BEHAVIOUR OF MULTIFILAMENTARY Nb-Ti CONDUCTORS WITH VERY FINE FILAMENTS UNDER A.C. MAGNETIC FIELDS

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BEHAVIOUR OF MULTIFILAMENTARY Nb-Ti CONDUCTORS WITH VERY FINE FILAMENTS

UNDER A.C. MAGNETIC FIELDS

P. Dubots, A. Février, J. Renard, J. Goyer, Hoang Ky

To cite this version:

P. Dubots, A. Février, J. Renard, J. Goyer, Hoang Ky. BEHAVIOUR OF MULTIFILAMENTARY Nb-

Ti CONDUCTORS WITH VERY FINE FILAMENTS UNDER A.C. MAGNETIC FIELDS. Journal

de Physique Colloques, 1984, 45 (C1), pp.C1-467-C1-470. �10.1051/jphyscol:1984195�. �jpa-00223751�

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JOURNAL DE PHYSIQUE

Colloque C1, supplkrnent a u n o 1, T o m e 45, janvier 1984 p a g e C1-467

BEHAVIOUR OF MULTIFILAMENTARY Nb-Ti CONDUCTORS WITH VERY FINE FILAMENTS UNDER AaC, MAGNETIC FIELDS

P . D u b o t s , A . FGvrier, J . C . Renard, J . C . ~ o y e r * and Hoang Gia KY*

Luboratoires de Marcoussis, C.R.

-

C.G.E., route LZe Nozay, 91460 Marcoussis, France

*Alsthom-AtZantique, 90001 BeZfort, France

Rdsume : D e s brins supraconducteurs multifilamentaires, c o m p o r t a n t plusleurs mil- h e r s de f i l a m e n t s d e Nb-Ti de 0 , 5 a I micron de d i a m e t r e , o n t kte' elaborks e n gran- d e s longueurs. C e s brins multifilamentaires, h m a t r i c e m i x t e Cu-Cu Ni ou a m a t r i c e e n t i e r e m e n t e n C u Ni d a n s la zone multifilamentaire, o n t d e s densltks de c o u r a n t

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critique e l e v e e s , a t t e i g n a n t 1,95 1 0 A / c m a 5 Teslas. Leur s t r u c t u r e leur conf6re une bonne stabilite magne'tique e t perrnet une t r e s f o r t e rdduction d e s p e r t e s

i

5 0 Hz C e s r e s u l t a t s p e r m e t t e n t d'envisager d e s a l t e r n a t e u r s dont le s t a t o r et le r o t o r se- r a i e n t I'un e t I'autre supraconducteurs e t , de f a ~ o n plus gknkrale, i l s ouvrent d e s perspectives e n t i e r e m e n t nouvelles d'applications industrielles d e l a supraconductivite e n r6gimes t r e s r a p i d e m e n t variables e t e n a l t e r n a t i f aux f r e q u e n c e s industrielles.

A b s t r a c t : Long lengths of multifilamentary Nb Ti composites, which comprise several thousands .5 t o 1 micron-diameter filaments, have been manufactured. These compo- sites, with a Cu-Cu Ni m i x e d - m a t r ~ x and some of t h e m with pure C u Ni b e t w e e n t h e filaments, c a r r y hight c u r r e n t densities u p t o 1.95 1 0 ,4/crn2 a t 5 Teslas. Their 5 s t r u c t u r e provides a good m a g n e t i c stability and l e a d s t o strongly reduced 5 0 H e r t z losses.

These r e s u l t s allow t o consider a l t e r n a t o r s with superconducting r o t o r and a r m a t u r e windings and, in a g e n e r a l way, t h e y open very new prospects for industrial applica- tlons of superconductivity in f a s t pulsed m a g n e t s and in A.C. c u r r e n t devices.

I. INTRODUCTION

The development of superconducting conductors for f a s t pulsed m a g n e t s and for A.C. cur- r e n t devices leads t o

z

revolution in the field of e l e c t r o t e c h n i c a l appGcation of s u q r c o n d u c - tivity. For about t e n years, s e v e r a l designs of such c o n d u c t o r s have been proposed /1,2,3/.

