Power circuit diagrams in the AC electric drives made on the condition of electrical losses minimum

The paper identifies the necessity of optimal power circuit diagram selection for electric drive with field regulated reluctance machine. The authors present computation of specific weight coefficients and give, in relation to the rated current, linear regressional dependences of specific losses in semiconductor frequency converters. It is found that increasing PWM carrier frequency improves output current waveform, but increases losses, so it is needed to choose the carrier frequency in a certain way according to problem. To solve the optimization problem considering minimal electrical losses the authors constructed regressional dependence of electrical losses in the frequency converter on current at a frequency of PWM signal of 0 Hz. The paper presents optimization criterion surface depending on the rated motor torque and the number of phases. The optimization criterion in electric drives with FRRM at low power is the worst for multiphase circuits. At power increase this trend persists, but difference between optimal solutions for three-phase and poly-phase circuits becomes insignificant. This is explained by linear dependence of electrical losses on the current.