Measurement of magnetic materials –using digital techniques to determine properties

for operational conditions

Harshad Virji PatelMaterials Team

Industry and Innovation Division

IET SMT for the EM Day29th November 2007

Introduction

• Measuring magnetic properties at operational conditions– Operational conditions– Introduction into the current project on-going

• Practical

• Digital techniques– Digital feedback– Diagrams

Operational conditions

• Waveforms are known not to be sinusoidal and so it is better to make measurements for these conditions - data can be used for modelling

• When in use the environment is such that other conditions will be far from the laboratory:– Temperature could vary from -55 °C to +450 °C – Stress levels from -400 MPa to +400 MPa

Project: Electric Concept (1)

Engine Energy BalanceIN: Fuel

Electric Start

OUT: ThrustElectricity

Cabin Air

Distributed Hydraulics(electrically

driven)

ElectricalWing Anti-ice

AirNew APU

Design

Fuel Electrical Power for Cabin Air

Confidential - Rolls-Royce Proprietary InformationEngine Energy BalanceIN: Fuel

Electric Start

OUT: ThrustElectricity

Cabin Air

Distributed Hydraulics(electrically

driven)

ElectricalWing Anti-ice

AirNew APU

Design

Fuel Electrical Power for Cabin Air

Confidential - Rolls-Royce Proprietary InformationEngine Energy BalanceIN: Fuel

Electric Start

OUT: ThrustElectricity

Cabin Air

Distributed Hydraulics(electrically

driven)

ElectricalWing Anti-ice

AirNew APU

Design

Fuel Electrical Power for Cabin Air

Confidential - Rolls-Royce Proprietary Information

Project: Electric Concept (2) Picture courtesy of Rolls-Royce

Active Magnetic Bearing

High PressureStarter/Generator (HPSG)

Fan ShaftDriven Generator(FSDG)

Power Electronics

T500 Modified Engine

AC measurements for extreme conditions

• AC properties at 450 °C and 450 MPa

• Frequencies up to 30 kHz• Magnetic filed strength up

to 35 kA/m• Open circuit geometry

Tensile strength of FeCo24

0

0.2

0.4

0.6

0.8

1

1.2

1.4

25°C 25°C 300°C 450°C 600°C

Temperature

Tens

ile s

tren

gth

(GPa

)Monolithic Composite

MMC

Measurements of electrical steel strips under stress

Measurements of electrical steel strips under stress (2)

DC magnetic measurements of steels under applied uniaxial mechanical stress between –400 MPa and +400 MPa (2)

0

0.01

0.02

0.03

0.04

0.05

0.06

-400 -350 -300 -250 -200 -150 -100 -50 0

Cycle 1Cycle 2Cycle 3Cycle 4Cycle 5Cycle 6Cycle 7

Applied Stress [MPa]

Mag

netic

Flu

x D

ensi

ty [T

]

Example of an operational waveform

Definition of feedback

• There is a controller, which• Compares input and output signals, to• Minimise the difference between them

Non-linear elements

• Components of system• Specimen under test

Digital feedback (1)

• Realizes the concept of feedback by means of comparing numbers rather than analogue signals

Digital feedback (2)

• Block diagram

Performance

Magnetisation at 50 Hz, 1.5 T, conventional grain-oriented electrical steel. (The insets show the magnifications of the final part of the controlling process).

* S. Zurek, P. Marketos, T. Meydan, A. J. Moses, “Use of novel adaptive digital feedback for magnetic measurements under controlled magnetising conditions”,

IEEE transactions on magnetics, Vol 41, 4242-4249, 2005

Waveforms of B (sinusoidal – controlled) and H

Waveforms of B (sinusoidal - controlled) and H Conventional 0.27 mm thick, grain-oriented 3.0%SiFe electrical steel cut at 90O to the rolling direction, Magnetised at 50 Hz, 1.4 T

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

-1000 -800 -600 -400 -200 0 200 400 600 800 100

H (A/m)

B (T

)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

B (T

)

-1500

-1000

-500

0

500

1000

1500

H (A

/m)

BH

Waveforms of B (triangular – controlled) and H

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

0 5 10 15 20

time [ms]

B [T

]

-50

-25

0

25

50

H [A

/m]

B H

Waveforms of B (triangular – controlled) and H of Conventional 0.27 mm thick grain-oriented 3% silicon iron electrical steel Magnetised at 50 Hz, 1.3 T

Waveforms of B (trapezoidal – controlled) and H

Waveforms of B (triangular - controlled) and H of Conventional 0.27 mm thick grain-oriented 3% silicon iron electrical steel Magnetised at 20 Hz, 1.7 T

Dangers…

B = 1.8 T Mag. Freq. = 50 Hz

Form Factor = 0.29 % from 1.11THD = 7.5 %

B = 1.8 T Mag. Freq. = 50 Hz

Form Factor = 0.01 % from 1.11THD = 1.1 %

Conclusion

• Why we need to make measurements at operational conditions

• Tested in frequency range from 5 to 1000 Hz

• Capable of controlling arbitrary shape of flux density

• Time of convergence slow, but

– It can be minimised down to a few periods of magnetising frequency

THANK YOU