Forces in machine end windings

THE ELECTROMAGNETIC FORCES experienced by the end windings of machines during the surge currents of a sudden short circuit can be large enough to cause serious trouble if the windings are not properly supported. Knowledge of these forces is particularly important in turbine-generators, where the increased loading associated with operation at elevated hydrogen pressures and with larger ratings tends to raise the machine forces to ever greater magnitudes. A step-by-step approach to the evaluation of force on any desired portion of the end windings of a machine, with sufficient accuracy for an engineering study, can be made using a method based on the following differential vector equation¹, expressed as a triple cross product: