Interior Permanent Magnet Generator: Generator of New Millennium

R. Dutta, F. Rahman


The rapid development in the field of permanent magnet material has rekindled interest inthe permanent magnet electrical machines. In the last couple of decades, the price of high densitypermanent magnet has come down to an affordable level. The availability of the material likeNeodymium-iron-Boron (NdFeB), has improved the characteristics of many permanent magnetmachines such as Brushless DC machine, Permanent magnet synchronous machine, Switch reluctancemachine etc. Due to decreasing natural resources, conservation of energy has become one of themost important aspects of our time. It has been proven time and again that higher the efficiency of amachine, the better is its energy saving performance. The use of magnet material can increase theefficiency of the electric machine to a great extent. In a permanent magnet generator, field excitationis provided by permanent magnet material. As a result, the carbon brushes, slip rings, field windingand its copper loss, dc supplies are eliminated. There is also possibility of reducing the size andweight. The concept of permanent magnet generator is not very recent. In fact there exist permanentmagnet generators (PMGs) for many years; still their applications are limited. The conventionalPMG has a very big disadvantage over other types of generators, due to the constant nature of thefield excitation, voltage regulation varies with load. But the interior type permanent magnet machinehas an inverse saliency ratio, which can be exploited to improve the voltage regulation characteristicas well as its constant power capability. In this paper, the performance of an Interior PermanentMagnet generator (IPMG) has been discussed. Its option as a grid connected generator has beenexplored. Its merit and demerit over a conventional synchronous generator have been discussed andanalysed.

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