Patent GB-191003117-A (GB)
Title: Improvements in Arrangements for Transmitting Power by Means of Polyphase Alternating Electric Currents.
Filed: 1910-02-08
Granted: 1910-10-13
Abstract: 3117. Siemens-Schuckertwerke Ges. Feb. 27, 1909, [Convention date]. Dynamos and motors combined for transmitting power.-For transmission of power by polyphase machines with rotating fields, connexions are made so that the stator and rotor fluxes of the generator or generators tend to rotate in opposite directions with respect to their windings, while the stator and rotor fluxes of the motor or motors tend to rotate in the same direction with respect to their windings. These connexions are 'shown in Fig. 2; the stators of the generator g and motor m are connected, and the rotors are connected with two of the leads crossed. The magnetizing-current is supplied by an external source s. In this arrangement, the speeds of the generator and motor are proportional to the sum and difference of the frequencies in the stator and rotor circuits. Energy may be supplied to the stator circuit from the rotor circuit through a commutator frequency-converter f, Fig. 3, and a variable voltage-ratio transformer. The frequency-converter may be coupled to the generator or motor shaft directly or through gearing; or it may be driven by a separate motor connected to the stator and rotor circuits, so that its speed depends on the sum or difference of the two frequencies. The motor that drives the machine s may be omitted, and a second smaller frequency-converter s<1>, Fig. 6, may be connected to series or shunt transformers. If the converter s<1> is connected to shunt transformers in such a manner that its speed corresponds to the difference between the frequencies, the converter f is not required; or, if the two converters are used, the machine s may be dispensed with. The phase at the brushes of the converter f can be adjusted by rotating the brushes or rotating the stator, or by displacing the phase of the current supplied to the stator. With the arrangement shown in Fig. 9, the converter f is driven by a motor m<1> at a constant speed such that the frequencies at the converter terminals always correspond to the frequencies of the generator windings. The speed of the main motor can be regulated by changing the pressure ratio of the converter and slightly altering the phase of the voltage at the commutator to keep the system self-excited. The frequency converter may be combined with the generator, as shown in Fig. 11, or with the motor. The commutator of the combined machine is con. nected through a variable-ratio transformer r to the stator leads. The leads between the generator and motor slip-rings may be disconnected, and the slip-rings of the motor m shortcircuited, directly or through a resistance. If the system is provided with magnetizing-current from the stator side by means of an external source, the rotors may be short-circuited. To reverse the motor, the stator and rotor voltages can be interchanged; or two conductors of the rotor circuit may be interchanged and two of the stator circuit interchanged. To hold the motor at rest, the stator and rotor leads are connected with one another, a transformer being used if necessary. Instead of a single motor being supplied from a single generator, additional machines may be connected in parallel.