CERN-ACC-2013-0303 Author to contact: [email protected] Magnetic Materials for Current Transformers S. Aguilera, P. Odier, R. Ruffieux CERN, Geneva, Switzerland Keywords: Magnetic materials, Current transformers Abstract At CERN, the circulating beam current measurement is provided by two types of transformers, the Direct Current Current Transformers (DCCT) and the Fast Beam Current Transformers (FBCT). Each type of transformer requires different magnetic characteristics regarding parameters such as permeability, coercivity and shape of the magnetization curve. Each transformer is built based on toroidal cores of a magnetic material which gives these characteristics. For example, DCCTs consist of three cores, two for the measurement of the DC component and one for the AC component. In order to study the effect of changes in these parameters on the current transformers, several interesting raw materials based on their as-cast properties were selected with the annealing process used to tune their properties for the individual needs of each transformer. First annealing tests show that the magnetization curve, and therefore the permeability, of the material can be modified, opening the possibility for building and studying a variety of transformer cores. CERN-ACC-2013-0303 01/09/2013 Presented at the IBIC 2013 conference – Oxford/UK – 16-19 September 2013 Geneva, Switzerland December, 2013 Proceedings of IBIC2013, Oxford, UK MOPF24 MAGNETIC MATERIALS FOR CURRENT TRANSFORMERS 6$JXLOHUD3Odier55XIILHX[&(51*HQHYDSwitzerland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¶ PDJQHWLF SURSHUWLHV DQG FKDQJHVLQWKHVHSDUDPHWHUV RQWKHFXUUHQWWUDQVIRUPHUV WKHLQIOXHQFHRIWKHPDJQHWLFPDWHULDO¶VSDUDPHWHUVLQWKH VHYHUDO LQWHUHVWLQJ UDZ PDWHULDOV EDVHG RQ WKHLU DV-FDVW WUDQVIRUPHUUHVSRQVHLQRUGHUWRLPSURYHWKHLQVWUXPHQW¶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¶V DFFHOHUDWRU FRPSOH[ FXUUHQW WUDQVIRUPHUV ODPLQDWLRQDQGWKHWLPHFRQVWDQWGHSHQGHQWRQWKHPDVV KDYH EHHQ XVHG WR PHDVXUH WKH EHDP¶V FXUUHQW VLQFH WKH RIWKHFRUH>@ -3.0) ¶V1RZDGD\VWKHUHDUHDWRWDORIWUDQVIRUPHUVRXW RI ZKLFK DUH '&&7V DQG DUH )%&7V7KHUH DOVR The power loss of the material is proportional to the H[LVWVSDUHVIRU'&&7VDQGVSDUHVIRU)%&7V area of the hysteresis loop. It is interesting to study the (CC-BY change in the losses with increasing magnetization &XUUHQWO\WKHROGHVWLQVWDOOHG)%&7GDWHVEDFNWR 3.0 frequency, produced by the damping from Eddy currents DQG WKH '&&7 WR 7KHUH DUH DOVR GLIIHUHQW VL]HG >@ /RVVHV DUH DQ LPSRUWDQW IDFWRU WR WDNH LQWR WUDQVIRUPHUV LQ RUGHU WR DGDSW WR WKH GLIIHUHQW YDFXXP ution FRQVLGHUDWLRQ DV WKH PDJQHWLF FRUH ZLOO KHDW XS GXULQJ FKDPEHUGLPHQVLRQV RSHUDWLRQ 7KH PD[LPXP VHUYLFH WHPSHUDWXUH RI WKH PDWHULDO WKHOLPLWWHPSHUDWXUHDWZKLFKWKHPDWHULDOVWLOO Attrib 0$*1(7,&0$7(5,$/)25 KDV DOO RI LWV FKDUDFWHULVWLF SURSHUWLHV VKRXOG EH KLJKHU WKDQ WKH RSHUDWLRQDO WHPSHUDWXUH WKH PDWHULDO ZLOO UHDFK 75$16)250(5&25(6 ZKHQ WKH WUDQVIRUPHU LV LQ XVH ,Q RUGHU WR OLPLW WKH WHPSHUDWXUHLQFUHDVHDQGWKHSRZHUORVVGLVVLSDWHGLQWKH Commons e '&&7VFRQVLVWRIWKUHHPDJQHWLFFRUHVRQHIRUWKH$& PDWHULDOLQVXODWLRQEHWZHHQOD\HUVLVXVXDOO\HPSOR\HG v FRPSRQHQW RI WKH VLJQDO DQG WZR IRU WKH '& ZKLOH eati )%&7VFRQVLVWQRUPDOO\RIRQO\RQHPDJQHWLFFRUH7KHVH ,QVXODWLRQ LQ FRUHV FDQ EH GRQH LQ VHYHUDO ZD\V 7KH Cr FRUHV DUH PDGH RXW RI ZRXQG ULEERQ RI VRIW PDJQHWLF PRVW FRPPRQ DUH SURGXFLQJ WDSH ZRXQG FRUHV ZLWK DQ cc PDWHULDO 7KH FKRLFH RI PDWHULDO DQG LWV PDJQHWLF LQVXODWRU OLNH 'XSRQW70 .DSWRQ RU XVLQJ D FHUDPLF WR — FKDUDFWHULVWLFV IRU FXUUHQW WUDQVIRUPHUV DIIHFWV WKH LQVXODWH WKH OD\HUV 7KH ODWWHU SURFHVV FDQ EH GRQH E\ SDUDPHWHUVRIWKHWUDQVIRUPHUVXFKDVWKHUHVROXWLRQLQWKH