IEEE Electrification Magazine - March 2016 - 38

Military equipment
is subjected to harsh
environments
in terms of
temperature
and also noise
and vibration.

torque demand. This is followed by a
reduction in torque demand from the
propulsion system, which includes
the electric motor. A simulated lanechange maneuver is described next.
In this case, the converter and the
HERMIT battery were controlled independently of the HERMIT control system. The power supply was controlled manually with the intent of
keeping peak currents below the
maximum rating of the converter.
Dynamometers were used to apply
the loads to the HERMIT traction
motors that a ten-ton vehicle would see during a typical
flat-course lane-change maneuver.

lane-change simulation, the bus voltage was very steady at 600 V.
The most strenuous tests conducted on the converter were the
150-kW cycling test and the peakpower test, both done at 100 °C; the
results were satisfactory. The duration of the cycling test was limited
by the HERMIT battery temperature
rather than the converter itself. The
peak-power test ran at 180 kW for 70 s,
i.e., 3.5 times longer than required,
before it was shut down by the operator. The successful completion of
the converter test at a 100 °C coolant temperature was
the most significant accomplishment pertaining to the
needs of the army applications.

Results
The results of a particular lane-change maneuver are
shown in Figure 6 (at 100 °C coolant temperature). The
high battery current (blue line) during acceleration is
clearly seen in this figure, until it subsides after the acceleration, when the lane change is complete.

Converter Efficiency
Some results on the efficiency of the converter are presented in Figure 7 and are based on data gathered during
steady-state (continuous-operation) testing over a range
of temperatures.

Summary of Tests Related to HERMIT
The various tests mentioned previously were intended to
make sure that the power electronics devices operated satisfactorily in a military environment. Overall, the converter
performed as expected in all areas of operation. The load
steps on HERMIT showed adequate control of the HV bus
within a real vehicle environment. During the HERMIT

0
Current (A)

-50
-100

Current Data for
20110823_DCC10_50 A_to_0 A_200 ms.csv

Ibatt
Idc
Iext

0
Current (A)

Managing temperature or the ability to survive high temperatures is a priority in power electronics applications
in general, and more so in military environment, where
the conditions are even harsher. With that perspective,
the military has invested significantly in research related
to WBG semiconductors, and particularly in SiC (Shenai
et al., 2014; Shenai, 2000). Some of those efforts are
described here.
It should be noted that, in power electronics applications at high-temperature conditions, it is important to
consider not only the main switching circuit but also
the control circuits (i.e., gate-driver circuit and any
other control circuits in the periphery), in terms of subjecting those to high-temperature conditions. Therefore,
developing the gate-driver circuit for such conditions is
also important. Some of the following efforts include
this consideration.

Current Data for
20110823_DCC10_0 A_to_50 A_200 ms.csv

-150

Examples of Sic-Based Power Electronics
applications in the Military

-50
-100

80 100 120 140 160 180 200
Time (ms)
(a)

-150

Ibatt
Idc
Iext
0

80 100 120 140 160 180 200
Time (ms)
(b)

Figure 5. The battery and bus current for a 50-A load step: (a) negative step change and (b) positive step change.

I E E E E l e c t r i f i cati o n M agaz ine / March 2016

Table of Contents for the Digital Edition of IEEE Electrification Magazine - March 2016