Patent GB-334953-A (GB)
Title: Improvements in or relating to synchronous alternating current dynamo electric machines
IPC: H02K19/10
Filed: 1929-06-14
Abstract: 334,953. Japolsky, N. June 14, 1929- Inductor-alternators; motors with unwound iron armatures; machines with two or more armatures.-The invention relates an alternating current dynamo-electric machine of the type in which the secondary member, usually the rotor, comprises a toothed magnetic core without windings and the stator comprises toothed salient poles. The tooth pitch is the same on both members but the poles are so disposed that the teeth are displaced on consecutive poles relatively to the adjacent teeth on the secondary member by a fraction of the tooth pitch which fraction is usually the reciprocal of the number 2f of phases. The speed of such a machine is - n where f equals the frequency and n the number of teeth on the rotor. According to the invention the secondary element comprises two independently rotatable coaxial members, namely, a working member which takes the load and a member running light arranged to oppose or compensate for the magnetomotive force of the working current in the primary member. The object is to reduce the cross flux established by the working current and so improve the power factor and efficiency. Fig. 2 shows a machine having three slotted salient stator poles, each pole carrying a winding 0 connected to one phase of a three-phase system. The working rotor R1 comprises a ring made up of laminated magnetic segments Z1 separated by nonmagnetic and preferably nonconducting spacers P which are secured by rivets p1 to end plates. The inner or idle rotor R2 has the form of a squirrel cage rotor of an induction motor and runs at a speed very near the synchronous speed of the rotating field set up by the stator winding. In the form shown, the rotating field is bi-polar. The idle rotor may be in the form of a synchronous motor rotor excited by continuous current or it may comprise magnetic segments S1 S2, Fig. 4, equal in number to the number of poles set up by the primary field, on a nonmagnetic core E. The idle member may be supplied with alternating current from the primary or a separate source either through slip rings or a commutator. By suitably shaping the teeth of the outer rotor R1, a sinusoidal back E.M.F. may be generated. The slots between the stator teeth Z2 may accommodate a winding for energizing the stator. Current may be led into the idle rotor R2 through a brush B2, Fig. 6 carried by the main hollow shaft A and bearing on a slip ring C2 on the idle rotor. The brush B2 is connected by means of a conductor C passing through the shaft A to a slip ring C1 on which bears a fixed brush B1. The idle member may be provided with amortisseur conductors if it is formed as a rotor of the synchronous type. In the case of a single phase machine, the stator has two or a multiple of two salient poles, opposite poles producing opposite polarity and the tooth displacement between poles is one half the tooth pitch. In a twophase machine, four or a multiple of four salient poles is one half the tooth pitch. In a twoa quarter of a tooth pitch between adjacent poles. The Specification explains with the aid of a vector diagram the compensation action of the idle rotor.