Byoke(T)
750 (rpm) 5000
(rpm) 750 (rpm) 5000
(rpm)
3.3 2.8 4.75 1.53 6.52 45.79 3.05 124.98 0.98 15.95 1.55 1.55
2.7 4.79 1.27 6.56 46.03 3.03 126.27 0.996 16.31 1.56 1.61
2.6 4.84 1.26 6.59 46.28 3.06 127.56 1.013 16.7 1.57 1.69
2.5 4.89 1.26 6.62 46.53 3.09 128.85 1.031 17.1 1.59 1.76
2.4 4.94 1.25 6.66 46.77 3.14 130.16 1.05 17.52 1.59 1.85
2.3 4.98 1.31 6.69 47.02 3.16 131.46 1.069 17.94 1.6 1.94
2.2 5.03 1.32 6.73 47.24 3.27 132.78 1.088 18.38 1.61 2.03
3.4 2.8 4.7 1.38 6.57 45.68 3.01 123.57 0.981 15.6 1.52 1.54
2.7 4.75 1.37 6.61 45.93 3.03 124.85 0.997 15.96 1.52 1.61
2.6 4.79 1.36 6.64 46.18 3.04 126.13 1.013 16.34 1.53 1.68
2.5 4.84 1.37 6.67 46.42 3.06 127.41 1.031 16.73 1.54 1.76
2.4 4.89 1.36 6.71 46.66 3.09 128.71 1.05 17.13 1.55 1.84
2.3 4.93 1.33 6.75 46.91 3.15 130 1.068 17.56 1.56 1.93
2.2 4.98 1.34 6.78 47.14 3.24 131.31 1.088 18 1.57 2.03
3.5 2.8 4.65 1.36 6.63 45.57 2.99 122.16 0.982 15.27 1.47 1.54
2.7 4.7 1.35 6.66 45.81 2.99 123.43 0.998 15.62 1.48 1.61
2.6 4.75 1.34 6.7 46.06 3.02 124.7 1.015 15.99 1.49 1.68
2.5 4.79 1.33 6.73 46.29 3.03 125.97 1.033 16.37 1.5 1.76
2.4 4.84 1.37 6.77 46.54 3.06 127.26 1.052 16.78 1.5 1.84
2.3 4.89 1.33 6.8 46.78 3.11 128.55 1.071 17.2 1.51 1.93
2.2 4.93 1.34 6.84 47.01 3.18 129.84 1.091 17.63 1.52 2.02
3.6 2.8 4.61 1.27 6.68 45.47 2.98 120.76 0.985 14.96 1.43 1.54
2.7 4.65 1.26 6.72 45.71 2.98 122.01 1.001 15.3 1.44 1.6
2.6 4.7 1.26 6.75 45.95 2.98 123.27 1.018 15.67 1.45 1.68
2.5 4.75 1.24 6.79 46.2 3.02 124.54 1.036 16.05 1.44 1.75
2.4 4.79 1.3 6.82 46.44 3.04 125.81 1.054 16.44 1.46 1.84
2.3 4.84 1.42 6.86 46.68 3.1 127.09 1.074 16.86 1.47 1.93
2.2 4.88 1.43 6.89 46.92 3.18 128.38 1.094 17.3 1.48 2.02
3.7 2.8 4.56 1.28 6.73 45.37 2.97 119.35 0.986 14.65 1.38 1.53
2.7 4.61 1.27 6.77 45.61 2.97 120.6 1.002 15 1.39 1.6
2.6 4.65 1.27 6.81 45.86 2.97 121.85 1.02 15.36 1.4 1.67
2.5 4.7 1.25 6.84 46.1 2.99 123.11 1.038 15.73 1.41 1.75
2.4 4.75 1.25 6.88 46.34 3.04 124.37 1.056 16.12 1.41 1.83
2.3 4.79 1.43 6.92 46.58 3.08 125.64 1.076 16.53 1.43 1.92
2.2 4.84 1.45 6.95 46.81 3.16 126.91 1.097 16.95 1.43 2.02
3.8 2.8 4.51 1.48 6.78 45.25 2.95 117.95 0.987 14.34 1.34 1.53
2.7 4.56 1.47 6.82 45.48 2.96 119.19 1.004 14.68 1.36 1.6
2.6 4.6 1.46 6.86 45.73 2.95 120.43 1.021 15.03 1.36 1.67
2.5 4.65 1.45 6.89 45.97 2.95 121.67 1.038 15.39 1.37 1.75
2.4 4.7 1.45 6.93 46.2 3.02 122.93 1.057 15.78 1.38 1.83
2.3 4.74 1.44 6.97 46.43 3.06 124.19 1.077 16.18 1.38 1.92
2.2 4.79 1.49 7 46.67 3.15 125.45 1.098 16.61 1.39 2.01
3.9 2.8 4.47 1.28 6.85 45.15 2.91 116.55 0.991 14.06 1.31 1.53
2.7 4.51 1.27 6.88 45.38 2.93 117.78 1.008 14.39 1.32 1.59
2.6 4.56 1.26 6.92 45.63 2.92 119.01 1.024 14.74 1.32 1.67
2.5 4.6 1.21 6.96 45.87 2.95 120.24 1.043 15.11 1.33 1.74
2.4 4.65 1.21 6.99 46.11 2.98 121.49 1.063 15.49 1.33 1.82
2.3 4.69 1.31 7.03 46.34 3.04 122.74 1.083 15.88 1.34 1.91
2.2 4.74 1.31 7.07 46.57 3.12 123.99 1.103 16.3 1.35 2.01
In a third step, a sensitivity analysis concerning the mean airgap diameter is implemented, considering the fact that by increasing the air gap diameter the torque is increased due to D2L considerations while the armature magnetomotive force is decreased. The simulation results for J=8A/mm2 for three mean airgap diameters are illustrated in table 5, while the respective calculated torque, as well as the power losses versus airgap diameter are shown in Fig. 10. This figure illustrates that higher airgap diameters are favoured, that is why a relatively small increase to D_ag=31mm is proposed, under the reserve that rotor inertial constraints are not violated.