Thanks t o progress c a r r i e d o u t in t h e last f e w y e a r s in t h e manufacturing of superconducting composites, we have considerably leapt forward in t h a t field. The c o m p o s i t e s we manufac- t u r e d four y e a r s ago, s t a n d e d f o r a f e w t e n s of T/S a t f r e q u e n c e s of a f e w H e r t z

141.

Now, we a r e manufacturing c o m p o s i t e s which s t a n d for m a g n e t i c induction time-variations higher

*than 4 0 0 T/S and in which losses per c y c l e have been devided by 7 0 for 1.5 T peak variations a t 5 0 Hz.

In t h e following t h r e e paragraphs, we present t h e r e s u l t s we g o t a t 1983 s u m m e r which c o n c e r n t h e c h a r a c t e r i s t i c s and c r i t i c a l c u r r e n t densities of t h e composites, t h e m a g n e t i c stability and 5 0 Hz short sample quenching current, and 5 0 Hz losses in t h e c o m p o s i t e s m e a s u r e d on t w o coils.

11. CHARACTERISTICS AND CRITICAL CURRENT DENSITIES OF THE COMPOSITES C h a r a c t e r i s t i c s of t h e c o m p o s i t e s

Basic studies on interdiffusion phenomenas in Nb Ti c o m p o s i t e s and o n t h e inner s t r e s s e s d i s t r i b u t ~ o n during cold-drawing, allowed us, t h r e e y e a r s ago 161, t o control t h e rnanufactu- ring of 1.25 mm-diameter c o m p o s i t e s which comprise several thousand 5 microns-diameter f i l a m e n t s in a Cu-Cu Ni mlxed matrlx.

For f a s t pulsed m a g n e t s and A.C. c u r r e n t devices, one needs t o lower m o r e t h e d i a m e t e r of t h e f i l a m e n t s and t o r e d u c e t h e t w i s t pitch length and t h e transverse e l e c t r i c a l

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984195

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C l -468 J O U R N A L D E PHYSIQUE c o n d u c t i v i t y of t h e m a t r i x . With t h e

e,im t o d e v e l o p Nb Ti c o m p o s i t e s for t h e s e applications, we designed c o m - p o s i t e s w i t h new s t r u c t u r e s and wc worked o u t t h e i r m a n u f a c t u r i n ~ , in long l e n g t h s of t h e o r d e r of a t h o u -

sand m e t e r . T h r e e cornposite g e n e - r a t i o n s have been m a n u f a c t u r e d : - 0 . 3 m m - d i a m e t e r c o n l p o s i t e

which c o m p r i s e s 1 3 0 6 8 1.3 rnicron- d i a m e t e r f i l a m e n t s in a Cu-Cu Ni m i x e d - m a t r i x .

- c o m p o s i t e s which c o m p r i s e f r o m s e v e r a l thousand t o s e v e r a l t e n

t h o u s a n d 0 . 5 t o 1 m i c r o n - d i a m e t e r T.L.I. I - P O ~ O - . ~ . . S or t h e co-~o,.te.

f i l a m e n t s .

- 0 . 1 2 m m - d i a m e t e r c o m p o s i t e s , which c o m p r i s e 14496 0 . 5 5 m i c r o n - d i a m e t e r f i l a m e n t s in a C u 3 0 At. % Ni m a t r i x and a Cu-Cu Ni c e n t r a l c o r e .

F i g u r e 1 shows a view of t h e b e s t c o m p o s i t e m a n u f a c t u r e d u p t o now, whose c h a r a c t c - r i s t i c s a r e given in t a b l e I.

C r i t i c a l c u r r e n t d e n s i t i e s of t h e c o m p o s i t e s

T a b l e 11 g i v e s c r i t i c a l c u r r e n t d e n s i t i e s of d i f f e r e n t m a n u f a c t u r e d c o m p o s i t e s . Up t o now, m a n u f a c t u r i n g p a r a m e t e r s ha1.e only b e e n o p t i m ~ z e d for 0 . 3 m r n - d i a m e t e r coniposites, w i t h

5 2

1 3 0 6 8 f i l a m e n t s , which c a r r y high c r i t i c a l c u r r e n t d e n s i t i e s : 1.95 1 0 A/c:m a t 5 Teslas.

