Patent GB-190605893-A (GB)
Title: Improvements in and relating to High Tension Electric Switches.
Filed: 1906-03-10
Granted: 1907-03-09
Abstract: 5893. British Thomson-Houston Co., [General Electric Co.]. March 10. Dynamos and motors combined for transmitting power.-Power is transmitted from a constantspeed prime-mover, e.g. a synchronous motor, through the intermediary of a unipolar or other dynamo-electric machine which acts as a slipping magnetic clutch between the prime-mover and the load, the prime-mover serving to drive one element of the unipolar or other machine, either the armature or the field magnet, and the other element itself driving the load. The prime-mover, in the arrangement shown in Fig. 2, is a synchronous motor with a stationary armature A and with a field magnet F consisting of two parallel magnetic disks with inwardly projecting pole-pieces, one pole-piece upon one disk projecting into the space between two poles of the other disk. Each disk carries an annular magnetizing-winding supplied with current from outside through the slip-rings f<1> and producing alternately opposite polarity in the projecting poles, the whole magnet structure being free to revolve upon the shaft D which is to be driven. Secured to this shaft and adapted to revolve between the magnet disks is a disk armature C of conducting-material, for which the synchronous motor magnet structure F serves as a unipolar field, so that, when there is relative motion between the armature C and the field F of this unipolar machine, a continuous current may be collected at the brushes b, b<1>. The outer brushes b, of which there is a set rubbing upon the portion of the periphery of the disks adjacent to each pole, are connected electrically to the several poles by connexions c, Fig. 3, which, together with the pole-pieces, form a complete turn round the fieldmagnet structure. The continuous current in these connexions, the circuits of which are completed to the inner brush through the field-magnet disks F, is dependent upon the load on the synchronous motor, so that the magnetizing effect of the current in the connexions c may be utilized to strengthen the field magnet f so as to compound the synchronous motor and secure unity powerfactor at all loads. At starting, the field-magnet coil f being de-energized, the armature circuit A is closed and the field magnet F is brought up to full speed as an induction-motor secondary, whereupon the field coils f are energized, locking the field magnet of the synchronous motor in synchronism, and supplying the field for the unipolar machine. The armature C of this machine begins to revolve, and increases in speed until the current induced between the brushes b, b<1> is reduced to the minimum sufficient to sustain the required torque. If the load is increased, the required induced current will be greater, so that the power shaft will be caused to revolve more slowly. The disk C is made of small inertia, so that high acceleration may be obtained at starting, and also quick stopping. In a modification, the current generated by the unipolar machine, and for the most part wasted in heating the magnet disks in the arrangement described, is utilized to drive, as a motor, a second unipolar disk c<1>. Fig. 4, the structure of the field magnet being modified, as shown. A separate source of excitation, which may be the same as that used for the windings f, is shown at E for the winding H upon the field-magnet structure of the second unipolar machine, and a variable resistance G enables the relative field strengths of the two unipolar machines to be varied so as to vary the speed ratio and torque between the synchronous motor and the driven shaft. The current in the brush leads may supply the excitation of the second unipolar machine, in which case regulation is obtained by shifting the brushes upon the periphery of the unipolar disks. The functions of the two unipolar machines may be interchanged.