Analyse et conception de moteurs synchrones chemisés à commutation électronique
The number of brushless DC (BLDC) motor applications has increased significantly, essentially due to reduced costs of semiconductors and permanent magnets, but also because of the emergence of new control strategies, such as closed-loop and sensorless control. Among the different electric drives, the heating circulation pump is a typical application which could greatly benefits from new BLDC technologies. Nowadays, the majority of low power heating circulation pumps is driven by AC induction motors. Despite of its low efficiency (< 20% for a single phase motor and < 50% for a three phase motor), this kind of motor is still used widely, because of its inherent simplicity since no electronic driver is needed. When a regulation is necessary (for example pressure, flow regulation), this advantage disappears. The aim of this work is a systematic analysis of the circulating pump motor. One solution is investigated in particular: the pump with a sealed BLDC motor. The following points are analysed in details: An analytical method to calculate the flux density distribution is tailored for motors with an important gap, as the sealed motors or slotless motors. The analysis of the electromagnetic characteristics for brushless DC motors shows the similarity of the various brushless DC motors. The calculation of tube losses determines their influence on the energetic balance of the motor. The determination of the acoustical motor noise shows the influence of the different modes of phases switching. The thermal aspects which take into account the motor environment are examined from the theoretical and practical point of view. The synthesis of these points results in a concept for the design and optimisation of BLDC motors; a series of pump prototype have been designed. For the heating circulation pump, the replacement of the AC induction motor with a brushless DC motor makes it possible to double the global installation efficiency. This solution is very promising from an energising aspect as well as an economical one and contributes to electrical energy savings, essential in this end of century.