IEEE Electrification Magazine - December 2017 - 12

mode and/or constant-power
mode, as required by the operation
200
taxiing profile. Both the speedAircraft Pushback
control and torque-control modes
Breakaway
160
Aircraft Taxi Up to
are required for the eTaxi. The
ISO Power 20.4 s
torque-control mode is generally
Aircraft Taxi Up to
120
implemented by the motor con9,929 r/min 90 s
troller in the EDS; the speed control
Maximum Takeoff
can be implemented in a separate
80
WT at 0.5% Slope 35 s
system controller or, optionally, in
the WACU.
40
The torque/speed profiles for
the EDS functional requirements
0
0
4,000
8,000
12,000
are shown in Figure 1. The characteristic points are defined with
Speed (r/min)
required speed, torque, and time
of duration.
Figure 1. The EDS torque/speed curves.
The aircraft's APU generator
provides power for hotel loads
The EDS contains an ac-to-dc power converter in the
while the aircraft is on the ground and when the main
form of an autotransformer rectifier unit (ATRU), a WACU
engines are not operating. For aircraft equipped with
that is a motor controller (dc-to-ac converter) with a clutch
eTaxi, the APU power generation system also provides
control, and a TM.
the power for the EDS. The EDS converts the high-voltage ac (115-Vac, three-phase, 400-Hz power) from the
EDS Major Requirements
generator into high-voltage dc power (±270-Vdc nomiThe EDS receives electrical power from the APU generator
nal) and distributes it to the motor controllers. The
and converts it to mechanical power for the aircraft to
motor controllers with high-frequency switching comtaxi in, taxi out, and push back. The EDS control system
mand ac voltage into the TM based on the speed and
operates in three quadrants: forward drive, reverse drive,
torque required by the system controller. There are cable
and reverse braking. The EDS must perform reverse brakharnesses that carry high-voltage ac and dc power. All
ing because, using mechanical brakes, the pilot could
EDS components must comply with strict power quality
apply them too abruptly and potentially lift the nose gear
and electromagnetic interference (EMI) requirements to
off the ground. The resulting regenerated power is dissiprevent any contamination on the aircraft power distripated in a resistor bank.
bution bus. The power drawn by the EDS is limited by
The EDS supplies the necessary torque to breakaway
the eTaxi system controller to prevent an overloading of
the aircraft from stationary state, and it maintains the
the APU generator.
speed control as the pilot commands. The EDS has a
The intention is for the EDS to be implemented in a
torque/speed profile requirement that calls for very high
new platform as well as retrofitted to an existing airplane.
torque at zero and low-speed operation, and it is power
All EDS high-power components must be air cooled
limited at high speed due to the APU generator power
because a liquid cooling system is not available in the
capability. The system should operate in constant-torque
existing aircraft at the targeted installation areas. A dedicated new cooling system would increase the overall system weight. All key components might be installed far
apart from one another and can, therefore, have different
System
environmental requirements. The TM must fit into the
Controller
Three-Phase 115 V
existing landing gear space without compromising the
ac Input
Data Bus
±270 Vdc
integrity of the landing gear and wheel braking system.
Communication
The EDS will need to have high-bandwidth data processing
capability to implement the motor control and protection
ATRU
WACU
TM
algorithms and monitor the health of the entire system. The
section "EDS Architecture" introduces the major requirements of each individual component.
Three-Phase ac
Hotel
Torque (Nm)

TM Torque Speed Characteristics

APU

Load

Voltage Output

EDS Architecture
Figure 2. The EDS architecture.

I E E E E l e c t r i f i cati o n M a gaz ine / DECEMBER 2017

Figure 2 shows a conceptual block diagram of the eTaxi
EDS architecture.

Table of Contents for the Digital Edition of IEEE Electrification Magazine - December 2017