A method of operating an asynchronously constructed generator with a commutator cascade machine, the excitation of which is supplied at least in part through a frequency changer

摘要

281,676. Akt.-Ges., Brown, Boveri, et Cie. Dec. 3, 1926, [Convention date]. Alternating - current induction machines. - A commutator machine 4 cascaded with an asynchronous generator 2 is excited wholly or in part by a frequency changer 7 fed by a synchronous generator 8 which is coupled with a synchronous motor 3 connected to the terminals of the asynchronous generator and with an independently regulatable driving motor, for instance a continuous-current motor 9. The machine 4 may be excited by a combination of the slip-ring voltage of the asynchronous generator and the commutator voltage of the frequency changer, and resistances, inductances or a separate exciter may be interposed. If the network frequency is to be determined by the motor 9, the motor 3 should be cut out of circuit to avoid overheating by generated current unless the resistance of the leads thereto is sufficiently high. The motor 3 may be kept in circuit if the change of slip of the asynchronous generator between full load and idle running as determined by the regulator of the main driving machine and the motor 9 is arranged to be equal to the change of slip between no load and full load when operating as a motor. If the generator 2 works in parallel with synchronous machines, proper distribution of the load between the different generators may be obtained by controlling the speed of the motor 9 in dependence upon the load on the generator 2. Alternatively, the machine 9 may be disconnected and the motor 3 connected to the network in which case the frequency is determined by the synchronous generators. The machines 3, 8 have the same number of poles, for enabling the phase position of the voltage of the generator 8 to be adjusted, the generator may be provided with two exciting windings relatively displaced by 90‹, or phase adjustment may be effected by regulatable transformers. In order to avoid disturbance when connecting the machine 3 to the network, the network voltage vector and that of the machine 3 are brought into phase either by regulation of the machines 2 or 8, or by turning the stator of the machine 3 or the position of the field poles with respect to the field magnet. According to the Specification as open to inspection under Sect. 91 (3) (a), the generator 2 may be given a synchronous character by feeding its rotor or the exciting winding of the cascade machine 4 with continuous-current. The same effect may be produced by coupling the converter group 3-8 'with the rotor of the generator 2 either mechanically or electrically. This subject-matter does not appear in the Specification as accepted.