Analysis of forces on coil ends of formed stator windings

An end-winding model in 3D FEM is built for investigation of magnitudes, distributions, and variations of the electromagnetic forces on coil ends of formed stator winding under both load and short-circuit. The results from the calculations on a turbo-generator under nominal load show that the radial force varies very much in circumferential direction and always tends to expand the stator windings. The forces between different coils can be either attracting or repellent, which depends on the phases of the coils. In the sudden 3-phase short-circuit, the maximum positive torque is more than 20 times higher than in the rated case and the total torque on coil ends can reach 15% of the main rated torque of the machine. The maximum of forces on one of 10 support bolts in the example machine may reach 52 kN at a half period after short-circuiting.