7.7
Field weakening and LookUpTable (LUT),
At their rated voltage, synchronous motors can also be operated above their rated
speed by injecting a current component in order to reduce their voltage
consumption.
Features
The method is relatively robust against parameter fluctuations.
The voltage controller can only follow rapid speed and torque changes to a
limited degree.
A non-optimized voltage controller may cause oscillation; the controller must
be optimized.
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 >
Factor * FluxNom
A value greater than 0.2 is recommended for
Factor.
MOOG
ID
No.:
CB40859-001
Date:
02/2018
MSD Servo Drive - Device Help
141
7 Control
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.
Failure to exercise caution or follow proper working
procedures may result in damage to your system/motor.
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.
There are two variants for field weakening of a synchronous motor. The choice of
variant 1 or 2 is made via P 435[0] - CON_FW_FWMode.
From firmware 124.20-08 additional document
CC41778-001 applies
synchronous motor
