Patent GB-108586-A (GB)
Title: Improvements in Methods of and Apparatus for Electric Ship Propulsion.
IPC: B63H23/24
Filed: 1916-10-12
Abstract: 108,586. British Thomson-Houston Co., (General Electric Co.). Oct. 12,1916. Systems for alternating- current motors only; systems depending on use of two or more motors.-In an electric system for ship propulsion the propeller shaft carries the rotors of a synchronous motor and an induction motor, the stators of which are supplied with current from an induction generator coupled to an elastic fluid turbine. The motors may be used separately for various torques and speeds or may be used in concatenation. The rotor 11 of the induction generator has a squirrel-cage winding and is driven by the turbine 10. The stator carries a three-phase winding 13 connected to the busbars 21. The synchronous motor 17 has a winding 25 on the rotor connected through a rheostat 29 to direct-current mains 24, and has a three-phase stator winding 18 connected through a switch 19 to the bus-bars 21. The slip rings of the induction motor 20 are connected to a resistance 32 and the primary windings 35 are included in or excluded from the circuit of the windings 18 by the switch 19. The slip rings of a synchronous condenser or motor 14 are connected to the generator armature and the field coil 27 is excited from the direct-current mains 24. The machine 14 provides the initial excitation for the generator and is geared to a direct-current machine 15 connected to the mains 24. These mains are energized by an independent exciter and may be used for lighting and heating throughout the ship. When starting or manoeuvring the ship the switch 19 is moved to its upper position as shown to connect the windings 35, 18 of the induction motor and the synchronous motor in circuit. The load at high speed is taken by the synchronous motor alone. In a modification two motors A, B, Fig. 2, replace the synchronous motor 17, their pole numbers being arranged to give equivalent speeds. The motor A has a stator winding 36 and a rotor winding 38 the latter 38 being connected to the three-phase stator winding 42 of the motor B. The rotor winding 43 of the motor B is supplied with direct current from the mains 24. A switch may be provided in the leads 41 to connect the rotor winding 38 to a resistance instead of to the winding 42, and the motor A is used with a resistance in its rotor circuit in conditions requiring high torque, and both motors A, B are used in normal conditions. In another modification both motors have three-phase rotor windings which are electrically connected. The stator winding of the motor A is connected to the generator and the stator winding of the motor B is a star-connected three-phase winding connected to a resistance or to the direct current mains 24. In another modification the induction motor A<11>, Fig. 5, has a stator winding which can be arranged for two different pole numbers, as, for instance, described in Specification 25858/03, [Class 35, Dynamo-electric generators &c.], or has two different windings 62, 63 for the different pole numbers. The rotor has two windings 65, 70 which act in conjunction with the windings 62, 63 respectively. The winding 65 is a double layer winding in deep slots and the conductors are offset near their centres so that each conductor is the bottom bar through half the slot and the top bar through the other half. This winding provides a short-circuited secondary with a relatively high resistance when the secondary currents are of high frequency. The three-phase winding 70 is connected to the three-phase rotor winding 71 of the synchronous motor B<11> the stator winding 72 of which is connected to the mains 24.