IEEE Electrification Magazine - March 2016 - 41

packaging. For military applications, the dual-voltage ISG
helps meet the increasing onboard electrical power needs
and also exports electrical power in an efficient manner.
The objective of the dual-voltage ISG project was to demonstrate a system comprising a generator with two outputs plus associated conversion and regulation electronics
as a feasible alternative to existing systems. It should be
noted that the ISG concept is not only applicable to hybrid
electric vehicles (HEVs) but can also be used beneficially in
legacy vehicles in terms of meeting high power demand
with more compact packaging.
The objective of the ISG work was to examine various
alternative architectures and concepts for a dual-voltage ISG and
power converter unit (PCU) resulting
in a recommended system-level concept. To that end, an evaluation of
potential constraints on generator
design from system requirements
was made. Next, the system's size
and efficiency, sensitivity to power
split and voltage ratio between the
two outputs were determined. Finally, a trade study was performed to
assess the performance of a dual
voltage ISG system in context of current alternative solutions.

MIL-STD-704 and MIL-STD-1275 (electrical military
standards available in public domain)
xx
having an HV output with a minimum of 35 kW
(threshold), 40 kW (objective) at 270 Vdc while complying with MIL-STD-704
xx
meeting various electromagnetic compatibility (EMC)
standards like MIL-STD-461, sections CE102, CS101,
CS114, RE102 (2 MHz-18 GHz), and RE103 (30 MHz-
18 GHz).
In addition, the dual-voltage ISG and PCU were required
to operate with a 75 °C (threshold), 100 °C (objective) coolant inlet temperature. Other items of interest were that
the dual-voltage ISG and PCU had to
meet the water proof standard
described in U.S. Army Tank Automotive and Armaments Command Document 12480561 (this is a government
internal document). The dual-voltage
ISG system also needed to have the
ability to develop sufficient motoring
torque to crank a typical 400-kW diesel engine.

To minimize losses
and reduce thermalmanagement needs,
it is extremely
important to
maintain high
efficiency and
enhance it wherever
possible.

Design Requirements

Since the applications pertain to the
military, various military standards were used during the
design and the trade study process. The dual-voltage ISG
was designed to meet certain requirements relevant for
the specific situation under consideration, including
xx
having a less than 7-in axial length
xx
having a power density greater than or equal to 4 kW/L
xx
supplying a minimum of 25 kW (threshold) and 30 kW
(objective) at 28 Vdc while complying with

Concept of Operations for the ISG

The ultimate goal of this work is to
confirm that a dual-voltage ISG is
suitable for use on tactical and combat wheeled vehicles. The concept
of operations can be summarized as
follows.
xx
The purpose is to
■ provide on-vehicle power for 28- and 270-V loads
while stationary or in motion
■ provide engine-starting capability.
xx
The use profile includes
■ an engine start that is transparent to the driver
■ generator power that is available soon after
engine start

Turn-On Pulse
1.8 A
Gate Current

Turn-Off Pulse
2.4 V On
Gate Voltage

Figure 10. The gate-driver waveforms into the dummy load.

-10 V Off

Figure 11. The breadboard inverter.

IEEE Electrific ation Magazine / March 2 0 1 6

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