The closed-loop control of tension used in speed mode:
In speed mode, it adjusts motor revolution by the closed-loop control to reach the constant tension status. By this way, it calculates the synchronous frequency command with line speed and reel diameter and then adjusting the frequency command of the AC motor drive by PID closed-loop control. The PID closed-loop control is calculated by tension signal and tension setting generated from the tension detector feedback.
The formula of synchronous frequency is shown as follows:
F= ¡] V¡Ñp¡Ñi ¡^ / ¡] £k¡ÑD ¡^ -x(OUTpid)
Where F is synchronous frequency command of the AC motor drive, V is material line speed, p is motor pole (auto generate from the motor parameters), i is mechanical transmission ratio, D is reel diameter.
In this control mode, it will have higher performance PID control of the AC motor drive and precise synchronous frequency command to make the system be more stable. Usually it is used for the continuous operation of wire drawing machine and steel rolling mill. If using torque control mode for wire drawing machine and steel rolling, it may have abnormal operation when the synchronous frequency is changed. Therefore, speed mode is more suitable for tension control.
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