AC-DC-AC inverter operation for three=phase motor supply - involves two thyristor inverters switched from sinusoidal phase current mode to indirect mode at transitional speed

摘要

Each of the inverters (1, 2) consists of two rectifying thyristor bridges (e.g. N1, M1) joined by an intermediate circuit choke (L1). The respective bridges (N1, N2) connected directly to the mains transformer (W) are linked on the DC side by a thyristor switch (V). The system is switched between direct and indirect invertor operation at an instant when the currents (id1, id2) flowing in the respective chokes (L1, L2) are equal and one phase current is zero. USE/ADVANTAGE - Pref. with synchronous motor. Affords optimal switching from direct invertor operation at low speeds to indirect operation at higher speeds, and vice versa.