26-29 Nov. 2003 - Superconducting magnetic levitated bearings for rotary machines Superconducting magnetic levitated bearings for rotary machines 5 th

26-29 Nov. 2003 - Superconducting magnetic levitated bearings for rotary machines

Superconducting magnetic levitated bearings

for rotary machines

5th International Symposium on Advanced

Nova University of Lisbon Electromechanical Motion Systems Marrakech

1

A Leão Rodrigues

[email protected]

Layout

Brief description of superconductor materials Calculation of magnetic levitation forces Journal magnetic bearings design Thrust magnetic bearings design Levitation experiment Conclusions

•Discovery of Superconductivity

Heike Kammerling Onnes in his Cryogenic Laboratory at

Leiden University, Holland, 1911



2

Hg

0,025

0,00

0,05

0,075

0,10

0,125

0,15

4o00 4o10 4o20 4o30 4o40T (K)

10-5

Onnes results

Resistence


Aiu

TV

Mercury

Thermometer

Liquid Helium

Onnes Experiment

• Magnetic Field Effect

Superconductor State

Normal State

0 Tc T

Hc

H(T) Magnetic Field

2

1c

c T

THTH

12

24

36

0 2 4 6 8

Hc

(kA

/m)

Leather (Pb)

Mercury (Hg)

Selenium(Sn)Indium(In)

Thallium (Tl)

T(K)

Low Temperature Superconductors (LTS), or 1st generation discovered until 1970.



3


Onnes Experiment

Aiu

TV

Material

Thermometer

Liquid Helium

H


Jc

Tc

Hc

Current density, J

Magnetic field, H

Temperature, T

0

Superconductivity region

Critical Surface

Region of normal state

• The superconductivity state of a material is destroyed if one of the following parameters are out of the critical surface:

• Critical superconductivity (TC)

• Critical magnetic field (HC)

• Critical current density (JC)

Lost of Superconductivity

SuperconductorI S

SI

J

Tc T

Superconductor state

Normal state

0

Jc

J(T) Current density

2

1c

c T

TJTJ



4


• Meissner Effect



5

Ferromagnetic

Magnet

R

Lpicoseconds

oI

Metal

t0

t

oeIti

t

oeIti

H

M

A superconductor is a diamagnetic material Negative magnetic susceptibility

Supercondutor

Magnet

R

L

• In 1933, Walter Meissner and Robert Ochsenfeld observed that the magnetic flux was expelled from the interior of the superconductor.

Supercondutor

Persistent current oI

Walter Meissner




6

Bardeen Cooper Schiffer

• BCS Theory• . In 1957 the scientists John Bardeen, Leon Cooper e John Schiffer, from Illinois University, presented a mathematical model that described the superconductivity phenomenon in the low temperature superconductors, called BCS theory.

F F

Cooper pair

Electron 1 Electron 2T < Tc

. Two free electrons when cooled down at temperature T<Tc are attracted forming a Cooper pair. Then, the pair travels through the crystalline structure without touching it and therefore finding no resistance.



7

H

Supercondutor

increasing

- M

HHc0Type I superconductor

H

M

Type I superconductors attain abruptly the normal state for a given critical magnetic field Hc

- M

HHc10 Hc2

increasing

Vortexes

H

Type II superconductor

Type II superconductors start attaining transition for a given critical magnetic field Hc1. Vortexes are

formed and for Hc2> Hc1

the superconductivity is totally lost.


Bednorz e Alex Muller, in IBM laboratories, near Zurique, in 1986.

Crystalline structure of La2CuO4

Transition curves of La2CuO4

Tc = 20 K

•High Temperature Superconductors (HTS)



8

• In 1986, George Bednorz e Alex Müller, from IBM laboratories in Rüschliko (Switzerland), discovered a ceramic composite based in lanthanum, which was superconductor around the transition temperature of 20 K.


•YBCO Superconductor (Yttrium, barium and copper oxide)

YBCO ceramic blocks

YBCO ceramic ringsYBCO ceramic disc

Paul Chu discovered YBCO in 1987 at the University of Huston.

Tc = 86 K



2

YBa2Cu3O7

Crystalline structure of YBCO

O

O

O

Ba

Ba

Y

Cu

Cu


• Superconductors evolution versus time



10

Liquid nitrogen 77 K




11

Superconducting Levitation Force

Superconductor

NdFeB Permanent Magnet

Superconductor


Superconductor materials applications

Evolution of the superconductors materials application

Source: ISIS – International Superconductivity Industry Summit.

1995 2000 2010 2020

Electronics

Energy - bearings

Transportation

Industry

Instrumentation



12

Year


LEVITATION FORCE CALCULATION

x

z(mm)0 2 4 6 8 100.1

1

10

100

HTS

REM z

YBCOBSCCO

Levitation force (mN)

Computed Experimental

t

Measured levitation force between a HTS and a REM versus vertical distance z



13

HTS material BmagnetJinduced

Permanent magnet

z

y

z

t

Levitation force

F

Liquid nitrogen

t (mm)0 5 10 15 20 25 0.1

5

10

BSCCO

Levitation force (mN)

15

20

HTS t

YBCO

REM

Thickness of bulk YBCO dependence on levitation force

z = 5 mm

n

i

n

i

r

mean

V

V

1

1

x

z

y

x

zyzxz

zyyxy

zxyxxor

z

y

x

dS

dS

dS

BBBBBB

BBB

BBB

BBBBB

B

df

df

df

2

2

21

22

22

22

Maxwell stress method




14


Journal magnetic bearing design



15

Shaft

HTS cylinder

NdFeB permanent magnet

f = 9.7 N/cm2

Force density distribution surface alongside the magnetic bearing

r

DB

A

F

o

s

24

3 2

Journal magnetic bearing layout

Shaft

Permanent magnet

Superconducting ring

Copper ring

g

Permanent magnet

Superconducting ring

Copper ring

Commercial journal magnetic bearing


Thrust magnetic bearing design

a) Lower part (HTS)

b)Upper part (PM)Layout of the thrust magnetic bearing

HTS blocks Stabilization

NdFeB blocksAir gaps

300

Thrust magnetic bearing flux plot

NdFeB NdFeB NdFeB

YBCO YBCO Liquid nitrogen

Levitator Thrust magnetic bearing



16

Liquid nitrogen


Magnetic Levitation



17


Conclusions



18

Maxwell stress method to evaluate levitation forces between a

permanent magnet and a YBCO superconductor under zero field

cooling was presented.

Results for magnetic pressures are of the order of 10 N/cm2. The method was applied to the design of journal and thrust bearings. These devices are now commercially produced and the market

expectation shows a broad and innovative potential of industrial

application.




20

Documents

26-29 Nov. 2003 - Superconducting magnetic levitated bearings for rotary machines Superconducting magnetic levitated bearings for rotary machines 5 th