Parasitic losses in synchronous-machine damper windings

The paper develops, from theoretical considerations, formulae for the parasitic losses in both squirrel-cage and insulated phase-wound damper windings of synchronous machines. It shows that in squirrelcage windings the parasitic losses can be substantially reduced but not (except in one instance) eliminated, by a suitable choice of stator and rotor slot pitches; and that the losses in phase-wound dampers can, with little difficulty, be eliminated. Methods are given for calculating both the pulsation and the surface losses in the rotor-pole laminations, thus showing to what extent these losses are dependent on disposable machine constants. Numerical examples are worked out for two machines, and the results, together with those of two other machines, are given in the form of open-circuit core-loss curves on which test results are plotted for the purpose of comparison.