stator windings. This induces ac current in the stator wind-
ings and power cables leaving the motor-generator.
Single Motor-Generator Hybrids
A single motor-generator hybrid uses only one large
motor-generator to assist the internal combustion 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.
As shown in Figure 38-10, the single motor-gener-
ator is the least complex type of hybrid drive train. Note
how the large motor-generator (shown in red) bolts
between the cylinder block of the engine and the housing
of the transaxle.
Dual Motor-Generator Hybrids
A dual motor-generator hybrid uses two separate
motor-generators to provide assist. The two motor-gener-
ators are usually located inside the transmission or
transaxle. Look at Figure 38-11.
During regenerative braking, both motor-generators
act as large ac 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. A cutaway view of a rear-wheel drive trans-
mission with two hybrid motor-generators is shown in
Figure 38-12.
Triple Motor-Generator Hybrids
In some cases, three motor-generators are used in a
hybrid vehicle, Figure 38-13. Two motor-generators are
located in the transmission or transaxle, and one is
located in the rear drive axle assembly.
A triple motor-generator arrangement is often used in
large four-wheel drive vehicles to help electrically drive
all four wheels. Figure 38-14 shows a front hybrid
transaxle and a rear hybrid transaxle for a three motor-
generator hybrid driveline.
702 Section 5 Electrical Systems
Figure 38-9. Three-phase ac flows through the three power
cables that run between the motor-generator and the power
control module. A—Three-phase ac is used to spin the arma-
ture in this motor-generator. Phase 1 current attracts armature
pole A. Phase 2 attracts armature pole B. Phase 3 attracts
armature pole C. B—Three-phase alternating current is simply
three single ac phases timed 120 degrees apart. The voltage
waves (shown as voltage waveforms) generate magnetic fields
that circle inside 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 38-10. Study this parallel hybrid arrangement. Note that
the single motor-generator is located between the engine block
and transaxle. The motor-generator can assist the gas engine
to propel the vehicle. The motor-generator can also serve as a
generator to recharge the battery pack. (Honda)
Internal
combustion
engine Motor-generator
Power cable
junction box
Continuously
variable
transaxle