Patent GB-245067-A (GB)
Title: Apparatus for compensating or regulating the power factor of dynamo-electric machines
IPC: H02K17/38
Filed: 1925-10-06
Abstract: 245,067. Matabon, J. L., and Foucault, C. M. Dec. 24, 1924, [Convention date]. Addition to 240,158. Alternating-current commutator and induction machines.-A compensating exciting machine as described in its application to an asynchronous machine in the parent Specification is used, according to the present invention, with a synchronous machine which may act as a generator or as a synchronous motor functioning as a compensated asynchronous motor when loaded beyond its synchronous working limit. The synchronous machine o, p, Fig. 1, is of normal construction as to air-gap width and the secondary winding p which furnishes the excitation, and the exciter has two rotor windings, one with slip-rings e and the other with a commutator d, as in the parent Specification, the brushes j being connected to rheostats in the exciter secondary circuit i and that of the main machine p. The primary exciting winding r is so dimensioned as to furnish the excitation required by the secondary compensating winding i together with that for the secondary p of the main machine. The rheostats v, x, are used for starting the synchronous machine and exciter respectively and the rheostats u, y are respectively for controlling the excitation of the synchronous machine and the compensation of the exciter. The voltage and frequency of the mains supplying the exciter mav be the same as or different from those supplying the main machine. When the main machine runs as a generator in parallel with others, it is connected to the mains and the arm of the rheostat x is moved to the compensating position n. Closure of the circuit of the brushes j on to the windings p gives the machine continuous-current excitation which may be, regulated by the rheostat u. Regulation of the exciter excitation by means of the rheostat y then modifies only the compensation and does not affect the volts at the brushes j. When the main machine runs as a synchronous motor, its primary coil o and the primary r of the exciter are connected to the mains w. The rheostat v is moved right over and the arm of the rheostat x is moved in the direction of the arrow m to start the main machine as an asynchronous motor. When the compensating studs n are reached, it runs into synchronism automatically, the continuous-current excitation being subsequently regulated by the rheostat u. If the synchronous load capacity be exceeded, the machine runs as a compensated asynchronous motor. In the form shown in Fig. 2, the secondary " motoring and compensating coils " of the exciter are directly connected to the commutator brushes d and the regulating rheostat of the exciting current of the main machine is combined at z with the starting resistance. The Specification as open to inspection under Sect. 91 (3) (a) states that this arrangement may also be used for compensating asynchronous machines, the excitation regulating resistance of the main machine " being reduced to the value necessary for limiting the short-circuiting current of the exciting primary winding when passing from running as a normal asynchronous machine to running as a compensated asynchronous motor." This subject-matter does not appear in the Specification as accepted.