IEEE Power Electronics Magazine - March 2016 - 41

1,000-V dc distribution system deployed in the U.S. Navy's
latest stealth-guided missile destroyer, USS Zumwalt (DDG1000). The system includes MV ac power generation and
propulsion with LV dc zonal electrical distribution. According to Prof. Boroyevich's presentation, future combat-ready
shipboard power systems will be designed for reconfigurability and survivability with the ability to isolate the damaged
section and reconfigure the electric plant in fewer than 100
ms. The presentation further highlighted the developments in
SiC power devices and MV dc distribution for future applications (Figure 11).
Challenges identified in this session, according to note
taker Robert Pilawa, include designing and building large
power thrusters (>250 kW) for in-space electric propulsion for human space exploration, better understanding
of reliability and failure modes of components and how to
improve modeling of component reliability, improving the
reliability of power devices and their packaging, continued
improvements in battery technologies, and rapid charging
and discharging of batteries. For MEA, improvements in inverters and motors are needed, in addition to storage.
Furthermore, he added, effective heat removal is critical
in many transportation systems, while electric transportation requires system-level thinking. In addition, continued
Pilawa, power electronics designer must concurrently work
with other experts (mechanical, materials, software, and so
on) at the system level.

New Power Devices, High Temperature
During this presentation, Prof. John Shen from the Illinois
Institute of Technology (IIT), Chicago, suggested that one
future direction might lie in the convergence of nanotechnology and power electronics. He calls it "big power on a
small scale" and cited a few early examples that his
research group is currently looking into-a nanoscaled silicon IGBT with three times more current capability, a
nanoscaled superjunction device with five times reduction
in on-resistance, and power devices based on GaN nanowire
arrays jointly investigated by Tyndall National Institute in
Ireland, Illinois Institute of Technology, and Queen's University Belfast in Northern Ireland (Figure 12).
Similar projections were also made by Prof. T. Paul Chow
of Rensselaer Polytechnic Institute, Troy, New York. In his paper "Living in a Wide-Bandgap World in 2025: What Conquered
and What Next?" Prof. Chow investigated wide-bandgap
(WBG) developments worldwide by 2025 and also presented
a ten-year road map for SiC and GaN devices (Figure 13).
Based on improvements in materials, structure, and
processes, Prof. Chow sees SiC MOSFETs handling up to
10 kV, with a current rating as high as 300 A, and SiC IGBTs
going up to 25-kV blocking voltage with a current rating of
up to 300 A. Likewise, the SiC gate turn-off thyristor (GTO)
is also expected to handle voltages as high as 25 kV and
300-A current. The GaN HEMT/MOSFET is projected to offer a voltage range of 30-6,500 V, with a current rating of up
to 300 A. GaN power ICs and optoelectronic ASICs are also

Solar Array Metrics

Current

Cell Efficiencies

29- 33%

40- 60

130-160+

Special Power (W/kg)
Power (kW)
Special Volume (kW/M3)

Next Generation

120

30-50+

a20- 30+

(a)
Thruster Metrics

BPT- 4,000

NASA TDU

Input Power (kW)

1- 4.5

1-13

Thrust (mN)
Specific Impulse (s)
Thruster Efficiency

50- 280

25- 685

1,100- 2,500

1,000-3,200

35-55%

20-61%

(b)
FIG 10 The (a) solar array and (b) thruster metrics for nextgeneration electric propulsion in space. (Figure courtesy of
Northrop Grumman Aerospace Systems.)

expected to emerge, as well as bidirectional power transistors in silicon, GaN, and SiC technologies. Bidirectional
power transistors under development include the 1,200-V
Si BD-IGBT, 600-V GaN BD-IGBT, and 10-kV SiC BD-IGBT.
Furthermore, diamond-based MOSFETs and aluminum nitride (AlN) HFETs are also expected to challenge silicon in
the next ten years.
Despite challenges from WBG devices, silicon is not going away any time soon. Franz-Josef Niedernostheide of Infineon Technologies AG confidently showed "Where Silicon
Will Survive and Thrive in 2025." His paper indicated that
there is still room for improvement for silicon. Superjunction
MOSFETs, for instance, will continue to scale for the next few
years and deliver improved RDS(on) ◊ A specs, as well as reduce the stored charge. Simultaneously, evolution in silicon
IGBTs will continue to improve switching losses and VCE(sat)
characteristics at high temperatures for the next five-plus

FIG 11 The developments in SiC power devices and MV dc distribution for future shipboard applications. (Figure courtesy of
CPES, Virginia Tech.)

March 2016

z IEEE PowEr ElEctronIcs MagazInE

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