| Slit Film Line Drive System |
This is a 6-motor drive system to control the speed of drives on a slit film line. This is the downstream portion of an extrusion process where film is extruded through a die into sheet form and then slit into thin ribbons. This is a good example of a common bus AC drive system. All drives which are Reliance GV3000 flux vector drives derive their power not from the AC line but from a DC power supply. When connected this way, the GV3000 drives have the ability to share energy which is a requirment for the slit film application. The extruded polymer when first extruded has very low strength and very high elongation properties. By stretching the material, the polymer chain is extended and gains strength. This stretching process requires that some drives run faster than others to cause the stretching. The slower drives will be overhauled by the faster drives, i.e. the forces needed to stretch the material causes the drives that hold back to try to overspeed. When the drive holds back to resist this overspeeding, power generated by the motor is returned to the drive which in turn returns the energy to the power source, in this case the common DC bus. The faster drives consume this regenerated energy. The result is a very efficient system with energy from the AC line only necessary to make up for frictional losses and motor losses. All the drives on this system are controlled by a Reliance PC3000 controller over the AutoMAX network. The PC3000 also has an Allen-Bradley remote I/O netowrk which is used to control A-B Flex I/O. The PC3000 is now obsolete and new systems of this type use A-B FlexLogix which is in the ControlLogix family.
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