An Integrated Capacitive Brushless Excitation System for Wound Field Synchronous Machines Using Low-cost Printed Circuit Boards

Download or read book An Integrated Capacitive Brushless Excitation System for Wound Field Synchronous Machines Using Low-cost Printed Circuit Boards written by Skyler Steven Hagen and published by . This book was released on 2019 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the current proliferation of electric machines taking over roles that were historically performed by mechanical transmissions and combustion engines, strides are being taken to make electric machines more power and torque dense, as well as less expensive. The wound field synchronous machine (WFSM) has advantages in power density, controllability, as well as cost of manufacturing, over other types including induction machines and permanent magnet synchronous machines. Its use for vehicle and traction applications has been limited due to the requirement of electrical power on the rotor field windings throughout the machine's entire range of speed, including stall. Field excitation requirements at stall and low speeds prohibit the use of conventional brushless exciters, commonly used in gen-sets, which rely on shaft rotation and torque to produce field current. Gapped rotating electromagnetic transformers allow excitation at stall but suffer from complexity of manufacturing and added volume to accommodate the ferrous core materials required to complete a magnetic circuit. All contactless field excitation methods require a rotating rectifier diode board or assembly to be installed on the rotor, alongside the brushless exciter or rotating transformer, in order to provide direct current to the field winding, from a contactless power coupler which is inherently alternating current. Capacitive power transfer (CPT) has been shown to be competitive with inductive power transfer in supplying full field excitation to wound rotor synchronous machines. In this thesis, a capacitive power transfer system is described in which the rotating rectifier board, manufactured using conventional printed circuit board techniques, dual-purposes as the capacitive power coupling structure, resulting in an efficient, low cost and compact means for transferring kilowatt scale electrical power to a wound field synchronous machine. A design process for the capacitive coupler itself in conjunction with necessary passive components and controls is laid out, and experimental results are given for a CPT system being used to provide full field excitation to a 55kW WFSM.