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Seminar on Developing High-Temperature Superconducting Transformers
1.
2. SEMINAR ON- Development of High-Temperature
Superconducting Transformers for Railway Applications
PRESENTED BY :
Mr. Amol Namdev Salokhe
T.E.Electrical Engineering
GUIDE :
Mr. Prof. H. M.Mallad Sir
3. INTRODUCTION
DESIGN OF 1-MVA TRANSFORMER SUBGROUPS
ASSEMBLY AND COOL DOWN
TEST RESULTS
CONCLUSION
REFRENCES
4. We describe the high-temperature superconducting (HTS) transformer project
run by Siemens. The project started in October 1996 and ended in September 2001. The
aim of the project was to show the future prospects for superconducting railway
transformers. To study the principle behavior of such a transformer, the authors as a
first step designed, constructed and tested a nominal single-phase transformer 100 kVA,
50 Hz, 5.5 kV/1.1 kV. After this was successfully tested, we started the design and
construction of a single-phase transformer 1 MVA, 50 Hz, 25 kV/1.4 kV. This unit
already has the full ratings of a commercial transformer in many respects, e.g., power
range, nominal voltage, 2-limb core with horizontal orientation, two secondary windings
and an impedance of 25% at nominal current. Further innovative features are
transposed conductor and a closed cooling cycle with sub-cooled nitrogen. The report
describes the 1-MVA transformer’s detailed design, and presents the results of electrical
and thermal transformer routine tests (e.g., measurement of load losses and no-load
losses). The conclusion highlights the future perspective of HTS transformers for
railway applications.
5. Transformer is a static device which transfer electrical energy from one circuit to
another circuit without changing its frequency.
Transformer is an heart of substation.
6. A. Ratings
The single-phase transformer has a nominal frequency of 50 Hz. It has two
identical LV windings taken toward the outside. The HV winding has a nominal
voltage of 25 kV and a nominal current of 40 A. The LV windings have a nominal
voltage of 1389 V and a nominal current of 360 A. The nominal impedance voltage
is 25%.
B. Core-and-Coil Assembly
The core-and-coil assembly consists of a 2-limb core, whereby each limb is
wound. The winding structures of the two limbs are identical except for the
direction of winding. The windings are arranged in a doubly concentric layout in
the radial sequence LV inside-HV-LV outside . The HV windings of the two limbs
are connected in parallel.
7. C. Core
Because the core is placed in liquid nitrogen and therefore contributes to the
cold losses, a high-quality plasma-treated type of sheet with a thickness of 0.23 mm
and specific loss of 0.85 W/kg (Epstein square value) at 1.7 T and 50 Hz was
selected, in contrast to 1.5 W/kg in conventional traction Transformers
D. Conductor
Bi-2223 tape made in 1999 by Vacuum schmelze GmbH with a pure silver
matrix and a silver-magnesium sheath was used as conductor. The tape consists of
55 filaments and is not twisted. A conductor length of 6.7 km, representing a mass
of 54 kg, was used in the windings.
E. HV Winding
HV1 and HV2 each consist of a stack of 9 identical coils, each
stack having 224 turns. The individual coils are connected in series
by means of a tot-to-top, bottom-to-bottom inter coil connection
and the total number of turns is 2016.
8. F. LV Winding
The inner and outer LV windings are layer wound, each with one layer and
56 turns per layer. At the lower end, the inner and outer windings are connected to
each other in series. The LV windings taken to the outside therefore have a total
number of turns of 112. The already mentioned transposed conductor is used.
G. Leakage Flux Iron
The leakage flux iron is a complex periodic structure made up of air gaps and
iron sheets with the size of a centimeter square.
H. Liquid Nitrogen Container
The LN container is made of stainless steel and its volume is optimally
matched to the core-and-coil assembly. During nominal operation, it contains 250 l
of liquid nitrogen with a mass of 200 kg. The inner and outer dimensions are 420
mm 832 mm* 1200 mm, and 430 mm* 842 mm *1245 respectively. Its empty mass
is 272 kg.
K. Cooling System
The cooling system consists of a 4-cylinder Stirling cryo
generator, an electric motor, a coupling cryostat and a control
cabinet. In order to save time and money, the cold head was not
optimized for 66 K.
9. Core-and-coil assembly of the 1-MVA HTS transformer.
3-d schematic arrangement of the
complete set-up.
10. 1-MVA HTS transformer with cooling system in test laboratory at
the Nuremberg transformer factory. (1): 4-cylinder Starling cry generator, (2):
coupling cryostat, (3): vacuum-tight conventional tank with LN container and
core-and-coil assembly inside, temperature inside 196 C, temperature outside
+20 C.
11. Pretest
After the operating temperature of 67 K was reached, the following were performed:
Measurement of winding resistance, insulation resistance test, insulation capacitance test,
coil-coil insulation test at 7 kV, 50 Hz for 60 s, measurement of frequency response
(impedance and ratio for 30 Hz–3 MHz), measurement of response characteristic of transient
voltages (full and chopped). These tests were all passed and the measured values were again
good.
B. Measurement of Impedance Voltage and Load Loss
After this, the impedance voltage and the load losses were measured for 50 Hz and
16.7 Hz at 67 K. The HV winding was charged. LV1 and LV2 were short-circuited. Fig. 5
shows the reactive component of the percentage impedance voltage as a function of the
current in the HV winding at nominal value. At nominal current, the reactance voltage was
measured and found to be 24.30%. This very closely agrees with the calculated value of 25%.
12. The advantages of stationary HTS transformers compared to transformers
1. normal conductivity are well
2. higher current densities
3. The efficiency is raised to over 99%, whereas the weight and volume can be
reduced by approximately 45%
4. It is mostly designed for superconducting application
13. After the plan to develop a 1-MVA HTS transformer was completed last
year, the engineering documents are now being drawn up to build a full power on-
board transformer with. A planned follow-up project envisages
construction, assembly, stationary and mobile tests and testing of the new
pioneering technology of a superconducting railway transformer on a trial vehicle.
14. 1. S. Mehta, N. Aversa, and M. S. Walker, “Transforming transformers,” IEEE
Spectrum,.
2. www.transforming transformer .com
3. P. Kummeth et al., “Development and test of a 100 kVA superconducting
transformer operated at 77 K,”
