IEEE Power Electronics Magazine - December 2019 - 40

PDIV (kV)

can happen in the air under 300 V when the air presThe following is a summary of the talks and follow-up
sure is low.
panel discussions during the session. For urban air mobilFor all types of high-power applications, the utilization
ity and small aircrafts, which are the focuses of on-demand
of WBG devices will bring challenges
mobility, as shown in Figure 1, distribrelated to dv/dt and di/dt, including
uted full electric and hybrid electric
common mode transient immunity
propulsion with submegawatt electric
The remaining
in gate drive designs; compliance
machines and power electronics are
technology challenges
with electromagnetic interference
expected. In recent years, there have
standards, current sharing between
been rapid technological advances for
of EAP for regional,
power modules; reflected waves at
EAP for small aircrafts, but more
single-aisle, and
the load terminals when long cables
innovations are needed to further
are implemented between the power
improve efficiency and power density.
double-aisle jets span
converters and loads; and insulaUnlike small aircrafts, regional
from the system level
tion reliability for power module
and single-aisle jets with 50-150 seats
packages, connections, and loads.
per aircraft will benefit more from
to the component
hybrid and turbo electric propulsion.
Recent studies have shown that highlevel.
The electric machines onboard these
er dv/dt in switching waveforms will
aircrafts will be at megawatt scales.
lead to reduced partial discharge
For double-aisle jets with up to 300
inception voltage (PDIV) in bus bars,
seats, due to the increased power ratings of the electric
motor windings, and power modules. For example, as
machines, superconducting technologies may be required.
shown in Figure 2, the average PDIV of a standard twisted
The remaining technology challenges of EA P
pair sample, which is designed to study partial discharge
for regional, single-aisle, and double-aisle jets span
mechanisms of motor windings, will decrease from 1.9 to
from the system level to the component level. At the
1.6 kV when the rise time of the applied pulsewidth-modusystem level, research on comparisons of different
lated voltage is reduced from 150 to 60 ns.
propulsion architectures, system-level control a nd
During the panel discussion, it was agreed that
diagnostics, a nd system testing methods are still
more dedicated workshops and seminars are needed
needed. At the component level, significant weight
for topics related to high power. It was also suggested
reduction for megawatt-level electric machines and
that more packaging studies on sensor integration
power electronics is required. The power density of
and a deeper understanding of device degradation
state-of-the-art electric machine onboard aircrafts is
mechanisms could enable the integration of artifiapproximately 2 kW/kg; the long-term goal in the next
cial intelligence in high-power converters, achieving
15 years and beyond is to reach greater than 25 kW/
further performance and reliability improvements. A
kg. At both the system and component levels, matestrong consensus was reached that multidisciplinary
rial and insulation innovations are needed to eliminate
curricula and research are needed to address insucorona at high voltages in high-altitude environments.
lation material, electrical, mechanical, thermal, and
Because of the increasing power requirements for
control related challenges faced by WBG-based highEAP, the voltage level of the electric system onboard
power converters.
aircrafts is expected to reach 10 kV. Currently, the voltage level of dc distribution systems on more electric
About the Author
aircrafts is limited to ±270 V, partially because corona
Jin Wang (wang.1248@osu.edu) is a professor in the
Department of Electrical and Computer Engineering at The
Ohio State University, Columbus. His research interests
include high-voltage and high-power converter/inverters,
2.5
integration of renewable energy sources, and electrification
of transportation.
2

References

1.5

[1] R. Dyson, "NASA hybrid electric aircraft propulsion," in Proc. NIEA

Biomimicry Summit, Cleveland, OH, Oct. 4, 2017. [Online]. Available: https://

PDIV (kV)
0.5
40

100 120 140
Rise Time (ns)

160

www.grc.nasa.gov/vine/wp-content/uploads/sites/91/Rodger-Dyson-NASA

180

-Hybrid-Electric-Aircraft-Propulsion-10-4-2017-FULL.pdf
[2] Z. Wei, H. You, B. Hu, and J. Wang, "Partial discharge behavior on twisted
pair under ultra-short rise time square-wave excitations," in Proc. Electrical

FIG 2 A graph of PDIV versus rise time for a twisted pair sample that emulates motor windings [2].

IEEE POWER ELECTRONICS MAGAZINE

z December 2019

Insulation Conf. (EIC), Calgary, Canada, 2019, unpublished.

https://www.grc.nasa.gov/vine/wp-content/uploads/sites/91/Rodger-Dyson-NASA-Hybrid-Electric-Aircraft-Propulsion-10-4-2017-FULL.pdf https://www.grc.nasa.gov/vine/wp-content/uploads/sites/91/Rodger-Dyson-NASA-Hybrid-Electric-Aircraft-Propulsion-10-4-2017-FULL.pdf https://www.grc.nasa.gov/vine/wp-content/uploads/sites/91/Rodger-Dyson-NASA-Hybrid-Electric-Aircraft-Propulsion-10-4-2017-FULL.pdf

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