Influence of rotor magnetic circuit structure on electromagnetic properties in nuclear half-speed turbine-generator

In order to reduce the radial magnetic flux leakage loss, lower temperature rise of stator coils and hot spots, improve efficiency, the rotor of the large-capacity nuclear turbine-generator is designed with bias slot. However, the magnetic circuit structure and the electromagnetic properties of the generator are changed by the bias of rotor slot, taking direct-axis reactance, quadrature-axis reactance and excitation current for example. A 1000MW nuclear half-speed turbine-generator was taken as an example to study the electromagnetic properties affected by the change of rotor magnetic structure caused by the bias of rotor slot with FEM in this paper. The features of the unsaturated reactance, saturated reactance, air-gap magnetic field, no-load and rated load excitation current impacted by different bias situations were systematically analyzed. The variation regularities of reactance, excitation current and air-gap flux density with different slot bias angles were deduced, which can provide reference for rotor slot bias design of large-capacity nuclear turbine-generator.