20
EMF as the actual speed value (p50083 = 3). Sheet 6810, normalization p50115.
CO: r52287. The EMF is the calculated induced motor voltage, generated from the measured
device output voltage and the voltage dips I*R and L*di/dt of the motor.
The precision of this type of control is largely determined by the change in resistance of the
armature winding of the motor via the temperature and amounts to approx. 5%.
For EMF control: Set speed actual value filtering p50200 = approx. 40ms.
Freely selectable speed actual value source (p50083 = 4), the number of the connector
parameter from which the actual speed value is derived is set in p50609. Sheet 6810.
P50083 = 5: Actual sped evaluation via SMC30.
If necessary, set a small filtering time for the actual speed value: p50200 = approx. 5 to
40ms. Actual speed value at speed controller input: r52166 as absolute value,
r52167 as bipolar signal. Irrespective of the signal used for the control and selected with
p50083, the other evaluated speed actual value quantities are also always available, e.g. for
the required display of the EMF actual value when controlled with a pulse encoder or analog
tachometer, or by using a second encoder for technological control.
Speed controller:
The output of the ramp-function generator is the speed setpoint value for the following speed
controller, Sheet 6810, 6815.
It calculates the deviation between the speed setpoint and actual value and prescribes the
setpoint for the following lower-level current controller after an intermediate torque
calculation.
The speed controller is implemented as a PI controller (an additional D component can be
connected via the derivative element p50205 / p50206). One characteristic of a PI controller
is that it adjusts the error variable, in this case, between the setpoint and actual value for
speed, to zero if the setpoint is constant.
The characteristic quantities of the controller, the gain Kp (p50225) and the reset time Tn
(p50226) can be adjusted based on an additional variable, such as an actual speed value.
Sheet 6805. This permits stable operation within a broad control range even with special
applications.
Used, for example, with low speeds on feed drives.
A droop function, Sheet 6805, is also available. The droop function, for example, is used to
achieve smooth load distribution for several drives coupled via the material.
Control method depends on the parameter assignment:
p50224 = 1, p50234 = 1, PI controller: Factory setting
p50224 = 0; p50234 = 1, P controller
p50224 = 1; p234 = 0, I controller
For optimization, see below.
Speed controller as the voltage controller: Some applications require control to a constant
output voltage of the SINAMICS DCM.
Settings of the voltage actual value for control: p50083 = 4; p50609 = 52292 (connector
actual voltage value).
The speed control stability is specified in the technical data of the Operating Instructions.
This is a long-term stability referred to a longer measuring time, e.g. 10 seconds. Deviations
within a short monitoring period, e.g. as the result of a load surge, are higher than specified.
Specific values cannot be given as these short-term deviations depend on the actual
conditions of the system and optimizations. See also below.
Speed controller pre-control:
Sheet 6820.
Compensation of the moment of inertia: The torque required for the speed change depends
on the moment of inertia of the load and the desired speed rate of change. The necessary
correcting quantity is calculated from the dv/dt of the ramp-function generator output (rate of
change of speed) and is added to the speed controller output.
Friction compensation: The friction is speed dependent, the torque required to overcome the
friction is derived and added to the speed controller output.
The above correcting quantities can be derived automatically with optimization run
