Patent GB-190923756-A (GB)
Title: Improvements in Dynamo-electric Machines.
Inventor: LIPPELT HANS
IPC: H02K13/14
Filed: 1909-10-16
Granted: 1910-10-13
Abstract: 23,756. Lippelt, H. Oct. 16, 1908, [Convention date]. Windings; commutators; motors, controlling. - In open-coil dynamo or motor armatures giving a flattop p e d voltage wave, sparking is prevented by connecting the coils in series with condensers and resistances prior to their connexion to or disconnexion from the external circuit. The resistances are introduced in steps, and auxiliary armature coils may be used to modify the wave form to aid the commutation. A flat-topped wave is produced at all loads in an armature 19, Fig. 1, by a rotating magnet 20 having unevenly - spaced m a i n poles 21, 22 ... and auxiliary poles 27, 28, the former being split, and the whole being excited by main and auxiliary coils 29, 30, as shown. This arrangement per se forms no part of the present invention. The coils, such as 31, 31<1>. Fig. 12, have two angularly-displaced brushes 35 at each end bearing on commutators 41, 43 .., 44, 46 ..., of which the segments of like polarity are joined together and to the terminal rings 39, 40. Subsidiary segments 51, 53 ..., 54, 56 ... are placed slightly to the right and left of the main segments respectively and are joined together and to a pair of intermediate slip-rings. Shunt resistances 66, 67 ... 66<1>, 67<1> ... are connected to the ends of the coils, and have angularly-displaced brushes 65 bearing on the commutator. Between the intermediate rings and the machine terminals 37, 38, are connected condensers 49, 50 and resistances 57, 58. The equivalent connexions of a single coil are shown in Fig. 11. In the position shown in this Figure, the resistance 58 and condenser 50 are connected in series with each other, and in parallel with the resistance 66. The whole group is in series with the armature coil 31, 31' and the machine terminals. When the commutator moves to the right, the two resistances and condenser are first connected in series between the coil and terminals, and finally the coil is cut out. A similar cycle occurs when the rotation is reversed, and a converse cycle prior to the entry of a coil into circuit, so that the current is always gradually established or stopped. It is shown in the Specification that, in order to secure good commutation in a dynamo having a flat-topped voltage wave, as shown in dotted lines in Fig. 7, the wave should have at the commutation point an horizontal line after a short sloping step, as shown in full lines at E. This is effected by means of an auxiliary armature 80, Fig. 12, which gives a curve as shown at z, the sign of these curves being reversed in the case of a motor. A motorgenerator having such auxiliary armatures 93, 94 on both sides is shown in Fig. 15. They are excited by poles 95, 96, and are mounted in rotatable rings 82 which are permanently locked by screws 83 when the correct angular position has been found. Alternatively, the auxiliary armatures may be fixed and the additional poles adjustable. In the case of motors, resistances are mounted on the armature in series with the coils, and are cut out after the machine has run up to speed. These resistances are primarily to prevent sparking, but they may also be used for speed-control.