cryogenic technology linked with power electronic performance characteristics of semiconductors at cryogenic temperature

1. CRYOGENIC
TECHNOLOGY
Presentation By : Francis Tomy
Roll No:10
S7 EEE
Guide: Ms Priya.S.Pai

2. Contents
 Introduction.
 Basic overview of cryogenics.
 Cryogenic power electronics.
 Behavior of devices and converters at cryogenic temperatures.
 Advantages.
 Applications.
 Conclusion
 References

3. INTRODUCTION
 Cryogenic technology has contributed greatly to scientific research and has found a wide range of industrial
applications
 Cryogenic condensation and distillation processes are widely used to produce high purity oxygen, argon,
nitrogen, hydrogen, and helium for the chemical, metal, and electronic industries.
 Its applications ranges from Aerospace industries to Food industry

4. What is Cryogenic temperature
 Cryogenics is the study of the production and behavior of materials at
very low temperatures.
 The word ‘cryogenics’ originates from Greek word ‘cryo’, which means
cold.
 It is not well-defined at what point on the temperature scale refrigeration
ends and cryogenics begins.
Basic overview

5.  The cryogenic temperature range has been generally defined as from
−150 °C (123K) to absolute zero (−273 °C or 0K),
 Cryogenic temperatures are usually described in the absolute or Kelvin
scale, in which absolute zero is written as 0 K, without a degree sign.
 Conversion from the Celsius to the Kelvin scale can be done by adding 273
to the Celsius scale.

6. Cryogenic Liquids
 Commonly used gases, in their liquid form, are nitrogen and helium. These are
the common cryogenic liquids.
 Liquid Helium and Nitrogen are usually stored in vacuum insulated flasks
called Dewars.
Nitrogen
 Nitrogen condenses at -195.8 C (77.36 Kelvin) and freezes at -209.86 C
(63.17 Kelvin). Liquid nitrogen is used in many cooling systems.
Helium
 Helium boils at -268.93 C (4.2 Kelvin) and does not freeze at atmospheric
pressure

7. Cryogenic Power electronics
 Silicon based power devices are generally designed to operate in the range between
–40 ◦C and +150 ◦C
 Commercially available power devices are not specifically designed for operation at
cryogenic temperatures.
 Use of cryogenically cooled power converters opens up numerous opportunities to
change the way we design and manufacture lightweight, low cost high power
converters for the global markets.
 A number of system level benefits; lower power losses, low-current feed through
connections and overall increased power density.
 Collocation of the power converter that converts the superconducting generator
output to required power within the cryogenic environment
 The cryogenic power converter provides extremely high levels of controlled generator
excitation with extremely low losses.

8. Power Devices and Cryogenic
Behavior of MOSFETs
 Significant performance improvements have been reported for many power devices when operated at
cryogenic temperatures
 The on-state resistance of power MOSFETs falls by about five times
 It is also reported that the MOSFET threshold voltage and transconductance increase at low temperatures.
 At 77 K (temp. of liquid Nitrogen), the threshold voltage has been found to increase by one volt due to carrier
concentration reduction when compared to room temperature
 The breakdown voltage of the power MOSFETs reduced by up to 23%. The drain current capability increased
three times from 300K to 77K for that particular device. This is due to the higher carrier mobility at lower
temperatures

9. On-State Resistance of Power MOSFETs
On resistance is the total electrical resistance between the
ource and source and drain during the on state of the device
 Three power MOSFETs of different voltages were tested from as temperatures of 300K to 77K. All
three power MOSFETs exhibited decreased on-state resistances as the temperature was reduced
from 300K to 77K.
 For a 1000 V rated power MOSFET, for a drain current of 2 A, the on-state resistance decreased by
a factor of 14 between room temperature and 77 K. The device also appears to be able to handle at
least twice the rated drain current at 77 K without serious degradation on the on-state resistance

10. Commercial Power MOSFETs at
low temperatures
 The commercially available MOSFETs in plastic or metal packages have been found to work well if
immersed in a bath of liquid nitrogen despite the fact that they have not been designed for such a cold
application.
 They can be operated at much higher current levels and hence high efficiency switching power
converters could be designed.
 It was also proven that heatsinks other than the liquid nitrogen are not required. This permits the design
of extremely small, lightweight and low-cost power conversion circuits for many applications.
 The on-resistance of commercially available high-voltage MOSFETs (500- 1000V) decreases by a factor 10-
30 or more depending on the drain current if cooled down to 77 K

11. SiC and GaN Devices at
Cryogenic Temperatures
 The measured SiC power MOSFET exhibited no improvements at 20K compared to room temperature.
 For the measured normally-off GaN HEMT, the on-state resistance improves from room temperature
down to 20 K and exhibits no carrier freeze-out effects.
 The turn-on voltage of the reverse body diode also reduced with decreasing temperatures which is the
opposite of the power MOSFET. This would reduce the voltage drop across the diode.
 In terms of operating with low power losses at temperatures below 50 K, the GaN
 GaN HEMTs have very good potential in cryogenic applications but still needs further investigation

12. Passive Components
 Many passive components and off-the shelf integrated circuits have been shown to operate satisfactorily
at temperatures down to 50K
 The low temperature impact on the capacitors depends on the dielectric medium such as polypropylene,
mica, film and ceramic. These capacitors function properly up to 77K and the leakage current and
dissipation factor shown to be decreasing at cryogenic temperature .
 It is shown that the magnetic losses generally increase with cooling unlike the reduction in copper losses,
and the power dissipation is not too much different than at the room temperature.

