Parameter descriptions
726 Minimum Acceleration
727 Mech. Time Constant
The minimum acceleration time defines the modification speed of the reference speed value as from
which a torque necessary for acceleration of the drive is pre-controlled. The acceleration of the mass
is a function of the
Mech. Time Constant 727 of the system. The value calculated from the increase
of the reference value and the multiplication factor of the torque required is added to the output sig-
nal of the speed controller.
726 Minimum Acceleration 0.1 Hz/s 6500.0 Hz/s 1.0 Hz/s
For optimal setting, the acceleration pre-control is switched on and the mechanical time constant is
set to the minimum value. The output value of the speed controller is compared to the minimum ac-
celeration time during the acceleration processes. The frequency ramp is to be set to the highest val-
ue occurring in operation at which the output figure of the speed controller is not yet limited. Set the
value of
Minimum Acceleration 726 to half the set acceleration ramp. In this way, it is ensured that
the acceleration pre-control becomes active.
During several acceleration attempts, increase the
Mech. Time Constant 727 until the output value
(signal source 37 – acceleration pre-control output) during the acceleration roughly corresponds to the
torque-forming current I
sq
(signal source 141). In the case of drives with a high friction or other high
resistance torque, deduct the corresponding portion from the torque-forming current I
sq
before. This
setting should also minimize overshooting of the speed controller. Alternatively, you can calculate the
mechanical time constant at a known mass moment of inertia. The mechanical time constant is the
time the drive needs during acceleration from standstill with rated torque applied until the
Rated
Speed
372 is reached.
7.9.5.5 Field controller
717 Flux Reference Value
741 Amplification
742 Integral time
The flux-forming current component is controlled by the field controller. The guided commissioning
optimizes the parameters of the field con-
t
roller by measuring the time constant and magnetizing
curve of the connected asynchronous motor. The parameters of the field controller are selected such
that they can be used without changes in most applications. The proportional and the integrating part
of the field controller are to be set via parameters
Amplification 741 und Integral Time 742.
No. Description Min. Max. Fact. sett.
717 Flux Reference Value 0.01% 300.00% 100.00%
741 Amplification 0.0 100.0 5.0
742 Integral Time 0.0 ms 1000.0 ms 100.0 ms
Please note, that changes within the Field controller parameters should only be done in the basic
speed area.
When an optimization of the Field controller is necessary, set the
Integral Time 742 = Act. Rotor
Time Constant
227 / 2, meaning to the half of the rotor time constant. In most application cases, this
change is sufficient.
When further optimizations are necessary, follow the step described in the following procedure.
• Set the output frequency in a way (i.e. via the frequency reference value), that the actual val-
ue
Modulation 223 = 80…90 % Reference Modulation 750.
• Now change the
Flux Reference Value 717 from 100 % to 90 %. Oscillograph the actuating
variable I
sd
. The course of the signal of the flux-forming current I
sd
should reach the stationary
value after overshooting without oscillation.
237
Control functions 06/2013 Operating Instructions
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