Chapter 22 Hybrid Drive Systems 425
AC fl ow sets up a three-wave magnetic fi eld that moves around
the stator to push and pull the armature around with it.
Modern hybrids use three-phase AC power for the same
reason that industrial applications and factories have used this
form of electrical energy for decades. A three-phase AC motor
can produce more horsepower and torque than an equal-size
DC motor while consuming less electrical energy. The same is
true when the motor-generator is serving as a generator.
When serving as a motor, the electromagnets can make
the permanent magnet armature spin with tremendous torque.
As AC current is fed into the windings of the electromagnets
from the power control module, the powerful magnetic fi elds
of each electromagnet push and pull the armature’s permanent
magnets in one direction so the armature rotates.
The motor-generator in Figure 22-8 uses 18 coil wind-
ings (electromagnets) and iron cores organized into an
array around the armature. Since the outer surface of the
armatures is close to the stator windings, the permanent
magnetic fi elds and the electromagnetic fi elds can repel or
attract each other with great force.
The AC voltage cycles from positive to negative in the sta-
tor coils, generating a north and then south magnetic pole in
the motor-generator electromagnets. Current is passed through
each set of coil windings in a circular pattern so that the arma-
ture is rotated with the movement of the magnetic fi elds.
Figure 22-9 shows a cutaway of a hybrid transaxle case
with the motor-generator exposed. Figure 22-10 shows the
relationship of the armature and stator.
Each armature pole is “pushed” by magnetic repulsion.
The next armature pole is “pulled” by magnetic attraction.
With multiple poles (permanent magnets) on the armature
and multiple stationary electromagnets, the hybrid traction
motor can generate high torque to propel the vehicle. Refer
to Figure 22-11.
Basically, motor-generator torque is controlled by cur-
rent fl ow, while speed is controlled by the frequency and
phase shift of the alternating current waves.
Motor-Generator as a Generator
When serving as an electrical generator, the drive
train or CV-axles spin the motor-generator’s permanent
magnet armature. The magnetic fl ux of the permanent
magnets cut across and through the stator windings. This
Figure 22-8. Photo shows segmented steel armature inside an
array of electromagnets. This motor-generator is for a parallel
hybrid drive system. (Honda Motor Co.)
High-Voltage,
High-Current
Connector
Segmented
Armature with
Permanent
Magnets
Figure 22-9. Cutaway shows the side view of a motor-generator
in a modern hybrid transaxle. (Ford)
Figure 22-10. Note the relationship of the armature and stator
windings in a hybrid motor-generator.
Transaxle Case
Oil Cooling Flow
Coil
Cutaway
Iron Core
Armature