Machinery and Magnetics > Traction Motors and Integrated Starter/Generators
SatCon has extensive experience in the development of high-speed motor
and generator systems for a variety of applications.
High Speed Induction Machines
SatCon has a long history of traction motor development starting with
the Chrysler Patriot Formula 1 hybrid electric powertrain
and the Chrysler EPIC minivan electric drivetrains. In each case we have
focused in on the particular customer requirements whether it be record-setting
power density or low cost manufacturability.
Traction motor and integrated
starter/generator applications are uniquely challenging for
motor drive design optimization due to the shape of the required
torque-speed curve; with high constant torque required from standstill
to a corner speed, and then a constant power speed range (CPSR) out to
the maximum speed. Machinery is not naturally size for constant power,
but constant torque, thus unless the designer has well-developed design
tools to exploit field weakening and a good system level understanding
an oversized system can result.
The Patriot racecar traction motor is
a 6-pole induction motor consisting of a rotor-stator assembly,
a housing, and a bearing assembly. The design is similar
to the starter-alternator machines but with interior cooling tubes in
the stator. It is rated for continuous power delivery between 11,600
and 20,000 rpm at up to 750 HP with 90 deg C coolant. Performance was
demonstrated up to 350 HP at 9000 rpm (limited by DC supply voltage).
Unique structural and thermal designs provide very high power density
in this 145-pound motor.
SatCon produced 350 drivetrains for the Chrysler
EPIC Minivan with production capacity of 5000. This includes
a 165 ft-lb, 12 krpm, 120 HP induction machine traction motor.
The traction motor is has an oil-cooled jacket. A longer version of the
same motor design was manufactured for more than 50 hybrid
and electric bus applications producing 230 HP at 12 krpm
through the addition of spray oil cooling directly to the end turns.
A switched reluctance (SR) machine traction motor was developed
for the automotive industry. The chief benefit of SR type
machines is the rugged construction for high temperature environment
and low cost, high volume manufacturing. The primary objective was to
optimize the design to achieve high system efficiency and low rotor inertia,
with no adverse impacts on manufacturing costs and structural integrity.
The machine’s
peak power requirement was 15 kW at 2850 rpm, 115-195 V,
at standard operating conditions for 10 sec per 10 min. of continuous
operation. The continuous rpm rating was 12,000. At peak torque and speed,
the machine’s
efficiency was greater than 90%. The electrical drive unit
waste heat was removed using a coolant made of 50-50 mix of water and
ethylene glycol.
In a DOE program SatCon developed an interior PM machine
(IPM) suitable for HEV traction and integrated starter/generator
(ISG) applications because the machine has inherent flux-weakening
capability resulting in a wide constant power speed range
(CPSR) capability with high efficiency and power factor
capability. This combines the compact machinery features of PM machinery
with the low voltage drive requirement features of SR machines
resulting in an overall motor-drive package that is lower cost in high
volume production. The HEV application design was for a 200 Nm starting
torque and 35 kW generating capability up to 6000 rpm exceeding
2 Nm/lb torque density.
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