Some aspects of the electromagnetic design of a convertor-fed high speed synchronous motor

The authors describe the principal design features of a typical high speed motor based on the 9 MW, 2-pole, 5600 r.p.m., 93.3 Hz motors supplied for the boiler-feed pumps of the Majuba Power Station in South Africa. The emphasis is on the electromagnetic design. Finite element field distribution methods are used to investigate various electromagnetic aspects of its design, and two cases of the application of these advanced methods are presented. The first example deals with the calculation of losses in the rotor due to the harmonic currents in the convertor supply. The second example illustrates the scheme of determination of reactances and time constants based on the finite element simulation of the standstill frequency injection tests, and compares the calculated results against those obtained from tests