1
Commercial Design and Performance Test of Large-sized HTS
Magnets with Conduction Cooling System for MW-class HTS DC
Induction Furnace
supercoil
supercoil
2016. 09.13 (Tue.), 14:45 ~ 15:00, in CCA 2016
Presenter : Jongho Choi
Super coil in Korea
Contents
2 /26
Super coil
I.
Introduction of the HTS DC induction furnace
II. Design specification of the HTS magnets and the 300 kW HTS DC IF
III. Fabrication process of the HTS magnets with the conduction cooling system
IV. Current flowing test results of the HTS magnets
V. Conclusions
Conventional Furnaces in industries
3 /26
Super coil
 These are available for the preheating process of the metal billets, in order to producing parts for
the airplanes, automobiles, and electric power machineries.
▲ Aluminum extrusion plant
located in Gyeongnam
▲ Gas furnace for busbar
▲ Forging company located in
Gyeongnam
Why we need to develop the HTS DC induction furnace
4 /26
Super coil
 The system efficiency is possible to reach over 90%.
Resistance
 Comparison with several induction heating methods
Normal conductor
Superconductor
0K
Tc Temperature
 Superconductor’s characteristic
curve depended on a temperature
 HTS wire has 100 times of the
current density than a copper wire.
Atmosphere furnace
AC induction furnace
HTS DC induction furnace
Loss
Conductive, convective, radiative loss
Joule’s heat at copper wire
No loss!! (HTS resistance is zero)
Machine Efficiency
20~30%
50~60% (High copper loss)
Over 90%
Additional device
Special chamber to minimize heat
loss
Inductor and capacitor bank and
water-cooling system for copper coil
Cryo-cooling system needed
Product quality
Bad! (Required enough heating time)
Bad! (System frequency: 50~60 Hz)
Good! (Operated with low speed)
Results of the 10 kW-class HTS DC induction heater developed
5 /26
Super coil
 We are convinced about the commercialization possibility through this results.
You tube link: Operation of a 10 kW HTS DC induction heating machine
▲ Experimental view
▲
Real-time monitoring system
▲
Thermal graphical image
▲
Trial performance
Design process for 300 kW HTS DC IF
6 /26
Super coil
 We finally adapted the candidate 2, because of the highest magnetic field we could get.
Target : 300kW class HTS DC induction
furnace
•
•
•
•
Several candidates
Metal billet type : Aluminum Billet
Average temperature : 540 (°C)
Temperature deviation : below ±5 (°C))
Magnetic flux density at the center of the billet : 1 (T)
Determination of the size
• Decide radius (mm), length (mm), weight (kg)
Candidate 2
Determine the resistive heating and operating
range for heating with FEM tool
• Rotating speed (rpm)
• Mechanical torque (N·m)
Determine the specification of the magnet to
generate the uniform magnetic field
•
•
•
•
Maximum magnetic field
Type of HTS wire
Shape of HTS magnet
Considering the perpendicular magnetic flux density
Design completion of an 300 kW-class HTS DC
induction furnace
1.1 T, 3.4 km, 1 ea
Considering metal billet sizes
No. 1
D180mm billet
D380mm billet
No. 2
Development of the electromagnetic FEM analysis model
7 /26
Super coil
 We developed the electromagnetic FEM model
of 300kW-class HTS DC IF.
 We designed the HTS magnet with the
magnetic flux density of 1.1 T at the center of
the billet.

FEM results of a 300 kW HTS DC IF

Design of the magnet
system
GM-cryocooler
with 2nd stages
Iron core
Cryostat
Heat invasion loads analysis
8 /26
Super coil
 We need to analyze heat loads of the conduction cooling system for HTS magnet operation. There
are three conditions, such as conduction, convection and radiation.

