Measured Savings of DC to AC Drive Retrofit in Plastic Extrusion

This paper presents the potential electrical energy efficiency improvements for utilizing alternating current (AC) motors controlled by variable frequency drives (VFD) in place of direct current (DC) motors to drive plastic extrusion machines. A brief background on the extrusion process is presented along with typical extrusion machine electrical drive performance requirements. Motor performance characteristics and control strategies are described for both AC and DC machines. A case study is presented, where detailed electrical measurements were performed on two similar extrusion machines driven by a DC motor and an AC motor respectively. Electrical energy, demand, and cost savings are analyzed.