Patent GB-190511703-A (GB)
Title: Improvements in and relating to Synchronous Alternating Electric Current Dynamo Electric Machines.
Filed: 1905-06-03
Granted: 1906-06-21
Abstract: 11,703. British Thomson-Houston Co., [General Electric Co.]. June 3. Armatures; commutators; dynamos and motors combined for transmitting power; dynamos, regulating; field magnets.-A synchronous alternating-current motor, made self-starting by a phase-splitting device, has an armature winding, in inductive relation to the main armature winding, adapted to supply current to a rectifying- commutator upon the same shaft for exciting the fieldmagne winding during running, and upon the field member a displaced s h o r t - circuited winding in inductive relation to the normal winding, this winding being adapted to be connected to the alternating-current source for starting the machine. The invention is particularly applicable to the combination of a single-phase motor and direct-current generator, used for traction, the motor being supplied with alternating current from the line and driving a continuous-current generator which supplies current to the traction motors on the vehicle. The armature structure A, Fig. 1, of the synchronous motor carries the distributed armature winding a, and in addition a polyphase auxiliary winding a<1>, the rectified current from which excites the fields of both motor and generator. The field structure F of the motor carries phase-splitting means, Figs. 1 and 3, consisting of one or more conductors e surrounding and in inductive relation to the main field-magnet poles, and a second set of conductors e' in circuit with the first and displaced 90 degrees with respect to the main field-magnet coils. At starting, the main field-magnet winding f is connected through the switch S', the switch S being thrown to the left, to a source of singlephase current. The relatively-displaced currents in the short-circuited windings e, e<1> coact with the normal field current to produce a rotary field, and the main armature winding a, shown as a Y-connected three-phase winding, is shortcircuited by means of the switch contacts 1, 4, 3, 6 through the resistance r. When the motor reaches synchronism, the switch S is thrown to the right, and the switch S<2> closed, thereby completing the circuit of the single-phase current from the trolly T through the switch contacts 7, 1 through two phases only of the three-phase armature winding, the remaining phase being idle. The auxiliary exciting-winding a', shown as a Y-connected three-phase winding, has its terminals connected to brushes b<1>, b<2>, b<3>, Fig. 2, bearing upon the rectifying-commutator C arranged between the motor A and the continuous-current generator upon the same shaft. This commutator has one segment, of length equal to the distance between adjacent brushes, per pole of the machine. With the rectifying-commutator in the position shown, the exciting-currents pass from the lower terminal of the exciting-winding a<1> to the brush b<3>, commutator C, collecting-ring c, brush b<5>, field rheostat R, switch contacts 8, 3, and through the earth connexion to the field-magnet winding f, collecting-ring c', commutator C, and through the brushes b<1>, b<2> in parallel to the two upper terminals of the exciting-field a<1>. A similar current may be traced from the lower terminal of the winding a' through the resistances R, R<1> and the field winding f<1> of the continuous-current generator back to the upper terminals of the winding a<1>. In this way, the auxiliary winding is connected through the rectifying-commutator to the fields of both motor and generator, the resistance R being in series with the motor field and the resistances R, R<1> in series with the generator field. The arms of these resistances are secured toa common operating- handle, so that, when resistance is cut out of the generator field, a certain smaller amount is cut out of the motor field, maintaining the proper field excitation of the motor for unity powerfactor on all loads. By means of the switch S<3>, Fig. 3, the pbase-splitting windings E may be opencircuited when the motor is up to speed, or the winding E may be left short-circuited on itself so as to maintain the motor in synchronism.