Environmental Engineering Reference
In-Depth Information
Power electronics stage and heat sink
D
D
D
G
G
G
S
S
S
+
dc
link
cap.
SPM
D
Vehicle
energy
storage
system
D
G
D
G
G
Rotor
position
sensor
(encoder resolver)
S
S
S
Current
sense
Logic
power
supply
Gate
driver
Gate
driver
Gate
driver
Communications network
Microcontroller
Figure 5.13 Brushless ac motor control
integrated commutation logic controller. External phase leg current sense resistors
are recommended for low cost applications. Overcurrent, overtemperature (via
internal NTC thermistor) and undervoltage lock-out are built-in features.
Six-step mode in 180
conduction is illustrated in Figure 5.14, where the top
three traces show the gate driver signals to the power switches. Since conduction is
180
, the bottom switch command for each phase leg is the complement of the
signal shown. For example, A
þ
is the command to switch S1 in the power inverter
and the complement of A
þ
is impressed on switch S2 in phase leg A.
During current regulation, the phase currents are as depicted in Figure 5.8(b)
and phase shifted 120
for phases B and C, respectively. The total rms voltage and
fundamental rms voltage of the brushless ac motor controller can be calculated
easily from the fourth, fifth and sixth traces in Figure 5.14 by noting that the pulse
takes on a magnitude of the dc link voltage,
U
d
, and has duration 2
p
/3 for every
half-cycle interval of duration
p
electrical radians. The total rms value of the line-
to-line voltages,
U
ab
,
U
bc
and
U
ca
, are calculated as
s
ð
2
p=
3
1
p
U
d
d
q
U
ab
¼
0
ð
Volts
1
1
, total rms)
ð
5
:
7
Þ
r
U
d
2
3
U
ab
¼
The fundamental component of
U
ab
is calculated from its first harmonic value as
p
p
U
d
6
U
an
¼
ð
Volts
1
1
, fundamental rms)
ð
5
:
8
Þ
