Conditions
To effectively reduce the voltage consumption, the ratio of stator inductance P 471[0]
- MOT_Lsig multiplied by the rated current P 457[0] - MOT_CNom to rotor flux P 462
[0] - MOT_FluxNom must be sufficiently large. In contrast to field-weakening of
asynchronous motors, synchronous motors can also be operated in the field-
weakening range with full rated torque at the nominal value of the q-current. Power
beyond the rated power output can therefore be drawn from the machine in field-
weakening mode, even at rated current. This must be taken into consideration when
configuring the motor.
CNom * Lsig >
Faktor * FluxNom
A value greater than 0.2 is recommended for
Factor.
Voltage demand
Rotor flux *
Maximum speed (in rad/s)
*
Number of pole
pairs
* <
800 V (400 V
devices)
400 V (230 V
devices)
P 462[0] *
P 458
[0]
*
P 328
[0]
*
* P 463[0]
* <
800 V (400 V
devices)
400 V (230 V
devices)
CAUTION!
Your system/motor may be damaged if put into operation in
an uncontrolled or inappropriate manner.
Improper conduct can cause damage to your system /
machine.
l
If the speed achieved by field-weakening is so high that
the induced voltage exceeds the overvoltage threshold
of the device (for 400 V devices approximately 800 V,
for 230 V devices approximately 400 V), this will result
in destruction of the Servo Drive if no additional external
safety measures are applied.
MOOG
ID No.: CB40859-001 Date: 11/2020
MSD Servo Drive - Device Help
147
7 Control
First of all, there are two variants for field weakening with synchronous motors,
variants 1 and 2. They can be selected via P 435[0] - CON_FW_FWMode.
P 347
CON_FM_VRef
Available Uzk
vmot
soll
vmot_filt
P 345
P 346
vreg_isdref
sdrefmod
isdref [1/n]
Ti
d-current control
1
P 344
Tf
Vmot
udref
uqref
Voltage
Calculation
Kp
Tn
x
2
x y
Voltage control
y
2
CON_FM_ImagSLim
P 341
0
iq
ωe
uzk
+
characteristic isd=f(n)
i
P 0435
CON_FM_FWMode
off
2
1
calculated map
sdref_tab
i
+
0
√2 * P 340 CON_FM_Imag
Variant 2:
Variant 1:
0
Image 7.34: Structure of field-weakening of synchronous motors
Additional modes (corresponding to P 435[0] - CON_FW_FWMode in the figure at
positions 0, 1 and 2) with their feed forward control of the d current are coupled with
additional multiplexer settings here as an alternative.
The voltage control implementation is active in all modes!
This ensures by means of P 347 CON_FM_VRef that adequate voltage reserves are
available to maintain a functional speed control at higher speeds.
