Control of Non-conventional Synchronous Motors

Chapter 1

Self-controlled Synchronous Motor: Principles of Function and Simplified Control Model ¹

1.1. Introduction

Every synchronous machine supplied by an electronic power converter and functioning with variable speed needs to ensure control of the converter that supplies it, in the sense that the rotational speed of its rotor imposes the frequency of the voltages and of the currents the converter provides to the stator windings. However the name “self-synchronous machine” usually refers to the case where the electronic power converter that supplies it is a thyristor bridge whose commutations are ensured by the voltages the machine develops at its terminals [BON 97, BUH 77, CHA 88, KLE 80, PAL 99]. This bridge is supplied with direct current (DC) via a smoothing inductance by an input converter that is itself usually a thyristor bridge connected to the alternating current (AC) mains. We thus obtain the principle diagram in Figure 1.1.

The synchronous machine can run as a motor or as a generator:

– to run as a motor, the input bridge works as a rectifier and supplies the intermediate DC circuit with electric power that is transferred to the synchronous machine by the bridge that supplies it, which works as an inverter.

– to run as a generator (braking operation) the bridge connected to the synchronous machine works as a rectifier and transfers the electric power generated by the synchronous machine to the network via the input bridge, which works as an inverter.

Operation with ...