Synchronous machines

Among electrical machines, synchronous machines are playing an increasingly important role in both power generation and actuation. Their principle, modeling and steady-state operation have been described in [D 3 520] , [D 3 521] and [D 3 522] respectively.

Self-piloted operation, as described in this dossier, consists in optimized control of the armature field, in order to significantly improve performance. Firstly, the risk of stalling inherent in non-self-piloted synchronous motors is completely eliminated; secondly, optimizing the amplitude of the armature field and the angle it makes with the field of the field coil enables very significant improvements in performance, whether in terms of energy efficiency or the extension of the power envelope curve at high speed. Whether in motor or generator mode, or on rotating or linear structures, autopilot operation has considerably increased the application possibilities of synchronous machines, and more particularly those with magnets, whose penetration is continuing in virtually all sectors, not least because the cost of magnets has fallen sharply, at least relative to the cost of other raw materials (copper and iron). However, to achieve self-steering operation and the control options mentioned above, an inverter, a control system and, a priori, position and current sensors are required. This dossier describes the operating principles of the "ideal" self-steering synchronous machines (with electromotive forces and sinusoidal currents), which offer the best overall performance, as well as those of other solutions which we describe as special. On the one hand, the latter make it possible to achieve very high power levels through the use of thyristors; on the other hand, they enable us to obtain economical systems thanks to simplified position sensing and control, solutions that are more commonly found in the low-power sector.