Parameters and firmware blocks
165
26.08 ACC COMP DERTIME FW block: SPEED ERROR (see above)
Defines the derivation time for acceleration (deceleration) compensation. Used to improve the speed
control dynamic reference change.
In order to compensate inertia during acceleration, a derivative of the speed reference is added to the
output of the speed controller. The principle of a derivative action is described for parameter 28.04
DERIVATION TIME.
Note: The parameter value should be proportional to the total inertia of the load and motor,
ie, approximately 50…100% of the mechanical time constant (t
mech
). See the mechanical time
constant equation in parameter 22.02 SPEED ACT FTIME.
If parameter value is set to zero, the function is deactivated.
The figure below shows the speed responses when a high inertia load is accelerated along a ramp.
See also parameter 26.09 ACC COMP FTIME.
The source for the acceleration compensation torque can also be selected by parameter 28.06 ACC
COMPENSATION. See parameter group 28.
0…600 s Derivation time for acceleration/deceleration compensation.
26.09 ACC COMP FTIME FW block: SPEED ERROR (see above)
Defines the filter time for the acceleration compensation.
0…1000 ms Filter time for acceleration compensation. 0 ms = filtering disabled.
26.10 SPEED WIN FUNC FW block: SPEED ERROR (see above)
Enables or disables speed error window control.
Speed error window control forms a speed supervision function for a speed and torque-controlled
drive (Add operating mode). It supervises the speed error value (speed reference – actual speed). In
the normal operating range, window control keeps the speed controller input at zero. The speed
controller is evoked only if
• the speed error exceeds the upper boundary of the window (parameter 26.11 SPEED WIN HI), or
• the absolute value of the negative speed error exceeds the lower boundary of the window
(parameter 26.12 SPEED WIN LO).
When the speed error moves outside the window, the exceeding part of the error value is connected to
the speed controller. The speed controller produces a reference term relative to the input and gain of
the speed controller (parameter 28.02 PROPORT GAIN) which the torque selector adds to the torque
reference. The result is used as the internal torque reference for the drive.
Example: In a load loss condition, the internal torque reference of the drive is decreased to prevent an
excessive rise of the motor speed. If window control were inactive, the motor speed would rise until a
speed limit of the drive were reached.
(0) Disabled Speed error window control inactive.
tt
%%
No acceleration compensation With acceleration compensation
Speed reference
Actual speed
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