Patent GB-190712578-A (GB)
Title: Improvements in Self Regulating Electrical Machines for Alternating or Direct Current.
Inventor: HEYLAND ALEXANDER
Filed: 1907-05-30
Granted: 1908-06-01
Abstract: 12,578. Heyland, A. May 30, 1906, [date applied for under Patents Act, 1901]. Field magnets ; dynamos, regulating.- Armature reaction is neutralized and compounding effected by controlling the excitation by currents produced by a dispersion field of unipolar form, which field varies as the armature reaction of the load current both in regard to magnitude and phase displacement. The invention is of general application but is especially applicable to alternating - current machines. Figs. 3 and 5 show a generator having a multipolar magnet P, the poles N of which are stronger than the poles S, so that a dispersion field is established through the machine frame and south magnetic poles S, Fig. 5, are produced at the ends of the shaft. Such a field may be caused by making the air-gaps unequal, by winding no turns on the poles S or fewer turns than are wound on the poles N, by making the poles N and S of unequal sections, or by a combination of these means. A threelimbed magnetic shunt may be mounted on the shaft adjacent to the poles S, and by displacing it slightly with regard to the poles the dispersion may be made more or less for wattless currents, thus allowing different regulations for currents of different phase displacements. The dispersion field is made to generate an exciting-current either directly in the pole winding p, Fig. 5, or in the case of separately-excited machines, in a separate regulating-winding wound on the poles. To avoid collecting large currents, the dispersion current may be used, as in Fig. 7, to control the field of the machine B which supplies the exciting-circuit E of the main machine. Fig. 8 shows the adaptation to an ordinary homopolar machine, in which the regulating-current generated by an internal dispersion field is carried by a winding p within the normal exciting-coil E. In the case of machines having direct-coupled exciters, the magnetic conditions of the exciter are modified to agree with the asymmetric conditions of the main machine as above described, the common dispersion fields being completed through the base-plate of the machines. The exciter field thus varies with the main dispersion, i.e. with the armature reaction. In place of being used directly, the dispersion current may be made to operate regulating-apparatus independent of the machine. In a modified method, which is particularly useful for leading load-currents, the dispersion field is arranged to vary inversely as the armature reaction, the regulating effect of the current being also reversed. Thus in the case of Fig. 3, where the poles N have the larger gaps and exciting-coils, the arrangement would be such that at light load the poles S are the more strongly excited and cause the dispersion field. As the load increases, the increased armature reaction at the poles S cancels their dispersion and allows the poles N to give a dispersion field, so that the regulating- current passes from a maximum negative value through zero to a maximum positive value. The normal excitation of the machine is adjusted to correspond to the load at which the dispersion current is zero. By suitably-proportioned dispersion fields, a machine may be regulated for over, under, or counter compounding.