Download M.D. Sumption, J. P Murphy, N N. Gheorghiu, T. Haugan, M. Majoros

AC loss in YBCO Conductors and Cables at High dB/dt Measured using a Spinning Magnet Calorimeter (Stator Testbed Environment)
M.D. Sumption4, J. P Murphy1,2, N N. Gheorghiu2,3, T. Haugan3, M. Majoros4, and E.W. Collings4
1 University of Dayton Research Institute, Dayton, OH 45469-0073 USA
2 Universal Energy Systems, Dayton, OH 45432 USA
3 Aerospace Systems Directorate of the Air Force Research Laboratory, Wright-Patterson AFB, 45433 USA
4 CSMM, Department of Materials Science and Engineering, The Ohio State University, Columbus OH 43210 USA
2. The SAM machine structure and materials used
Figs. 1 and 2. Configurations
•
of the SAM machine
•
•
•
•
3. AC loss and Calibration
the normal metal eddy
current loss :
𝑃𝑒𝑑,𝑣=
𝐵𝑚𝑎𝑥 𝑤𝑓 2
𝜋2
[
]
6𝜌𝐶𝑢
power loss per unit length ∶ 𝑃𝑡𝑜𝑡,𝐿 =
𝑤 𝐼𝐶 𝐵𝑚𝑎𝑥 𝑓 +
𝐵𝑚𝑎𝑥 𝑤𝑓 2
𝜋2
[
] 𝑤𝑡𝐶𝑢
6𝜌𝐶𝑢
*Originally from the work of Brandt
[2,3] and then in a modified form in
Muller [4]
• First, the calorimeter was filled with LN2 as was the outer can of the
double wall calorimeter. With the resistor excited with DC current and the
current and voltage recorded the flow rate of the nitrogen gas boil-off, GF,
was measured by the flowmeter in standard liters per minute (SLPM).
• the smaller one is for one- watt
resistors soldered in series (each
33 Ω at room temperature and
126.6 Ω at 77 K)
• the larger one includes two
aluminum plates with a total
surface area of 90 x 39 x 5 mm
surrounding a Kapton film heater
(Omega #KHLV 103/5-P,
Figure. 3. Calibration of calorimeter. P(W) =
measuring 51.3 Ω at 77 K).
-0.0096+2.7581*GF + 1.0575*GF2 -0.2346*GF3
References & Acknowledgement
Fig. 4. Power Loss for YBCO tape
samples 2 and 3. Black line is
Brandt equation fit with Ic = 38 A,
and red line includes eddy current
contribution for RR (77 K) = 4.0.
20
YBCO-2A
YBCO-2B
YBCO-2C
YBCO-2D
15
10
5
0.30
0
0
0.25
50
100
150
200
250
dB/dt, T/s
Large Heater
Small Heater
0.20
P/(LBf)
Power, P, Watts
6
0.15
YBCO-1, 50 Hz
YBCO-1, 75 Hz
YBCO-1, 100 Hz
YBCO-1, 150 Hz
YBCO-1, 200 Hz
YBCO-2-A
YBCO-2-B
YBCO-2-C
YBCO-2-D
4
0.10
2
0.5
1.0
Gas flow, SLPM
1.5
2.0
YBCO-3A
YBCO-3B
YBCO-3C
YBCO-3D
YBCO-3E
YBCO-2A
YBCO-2B
YBCO-2C
YBCO-2D
CORC-1 *Pi/2
CORC-2 *Pi/2
CORC-2*Pi/2
20
YBCO-3A
YBCO-3B
YBCO-3C
YBCO-3D
YBCO-3E
YBCO-2A
YBCO-2B
YBCO-2C
YBCO-2D
CORC-1
CORC-2
CORC-2
15
10
15
10
5
5
0
0
50
100
150
200
250
0
0
50
100
150
200
dB/dt, T/s
250
dB/dt, T/s
Fig. 6. . CORC cable loss per
unit meter of tape, as
compared to tape loss per unit
meter of tape. CORC cable was
oriented horizontally.
