426 Auto Electricity and Electronics
Figure 22-11. Three-phase AC fl ows through the three power
cables between the motor-generator and the power control mod-
ule. A—Three-phase AC is used to spin the armature in this motor-
generator. Phase 1 current attracts the armature pole A. Phase 2
attracts armature pole B. Phase 3 attracts armature pole C. This
attraction and repulsion cycle is repeated around the set of stator
windings. B—Three-phase alternating current is simply three single
AC phases timed 120° apart. The voltage waves (shown as voltage
waveforms) generate magnetic fi elds that circle around the inside
of the motor-generator to make the armature spin. (Toyota)
A
B
Phase 1
Phase 2
Phase 3
Phase 1
Phase 1
Phase 2
Phase 3
(+)
Phase 1 Phase 2 Phase 3
A
B
C
A
Figure 22-12. Photo shows three power cables as they enter the
high-voltage junction box on a hybrid transaxle.
induces AC current in the stationary windings as each
magnet moves past one of the electromagnets.
The motor-generator acts as a generator during regen-
erative braking and when recharging the high-voltage
battery pack. When the driver presses lightly on the brake
pedal, the hybrid ECU engages the power split device so
that the rotating force of the spinning tires, wheels, axles,
and transmission shaft transmit this rotating force to the
motor-generator armature. This induces high-voltage levels
in the coil windings and power cables leaving the motor-
generator. Refer to Figure 22-12.
Three-phase AC power is produced in the motor-
generator by wiring the electromagnets into three sets of
windings arranged 120° out of phase with each other. For
example, if the motor-generator has 18 electromagnets,
three groups of 6 coil windings can be wired together to
get a three-phase wye confi guration.
Motor-Generator Sensor
A motor-generator sensor is used by the hybrid drive
system to detect armature speed and position, Figure 22-13.
A rotor on the motor-generator armature spins inside three
sensing coils. The motor-generator sensor produces AC
signals, which are sent to the power control module. Based
on these signals, the power control module changes the
amount of current and the phase shift of the three-phase AC
for effi cient motor-generator operation.
Single Motor-Generator Hybrid
A single motor-generator hybrid uses only one large
motor-generator to assist the gas engine. This is a compact
design with the motor-generator assembly bolted to the rear of
the engine block in front of the transaxle or transmission. The
motor-generator armature is connected to an engine crankshaft
and to the transmission input shaft. The motor-generator is a
large-diameter, high-torque motor with minimum complexity.
As shown in Figure 22-14, the single motor-generator is
the least complex type of hybrid drive train. Note how the
motor-generator (shown in red) bolts between the cylinder
block of the engine and to the bellhousing of the transaxle.
Dual Motor-Generator Hybrid
A dual motor-generator hybrid uses two separate
motor-generators located at different locations in the drive
train. The two motor-generators are usually located inside
the transmission or transaxle. Look at Figure 22-15.
During regenerative braking, both motor-generators
act as generators to recharge the HV battery pack and help
drag the drive train to a stop. Under all-electric drive, both
motor-generators act as motors to help propel the vehicle.
In the all-electric mode, the larger rear motor-generator
is used to propel the vehicle, Figure 22-16A. The power con-
trol module feeds battery pack power into the rear motor-
generator. The motor-generator drives a planetary gearset.
The gearset transfers mechanical torque out of the transmis-
sion and to the drive wheels through the drive train.