1134 IEEE TRANSACTIONS ON ENERGY CONVERSION, VOL. 26, NO. 4, DECEMBER 2011 Determination of Hydro Generator Efficiency Using Infrared Thermal Imaging Techniques Edson da Costa Bortoni, Senior Member, IEEE, Roberto Teixeira Siniscalchi, and Jos´ e Antˆ onio Jardini, Fellow, IEEE Abstract—The calorimetric method has for a long time been ap- plied for energy conversion efficiency measurement in electrical machines. The number of temperature sensors necessary for its successful application in the field constitutes in one of the major drawbacks of the method. This paper shows how the usage of IR thermal imaging techniques can reduce costs and the necessary time for the calorimetric method application. In addition, contri- bution to the heat transfer coefficient determination and a new approach to consider conduction losses in the generator shaft are also presented. Index Terms—Electric machines, energy efficiency, hydroelec- tric generators, IR imaging. I. INTRODUCTION T HE practical determination of the energy conversion ef- ficiency of a synchronous generator is of utmost impor- tance for both manufacturers and end users, who are interested in calibrating their design techniques and during acceptance tests, respectively. In addition, efficiency indicates how primary source has been utilized and can work as a good threshold for maintenance procedures. The efficiency of any energy conversion system is the relation between the output and the input of this system. This basic concept forms the basis of direct efficiency test methods, where input and output powers are measured and related to each other. The difference between input and output powers gives the power losses, which are inherent to any energy conversion sys- tem. The determination of the power losses is the heart of the indirect efficiency test methods. As long as the input power can be obtained by the summation of the output power with the power loss, efficiency η can be calculated as follows. For synchronous machines of hydro power plants, the measurement of the output electric power is simpler than the input power, which is mechanical in nature, resulting in η = P output P input =1 − P losses P output + P losses . (1) Manuscript received January 3, 2011; accepted August 22, 2011. Date of publication September 29, 2011; date of current version November 23, 2011. The work of E. C. Bortoni was supported by CNPq and FAPEMIG to conduct research. Paper no. TEC-00006-2011. E. C. Bortoni is with Itajub´ a Federal University, Itajub´ a, MG 37500-903, Brazil (e-mail: bortoni@ieee.org). R. T. Siniscalchi is with Furnas Centrais El´ etricas, S˜ ao Jos´ e da Barra, MG 37945-970, Brazil (e-mail: rsinisca@furnas.com.br). J. A. Jardini is with University of S˜ ao Paulo, S˜ ao Paulo 05508-900, Brazil (e-mail: jardini@pea.usp.br). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TEC.2011.2166400 Fig. 1. IR thermal image of synchronous generators in a power plant. It is worth noticing that when applied to large machines, direct methods work with the measurement of large amounts of input and output powers. The unavoidable measurement errors would fall upon both measurements, leading to high inaccuracy of the results. Indirect methods, on the other hand, bring the advantage of measuring only one high power (output) and one relatively small power (losses). As long as the errors involved in loss determina- tion are proportionally reduced, a lower overall uncertainty on the efficiency measurement is eventually obtained. Losses segregation methods such as retardation and calori- metric techniques are described by the most popular stan- dards [1], [2]. Losses determination has been the subject of several recent efforts. Some of the recent works apply the calorimetric method for loss determination on small motors in laboratory [3], [4]. The- oretical models to study some losses of the synchronous ma- chines have been developed, showing good agreement with test results [5]–[8]. Application of the calorimetric method in a hy- dro power plant is presented in [9] and [10]. Unfortunately, none of the previous works have been focused on the evolution of the calorimetric method, neither on its theory nor on its application. The contribution of this work relies on the application of the calorimetric method to determine the efficiency of energy conversion of synchronous machines in situ. IR thermal imaging is used to determine released losses through the machine surface as shown in Fig. 1. A different approach to define the heat transfer coefficient and the consideration of conduction losses in the generator shaft are also presented. 0885-8969/$26.00 © 2011 IEEE