Fig. 7. CORC cable loss per unit
meter of tape multiplied by the
factor /2
5. Summary
8
0
0.0
20
• Samples were striated
• L = 10 cm, untwisted
Power, P, W/m
the hysteretic loss :
𝑃ℎ𝑦𝑠,𝑣≈𝑤𝐽𝑐𝐵𝑚𝑎𝑥𝑓 *
8-pole permanent magnet rotor. in a
Halbach configuration.
The N-S-N variation of the poles around the
rotor periphery are consistent with the N-SN arrangement of the magnets aligned
along 𝜃.
This test instrument has a 1.5 inch annular
gap to permit placing HTS samples or test
windings for exposure to a high dB/dt
environment.
Outside of this region, the presence of the
back-iron allows the sample or coil to be in
a field which is relatively uniform along the
radial direction but changing with time (or
angular position).
The SAM machine is under vacuum during
operation to minimize heat leak to the
calorimeter, and any accompanying LN2
boil-off
baseline.
4. Results
Power, P, W/m
o Numerous important applications, such as motors, transformers, of
superconducting wires and cables are used under rapidly changing magnetic fields.
o Turbo-electric distributed power aircraft design calls for a motor/generator set to
deliver power to motor-driven fans positioned along the wings. There is some
power loss associated with the conversion, this is more than made up for by the
increased efficiency by what is in effect an enhancement of the fan by-pass ratio.
o YBCO coated conductor is of great interest because of its high Tc (90 K), and its high
critical current density. However, it has significant AC loss in these environments
because of its wide tape geometry. In addition it is difficult to fabricate the
filamented types favored for hysteretic loss reduction.
o Existing test devices have serious limitations: they can either reach the target B or
the needed dB/dt, but not both simultaneously. In this work, we discuss the
development of a machine (Spin- Around-Magnet, SAM) which can provide both
an acceptably high B as well as dB/dt for the needed study and analysis of coated
conductors (and small windings) required for the windings of motors and
generators.
o Good agreement was obtained between the results of the SAM AC loss
measurement and the solenoidal magnet AC loss measurement . This more
detailed work is based on our previous work[1] on the machine.
Power, P, W/m
1. Introduction
0.05
0.00
0
10
20
30
Bf, T/s
1. J.P. Murphy, M.J. Mullins, P.N. Barnes, T.J. Haugan, G.A. Levin, M.Majoros, M.D. Sumption, E.W. Collings, M.Polak,
and P. Mozola, “Experiment Setup for Calorimetric Measurements of Losses in HTS Coils Due to AC Current and
External Magnetic Fields”, IEEE Trans. Appl. Supercond. 23 (2013) 4701505.
40
50
60
Fig. 5. Power loss (per unit length)
normalized by B*f vs B*f for SMC
(shown in red) (YBCO-2) and
solenoidal susceptibility rig (shown
in black, for YBCO-1).
• A new facility for the measurement of AC loss in
superconductors at high dB/dt has been developed. In
addition, the relatively large sample space will allow the
insertion of small windings, which will effectively allow a
small scale generator test bed for prospective
motor/generator coils.
• The radial and tangential fields are approximately sinusoidal,
90Ω out of phase, and with peak amplitudes of 0.566 T for
the radial direction, and 0.242 T for the tangential direction.
• The rotor can reach 3600 RPM, the frequency 240 Hz, the
radial dB/dt 543 T/s, and the tangential dB/dt 249 T/s.
• Loss is measured using nitrogen boiloff from a double wall
calorimeter feeding a gas flow meter.
• The data for all samples agreed well, and the range of the
data spread for a given ramp rate was ± 5%.
This work was supported by the Air Force Office of Scientific Research
(AFOSR), the Air Force Research Laboratory, and the Summer Faculty
program at WPAFB.
2. E.H. Brandt, M. Indenbom, Phys. Rev. B 48 (1993) 12893
3. E.H. Brandt, Phys. Rev. B 49 (1994) 9024
4. K.-H. Muller, “AC power losses in flexible thick-film superconducting tapes”, Physica C 281 (1997) 1-10