Customizing adjustable-speed drives for injection molding.

Adjustable-speed drives (ASDs) provide high-performance control and also energy savings for such loads as pumps, fans, and blowers. The success of ASDs in these applications has led to their widespread acceptance and use.

In contrast, ASDs are not widely used in complex processes like plastic injection molding. Moreover, the requirements for implementing them in such processes are not well understood, and the benefits are not well documented. Given the complexity of injection molding, it is not possible to purchase off-the-shelf ASDs and plug them into the manufacturing process. Attempts to do so have led to disappointing results. However, the outstanding control and energy savings provided by ASDs in other applications have led industrial customers to continue to look for ways to successfully introduce ASDs into more-demanding processes.

Against this backdrop, Potomac Edison Company - part of Allegheny Power System (APS) - hosted a seminar that brought together one of its customers, Automotive Industries, and an ASD vendor. The vendor identified substantial potential economic benefits of using ASDs with large injection mold machines. A trial drive had been installed, and savings were demonstrated. Realizing the energy efficiency potential of the ASD retrofit, Potomac Edison contracted with EPRI's Adjustable-Speed Drive Demonstration Office (ASDO), an applications center of the Power Quality Business Unit, to assist with the planning and engineering necessary for a full-scale effort.

The practical problems of customizing ASDs and of determining the overall benefits of applying ASDs in the highly complex injection-molding process were challenges that APS, Automotive Industries, and EPRI's ASDO were eager to meet. Although the focus of the study, which started in late August 1993 and was completed in January 1995, was to investigate and document both the energy and nonenergy benefits of using ASDs, one of its most practical and immediate results has been the development of a method for customizing …