Frequency Inverter ST600 Series High-Performance Multifunction VFD Basic Operation Instructions
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Related modules:
(1) Linear speed input module: It is important for the calculation of the basic setting frequency
according to the linear speed and the calculation of roll diameter according to the linear speed.
(2) Real-time roll diameter calculation module: The calculation accuracy of roll diameter determines
the control performance. The roll diameter can be calculated according to the VFD output frequency
and the linear speed. In addition, it can also be calculated through the thickness or sensor. The linear
speed is widely used for the calculation. If the set linear speed is used for the calculation, you you
choose whether to enable the function of roll diameter change limiting.
(3) PID regulation module: There are two groups of PID parameters in P09. The linear speed
synchronization and stable tension can be kept through PID regulation. PID parameters can be
modified based on site commissioning. The two groups of PID parameters can be switched for PID
regulation improvement.
(4) Material feeding interrupt detection and processing module: The function is valid when material
feeding interrupt detection has been enabled.
(5) Pre-drive: This function is applied to automatic reel change. After the VFD is started if the pre-drive
function terminal is valid, the roller runs at the set linear speed. When the terminal is invalid, the VFD
will automatically switch to the corresponding control mode after a period of time.
5.5.20.3 Open-loop torque mode
Open loop means there is no tension feedback signal. In this mode, stable tension can be achieved
by means of motor torque control. The rotation speed automatically changes with the linear speed of
material. The control basis is as follows: For a reel control system, the relationship between the tension
F of the roller with materials, present roll diameter D and output torque of the shaft is: T = F × D /2. If
the output torque can be adjusted according to the variation of roll diameter, the tension can be
controlled. In order to ensure the constant tension in the process of acceleration and deceleration, the
internal friction compensation module and inertia compensation module have been built in the VFD to
calculate the real time rotation inertia, and compensate the torque according to the actual speed
change rate. The control principle is shown in the following figure.
Relevant modes:
(1) Linear speed input module: It has two functions: calculating the synchronous frequency in torque
control according to the linear speed, and calculating the roll diameter according to the linear speed.
(2) Tension setting module: Used to set the tension adapting to the control system. It needs to be
adjusted according to the actual situation. After confirmation, the value remains the same. In some
scenarios where the forming effect after winding needs to be improved, the tension taper function can
be used so that the tension decreases as the roll diamter increases.
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