Patent GB-190723224-A (GB)
Title: Improved Means for Obtaining Motive Power from Single-phase Circuits.
Inventor: FYNN VALERE ALFRED
Filed: 1907-10-21
Granted: 1908-10-15
Abstract: 23,224. Fynn, V. A. Oct. 21. Converting alternating and direct currents; distributing; motor control systems.-Motive power is obtained from singlephase circuits by the aid of at least one motorgenerator and at least one polyphase induction motor. The single-phase supply leads l, Fig. 1, are connected to the stator P<1>a of a motor-generator A and to the stator winding P<1>b of a polyphase induction motor B either directly or through transformers. The motorgenerator A is supplied with a second stator winding P<2>a placed at 90 degrees to the winding P'a, the former being connected to a winding P<2>b on the motor B. The motor Ra is provided with a winding fa supplied with current from an exciter E and with a short - circuited winding xa for starting purposes. Condensers C1, C2, C3 are placed in parallel with the slip rings S1, S2, Ss, and in the case of high voltages are connected through transformers T1, Ta, T3. To start the motor B, the switches Mb and the reversing - switch Zb are closed, and the motorgenerator A is run up to speed by any known device or by the aid of the winding xa, after which the winding fa is connected to the exciter E to bring it into step. The motor B is then started as an ordinary induction motor by gradually switching out the resistances W1, W2, Ws, and varying the transformation ratios of T1, T2, T3 simultaneously if required. In the modification shown in Fig. 2, the winding P<1>b of the motor B is connected in parallel with a portion p<1>a of the winding P<1>a. The condensers are wholly or partly replaced by a polyphase synchronous motor D for starting and speed regulation. The rotor Rd of the motor D carries a winding fd supplied with current from the exciter E and a winding xd capable of being shortcircuited. When the switches Mb, Zb are closed, the motor D will start as a polyphase asynchronous motor, after which the excitation of the winding fd may be adjusted. The motor B is brought up to speed and its speed regulated by resistances W1, W2, W3, when employed. When the speed of the motor B increases, the speed of the motor D decreases, and vice versa. In the modification shown in Fig. 3, the winding P<1>b of the motor B is connected to a winding p'a placed co-axially with the winding P<1>a, while the synchronous motor D shown in Fig. 2 is replaced by a rotary converter K, which may have stator windings x<1>k, x<2>k capable of being short-circuited, and a direct-current winding fk. The converter K supplies a direct-current motor G which assists the motor B. The speed of the motor G at starting may be varied by changing the position of the brushes of the converter K. Between the motor B and the converter K may be placed inductances capable of being short-circuited. In the modification shown in Fig. 5, variable-ratio transformers t1, t2, t3 may be arranged between the motor B and the converter K, while the motor G is arranged as a series machine, the field strength of which is regulated by a variable resistance Nfg placed in parallel with the field; in another modification, a booster is placed between the motor B and converter. The converter K may be replaced by a polyphase motor driving a direct-current generator, in which case the speed of the motor G may be altered by varying the excitation of the generator. In the modification shown in Fig. 7, there are two main polyphase induction motors B, B' connected in cascade ; the stator of the latter is provided with a direct-current winding f b<1> and a polyphase winding such as P<2>b<1> and P<1>b<1> capable of being short-circuited over the resistances W1, W2 and connected to the synchronous motor D. Condensers or synchronous motors may be connected across one or both sets of induced windings. Condensers or synchronous motors may be connected in parallel across some or all of the induced circuits of the polypbase motor or motors, with or without a rotary converter or its equivalent. The main motors of all these combinations may have the number of their poles changed to vary the speed, while they may be adapted for excitation by direct current. Induction motors of the commutator type may also be used, while the combination as a whole or part may be used for braking purposes and for returning energy to line. One or more motor-generators may be employed, and usually more than one main motor, in which case it is preferable to use a common synchronous motor or converter. When the latter is used, more than one direct-current motor may be employed grouped on the series-parallel system.