GB203861A - Improvements in electrical marine propulsion - Google Patents

Abstract

203,861. Field, A. B., and Metropolitan-Vickers Electrical Co., Ltd. Aug. 1, 1922. Dynamos and motors combined for transmitting power.-A ship propulsion system comprises an induction motor and synchronous motor adapted to be connected in cascade for relatively low speed and to be connected direct to the supply system for high speed. To brake the induction motor is disconnected from the supply, the running cascade connection between the motors is changed to reverse the phase rotation, the stator of the induction motor is short-circuited, and a resistance is connected across the system connecting the motors. In a modification, the cascade connection is unchanged and a resistance is connected across the stator of the induction motor after this motor has been disconnected from the supply. For low speed the induction motor 2, Fig. 1, is connected in cascade with the synchronous motor 3, the motor 2 being connected to a generator 1. For high speeds the motor 3 is disconnected from the motor 2 and connected to a second generator the frequency of which differs from that of the first generator to compensate for the slip of the motor 2. In a modification, the motors 2 and 3 are on separate shafts. To effect braking, the motor 2, Fig. 5, is disconnected from the generator 1, the connection between the motors 2 and 3 is changed to reverse the phase rotation, and a resistance 7 is connected across the system connecting the motors. In a modification, the motor 2 is disconnected from the generator 1 and a resistance is connected across the stator of this motor. In the arrangement shown in Fig. 7, a single generator 1 supplies two induction motors 2 which are in turn connected in cascade with synchronous motors 3 for low speed. For high speeds the four generators are connected to the bus-bars 6 to which the motors. 2 and 3 are separately connected. In a modification each propeller shaft is provided with two motors, induction motors being placed on the outboard shafts and synchronous motors on the inboard shafts. For high speeds the pairs of motors on each shaft are connected in parallel to a separate generator or the four generators may be connected bo common bus-bars. In another arrangement one generator may feed in parallel an induction motor on an outboard shaft and a synchronous motor on an inboard shaft. In the arrangement shown in Fig. 10, each shaft is provided with an induction motor 2, and a synchronous motor 3, the motors being connected as shown for low speed. For high speeds the induction motors 2 on the starboard side are connected in parallel to a generator, and the synchronous motors 3 are connected in parallel to a record generator. A similar arrangement is provided on the port side. If it is desired to operate only one motor on each shaft for low speed, the synchronous motor on the inboard shafts on each side is connected in cascade with induction motor on the outboard shaft on the same side. To obtain a two to three ratio between low speed and full speed three generators 1, Fig. 11, are provided. Two synchronous motors 3 having half the number of poles of the induction, motors 2 are mounted upon the centre shaft, while the induction motors 2 are mounted upon the port and starboard shafts. For low speeds the generators and motors are connected as shown in Fig. 11. The synchronous motors 3 have half the number of poles of the induction motors 2. For low speeds a generator 1 and the motors are connected as shown. For high speeds the motors 2 are connected respectively to the outer generators while the motors 3 are connected in series or parallel to the centre generator the frequency of which is half that of the outer generators. In the modification shown in Fig. 12, a single synchronous motor 3 is employed.