Environmental Engineering Reference
In-Depth Information
following sections explore the merits and disadvantages of the four machine tech-
nologies in the context of hybrid propulsion.
5.2.1 Brushless dc
The electronically commutated motor most closely related to the brushed dc
machine described earlier is the brushless dc machine configured with SPMs. A
BDCM may be of either 120
or 180
current conduction in the stator windings.
When the machine's back-emf due to the permanent magnet rotor has trapezoidal
shape, the machine will be brushless dc and having current conduction in block
mode of 120
duration. If the rotor magnets are designed for sinusoidal back-emf,
the machine will be of the brushless ac variety and stator currents should be in 180
conduction. Figure 5.9 illustrates both types of brushless dc machines.
U
(
q
e
)
I
(
q
e
)
q
e
(a)
U
(
q
e
)
I
(
q
e
)
q
e
(b)
Figure 5.9 Brushless dc motors: (a) brushless dc or trapezoidal flux and
(b) brushless ac or sinusoidal flux
