26
Note
: During current controller optimization the motor must be at standstill; if necessary, lock
the motor shaft.
On highly dynamic drives, such as are used for cross cutters or feed drives, it may be
necessary to manually optimize the armature current controller, for this, the controller is
supplied with current setpoint step changes and the step response at the output of the
controller is evaluated with the Trace (using the STARTER), see below.
The optimization run optimizes the current controller based on the absolute value optimum.
Speed controller optimization run with p50051 = 26. Optimization of speed control loop and
moment of inertia.
Supplies satisfactory results for many normal applications. In the case of high moments of
inertia, a high Kp (p50225) is often determined by the automatic optimization; if the
mechanical system is not optimum, it may frequently be necessary to reduce this derived Kp
by approx. a factor of 2.
Before performing the optimization run with p50236, set the required extent of dynamic
response of the speed control loop (100% corresponds to the highest dynamic response).
Recommended values: 100% is possible for optimum mechanical systems. In practice, a
setting of p50236 = 30 is usually sufficient and suitable.
In the case of backlash in the gear: p50236 = set approx. 30%. If the optimization is
performed under load, both the centrifugal force of the motor and the load for the
optimization is taken into account.
The optimization run optimizes the speed controller based on the symmetrical optimum.
If the motor is operated in field weakening, the field characteristic curve recording must be
performed with p50051 = 27. (If no field weakening is required, this optimization run need not
be performed). After the optimization run, activate field weakening with p50081 = 1.
Do field characteristics manually::
http://support.automation.siemens.com/WW/view/en/41165031
p50051 = 29 Optimization run on an mechanically oscillating system (long shaft or belt drive)
Manual controller optimization using the square-wave generator
Step changes in the setpoint can be defined for the controllers using the square-wave
generator, Sheet 3120. The controllers can be adapted manually by suitably setting the
controller variables, the gain Kp and the reset time Tn, and analysis of the step response.
The setpoint step change and the step response of the controller can be recorded and
evaluated using the Trace function of the STARTER.
The setpoint step change should only be high enough to keep the controller within the control
range, i.e. so that the controller does not reach a limit, e.g. the current limit.
Extent of step change approx. 2% to 5%, depending on the system configuration.
Setting of the square-wave generator:
p50480: Higher value of the setpoint step change
p50482: Lower value of the setpoint step change, e.g. 2% lower than p50480
p50481: Duration for the setpoint as per p50480, e.g. 0.1 seconds
p50483: Duration for the setpoint as per p50482, e.g. 0.1 seconds
Activation of the output of the square-wave generator of connector r52208, by setting the
binector number in p50485.B; e.g. p50485 = 1 (permanently "Oscillation On").
Setpoint step change for current control loop:
p50601[4] = 52208, couple output of square-wave generator with input of current control loop
(current controller plus current controller precontrol). Sheet 6840.
Operate motor at standstill. Switch off field with p50082 = 0 and enter an ON signal plus
operation enable via terminal X177.12 and .13.
Check effects of settable filters p50191 and p50190.
Step reponse for discontinous current, e.g. p50480 = 15% and continuous current
