Development of a 8 kW HTS Axial Flux Machine for Electric ...

Development of a 8 kW HTS Axial Flux Machine for Electric Aircraft Propulsion*

Min Zhang1, Jie Sheng1, Jay Patal1, Weijia Yuan1, Fred Eastham1, Xing Dong1, Frederick Berg2

1University of Bath, United Kingdom, 2Airbus Group Innovations, United Kingdom

This work is supported byunder grant: developing fully HTS machines for future electric aircraft

Why superconducting machines for electric aircraft propulsion:

Fully superconducting machines for electric aircraft propulsion:

Short term:

• AC loss in rotational magnetic fields has a significant impact on the weight and cost of cooling system

• Experimental and numerical tools required

• AC loss minimization

Long term:

• Flight profile affects machine design

• Impact of air turbulence

……

Challenges for fully HTS machines

Three objectives:

1. To characterise AC losses in a machine environment

2. To investigate new ways to reduce AC losses

3. To study the impacts of flight profile to the machine performance

8 kW HTS Axial Flux Machine project


Strucutre Performance

Rotor diameter 187.5mm Peak phase current 30A

Air gap 60mm Average phase current 21.21A

Stator inner diameter 175mm Maximum torque 32Nm

Turns per coil 60 Speed 1500RPM

Coil per phase 2 Average power 8kW

Width of tape 4mm Air-gap field 0.4T

Total length 20m Volume 0.15m3

2G HTS double pancake stator coils:Material 4 mm 2G HTS

Self field Ic 120 A

Total turns 60

Total length 20 m

Inner diameter 175 mm

Coil Ic 71 A

Insulation Heat shrink tube

Calculated coil Ic under 0.5 T field is 44.4 AMeasured coil Ic without external field is 71 A


NdFeB rotor design:

60 mm airgap, peak airgap field is about 0.4 T


AC loss measurement: Calorimetric chamber


• Measuring the boil-off rate of LN2• Background flow is minimised by a

double-cryostat design

Glass-metal sealing test:

N Grease + Indium

AC loss test steps:1. Heater calibration2. Background flow rate determination3. Transport loss measurement 4. Magnetization loss with rotational magnetic fields5. Total loss with AC current and rotational fields


Base Frame

Speed

Pickup10 kW Dynamometer

DC power supply

Real time digital simulator

Rotor position

Power

ABB drive

*Superconductor Science and Technology 28 (11), 115011

AC loss reduction investigation:1. Striated 2G HTS* coil2. Roebel cable coil


*AC loss comparison between multifilament and nonstriated YBCO coils designed for HTS propulsion motors, IEEE Transactions on Applied Superconductivity, 27 (4), 5203005

Aircraft propulsion hardware-in-the-loop test:


Base Frame

Speed

Pickup10 kW Dynamometer

DC power supply

Dynamic torque

simulation

Real time digital simulator

Wind turbulence

model

Propeller model

Measured

Speed/torque

Simulated

torque

Hardware-in-loop test

Flight profile

Power

Rotor position

ABB drive

Multi-physics HTS machine model:

HTS machine modelling

A new 3D 2G HTS model using T-A formula*:

*Huiming Zhang et al 2017 Supercond. Sci. Technol. 30 024005


A fast 3D HTS coil model using T-A formula*:

20 turns double racetrack coil

NoD: 786245

Time: 4 hours

CPU: i7-4790@ 3.6GHz

*An efficient 3D finite element method model based on the T–A formulation for superconducting coated conductors, 2017 Supercond. Sci. Technol. 30 024005

Six filament roebel cable

NoD: 58440

Time: 20 mins

CPU: i7-4790@ 3.6GHz


Thank you for your attention

For questions and collaborations,

please contact: [email protected]

or [email protected]

mailto:[email protected]

mailto:[email protected]

Shaft design:


Deflection at bearing points < 0.5 degrees

• PM force exceeding 2.5kN• Necessary to ensure shaft

bending does not interfere with cryogenic bearing operation

Calculated total AC losses:

(Angle is the phase difference

between the applied current and

magnetic field)


Power feedthrough

Vacuum Outlets

Outer Wall

Inner Wall

Motor Bed

Coolant Feedthrough

Isolated Measurement Chamber

Glass Vessel

Shaft

Coil Former

Windings

Rotor Discs

Development of a 8 kW HTS Axial Flux Machine for Electric ...

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