111. MAGNETIC STABILITY AND 5 0 HZ. SHORT SAMPLE QUENCHING C U R R E N T It i s well known t h a t a good m a g n e t i c s t a b i l i t y c a n be a c h i e v c d w i t h a high r e s i s t i v i t y m a t r i x by lowering d i a m e t e r s of t h e f i l a m e n t s and of t h e c o m p o s i t e s . This i s i l l u s t r a t e d on f i g u r e 2 which p r e s e n t s s t a b i l i t y d o m a i n s of B 3 1 / 3 3 0 0 and H15/14496 c o m p o s i t e s a s a f u n c t i o n of t h e d i a m e t e r s of t h e f i l a m e n t s and of t h e c o m p o s i t e s . T h e c h a r a c t e r i s t i c s of t h e s e c o m p o - s i t e s a r e given on t a b l e I f o r a d i a m e t e r of 0 . 1 2 r~irn. It c a n be s e e n t h a t a good m a g n e t i c s t a b i l i t y i s a c h i e v e d on t h e whole m a g n e t i c i n d u c t i o n ran'e w i t h f i l a m e n t d i a m e t e r s l o w e r t h a n I micron. For a given m a g n e t i c Lnduction,

t h e r n a g n e t i c s t a b i l i t y of t h e B15/14496 c o m - posite i s a c h i e v e d w i t h s m a l l e r f i l a m e n t s t h a n for t h e B 3 1 / 3 3 0 0 c o m p o s i t e since, f o r a given f i l a m e n t d i a m e t e r , t h e B15/14496 c o m p o s i t e h a s a higher d i a m e t e r .

l u b l . II - C r l t l c o l c u r r e n t d.nsitr o f the conooslt..

Figure 1 - 13 15/14496 co!nposite.

S h o r t s a m p l e m e a s u r e m e n t s on t h e t\15/14496 c o m p o s i t e , a t a d i a m e t e r of 0 . 2 rnm, h a v e shown t h a t t h e 5 0 Hz. q ~ e n c h i n g ~ c u r r c n t i s very c l o s e t o t h e D.C. c r i t i c a l c u r r e n t a t .I pV/cm.

IV. 5 0 HZ. LOSSES IN T H E COMPOSITES

5 0 Hz. losses have been m e a s u r e d o n t w o coils wound from t h e O.3Q rnm-diameter B 1 2 / 1 3 0 6 8 c o m p o s i t e for t h e f i r s t one, and f r o m a cable made of t h r e e 0.12 m m - d i a m e t e r B15/14496 c o m p o s i t e s for t h e second one. T a b l e 111 g i v e s p a r a m e t e r s of t h e s e c o i l s a s also

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o f t h e coil t e s t e d by HLASNIK a n d SElBT 171, made of t h e DC/14496 composite.

C/13068 c o i l

3 .

1

This coil have been t e s t e d a t 4.2 K under several cooling conditions in which t h e o u t e r layer of t u r n s w a s in close c o n t a c t with t h e helium b a t h o r

I

insulated f r o m i t by "mylar" layers.

I

^.

,

^-

I

-

,.,,

⁹⁶^;,

'

The D.C. quenching c u r r e n t i s 8 0 A, e q u a l t o t h e short sample c r i t i c a l current. The 5 0 Hz. s t e a d y s t a t e peak value quenching c u r r e n t i s 7 0 A under t h e b e s t cooling conditions ; t h i s value which i s only 12.5 % lower t h a n t h e D.C. quenching c u r r e n t , i s r e l a t e d t o a 0 . 6 K h e a t i n g of t h e wire. Under bad cooling conditions, t h e 5 0 Hz. peak , i value quenching c u r r e n t i s 5 0 A and is

r e l a t e d t o a 1.9 K h e a t i n g of t h e wire.

