DIGITAL DRIVE SYSTEMS
In response to changing raw material supplies, higher costs, and veneer plant specialization, McDiarmid Controls, Inc.has developed the PLC based digital DC drive system. Allen-Bradley PLC 5/40 processors are used to control both veneer line logic functions and drive velocity regulation. All field devices such as limit switches, operator console devises, and veneer position encoders are connected to Allen-Bradley 1771 PLC I/O racks. Allen-Bradley bulletin 1395 Digital regenerative converters, configured to emulate PLC remote racks, are used for all system drives. The results is a truly integrated system in which all components are linked via the plc peer link. This approach greatly minimizes installation time and costs, enhances noise immunity, and simplifies drive logic interfacing. Unlike many systems currently available there are no potentiometers to adjust. All parameters and commands are absolute values entered in digital format via the color touch screen, hand-held terminal or computer interface. All components are standard devices, most of which are available world-wide through Allen-Bradley support and distribution. There are no "black boxes" or other "single source" devices in the system. Each application is carefully evaluated to assure optimum component selection and performance. Whether the product is softwood veneer, tongue depressor and crutch stock, or chopsticks, McDiarmid Controls has the solution for increased production and recovery.
Key Benefits
· Current loop control, Velocity loop control, and system supervisory control are provided by three separate microprocessors within each drive.
· Each system drive velocity loop is closed within the drive controller by digital, line driver output motor shaft encoders to realize speed regulation of .01% of set speed over a 20:1 speed range.
· Drive parameters are stored in eeprom, battery back-up is not required. Parameter tables may be uploaded and downloaded by computer.
· Comprehensive fault detection system which continually monitors the drive and performs an orderly shut down in the event of a malfunction. The diagnostic system archives faults in order of occurrence for evaluation. A detailed manual lists faults by code number with an explanation and suggested corrective actions.
· Four trend buffers may be used to monitor selected parameters and retain data for later use. Parameter to be trended, time between samples, trigger point, trigger source and ratio of samples before trigger point are all programmable for each buffer. Captured data may be directed to an analog channel, viewed on a 1395 program terminal or sent to the plc via the node adapter for further evaluation or display. This feature eliminates the need for an oscilloscope and other sophisticated test equipment.
· Overspeed detection, Field loss, zero speed, current regulated shunt field supply, phase loss detection, over/under voltage detection, current taper, and programmable electronic motor overload protection are standard for all ratings.
check out Allen-Bradley's web site at http://www.ab.com