GB725428A - Improved power converting device or system - Google Patents

Abstract

725,428. Generating arrangements. PESTARINI, J. M. Feb. 4, 1953 [Feb. 4, 1952], No. 3201/53. Class 38 (4). A constant frequency network L is supplied from a variable speed prime-mover 1, such as a water turbine, by plant comprising an alternator 2 driven by the prime-mover, a constant current D.C. generator 6, such as a metadyne machine, a rotary frequency converter 3 having a " stator " rotatable by a D.C. machine 4, and a rotary D.C. to A.C. converter 7 (preferably of the metadyne type) driven by a synchronous motor 5 having means whereby its running phase angle with reference to the network L may be adjusted. The last means may comprise a phase shifting transformer arranged between the network L and the A.C. winding of the motor, or, as shown, the motor may have two angularly displaced field systems separately and adjustably excited by D.C. generators 12, 13. Over a high-speed range of the primemover, the alternator 2 feeds the network over the converter 3, the output frequency of which is controlled by adjustment of the fields 8, 29 of the D.C. machines 4, 6, respectively. During this stage converter 7 is short circuited and isolated from the network. Over a lower speed range the alternator is isolated from the converter 3, and power is supplied to the network by the machine 6 over the converter 7, from which the short-circuit has now been removed and which is connected to the network. Instead of the machine 6 being directly driven by the prime-mover, it may be arranged to be driven by one or two synchronous motors alternatively from the network, or alternator. Variable ratio transformers may be interposed between the network and the converter 3.