AN1931D Freescale Semiconductor / Motorola, AN1931D Datasheet - Page 15

• Manufacturer Part Number: AN1931D
• Description: 3-Phase PM Synchronous Motor Vector Control
• Manufacturer: Freescale Semiconductor / Motorola

MOTOROLA
3.3.4.2 Control in Field-Weakening Range
0
As demonstrated from PM synchronous motor equations, the maximum efficiency of the ideal PM
synchronous motor is obtained when maintaining the current flux-producing component i
Therefore, in the drive from
operating range. The speed regulator controls the current torque-producing component i
A real 3-phase power inverter has voltage and current rating limitations:
1. The absolute value of stator voltage u
2. The absolute value of the stator current i
In the normal operating range, the current torque-producing component i
I_SDQ_MAX
Due to the voltage limitation, the maximum speed in the normal motor operating range is limited for
i
Where a higher maximum motor speed is required, the field-weakening technique must be used. That
is provided by maintaining the flux-producing current component i
shown in
Due to the limitation of absolute current value, the current torque-producing component i
be maintained below a limited value.
One possibility to maintain the flux-producing current component i
look-up table.
sd
= 0, to a nominal motor speed as shown in
u_sdq_max limit
given by the maximum current rating
stator voltage u
Figure
,
normal operating
since i
3-9.
Figure 3-9. Normal Operation and Field-Weakening
range
sd
s
= 0.
Freescale Semiconductor, Inc.
i
3-Phase PM Synchronous Motor Vector Control
Sq
For More Information On This Product,
Figure
I_SDQ_MAX
Go to: www.freescale.com
nominal speed
3-6, the Field-Weakening Controller sets i
s
is physically limited according to DCBus voltage to
s
should be maintained below a limit of I_SDQ_MAX
Figure 3-9
2
–
i
2
Sd
field weakenning
and
(EQ
range
stator current i
3-30.).
sd
sd
, in the field-weakening range, as
for field weakening is to use a
d
sq
sd
Target Motor Theory
can be set up to
= 0 in the normal
speed
u_sdq_max
sq
.
sq
, then must
(EQ 3-31.)
sd
at zero.
15