5 0 Hz. losses of t h i s coil a r e presented

Figure

2

- Stability domains of B31/3300 and

on figure 3 which shows a very good

B15/14496 composites as a function o f the magnetic

agreement b e t w e e n measured and cal-

induction

US

the diameter of the filaments

c u l a t e d values /5/. The 1 0 % gap, in t h e

and the diameter of the composites

high c u r r e n t range, i s due t o t h e h e a t i n g

of t h e coil which h a s not been t a k e n i n t o a c c o u n t in a preliminary calcula- tion. A t 7 0 A, 0 . 9 4 T peak value ma- g n e t i c induction, losses a r e e q u a l t o 3 1 0 w/m3, of which 3 0 5 % a r e hyste- r e t i c losses, 5 5 % e d d y c u r r e n t losses b e t w e e n f i l a m e n t s and 15 % e d d y cur- r e n t losses in t h e c e n t r a l core. Surroun- ding s h e a t h losses a r e negligible.

C/14496 c o i l

s.. ^I- TM cab^. is transwsrd r l t n patch 1 . ~ 1 ' o l 4

-.

This coil h a s been wound with . 6 x l m m 2

,able III - D I . . ~ . I ~ ~ . a n d polo..t..s .r the t e s t COIL.. c h a n n e l s b e t w e e n e a c h l a y e r t o a c h i e v e a v e r y good cooling. The D.C. quenching c u r r e n t is 42.8 A, equal t o t h e s h o r t s a m p l e c r i t i c a l c u r r e n t . The 5 0 Hz.

...

-

H"s'.,.~.~ I-,.. s t e a d y s t a t e peak value quenching cur-

E d y eurr.," b".. r e n t i s e q u a l t o 41.15 A ; this value

be,.r.-...

.=,I-.-

which i s only 4 % lower t h a n t h e D.C.

--- ^{E d d y}c u r - q r *.-

," ,h. loo., cer. c r i t i c a l c u r r e n t , i s r e l a t e d t o a 0 . 2 K h e a t i n g of t h e wire. For t h e maximum value of t h e c u r r e n t , t h e m e a n v a l u e of t h e r a t e of variation of t h e m a g n e t i c induction i s e q u a l t o 329 T/S, i.e.

517 T / S maximum r a t e .

5 0 Hz. losses of t h i s coil a r e p r e s e n t e d on figure 4 which shows t h e s h a r p rajuc- tion o f losses obtained with B15114496

0.2 4 4 0.6 0.8 I composite. A t 37.5 A, 1.5 T peak value

B nos (rJ m a g n e t i c induction, losses a r e e q u a l t o

5 3

Figure 3 - 5 0 Hz. losses in the B2/13068 cornposite

1.4 1 0 W/m

.

[C/l3068 coil

-

see table

I l l ]

Volume of c o n d u c t o r f o r 5 0 Hz. losses l i m i t e d to 1 kW

For feasibility studies of A.C. superconducting equiprnents, loss level i s t h e major p a r a m e t e r of which depend conductor cooling conditions, r e f r i g e r a t o r s i z e and t h e i n t e r e s t of t h e cryo- g e n i c solution. Figure 5 shows t h e i n c r e a s e of conductor volurne, which c a n be used a t 5 0 Hz.

with a I kW cold r e f r i g e r a t i o n power, we o b t a i n e d during t h e l a s t four years. A t 0.7 T peak value, t h i s volume has been increased from 0.25 l i t e r in 1979, with t h e C A I 3 3 0 0 composite

C o i l ,

I me, d1oaet.r 1-1 O u t e r dlome1.r 1-1 C o l l l s n p l h 1-1 Hu.6.. o f turn.

C o n d u c t o r

c o n d u c t o r I . n p t h 1.1

~ . ~.oo.toot ~ t t(?/A, ~ ~ (Ilo. .ol.. o n the

c o n d u c ~ o ~ ~

C 11068

5 7 . 5 80 4 x 2 1 5 8 2 / 1 3 0 6 8 *

1 8 . 5 1.11 l o - 2

"lASH11:

o n d s t 1 8 1 1 1 1 1

I

1 0 4 x 2 4 1 B G I 1 1 6 9 6 '

1 9 . 0 1

C 14476

6 2 4 27 1 2 x 8 5 C o b l s - 1 l h 3 ~ 8 1 5 / 1 4 4 9 6 ~ ..re3

4 8 4 1 0 - 2

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C1-470

JOURNAL DE PHYSIQUE

dB-+, [rh) 141, t o 2.2 l i t e r s i n 1982, with t h e BC114496 conlpo-

site, and t o 14 l i t e r s in 1983 with t h e B15114496 c o m - posite. At 5 T peak value, t h e i m p r o v m e n t i s more t r e m e n d o u s since t h i s volume h a s been multiplied by 3 0 0 b e t w e e n 1979 and 1983.

