| 摘要 |
Undersynchronous and oversynchronous rectifier cascades having an asynchronous machine (5) with a slip-ring rotor, in which the slip power released when running undersynchronously as a motor or over- synchronously as a generator is fed back to the power supply network (1) via an invertor (36), are used for driving pumps, ventilators and compressors in the power range from 500 kW to 5 MW. in order that the undersynchronous and oversynchronous rectifier cascade can also be used as a generator in the undersynchronous region and as a motor in the oversynchronous region, the invertor (36) is operated with a DC intermediate circuit such that the intermediate circuit current (Id) disappears for a short period so that commutation of the valves of a rectifier (10) on the machine side is possible. In this way, the rotor current of the asynchronous machine (5) is predetermined by means of a coordinate converter (31), via a trigger pulse transmitter (23) on the machine side, in terms of its magnitude (Is) and phase angle ( phi ). A zero-current detector (26) is used to determine whether the intermediate circuit current (Id) is < 10 A for a predeterminable short time interval of 10 mu s, and the voltage on the thyristors of a rectifier (12) on the mains side is < 20 V, in order that the commutation of the thyristors of the rectifier (10) on the machine side can be released via the trigger pulse transmitter (23) on the machine side. <IMAGE> |
