Theory of the Three Phase Salient Pole Type Generator with Bridge Rectified Output-Part I

Abstract

The theoretical equations, describing the characteristics of a three phase salient pole type AC generator with asymmetrical damperwindings and bridge rectified output are derived. All resistance and rectifier drops are neglected; only the first winding MMF's and the first two permeance harmonics are considered. All winding inductances are defined in detail in App. I and are expressed in absolute and per-unit values. A set of equations is derived, defining the mutual relations between DC output voltage and current, start and duration of commutation, commutation current, constant and variable field current, damper circuit currents and instantaneous DC voltage fluctuations. By the use of two simplifying assumptions, this set is converted into explicit equations for the above values. These show that the inductance, determining the length of the commutation period is the equivalent of the average between the direct and quadrature subtransient inductances. Both a Star as well as a Delta connected stator winding is discussed. All equations can be expressed in generalized machine parameters. A numerical example is included.