GB210482A - Improvements in and relating to variable-frequency alternatingcurrent generators - Google Patents

Abstract

210,482. Japolsky, N., and Kostenko, M. Oct. 3, 1922. Alternating-current commutator machines; exciting.-In an installation in which for speed control alternating-current motors are fed with current cf variabe frequency derived from a compensated alternating-current commutator generator driven at constant speed and fed with exciting current of variable frequency and voltage, the commutator generator is constructed without projecting poles in order to enable high periodicities and plain rotating fields to be obtained. In the arrangement shown in Fig. 5, the compensated commutator generator A.C.C.G, which gives variable frequency to the motor AM under control, is driven by a constant-speed motor T which also drives a continuous-current machine D for supplying the exciting group of the generator A.C.C.G. This group comprises a variable-speed motor M, on the shaft of which is the variable-frequency alternating-current exciter WE and its exciter E. The voltage of the exciter WE is proportional to the square of its frequency and the voltage of the generator A.C.C.G is proportional to its frequency. The volts of the generator A.C.C.G. may also be varied independently by means of a resistance r. Alternatively, the exciter E may be driven by the motor AM, in which case the exciter WE is separately excited until the machine E gives the requisite voltage. This arrangement is used when the rotor of the machine A.C.C.G is excited instead of the stator. A square law relationship between the voltage and frequency of the alternating- current exciter mav also be obtained by means of a non-saturated self-exciting alternator running as a rotary converter. Fig. 1 shows a non-salient pole construction of the machine A.C.C.G in which the exciting and compensating windings W<s>, W<1> are both carried by the stator, but the exciting winding mav alternatively be carried by the rotor with the normal rotor winding which is connected to the commutator. In Fig. 4 a form of winding for the commutator generator is shown in which three-phase variable-frequency exciting current is fed to a twelve-phase rotor winding W<R>, Specifications 28081/10 and 223/11 are referred to.