Synchronous Machine

Abstract

In the following chapters signal-flow graphs of synchronous machines will be deduced and, from these, also the control strategies. To avoid going into too many details for the signal-flow graphs, the following simplifying assumptions apply:

• The state of saturation of the machine will be considered constant, but may vary in a longitudinal and transverse direction.

• The influence of skin effects on the conductors will not be considered.

• Losses in the iron will be neglected.

• Only the reciprocal damping of the basic magnetic fields (simple number of pole pairs) in the magnetic gap will be considered.

• The asymmetries of an irregular or incomplete damping cage may be considered in the form of asymmetrical resistances and inductances in the twin-coil compensating winding of the damper.

• The excitation axis must be aligned with the centre of one mesh of the damper or with the centre of one damper bar.

• The machine’s main and mutual inductances may vary in the longitudinal and transverse directions.

• The stator has a three-coil symmetrical winding that can be converted to an equivalent two-coil winding, rotating with the rotor.

• A magnetic coupling between the branch winding and damper cage through the transverse inductance (if the two windings are arranged in common slots) may if necessary be considered by means of high mutual inductance M _ED .

• The three-phase power supply system is fixed and does not contain any neutral component.

• The parameters on the rotor side are converted to the stator side.