tailieunhanh - Basic principles and functions of electrical machines

Recent advances in power electronics and highspeed microprocessors have led to considerable attention in electrical machines with regard to their applications in industrial drives. This paper brings to the fore, various types of electrical machines, their operations, and applications, as well as the method of determining their parameters. Various ways of protecting electric machines against overloads and mechanical faults are also highlighted. It is anticipated that the work presented in this paper will be of immense benefit to practicing engineers especially in areas of machine design, maintenance, and protection. | Basic Principles and Functions of Electrical Machines . Okoro . Agu and E. Chinkuni 1Department of Electrical Engineering University of Nigeria Nsukka Enugu State Nigeria E-mail oiokoro@ 2Polytechnic University of Namibia Windhoek Namibia E-mail chikuni@ ABSTRACT Recent advances in power electronics and highspeed microprocessors have led to considerable attention in electrical machines with regard to their applications in industrial drives. This paper brings to the fore various types of electrical machines their operations and applications as well as the method of determining their parameters. Various ways of protecting electric machines against overloads and mechanical faults are also highlighted. It is anticipated that the work presented in this paper will be of immense benefit to practicing engineers especially in areas of machine design maintenance and protection. Keywords electrical machines operation design maintenance protection stator INTRODUCTION The Direct Current . machine the synchronous machine and the induction machine are the major electromechanical conversion devices in industry 1 . The merits of the squirrel cage induction machine are lightness simplicity ruggedness robustness less initial cost higher torque-inertia ratio capability of much higher speeds ease of maintenance etc 2 3 . The most important feature which declares it as a tough competitor to . machines in the drives field is that its cost per KVA is approximately one fifty of its counter-part and it possesses higher suitability in hostile environment. Unfortunately induction machines suffer from the drawback that in contrast to . machines their speed cannot be easily and effectively adjusted continuously over a wide range of operating conditions 4 . On the other hand the synchronous machine has the merit of being operated under a wide range of power factors both lagging and leading and are much better suited for bulk power .