Conduction

Convection
 Heat invasion loads

Radiation
 Conduction
①Metal current
leads
②Supporters
(300K1st stage)
③Supporters
(1st stage2nd
stage)
④HTS current leads
 Convection
①From metal billet
813 K
 Radiation
①Metal billet 
Outer cryostat
②Outer cryostat 
Inner radiation
shield
③Inner radiation
shield  HTS
magnets
Lorentz forces and their directions
9 /26
Super coil
 We calculated Lorentz forces of the HTS magnets for mechanical structure design.
 The volume integral of
 Fx is caused by the attracting force between
Lorentz force by each
iron core and HTS magnet
ǀFxǀ
component according
to the operating
current
Self-weight of a DPC
of HTS magnet : about
150 kg
Iop (A)
Fx (ton)
Fy (ton)
Fz(ton)
100
-0.20
0.0030
0.00075
200
-0.82
0.012
0.0030
300
-1.76
0.027
0.0068
440
-2.40
0.057
0.015
500
-2.28
0.073
0.019
600
-1.73
0.106
0.027
Target current
ǀFxǀ
Results of the heat transfer and mechanical analysis
10 /26
Super coil
 Total heat load was expected to 45 W at the 1st stage.
 7 W was expected for the 2nd stage and HTS magnet.
 Expected heat loads of the 2nd stage cryo-cooler
 Mechanical analysis model
45 W (1st)
7 W (2nd)
1st stage temp. :
55.9 K
Highest temp. in the
radiation shield : 91.3 K
2nd stage temp. :
6.99 K
Highest temp. in
the HTS magnet:
9.65 K
Maximum stress:
29.5 MPa
Real drawing of the 300 kW HTS DC IF
11 /26
Super coil
 The 300kW induction motor was selected with 12 poles at 60 Hz.
 Machine size: Length 7.4m X Height 2.9m X Width 4.7m
3 Phase 380V, 12 poles, 300 kW induction motor
(Weight : 6 tons, Torque: 484 kg･m, Rated speed: 592 rpm, current 682 A)
HTS magnets and their
conduction
cooling
system
Aluminum billet
(Length: 700mm, Diameter: 240mm)
Gripping system
Supporting system for Heavy weight parts
Loading/unloading machine of Aluminum billet
Winding composition of HTS magnet
12 /26
Super coil
 We fabricated the large-sized two HTS
magnets for induction furnace in the world.
 The HTS magnet size: length 1.25m X
height 0.62 m
 HTS magnet wound
 Co-winding
method
 HTS magnet
bobbin
 SUS tape
(1km)
 HTS tape
(1.7km)
Critical current estimation process – Only B//c considered
13 /26
Super coil
 We estimated the critical current of the magnet in 77 K. It was 140 A with the
perpendicular magnetic flux density of 4 mT/A.
540 A@30K
140 A@77K
Max. 4.01E-3 (T)
Max. 5.6E-3 (T)
5.0E-3 (T)
2.0E-3 (T)
4.0E-3 (T)
0E-3 (T)
3.0E-3 (T)
2.0E-3 (T)
2.0E-3 (T)
(a)
Min. -4.02E-3 (T)
1.0E-3 (T)
(b)
Min. 0 (T)
Experiment preparation of the magnet under the LN2
14 /26
Super coil
 We installed the magnetic sensor at the center of the magnet.
 We performed the critical current test and measured magnetic flux density.
 Magnetic flux
density
measurement
 Installed magnetic
sensor
 (+) Current
terminal
 (-) Current
terminal
▲ Installation of the magnetic sensor at the center of the magnet
▲ Critical current and magnetic
field curves under the LN2
▲ Cooling HTS magnet in
liquid nitrogen, 77.4 K
 Quench occurrence
point
 Ramping rate: 0.5 A/s
145 A
Critical current comparison – DPC No.1 and No.2
15 /26
Super coil
 This picture shows the critical current curves of the two HTS magnets.
Total length of HTS wire
for an HTS magnet:
1.7 km 170mV
Ic1: 145 A
Ic2: 165 A
Assembly for the magnet experiment
CEO
Me
16 /26
Super coil
 We completed the experimental set-up.
 HTS magnet with the conduction cooling system
 MLI shielding against radiation
System composition of the cooling down test
17 /26
Super coil
 We composed the system components for cooling down test
of the HTS magnets with the conduction cooling.
 Cryostat B

GM 2nd stage
Cryocooler

Compressor

Chiller
 Cryostat A
Cooling down test results of Cryostat B
18 /26
Super coil
 The total cooling time took 3 days and 2 hours.
 The temperature at the 1st stage of cryo-cooler was saturated at 74K.
 Temperatures of the 2nd stage was cooled down and saturated at 5.3 K.

Saturated temperature of the HTS magnet and conduction cooling system
Current flowing test results of the HTS magnets
19 /26
Super coil
 We composed the measurement program for HTS magnet
 Magnetic field
measurement field
 Detecting two
terminal voltages
fields
 HTS current lead voltage
measurement fields
 Current control
field
 Terminal voltages according to
the current
 Temperature monitoring field
 Current measurement field
Current flowing test results of two magnets connected in series
20 /26
Super coil
 When the current with 0.5 A/s ramping rate was supplied into the magnets, the
terminal voltages increase with inductive voltage and the temperatures of HTS magnet
increased at 6 K owing to AC losses.
 When discharging with (-) 0.5 A/s, the voltage variation occurs. It means that the
magnet is unstable condition at that time. The current bypasses into the other turns.
Temperature
Current
Voltage
Temperature
Current flowing test results of two magnets connected in series
21 /26
Super coil
 Maximum magnetic flux densities were measured to 0.33 T of the cryostat A and 0.325
T of the cryostat B when the current of 360 A flew into the magnets in series
connection. This results are almost same as the FEM simulation results.
 0.33 (T) (Cryostat A)
 0.325(T) (Cryostat B)

Electromagnetic FEM analysis results
Max. 1.24E-3 (T)
 0.328 (T) @360 A
1.0E-3 (T)
0.8E-3 (T)
0.6E-3 (T)
0.4E-3 (T)
0.2E-3 (T)
Min. 1.13E-5 (T)
 360 A
Test video of the excitation of the magnets
22 /26
Super coil
 The operational characteristics of HTS magnet with the conduction cooling system were
demonstrated by the experimental test.
SuNAM
HTS
wire (12mmx
0.15mm), 3.4 km
Metal
insulation(MI)
type
528 mH without
iron core
(Cryostat B)
Rc: 23.6 mΩ
(Cryostat B)
Tc: 22.4 s
(Cryostat B)
Je: 200A/mm2
(Cryostat B)
Excitation ceremony on the 9th of August, 2016
23 /26
Super coil
 The excitation ceremony of the magnets was successfully held on the 9th of August.
Conclusion and discussion
24 /26
Super coil
 We developed the HTS magnet with the conduction
cooling system for HTS DC induction furnace.
 The successful excitation ceremony was held on the
9th of August, 2016.
 Now, we are going on developing the rotating system
for HTS DC induction furnace.
 Super coil for the commercialization of the HTS DC
IF was established on the 1st of September.
 Super coil aims for the design and engineering works
of the HTS magnets and their application system.
 View of the experimental site
25 /26
Super coil
Thank you for your attention.
Technologies are not developed by people.
Technologies are not developed by supplier.
Technology has to focus on only NEEDS.