Frequency-dependent operation of parallel three=phase inverters - involves switching to indirect inverter operation at higher machine frequencies when one bridge current is zero

摘要

Two indirect inverters (1, 2) are supplied from a three-phase network via a transformer (W), and feed the three stator windings (R, S, T) of an AC machine. Each inverter consists of two rectifying thyristor bridges (e.g. N1, M1) joined by an intermediate circuit choke (L1). Two of the machine line currents are provided by the respective invertors (1, 2). The third line current is formed from the sum of the currents through the machine-side bridges (M1, M2). USE/ADVANTAGE - For direct inverter operation and for switching between direct and indirect operations with allowance for commutation processes in rectifiers