A measurement of rotation loss characteristics of high-Tc superconducting magnetic bearings and active magnetic bearings

Abstract

R&DcentA; KOYO SEMO CO, L m . No24-1, Kokubu, Higanjwh, Ibbimi, Osaka 5824023, J q m Ala~lwd -As the demand for elechic power has been incrrssiOg -, the introdwction of a Qwhd energy -age system 0 using a supemnducting magnetic bearing ( S m is needed to level daily bad as much as passible (daily load-leveling). We have studied rotation loss c m of SMB6 with high 'k supenmductors (YBCO) & permaneat magnets (PM) for supporting a nywheel in FESS We have designedandmanufhctuda~machineformeasuringmtalion laps characte-of SMBa The rotor is suspendd by two sets of ladial active magnetic bearings (1RaAMBs), a set of axial adive magnetic bear@ (AxAMB) and a set of SMR Then, we obtained dation loss cbal.rtcteristirs of the mtor levitated by RaAMEk, AxAMB and SMB on tbi3tegtingmachheIn order to allow the realization of a FESS, we recently performed some f m h n d a l studiesto clarify technical issues of a FESS. For example, a ptotype of 0.5kWh class FESS [l] was built. In such FESS, a sqemndudng magnetic bearing (SMB)7 its roGrtian loss ideally zero, being composed of high-Tc zupem-and permanent magnets, is used-So, it is necessary to clarify characteristics of SMB (spring constan& damping ca&icient, rotation loss).By the way, two kinds of structuresof SMB (AXSMB 8L R a S m ; sqem-Iwh a wostww and permanent magnetso.)SMB is mmposed of following three elements, YBCO weie suggested and it was reportedthat a spring umstantof AXSMB & RaSMB is practical but adamping d c i e n t is not sullicient [2]. In order to assist the damping fimdion of SMB, it is necesssnyto add adamping fkction of other devices (ex. M). On the other hand, there are some lhatum [3][4][5l that reported about the rotaton loss of SMB. ?hese literadures have reported w l y low loss of SMB, but under a special experimental condition. Inthis paper, we repoa rotadion loss c-. 'cs of RasMB (as well SMB) measured uder various load conditions. There are one SMB stator with sc and two SMB mtors with difxmt PMS having different magnib& of irregularity of magnetic density in M & d i r e c t i o n . We designed and man-a testing machine for a of rotaton loss c -'cs of SMBs. A cross section view of the apparatus is s h o w in Fig.1. ?his apparatus, composed of following parts, is in a vacuum chamk. A)a main shaft with PM attached at lower part, B)an inducton motor mounted at middle paa of a main shaft, c>two sets of radial active magnetic -s) mounted above and UIhder an induction motor, D)a set of axial active magnetic bearin&AxAIVlB) mounted at the upper part of the main shaft, E)SC(YBCO) & C/S(SUS304) mounted at lower part of main shaft. The SC and US are able to be moved in axial direction by a z-stage with aload-cell unit driven by a stepping motor: B. Pdornumce ofSMB SC contained in US was assembled firm eight pieces of bulk yBco(see in Fig.2). On the other hand, PM has thm layers magnetized in m w directon( ?, . 1 ;see in Fig.3). 'Ihe gap between SCandPMinradialdirectionis 1.4mmincludingaseal-plateofC/S. We tested the SMBs using two kinds of PM (Pr type:WMPr and...

Interaction of bulk superconductors with flywheel rings made of multiple permanent magnets

“…if the radius is increased twice, the total mass will be increased to 650 kg. In addition, the field variation of ±76.7 gauss at 15 mm gap was small enough to be applied to the application system [13]. It should also be noted that the field variation is caused by the presence of inner ring magnets for which the variation is large.…”

Numerical and experimental analysis of the rotation speed degradation of superconducting magnetic bearings

“…But the characteristics of measurement results were against the prediction derived from cause-A and B. Namely, the degradation was remarkably enhanced when the levitation force of the SMB increased [2]. Such an enhancement cannot occur due to cause-A and B, because the degradation by the inhomogeneous magnetic field of the PM rotor should be independent of the levitation force [3], [4].…”

“…Because the torque should be proportional to the rotation speed , the following equation is obtained, (2) where is the friction constant. From (1) and (2), the rotation speed is denoted by the following equations,…”

Effect of perimeters of induced shielding current loops on levitation force in melt grown single-domain YBa2Cu3O7−x bulk

“…Many efforts have been made on superconducting flywheel energy storage systems. [1][2][3][4][5][6] It is believed that the energy losses are as little as 0.1% per hour, and are only one tenth of that with conventional bearings. The commercialization of this technique will not only reduce the cost, but also make the electricity consumption more economical and reasonable according to our demands.…”