Where N is the rotor angular speed, f is the frequency of the AC voltage generated in the stator windings, P is the number of poles in the transmission system for a variable speed is not permissible.
32.
Each coil side of the stator winding consists of rectangular copper tubes, each tube being insulated with resin-impregnated glass braid, and the tubes are transposed within the coil length by the Roebel method to minimise stray copper losses.
33.
Thus, an influence of drive system vibratory behaviour on the electric machine rotor angular speed fluctuation, and in this way on the electric current oscillations in the rotor and stator windings, can not be investigated with a satisfactory precision.
34.
In large machines, different systems may be used according to the predicted temperature rise of the machine; for example, in large hydroelectric generators, stator windings may be Class B but the more difficult to cool rotor winding may be Class F.
35.
Larger single phase motors are split-phase motors and have a second stator winding fed with out-of-phase current; such currents may be created by feeding the winding through a capacitor or having it receive different values of inductance and resistance from the main winding.
36.
The electrical energy efficiency of a typical industrial induction motor can be improved by : 1 ) reducing the electrical losses in the stator windings ( e . g ., by increasing the cross-sectional area of the tolerances . " For further discussion on this subject, see Premium efficiency . )"
37.
Large brushed machines which are run with DC to the stator windings at synchronous speed are the most common generator in power plants, because they also supply reactive power to the grid, because they can be started by the turbine and because the machine in this system can generate power at constant speed without a controller.