1 # , A )

^V.

CONCLUSIONS

The results, which have been obtained o n new Nb Ti c o m p o s i t e s during t h e l a s t months, show t h a t t h e pos- sibility of applications of superconductivity in A.C.

c u r r e n t e q u i p m e n t s b r e a k s out. Most i m p o r t a n t r e s u l t s of our s t u d i e s c a n be s u m m a r i z e d a s follow :

- High c r i t i c a l c u r r e n t densities have been achieved

5 2

on very fine Nb Ti f i l a m e n t s : 1.95 1 0 A/cm a t 5 T.

- Good m a g n e t i c s t a b i l i t y h a s been o b t a i n e d without C u b e t w e e n t h e filaments, providinn t h a t f i l a m e n t and composite d i a m e t e r s a r e small Gnough.

Figure

- H z . losses

in BG/144967

- Cooling condition of t h e conductor i s a major para-

B2/13068 and B 1 5 / 1 4 4 9 6

m e t e r f o r superconducting c o m p o s i t e A.C. use. Thus,

5 0 Hz. s t e a d y s t a t e losses, under 1.5 T peak value m a g n e t i c induction, a r e e q u a l t o 1 4 0 W/liter in o u r best composite. We guess t o develop n e w coniposites in which losses should be LO t i m e s lower t h a n k s t o a suitable c h o i c e of f i l a m e n t s and c o m p o s i t e d i a m e t e r s , of the t w i s t pitch length and o f t h e composite s t r u c - ture. The r e s u l t s we obtained allow t o consider a l t e r - n a t o r s with superconducting r o t o r and a r m a t u r e windings and, in a g e n e r a l way, t h e y o p e n very new pros- p e c t s for industrial applications of superconductivity in f a s t pulsed m a g n e t s and in A.C. c u r r e n t d e v i c e s 181.

with good cooling conditions, t h e 5 0 Hz. quenching

dB-s/d, ( ~ h )

1 lA&hw 1 Ahnowledgment

The authors thonk

J . P .

TAVERGNIER,

C. BOTTINI and W .

WEBER for their assistance in obtaining the repor-

0.1 I

ted experimental results.

Bmo. (11

Figure

5 -

Superconducting conductor volume which can

be

used a t 5 0

Hz.

with a

1

kW cold refrigeration power.

F

^Jf+

/ I / FEVNlEH A. - Comportement lhermique d'un bobinoge supmconducteur impr6gnd en regime w r i a b l e , Thdse Paris-Sud (1974) /2/ HLASNIK I. - Review on AC losses in superconductors, MT7 Karlsruhe (1981)

/3/ OCASARAW T. and al. - Low l o ~ s Nb-Ti multifilamentory composite conductor for AC. use, IEEE Vol. M o p 19 no 3 (1983) /4/ FEVRlEX A. and al. 8 t h internotlonol cryogentc engineering conference, G e n o w , (1980)

/5/ FEVRIER A. - Losses in a twisted multifilamentary superconducting composite submitted t o any spoce and t i m e w r i a t i o n o / the electromagnetic surrounding, Cryogenics, ~ p r i l 1983, p 185.

/G/'DUBOTS P. and 01. 8 th. international cryogenic engineering, conference, C e n o w , (19801.

/7/ HLASNIK t, SEIBT E.W. : 5 0 Hz. o c losses In znductlve coifs w i t h mixed matrix fine filament N b T i composites a t fields up t o I Tesla t o be publlsh&d (1983).

/8/ SABRIE J.L. - Feasibility of large A.C. superconductivity equipments (This Conference).

c u r r e n t of t h e coil wound from our best composite i s only 4 % lower than t h e D.C. quenching c u r r e n t .

fLIC I570

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