Sub-transients in PM synchronous generator with diode rectifier load

Permanent magnet synchronous generators are mostly designed without an explicit damper cage. When feeding into an intermediate d.c. circuit via a diode rectifier, as in small-scale wind turbine systems, the currents induced in conductive rotor parts may influence the generator operation. A simplified model is used to study sub-transient machine behavior. In quasi steady-state harmonics of order 6
^th
order and above in the rotor give rise to eddy-current loss, and the harmonic distortion may require a de-rating of the drive. Simulations are offered, and problems in determining the model parameters from test are discussed.