IEEE Electrification Magazine - March 2016 - 37

lower, the generator losses are also lowered because the
frequency of the harmonic content is reduced for at least
some operating regions.

P

Traction Motor Inverter

dc Voltage

Inverter

Idc

The HERMIT traction motor inverters are high-temperature, liquid-cooled inverters. The inverters use oil cooling
instead of the more conventional water cooling to allow
sharing of coolant with the oil-cooled traction motors. The
use of oil cooling allows some of the insulating layers of
the inverter IGBT modules to be removed, thus improving
their thermal performance compared to using an inverter
designed for water cooling.

M
Ia

Ib
A

Ic
B

C

External
Choke

dc-dc Converter
The dc-dc converter is a six-phase bidirectional system
that is connected between the HERMIT battery pack and
HERMIT's dc bus. The main function of the converter is to
regulate the bus voltage to 600 V. The converter performs
this function by sourcing (boost mode) or sinking (buck
mode) power to and from the batteries (300 and 600 V). It
can source or sink up to 100 kW continuously, with a
150-kW peak, and it makes use of hybrid Si/SiC switch
modules, which pair a Si IGBT with a SiC freewheeling
diode. This SiC diode has a faster reverse recovery time
than a standard Si diode, which reduces switching losses
in the module, leading to a reduction in heat generated by
the module.

G

Idc

HERMIT dc-dc Converter System Tests
Figure 3. A schematic of the HERMIT generator, external inductors, and
generator inverter.

Figure 5 shows a sample dc-dc converter (buck mode) comparison test at 50 A (a 50-A load step is the lightest load
placed on the converter in this test). Another test was done
to verify the performance of a particular dc-dc converter
from a manufacturer. The goal was to develop a 150-kW
battery-to-bus dc-dc converter capable of running with a
coolant temperature of 100 °C using SiC switch modules.

Auxiliary Power

Power Supply

Example of HERMIT Testing-Lane Change
One particular test of interest relates to lane changing in
a hybrid vehicle, where, typically, increased acceleration
is demanded for a brief period, leading to increased

CAN Communication
External Input/Output

Gate Drivers/DSP
Controller

Protection

dc+
Current Sensors
Temperature Sensors
Voltage Sensors

ac
φ1
φ2

dc-

φ3

dc-Link
Capacitor
Integrated Heat Sink

CAN: Controller Area Network
DSP: Digital Signal Processor

Figure 4. A block diagram of the HERMIT inverter.

IEEE Electrific ation Magazine / March 2 0 1 6

37



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

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https://www.nxtbook.com/nxtbooks/pes/electrification_september2022
https://www.nxtbook.com/nxtbooks/pes/electrification_june2022
https://www.nxtbook.com/nxtbooks/pes/electrification_march2022
https://www.nxtbook.com/nxtbooks/pes/electrification_december2021
https://www.nxtbook.com/nxtbooks/pes/electrification_september2021
https://www.nxtbook.com/nxtbooks/pes/electrification_june2021
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https://www.nxtbook.com/nxtbooks/pes/electrification_september2017
https://www.nxtbook.com/nxtbooks/pes/electrification_march2018
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