The spread of wind energy converters is progressing in recent years and its capacity is becoming larger and larger. In order to capture more energy from the wind, it is important to analyze loss characteristics of wind generators for the operating speed which is determined dependent on the wind speed. This paper presents a method to evaluate various losses in a wind generator as a function of wind speed, which is based on steady-state analysis and thus the calculations can be performed quickly. By using the proposed method, wind turbine power, generator output, various losses, and the total energy efficiency are calculated for three types of wind speed data which are represented by a Weibull function. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(3): 52–62, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20426 Copyright © 2006 Wiley Periodicals, Inc.