Synchronization of rotor angles of fixed speed wind energy converters with an induction generator has been reported in several wind farms. In terms of impacts on a power system, the synchronization could worsen the voltage flicker problems. Although many articles have examined this synchronization, there remains considerable room in the physical interpretation of the phenomena. This article discusses the physical context of the synchronization phenomena of wind turbines in a wind farm. After analysing interaction among electric power output, voltage, generator slip and rotor angle, differential equations describing the phenomena are presented. The synchronization phenomena are examined through a study on equilibria of the equations and their stability. Fundamental characteristics of the phenomena such as pull-in force, speed of synchronization and the impact of discrepancies among generator characteristics are discussed for two- and three-machine systems. The results show that synchronization tends to occur in wind energy converters with large 3p components and a low power factor, which are interconnected into a grid with large short-circuit impedance of high X/R ratio. Copyright © 2005 John Wiley & Sons, Ltd.