13.  If superconducting windings are substituted with the copper windings, then the loss comparison between
core and windings becomes more promising.
 Another study showed that most powder cores maintain a constant inductance value and exhibit
dependency, with varying degrees, in their quality factor and resistance on test frequency and
temperature. Also most cores exhibited good stability with changing temperature as well as frequency

14. Power Electronics: Converters
 A 175 W buck dc-dc converter operating at 50 kHz was tested at 77K. Full load efficiency
increased from 95.8% at room temperature to 97% at 77K
 A similar test was conducted using three level 60 W dc-dc buck converters which reports
a fully functional converter at 77K with slight efficiency degradation .
 Among these converters, zero voltage switching (ZVS) has been suggested as the most
efficient option; the overall losses reduced 18% of the room temperature.
 In another study, a 50 kW three phase inverter with soft switching was tested at 77K,
where the total inverter loss was about 1% of the input power.

15. Cryogenic Power Advantages
 Reduced size and higher power density
 Higher switching speed of devices due to reduced carrier lifetimes • Lower conduction and
switching losses
 Higher efficiency
 Reduced package volume and higher operating current densities due to an increase in the thermal
conductivity of silicon and packaging material. No additional heat sinks
 Reduced device leakage currents because of lower temperatures. Also higher reliability for the
same reason.

16. Cryogenic Power Conversion Applications
 Magnetic resonance imaging (MRI)
 HVDC system based on cryogenic cooled cables
 Deep space and terrestrial applications
 Magnetic levitation transportation systems Military all-electric vehicles
 Medical diagnostics
 Cryogenic instrumentation
 Super conducting magnetic energy storage systems
 Propulsion motors for aircrafts and ships

17. Few Applications
1.Hybrid Electric Distributed Propulsion (HEDP) Aircraft
30 MW Superconductor
Power
Transmission
6 MW Superconductor Electrical
Motor Turbo Fans
Fuel Efficiency + 70%
Potential World
Supercondu
ctor
Applications
Needed
Generato
rs
Motors
Power
Transmissi
on Cables
Power
Inverters
Power
Electroni
cs
Power
Levels
30–40
MW
4–6 MW 5–70
MW
1–30
MW
30–40
MW

18. 3.Cryogenic rocket engine
 Produces specific impulse up to 450 s
 Exhaust velocity upto 4.4 Km/s
 high enthalpy released during
combustion.

19. 2.The ultra-high-speed superconducting maglev train
 CO2 emissions are about one-third of traditional
transportation systems
 Speed more than 500 Km/h

20.  The ZEFIRO features sustainable technologies and an aerodynamic design that
generates 20% energy savings. It requires the lowest energy consumption per
seat in its segment. It also offers the highest service speed among the ZEFIRO
class of trains
 Power
– Voltage/frequency nom.: 25 kV-50 Hz; min. 17.5 kV; Max 30 kV,
– Asynchronous motors, forced cooling
– Distributed drives
– 20 MW (16 cars, 380 kph)
The ZEFIRO is the latest class
of very high speed (VHS)
trains from Bombardier. It is
one of the fastest sleeper
trains in the world and is
currently being operated in
China. Operating speed of
250kmph to 380kmph
Bombardier ZEFIRO Very High Speed Trains

21. Tesla Electric Roadster

22. Some the Companies
 STIRLING.B.V
 SUMITOMO
 DAIKEN
 RICOR
 ROLLS ROYCE
 TESLA
 ASIAN SEIKI
 ADVANCED RESEARCH SYSTEMS(ARS)
 SUZUKI SHOGUN

23. Conclusions
 The selection and integration of the right cryogenic system for a given application contributes to the
overall performance, efficiency, power density, and cost of the overall system
 A significant advancements in cryogenic converter/inverter technology is required for its application in
wind energy, NASA distributed propulsion system based aircraft, ship propulsion, and other high power
applications.
 Cryogenic power electronics technology is the next step in the evolution of power electronics technology
to obtain high power density, high efficiency, and superior performance for various applications

24. REFERENCES
 B. Ray, S. S. Gerber, R. L. Patterson, and I. T. Myers,“Power control electronics for cryogenic
instrumentation, ”Adv. Inst. Control, vol. 50, no. 1, pp. 131–139, 1995.
 T. Vogler, A. Schlogl, and D. Schroder, “Modeling and characterizing power semiconductors at low
temperatures” in Proc. 6th Int. Symp. Power Semiconductor Devices and ICs, ISPSD’94, Davos,
Switzerland, 1994, pp. 237–242.
 T. Curcic and S. A. Wolf, “Superconducting hybrid power electronics for military systems,” IEEE Trans.
Appl. Supercond.,vol. 15, no. 2, Part 2, pp. 2364–2369, June 2005

25. THANK YOU