IFM Electronic CR0403 Programming Manual page 178

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CURRENT_CONTROL
Unit type = function block (FB)
Unit is contained in the library ifm_CR0403_Vxxyyzz.LIB
Symbol in CODESYS:
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Description
CURRENT_CONTROL operates as a current controller for the PWMI outputs.
The controller operates in dependence of the period duration of the PWM signal. The setting
parameters KI and KP represent the integral and the proportional component of the controller.
► It is recommended to set KI=50 and KP=50 as start values so as to determine the best setting of
the controller. Depending on the requested controller behaviour the values can gradually be
incremented (controller is stronger / faster) or decremented (controller is weaker / slower).
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At the desired value DESIRED_CURRENT=0 the output is immediately switched to 0 mA and is
not adjusted downward to 0 mA in accordance with the set parameters.
The controller has a fast compensation mechanism for voltage drops of the supply voltage. In addition
to the controller behaviour of the controller and on the basis of the voltage drop, the ratio of the PWM
is increased such that the controller reaches as quickly as possible the desired value.
Depending on the controller hardware used, a different teach performance has to be noted.
NOTE
► When defining the parameter DITHER_VALUE make sure that the resulting PWM ratio in the
operating range of the loop control remains between 0...1000 %:
• PWM ratio + DITHER_VALUE < 1000 ‰ and
• PWM ratio - DITHER_VALUE > 0 ‰.
Outside of this permissible range the current specified in the parameter DESIRED_CURRENT
cannot be reached.
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With PWM frequencies below 100 Hz plus additional dither, the current control can no longer reach
the indicated accuracy (→ data sheet).
BasicController (CR0403) Runtime System V03.02
178
2015-04-01
ifm function elements for the device CR0403
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