Texturing Machine Control with AC Drive
Texturising is a process by which required properties are imparted to Partially Oriented Yarn (POY), which then may go as direct production input to fabric manufacturing textile units.
The texturising machine is a longitudinal multi-section machine. The length of the machine is decided by number of bobbins/spindles. The yarn passes from feed end to last stage winding end through a complicated path of separate driving shafts or sections. Through a mechanical arrangement, twist is imparted to yarn for strengthening. Compressed air, steam, & heat are used in the machine. The final yarn has superior properties to the input yarn.
Depending on the grade of the feed yarn and quality of finish desired, different draw/stretch have to be maintained between various sections. This means the ratio of angular speeds of different driving shafts in a given machine have to be decided depending on line-speed, grade of incoming yarn and quality of finish to be imparted. A typical yarn path is shown below:
To meet this basic requirement, two co-existing machine technologies are available:
Line shaft drive systems
Sectional drive systems
In the machine driven by line shaft, a single AC induction motor drives the machine master shaft. Speeds of various other machine shafts in the machine are decided by operator based on pulley belt /gearing arrangement to achieve speed either higher or lower than that machine master.
The limitations of this design are:
The line-speed is fixed and hence not too many different grades of incoming yarn can be handled.
Since pulley belt /variable mechanical gearing can be adjusted in fixed finite steps, different combination of ratiometric speed adjustment between various machine — shafts are difficult to be achieved. This means a restriction on available variety of finished yarn for a given machine.
Any change of speed ratio implies mechanical changes, longer changeover time and hence loss in production.
Machine line speed varies due to variations in input voltage supply, frequency and machine load.
Use of AC drive for the main motor does take care of some aspects mentioned above.
Owing to relative inflexibility of such line shaft machines, sectional machines have now gained popularity. Independent squirrel cage motors drive each driving shaft of the machine. AC drives are used for each of the motors.
The requirements of sectional machine are described below:
Each shaft has to be run at a predetermined speed. This necessitates use of A.C drives on each shaft for speed variation.
High speed holding accuracy is required to prevent speed errors eventually leading to increased tension in the yarn between shafts and hence yarn breakage.
During machine start up, all shafts should reach top speed simultaneously and during shut down, all shafts must slow down to zero speed simultaneously to prevent yarn breakage.
On power failure, all shafts must come down to zero speed simultaneously to avoid yarn breakage.
Use of external power source for prolonged deceleration time expected under power failure.
Since environmental conditions, where these machines are installed, are harsh the control system used has to be tropicalised to withstand the elevated temperatures, humidity and oil mist.
Advantages of using sectional texturising machine with inverter control:
Improvement in yarn quality
Minimum changeover time for different yarns
Increased life of machine mechanicals
— S.Y. Shelar