PHDQV RI WKH 6RO-*HO PHWKRG E\ LPPHUVLQJ WKH ULEERQ oW FDVHIRUWKH'&&7 LQWR D VROXWLRQ WKDW EHFRPHV FHUDPLF DIWHU D WKHUPDO AC WUHDWPHQW>@ J by 7KH PDJQHWLF PDWHULDO LQ WKH WUDQVIRUPHUV XVHG DW &(51 ZDV VSHFLILHG IRU PDNLQJ WKH LQVWUXPHQW DV VHQVLWLYHDVSRVVLEOH)RUWKLVVRIWIHUURPDJQHWLFPDWHULDO 2013 c ZLWK D PD[LPXP UHODWLYH FRPSOH[ SHUPHDELOLW\ RI PRUH WKDQ KDV EHHQ XVHG 2WKHU FKDUDFWHULVWLFV VRXJKW ISBN 978-3-95450-127-4 Beam Charge Monitors and General Diagnostics 263 Copyright MOPF24 Proceedings of IBIC2013, Oxford, UK As can be seen from Table 1, iron-based alloys have a higher Curie temperature than cobalt-based alloys. 6KDS LQJWKH0DJQHWL]DWLRQ&XUYH For the different types of transformers, the requirements of the magnetization (B-H) curve are 7DEOH0DWHULDOV6XPPDU\ different. - '&&7V UHTXLUH D URXQG VKDSHG FXUYH ZLWK D &XULH &U\VWDOOL]DWLRQ 7\SH FRHUFLYHILHOGRIDERXW$P ZKLOVWWKH)%&7VUHTXLUH WHPSHUDWXUH>q&@ WHPSHUDWXUH>q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he Barkhausen Effect is a physical phenomenon Barkhausen Noise tests were performed following the which is manifested as a series of jumps in magnetization setup described in [5] for all the materials, but using a of ferromagnetic material when exposed to a varying triangular current for the driving solenoid. magnetic field. Surrounding the sample by a secondary coil, the induced voltage can be transformed into acoustic Figure 1 shows a comparison of the BN for cobalt- noise, from which the term Barkhausen Noise (BN) based amorphous materials. What can be seen is the derives [5]. voltage induced in the secondary coil surrounding the magnetic sample while it is subjected to the triangular This effect is often used as a non-destructive test to current. Time zero indicates when the pulse¶V YDOXH LV check changes in microstructure (grain boundaries, zero volts. As can be seen, most of the BN occurs around -3.0) dislocations, inhomogeneities, etc.) and stress this region, and drops to zero when the sample is configurations of materials. It is because of this, that this saturated. It has been observed that there is not a significant difference between them. (CC-BY technique offers a good overview of changes in magnetic domains. 3.0 It is clear that the BN influences the transformer ution performance and its resolution [6], therefore it is an interesting characteristic to study to see the effect of the Attrib WKHUPDOWUHDWPHQWRQWKH%1DQGWKHQRQWKHLQVWUXPHQW¶V response. Commons e v 6XP PDU\RI0DWHULDOV8VHG For this study, the materials used were iron-based eati amorphous and nanocrystalline alloys and cobalt-based Cr amorphous alloys. The iron-based alloys were purchased cc from Qinhuangdao Yanqin Nano Science & Technology — Figure 1: Barkhausen Noise response for amorphous Co., Ltd (http://www.yanqin.com), and the Cobalt-based cobalt-based materials (Nanoamor in green, Metglas in oW were purchased in Nanostructured & Amorphous red and VAC in blue). AC Materials (Nanoamor), Inc. (http://www.nanoamor.com), J Vacuumschmelze GmbH & Co. KG However, Figure 2 shows the difference between the by (http://www.vacuumschmelze.de) as VC 6025 G40 and iron-based amorphous and nanocrystalline and the Hitachi Metals Europe GmbH (http://www.metglas.com) Vacuumschmelze materials. As can be seen, the iron- 2013 as 2705M. c based materials present a lot more BN than the other sample and does not completely reach saturation as the ISBN 978-3-95450-127-4 Copyright 264 Beam Charge Monitors and General Diagnostics Proceedings of IBIC2013, Oxford, UK MOPF24 VAC material, which can be observed from the existence IXUWKHUDQQHDOLQJWHVWVVKRXOGQRWEHSHUIRUPHGRQWKHVH