Reduction of open-circuit dc-winding-induced voltage in wound field switched flux machines by skewing

In this paper, the open-circuit dc-winding-induced voltage in a wound field switched flux (WFSFs) machines is analyzed. The phenomenon of open-circuit dc-winding-induced voltage is illustrated and the mechanism is explained. Rotor skewing is proposed to reduce the open-circuit dc-winding-induced voltage, and the optimal skewing angle is analytically derived based on the analytically deduced harmonic orders of the open-circuit dc-winding-induced voltage. Finite-element (FE) analyses show that the open-circuit dc-winding-induced voltages in the analyzed 12-stator-pole partitioned stator WFSF machines having 10-, 11-, 13-, and 14-rotor-pole rotors can be effectively reduced by >94%, while the ac-winding phase-fundamental back-EMFs can be maintained by >95%. Twelve/ten-stator/rotor-pole prototypes with skewed and nonskewed rotors are built and tested to verify the analytical and FE results

Configuraciones de generadores eléctricos para pequeños aerogeneradores con mínimas condiciones tecnológicas de fabricación

Esta investigación presenta una revisión de las tendencias existentes en el desarrollo de generadores eléctricos para pequeños aerogeneradores. En la actualidad, los sistemas de energía eólica funcionan a velocidad variable o fija, utilizando el principio de generadores de corriente directa, generadores de inducción que utilizan un sistema con caja multiplicadora y los generadores sincrónicos, que funcionan a bajas velocidades del viento sin caja multiplicadora, siendo estos los más utilizados en pequeños aerogeneradores a nivel comercial. Se discuten tanto las fortalezas como las debilidades de las configuraciones existentes, se investigan las tecnologías emergentes en generadores eléctricos a baja velocidad y se realiza un análisis comparativo de los mismos. Se cumple el objetivo de seleccionar cual es el generador o generadores más adecuados para su construcción en talleres de mínimas condiciones tecnológicas para ser usados en sistemas eficientes de energía eólica pequeños, y se presenta una muestra de los aerogeneradores comercialmente disponibles

Analysis and Suppression of Induced Voltage Pulsation in DC Winding of Five-Phase Wound-Field Switched Flux Machines

In wound-field (WF) switched flux (SF) (WFSF) machines, the DC winding induced voltage pulsation causes current ripple in the DC winding and challenges the DC power source, and deteriorates the control performance. In this paper, the induced voltage pulsation in DC winding of five-phase WFSF machines is analyzed and its reduction methods are proposed. The cycles per electric period of the open-circuit and armature reaction induced voltage pulsation in DC winding are derived analytically. Modifying the airgap permeance by optimizing the rotor pole arc or chamfering the rotor pole surface, and axial pairing of rotor segments having rotor pole with different arcs are used to suppress the induced voltage pulsation in DC winding, with >90% average torque maintained. Finite element results show that, by optimizing the rotor pole arc, the peak-to-peak value of the induced voltage pulsation in DC winding can be effectively suppressed to 59.59%, 30.67%, 29.99% and 43.35% for the 10-stator-pole five-phase WFSF machines with 8-, 9-, 11- and 12-rotor-pole rotors, respectively. By applying rotor pole surface shaping, the induced voltage pulsation in DC winding peak-to-peak value can be effectively suppressed to 61.76%, 45.47% and 40.21% for the 8-, 9- and 12-rotor-pole machines, respectively, while by applying axial pairing, it can be suppressed to 46.89%, 7.16%, 15.64% and 12.04%, respectively. The 10-stator-pole/12-rotor-pole WFSF machines having the original rotor, optimized rotor, chamfered rotor and axial paired rotor are prototyped and the experiments validate the analytical and finite element results