75 unit: mm Fig. Structure of model three-phase stacked transformer cores (a) Alternate-lap joint (b) Step-lap joint 3 4)

3 * 35 (3), 7 Analysis of Local Magnetic Properties and Acoustic Noise in Three-Phase Stacked Transformer Core Model Masayoshi Ishida Kenichi Sadahiro Seiji Okabe 3.7 T 5 Hz..4 3 Synopsis: Methods of local measurement and analysis of magnetic properties and vibration and noise levels in a three-phase stacked transformer core were developed and applied to the evaluation of the influence of core structure and material on these properties. Inhomogeneous distribution of local flux density arising from rotating flux and circulation flux in the vicinity of core joining parts and local iron loss distribution caused by them were quantitatively clarified. The building factor at.7 T, 5 Hz was evaluated by using a T-joint simulation model measurement and magnetic field analysis using an integral element method. It was. by the former method and.4 by the latter, both in good agreement with practical values. Local vibration and noise level in the same core were measured, and the influence of core structure and material on the distribution of vibration and noise in the vicinity of core joining parts was clarified. CO,) 3,4) 5) (BF) 5) BF * 4 5 5 7) 8) 9 ) 3 3 BF 3 V T,3) BF

75 unit: mm 75 75 5 5 5 5 5 5 75 5 5 5 5 Fig. Structure of model three-phase stacked transformer cores (a) Alternate-lap joint (b) Step-lap joint 3 4) 4 3,4) 5,5 7) 5 3. 3 Table Fig. 3 V 6 kg 75 mm 6 6 JIS 8). Fig. 9,) / Table Specifications of model three-phase stacked transformer cores Joint geometry Number of steps Shift length Number of laminations/unit lap Total number of laminations Total core weight Needle probe Hall probe Flux Fig. V Amplifier Magnetic field Eddy current Integrator Alternate lap Amplifier Step-lap 6 mm mm 5 44 ca. kg Iron loss W loc ( area) Magnetic field, H Principle of local iron loss measurement using needle probes and a Hall probe x y x y 5 mm. mm.5 mm 3 B H x W x y W y W d W d (f/ρ) H db W x W y () W i (f/ρ) H i db i (i: x, y) () f ρ Flux density, B

//RD B x FS:.5 T //TD B x W (W/kg) H x FS: A/m H x.5..5..5. //TD B y //RD B y (a) Before PJ irradiation (b) After PJ irradiation H y H y Fig. 5 Change in iron loss distribution in stacked core by plasma-jet irradiation (The dotted triangle shows the plasma-jet irradiated area) Fig. 3. T W d (W/kg) y.5..5..5. Example of measured -dimensional iron loss distribution in stacked core using 3New x,) V Fig. 5 V 3 V 45.5 T.8 T Fig. 4.3 3 W d (W/kg).5..5..5. Change in iron loss distribution in stacked core with excitation flux density 3New 3 V T W d Fig. 3 V 45 V B-H x y (RD) (TD) V Fig. 4. T V 3 3 T 3. T 3 T 5 7) T T,3) T Fig. 6 3 V T U V W B Fig. 6 8 mm Exciting coil W B-coil 8 mm V Local flux sensor U Yoke Specimen Simulation model for T-joint part of three-phase stacked core

. Fig. 7 T T Distribution of flux density loci measured in the T-joint simulation model Fig. 9 Local flux density,. f e. d f e d.. 5 5 Time, t (ms) Measure distortion in local flux density waveform in the V leg Iron loss (W/kg)..8.7.6.5.4... Distortion factor.3.8.4..6..8.4. Fig. 8 Estimated rotation iron loss distribution in the T-joint part Fig. Distribution of distortion factor in local flux density waveform measured in the V leg 5 mm 3. T.7 T 5 Hz T Fig. 7 35.35 mm W 7/5.7 W/kgV.8 T B L B C.7 T 5 Hz Fig. 8 B C.8 W/kg.34 W/kg.7 W/kg 5 T.7 T 5 Hz.5 3.3 T BF V 3 Fig. 9 V T 3 B L Fig. B L D k D {h e(k /.) } / (3) h e 46.7 T 5 Hz D U.7 V.3 W.4 U W V V.7 T 5 Hz 5 BF...3 BF,9) 4 ) 4) 3 Fig. 3.3 mm 3New.3 mm (B-H) V Fig. V V New New

..... New. Fig. Loci of rotational flux density around T-joint part of 3-phase stacked core Fig. Fig. 3 New New New (4) (5) (6) W L W(B L ) W C W(B C ) x// h e k. h e k. y// 75 mm Mesh structure of analysis model for stacked 3-phase transformer core / (4) / (5) W total W L W C (6) W(B L ) W(B C ) y x h e 5 k db/dt BF.4 New BF New 9) T 3 55 ) 5 3 3,4) 5. 3 mm JIS A )

.......... Fig. 3 Flux density waveforms around T-joint part of 3-phase stacked core New.. 3 db. MPa 5. 3 6,7).7 T 5 Hz 3 Fig. 4.3 mm 3 3New db New.7 T 5 Hz 3 Fig. 5 3New 3 4 Hz 6 Hz (A, E) (C) Hz (C) Hz 3New.7 T 5 Hz 3 Fig. 6 Fig. 4 Fig. 5 Fig. 4 Conventional lap joint New Step-lap joint New Acceleration level 75 7 65 6 db Distribution of normal vibration acceleration level measured in the surface of a 3-phase stacked core using.3 mm thick material Frequency (Hz) Fig. 5 8 6 4 8 6 4 A B C D E 3 4 5 6 7 Position (mm) Noise level (db) 8 7 6 5 4 Distribution of noise level harmonic intensity measured in the slit side of the yoke part

Fig. 6 H x H y H z y z x H (Oe) Distribution of normal vibration acceleration level measured in the surface of a 3-phase stacked core using.3 mm thick material Microphone Precision Sound level meter 75 Noise level (db) 7 65 6 55 5 A B C D E Alternate lap; clamping pressure. MPa 7th superposed 5th superposed Sinusoidal.7 T, 5Hz A B C D E 3 4 5 6 7 8 9 3456 Position 5.3 Fig. 7 Distribution of local noise level measured in a stacked core using 3RG.7 T 5 Hz 5 7 3 Fig. 7 3New. MPa (A, E) (C) db 5 C 3 db 7 C 6 () 3 () 3 T (3) 3 (4) 3 ) 999/ (999) ) II 76 (988) 3) 575 (995) 4) 575 (996) 5) II 85 (979) 6) B. Thomas: IEEE Trans. Magn., (975), 65 7) B. Fukuda, K. Sato, Y. Shimizu, and Y. Ito: J. Appl. Phys., 55(984), 3 8), MAG-83-54 (983) 9) A, 5(995), 5 ) A, 7(997), 94 ) MAG-96-5 (996) ) MAG-97-84 (997) 3) (998), 73 4) 33()3, 3 5) MAG- 93-87 (993) 6) MAG-95- (995) 7) 9(997)3, 64 8) JIS C 55(996) 9) 9(997)3, 77 ) ELF/MAGIC ) 9 S9-5 (997) ) JIS C 55 (988)