A smart ac-motor drive lets Centrilift Cable, Claremore, Okla., eliminate a PLC while quickly winding finished cable onto drums.
The H2 drive from Baldor Electric Co., Fort Smith, Ark., acts as both machine and motion controller in one package.
Centrilift Cable makes specialized electrical cabling for submersible pumps used in oil and gas wells. Each cable is custom made for a specific application and includes different sizes and quantities of wires, types of insulation, and armor coatings. So every cable has a different outer diameter. Finished cable is wound directly onto a large drum as it feeds from the wire drawing, coating, and spooling machinery.
The original winding operation was controlled by a PLC that sent 0-to-10-V control signals to two ac-motor drives. One drive controlled drum rotation while the other controlled the traverse motion of a guide that ensured the cable wound properly on the drum. Operators programmed the PLC to control the drives for different cable sizes and feeding speeds with data from charts, tables, and manual calculations — a process prone to many errors.
Automation supplier Motion Industries helped simplify the winding system and recommended the electronic gearing feature in the Baldor drive. Electronic gearing lets one motordrive control the speed and position of another through a ratio function as if the two motor shafts were linked with mechanical gears.
A potentiometer, attached to the dancer arm that tensions the cable, monitors slack in the cable as it feeds to the drum. Output voltage from the potentiometer controls the first drive, varying drum rotation speed to keep the cable properly tensioned.
The second drive, for the traversing guide, uses electronic gearing with the first drive to synchronize its operation to drum rotation. Operators simply input the cable diameter using the keypad and display on the drive. The drive calculates the proper gear-ratio speed for uniform spooling for that diameter cable.
The two smart drives let Centrilift eliminate the PLC and complicated manual programming steps. The new setup also got rid of many signal wires for a cleaner installation with more reliable operation. The change improved productivity more than 25%.