Single to Three-Phase Conversion by High-Leg Phase Derivation
AuthorJensen, Michael J.
Electrical and Biomedical Engineering
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Three-phase motors are common and required for water and wastewater pumping applications in residential developments. However, three-phase electrical distribution is not common within residential sub-divisions and single-phase connections are typically the only type of electrical service available. Since single-phase motors are limited in size and application, electrical power converter devices are used in connecting single-phase utilities with necessary three-phase motor loading and types.This paper explores two novel methods of single to three-phase conversion. Each method relies on creating or deriving a third phase to complement existing single-phase, three-wire configurations. These conversion methods present advantages over existing technologies such as AC/DC/AC converters (variable frequency drives / adjustable speed drives) by reducing component count, increasing operational reliability and ease of use, yet offering the enhanced three-phase performance.The first method proposed makes use of a three-winding transformer to raise and rectify a DC bus voltage to a level required to complete the single to three-phase conversion. The second method proposed implements a fully electronic converter to reduce size, weight, and cost. An ideal three-phase voltage source case is modeled and these two cases are compared against the ideal three-phase source conditions. Each case analyzes line and motor current, as well as torque and speed profiles.Required concepts in electrical machinery, power distribution, and power electronics are discussed to familiarize the reader with the proposed conversion techniques. Some concepts are modified for application specific use, but retain basic form and functionality. Future work and additional analysis are presented at the end.