RU2173283C2 - Marine powerplant with synchronous motor mounted in form of nacelle - Google Patents

Abstract

FIELD: shipbuilding; manufacture of marine powerplants with synchronous motors. SUBSTANCE: shiboard drive has housing in form of nacelle mounted on ship's hull. Three-phase synchronous motor is arranged in this housing. Power of drive is equal to at least 2 MW. Rotor of motor is excited from permanent magnets. At least one propeller is connected with rotor axle. Stator cooled with water flowing over part of housing is built in this part at form closure. Outer diameter of streamlined part of housing is equal to 40% of outer diameter of propeller. Inner space of part of housing where electric motor is located is free from cooling medium. Drive may be provided with additional cooling unit in form of fan located inside respective front portion of winding on rotor shaft or in form of spraying unit consisting of pipe- shaped perforated ring. Interior of this ring may be communicated with oil settler located under rotor shaft. EFFECT: enhanced propulsive efficiency. 5 cl, 2 dwg

Description

 The invention relates to the field of marine propulsion systems and is intended for use in the constructive implementation of a three-phase electric motor, which for direct drive of at least one propeller is located in the streamlined part of the hull mounted on the underside of the ship's hull.

 In a known marine propulsion system of this type, a three-phase alternating current electric motor with a squirrel-cage rotor is used as an electric motor, the rotor being mounted on a hollow shaft, which in turn is connected via a clutch to a drive shaft passing inside the hollow shaft. The drive shaft is connected directly to the propeller shaft. In such a marine power plant, the stator of the electric motor is surrounded by a tube-shaped hull, which in turn is integrated into the saddle-shaped tube support part of the hull, mounted on the underside of the hull in the form of a gondola.

 The cooling of the electric motor, including the rotor bearings, is carried out with fresh water, which is pumped from the tank located in the vessel’s hull into the electric motor’s hull and carried out in a closed circuit (US-A 2714866).

 In a similarly made marine power plant, the stator of a three-phase electric motor for cooling with water flowing around the streamlined part of the hull is integrated with a geometric circuit into this part of the hull. In this case, the internal space of the housing part in which the three-phase electric motor is located is filled with water under pressure. This water is used to lubricate bearings and to transfer heat (DE-C-917475).

 In another marine propulsion system of this type, which can be performed for drive powers of 10 MW or more, the dynamoelectric motor is supported by its stator on radially arranged sheet metal jumpers in the surrounding hull; the sheet metal jumpers used for this serve simultaneously to form cooling channels for the gaseous coolant supplied from the ship's hull. As an electric motor, a synchronous squirrel-cage synchronous motor is usually used, and the rotor can additionally be cooled due to its location on a hollow, water-passing drive shaft. In such a drive device, it is usually sought that the ratio between the maximum diameter of the drive housing and the diameter of the propeller is less than 0.65, preferably in the range from 0.4 to 0.5. It should be borne in mind that the diameter of the propeller can not be chosen of any size. This indicated ratio of external diameters affects the propulsion efficiency; the larger the smaller the specified ratio of diameters (USA 5403216; publication "New Generation of Standard Diesel-Electric Roller Ferry" by Kv & rner Masa-Yard at the session "RoRo 94" on 27.04.1994 in Gothenburg, Denmark).

 The basis of the invention is the task, based on a marine power plant with the signs of the restrictive part of paragraph 1 of the claims (DE-C-917475), to create such a drive for drive power in the megawatt range and at the same time provide a favorable propulsion efficiency.

 To solve this problem, according to the invention, it is provided that the three-phase electric motor is designed as a synchronous electric motor and has a drive power of at least 2 MW, that the rotor (10) of the synchronous electric motor is made as a rotor with excitation from permanent magnets, and that the inner space of the housing parts in which a synchronous electric motor is placed, free of cooling medium flowing through them.

 With such a power plant, due to the use of a synchronous motor with a rotor with excitation from permanent magnets that practically does not create Joule heat losses, there is no need for additional measures to cool the drive motor, since a rotor with excitation from permanent magnets has smaller radial dimensions than a short-circuited rotor, then at the same time, the need for radial space of the drive motor is reduced. This leads to a favorable relationship between the outer diameter of the drive housing and the outer diameter of the propeller shaft, so that the drive device for a marine power plant of such power has an excellent drive efficiency. Through the use of measures according to the invention, ship power plants can be designed in which the ratio of the outer diameter of the streamlined body part to the outer diameter of the propeller is less than or maximum 0.4.

 The use of rotors with permanent magnet excitation instead of squirrel cage rotors or rotors with external excitation through slip rings for synchronous motors is known per se, in particular for motors with drive power up to about 30 kW (Siemens-Z., 1975, No. 49, pages 368 - 374). Such electric motors with a driving power of about 2 to 5 MW have already been created to drive the propellers of submarines, and the electric motor, made very short in the axial direction and thereby relatively large in outer diameter, is located inside the ship's hull. In this electric motor, all pole tips of the rotor are made of several permanent magnets from a special alloy of samarium and cobalt and glued to the pole core. The stator package of this electric motor is surrounded by two cooling rings through which fresh water flows. Fresh water is cooled in heat exchangers with sea water (PERMASIN-electric motors for driving propellers of submarines from Siemens AG, order number E 10 001-A930-A29, Jahrbuch der Schiffsbautechnischer Gesellschaft, 1987, pages 221-227).

