Simplified Parameter Estimation Technique of Brushless DC Generators M. J. Khan * ,M. T. Iqbal,and J. E. Quaicoe Faculty of Engineering and Applied Science Memorial University of Newfoundland, St. John’s, NL, A1B3X5 * Email: mjakhan@engr.mun.ca Telephone: (709) 737–2049, Fax: (709) 737–8975 Abstract— Multipole Permanent Magnet Alternators, commonly known as Brushless DC (BLDC) generators are popular choices for use in small wind/hydro energy con- verters. For analysis and system design purposes, various parameters of such machines need to be determined. Based on a simplified model of BLDC generators, a set of nominal yet adequate tests for parameter estimation is proposed in this article. Validity of such approach is also discussed through experiments. Results have been found to conform to the expectations. I. I NTRODUCTION In wind/hydro applications permanent magnet gen- erators are attractive options, because of advantageous features such as, direct-drive coupling, higher energy density, low speed-high torque operation, and higher efficiency. In the literature these generators are com- monly termed as Permanent Magnet Alternator (PMA) or Permanent Magnet Synchronous Generator (PMSG). Axial flux and radial flux multi-pole machines are par- ticularly common in small wind turbines (Fig. 1). Even though, the fundamental operational characteristics of all these machines are the same, there are certain subtle differences. With regard to wind/hydro applications, the term Brushless DC (BLDC) generator is probably more suitable considering the associate machine structures and characteristics [1].          Fig. 1. Radial flux (inner & outer rotor) and axial flux (double & single stator) PM generators For system design and analysis it desirable to have a set of parameters that can adequately describe the generator model. This is even truer for BLDC generators because: • Many generators are of improvised type, originally meant for some applications other than power gener- ation. Some generators are hand-built or developed in the labs where system parameters are unknown. • Manufacturers of commercially available machines do not provide adequate information to ana- lyze/synthesize the system model. • From machine design perspective Finite Element Methods (FEM) may yield accurate parameters. However, this approach requires extensive compu- tations and needs machine mechanical dimensions [2]. • BLDC generators constitute a subclass of the syn- chronous machines. Standard testing methods for the synchronous generators include open circuit test at synchronous speed, short circuit test at rated current and resistance test. On the contrary, BLDC generators operate in wide variable speed range. Moreover, mechanical constraints make the short circuit test very difficult owing to the high cogging torque arising from the interaction of armature cur- rent and the permanent magnets. Therefore, such testing is inadequate for BLDC generators. • There is no standard for BLDC generator testing. The field of application is very limited and it is unlikely that there will be any IEEE standard for such machine in the near future. Most of the previous attempts on parameter estimation of BLDC generators are heavily dependent on theoritical analysis [2]–[4]. While these methods are of high significance, a simpler technique proposed here might also be useful for many system-level analysis.