Meeting customer requirements for ROEBEL cable for ac applications ROEBEL cable is a known approach to produce low ac loss, high current conductor/cable Conductor exposed to severe mechanical cutting at sharp angles 12 mm ROEBEL cable made by Forschungszentrum Karlsruhe with SuperPower 2G HTS Wire No failure, no delamination Only 3% loss in current from conductor to ROEBEL cable Cable engineering current density = 11,300 A/cm 2 Degradation in Ic in a ROEBEL cable can be due to mechanical defects caused by cutting or non-uniformity of current flow across width Useful to separate the two 4 mm I in I out mechanisms and study 4 mm 4 mm current flow across width by itself 4 mm 4 mm4 mm 9
Dependence of I c with different angles of current flow evaluated for ROEBEL application 300 12 mm wide 2G wire patterned in multiple segments for measurements of Ic at different angles of current flow Ic (A/cm) 250 200 150 100 50 0 Buffer -10 0 10 20 30 40 50 60 70 80 90 100 Angle between curent and tape length (deg) Tape 1 Tape 2 Tape 3 No systematically discernible Ic reduction in intermediate angles that are employed in ROEBEL conductor fabrication 10
Meeting customer performance requirements for joints: mechanical robustness proven in Production Mode At ASC 2006, we reported good performance of joints made in test lab. A customer required 1,200 m of 2G wire with 11 joints for a coil application. The Ic of entire wire length and resistance of all joints had to be tested after joining A production operation was developed to make consistently high-quality joints Also, the mechanical robustness of joints had to be established since the joined wire had to be moved through 4 and 2 diameter rollers in the 5 m transport Ic measurement rig at a speed up to 400 m/h Roller A (4 ) Roller D (4 ) Roller B (4 ) Roller C (4 ) Roller F (2 ) Roller E (4 ) Roller G (2 ) Voltage (Volt) 4.00E-05 3.50E-05 3.00E-05 2.50E-05 2.00E-05 1.50E-05 1.00E-05 1st test After running thru 4" roller 3 times After running thru 2" rollers 6 times 0 20 40 60 80 Current (A) 11
Ic measured every 5 meters over 1,218 m of wire with 11 joints 180 160 140 120 Location of joints Ic (A) 100 80 60 40 20 0 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100 1150 1200 1250 Position (m) Arrangement of the 12 segments along the length was decided based on communication with customer so that the Ic profile would fit the coil winding requirements 12
I-V curves of the 11 sections containing the joints 6.00E-04 g Voltage (Volt) 5.00E-04 4.00E-04 3.00E-04 2.00E-04 Joint#1: 70-75m Joint#2: 175-180m Joint#3: 250-255 m Joint#4: 350-355m Joint#5: 440-445m Joint#6: 560-565m Joint#7: 670-675m Joint#8: 760-765m Joint#9: 890-895m Joint#10: 980-985m Joint#11: 1120-1125m 1.00E-04 0.00E+00-1.00E-04 0 20 40 60 80 100 120 140 Current (A) All 11 joints show smooth transition at their respective Ic 13
Excellent resistance measured in all joints 6.00E-05 Voltage (Volt) 5.00E-05 4.00E-05 3.00E-05 2.00E-05 Joint#1: 70-75m Joint#2: 175-180m Joint#3: 250-255 m Joint#4: 350-355m Joint#5: 440-445m Joint#6: 560-565m Joint#7: 670-675m Joint#8: 760-765m Joint#9: 890-895m Joint#10: 980-985m Joint#11: 1120-1125m 1.00E-05 0.00E+00-1.00E-05 0 20 40 60 80 100 120 140 Current (A) All but one of the joints showed a resistance around 33 nω, One joint showed a resistance of 100 nω, still within limit 14
Customer-driven development of insulated wire Several customers, primarily for coil applications, required insulated 2G wire After evaluating a number of vendors, we procured a system for in-house fabrication of insulated wire System in place and being used for both 12 and 4 mm wide wire Preliminary test showed no breakdown at 1000 V with 0.0025 mm polyimide film Deliveries of insulated wire already being made. 15
Wire quality is confirmed after insulation After insulation, wire is not accessible for transport current measurements every 5 m in reel-to-reel test rig Non-contact Ic technique used to confirm the quality of wire after insulation 600 500 Non-contact Ic (A) 400 300 200 100 After insulation Before insulation 0 0 20 40 60 80 100 120 140 160 180 200 220 240 260 Position (m) 16
Summary SuperPower 2G HTS wire is being further developed with a variety of configurations through conductor design and engineering: Striation Dependence on current flow direction w.r.t. tape length (for ROEBEL conductor) Low-resistance joints High-quality insulation These new configurations make the wire more suitable for real-world electric power applications and promote the wide use of 2G HTS wire 17