Potential Impact:
The use of electrically powered actuators integrating speed and position sensors is expected to enable to save weight, and to increase engine monitoring and diagnostics. Moreover, HPEM project findings will allow to reduce the size of components of generation equipment as well as to achieve significant reduction in maintenance. Another aspect of HPEM developments is increased reliability because safety has a great impact in aeronautic transports.
The main objective of the dissemination plan was to guarantee proper diffusion of knowledge and project results. The dissemination process was handled so as to spread information among all potentially concerned stakeholders and all levels of policy-makers: such as aeronautics supply industry, Safety and certification bodies, Standardization bodies, Engineering Organizations, European and national policy makers, Universities, Schools and European citizens. The activities that disseminated HPEM results are as follows:
• Presentations in International Conferences and Workshops.
▪ A. Sarigiannidis and A. Kladas, “Switching frequency impact on Permanent Magnet Actuators for Aerospace Applications,” The 16th Biennial IEEE Conference on Electromagnetic Field Computation, Annecy, France, 25-28 May 2014.
▪ T. Kefalas, A. Kladas, “3D FEM and Lumped-Parameter Network Transient Thermal Analysis of Induction and Permanent Magnet Motors for Aerospace Applications,” Ninth Japanese-Mediterranean Workshop on Applied Electromagnetic Engineering for Magnetic, Super-conducting, Multifunctional and Nanomaterials (JAPMED’9), Sofia, Bulgaria, 5-8 July 2015.
▪ K. Anagnostopoulos, M. Beniakar, A. Sarigiannidis and A. Kladas, “Investigation of alternative actuator configurations for aerospace applications,” European Conference on More Electric Aircraft –MEA 2015, Toulouse, France, 4-5 February 2015.
• Graduate students training involved in the project
PhD students M. Beniakar and A. Sarigiannidis, that are with the Department of Electrical and Computer Engineering, Laboratory of Electrical Machines and Power Electronics, National Technical University of Athens, were involved to the developmental activities of the project.
The intellectual property monitoring and patent survey is an indispensable prerequisite to ensure that the research and developments are driven properly. It consists in a continuous identification, monitoring and qualification of tangible and intangible results that should be either kept confidential, legally protected, disseminated or transferred to third parties. Dissemination and exploitation of the results is ensured by the Coordinator. They ensured that the issues related to Intellectual Property Rights were properly assessed and managed. The IPR management shall cover milestones and deliverables of the HPEM project to identify any commercial potential of generated knowledge and information.
List of Websites:
No website