 If the marine propulsion system made according to the invention is used in the upper power range (more than 5-10 MW), it is also necessary to pay attention to the effective cooling of the frontal parts of the winding. In this case, it may be appropriate to provide each frontal part of the stator winding with an additional cooling device. Such additional cooling devices can be located without any special additional costs in the cavity due to the design of the electric motor, if either the fans located inside the frontal parts of the winding on the rotor shaft or each frontal part from the end face are given a pipe-like cross-sectional ring as the cooling device, which is equipped with spray holes and the cavity of which is connected by means of a pump to a sump of insulating oil located below the rotor shaft . In both cases, heat from the coolant - whether it be air or insulating oil - is also removed from the stator through the surrounding walls of the motor housing.

 A longitudinal section of the respective two exemplary embodiments of the new drive device is shown schematically in FIG. 1 and 2.

 FIG. 1 - drive device with air cooling of the frontal parts of the stator winding.

 FIG. 2 - drive device with spray cooling of the frontal parts of the winding.

 The drive device of FIG. 1 consists of a streamlined, nacelle-shaped part of the hull with a synchronous motor located in it, consisting of a stator 7 and rotor 10, and of a shank 20, through which the drive device can be attached to the bottom of the ship's hull. The housing 1 consists of a part 2 made in the form of a hollow cylinder and end caps 3 and 4, in which the bearings of the drive shaft 5 are placed. A propeller 6 is installed on one end of the drive shaft.

 The stator 7 of the synchronous electric motor is inserted with a geometric circuit into the hollow cylindrical part 2, for example, this part of the housing 1 is hot pressed into the stator package. The stator windings are the frontal parts 8 and 9 of the winding. The rotor 10 of the synchronous electric motor is made in itself in a known manner as a rotor with excitation from permanent magnets and through the supporting structure 11 rests on the drive shaft 5. The supporting structure 11 is provided with axial slots 16.

 One fan 12 is located inside both frontal parts of the windings 8 and 9. With this fan, the air in the cavity of the synchronous electric motor swirls and flows around the frontal parts 8 and 9 of the winding. The cooling of the synchronous motor as a whole occurs mainly through the hollow cylindrical part 2 of the housing 1, which, when the vessel moves, transfers heat to the flowing water.

 In the exemplary embodiment of FIG. 2 for cooling the frontal parts of the winding 8 and 9 from the end sides of the frontal parts of the winding there is one pipe-shaped cross-sectional ring 13, which is provided with spray holes in the direction of the frontal parts of the winding. Through these spray holes it is possible to spray insulating oil, which is located in the sump 14 under the drive shaft 5 and from there is pumped into the ring 13 using the pump located outside the casing 1. Heat is also removed from the sump 14 for the insulating oil through the casing 1, as well as from swirl according to FIG. 1 air. The sump 14 should not capture the air gap of the motor. Spray rings may be provided in addition to or alternatively to fans 12.

 Due to the fact that the stator with a geometrical closure is inserted into the streamlined housing 1 and the rotor 10 with excitation from permanent magnets in the radial direction requires less space than a squirrel-cage rotor, the housing 1 can have a relatively small outer diameter d, so that the ratio between the outer diameter d the housing 1 and the outer diameter D of the propeller 6 reaches a relatively small value, for example 0.35, even if the synchronous motor is made for a driving power of 2 to 20 MW or more.

 The implementation of the new drive device does not depend on whether the nacelle is mounted on the hull vessel stationary or with the possibility of rotation. Thus, it is also suitable for the so-called Schottel drives.

Claims (5)

 1. An electric drive device for a ship, consisting of a hull mounted in the form of a nacelle on the underside of the hull, with a streamlined body part for accommodating a three-phase electric motor, with at least one propeller connected to its rotor axis, the stator of a three-phase electric motor for cooling with water flowing around the streamlined part of the housing, it is integrated with a geometric circuit into part (1) of the housing, characterized in that the three-phase electric motor is designed as a synchronous electric the motor has a drive power of at least 2 MW, that the rotor (10) of the synchronous electric motor is made in the form of a rotor with excitation from permanent magnets, that the outer diameter (d) of the streamlined body part (1) is at most 40% of the outer diameter ( D) of the propeller (6), and that the interior of the housing part (1) in which the electric motor is located is free of cooling means flowing through it.  2. The drive device according to claim 1, characterized in that each frontal part (8, 9) of the stator winding (7) is given an additional cooling device (12, 13).  3. The drive device according to claim 2, characterized in that the additional cooling device consists of a fan (12) located inside the corresponding frontal part (8, 9) of the winding on the rotor shaft (5).  4. The drive device according to claim 2, characterized in that each frontal part (8, 9) of the winding is endowed with a tube-shaped cross-section ring (13), which is equipped with spray holes, and the cavity of which is connected by a pump (15) with a sump (14) of insulating oil located under the rotor shaft.  5. A drive device according to any one of claims 1 to 4, characterized in that the hollow cylindrical part (2) of the body part (1) is mounted on the stator package (7) by hot pressing.

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