FR2622064A1 - Electric machine with cooling by liquid fluid - Google Patents

Abstract

Electric machine with cooling by liquid fluid, characterised in that it comprises, on the one hand, in the lower part of its casing 15, a store 17 for a cooling liquid 23 and, on the other hand, two discs 18, 19 for projecting this cooling liquid 23 onto its stators 5 and stator coil holders 20, which are fixed coaxially on a shaft 9 of this electric machine, in proximity to the ends of its stator coil holders 20, and the lower parts of the edges 21 of which are plunged into this store 17 of this cooling liquid 23.

Description

COOLING MACHINE
BY ElvlJlDE LIQUIDE.

 The present invention relates to an electric machine cooled by liquid fluid.

 An electric machine such as an asynchronous motor usually heats up during operation. This heating is due to stator and rotor losses. The heat produced by this heating can cause significant damage to this engine and even its destruction.

Several solutions have been proposed and used for removing this heat. Some are based on a thermal conduction of the organs of this engine to guide this heat from inside the engine to its outer carcass in order to evacuate it into the ambient atmosphere. The others are based on a forced convection of the air inside this engine to transfer this heat To the carcass of this one and a natural or forced convection of the air outside to evacuate this heat of this carcass in the ambient atmosphere. However, these known solutions prove to be ineffective or insufficient when the amount of heat becomes too large. The operation of known electrical machines and their very lifespan, suffer bad consequences.

 The present invention, aimed at avoiding these drawbacks, makes it possible to produce an electric machine cooled by a liquid fluid, economical and effective in removing the heat produced by its stator and rotor losses.

 According to the invention, an electric machine cooled by liquid fluid, is characterized in that it comprises on the one hand in the lower part of its casing, a reserve of coolant, and on the other hand two discs of projection of this coolant on its stator and stator windings, which are coaxially fixed on a shaft of this electric machine, near the ends of these stator windings, and whose lower edges are immersed in this reserve of this liquid cooling.

 In order to better understand the invention, an exemplary embodiment thereof is described below, illustrated by an appended drawing representing an electric motor which drives a pump.

 The present invention is applicable to any electric machine cooled by liquid fluid.

 In the example illustrated, the electric machine is an electric motor 1 which drives a high-pressure pump schematically shown in 2 and intended for high-pressure cleaners or hydro-cleaners not shown. The high-pressure pump 2 and the hydro-cleaners which are those of known types and which do not form part of the present invention, are not described in detail below.

 The electric motor 1 comprises a body 3 provided on the one hand on a first face in the periphery, with a cylindrical flange 4 and longitudinal feet not shown intended for fixing a stator 5, and in the center, an axial hub 6 in which are mounted roller or ball bearings or bearings 7, 8 of a shaft 9 of the motor, one end of which carries a rotor 10, and on the other hand on a second face, of a open tubular axial chamber 13 serving as a pump body and containing pump members 2, the rotary element 12 of which is mounted on the second end of the shaft 9. A cylindrical casing 15 is mounted on the cylindrical flange 4 of the body 3 , sealed by a seal 14. This casing 15 protects the stator 5 and the rotor 10 of the motor 1. The electric motor 1 normally operates in a horizontal position or in an inclined position at an angle less than 45 degrees. The stator 5 is provided with stator windings 20.

The body 3 of the electric motor 1 is made of a material which is a good conductor of heat and resistant to the fluid conveyed by the pump 2.

 According to an important characteristic, the electric machine or motor 1 comprises on the one hand in the lower part of its casing 15, a reserve 17 of a cooling liquid 23 and on the other hand two projection discs 18, 19 of this liquid cooling 23 on the stator 5 and the stator windings 20, and the lower parts of the edges 21 of which are immersed in this reserve 17 of this cooling liquid 23.

 The casing 15 and the projection discs 18, 19 are made of a material resistant to coolant 23 and a good conductor of heat, such as steel, aluminum, copper, etc.

 The cooling reserve 17 comprises a level 22 which is preferably located below the lowest generator of the rotor 10 of the electric motor 1.

Part of the stator windings 20 is thus completely submerged in this reserve 17, of coolant.

In the example illustrated, the projection discs 18, 19 of the coolant 23 have the general shape of a cup with a large turned-up edge.

 During operation of the electric motor 1 the shaft 9 rotates and drives the projection discs 18, 19 which, by their turned edges 21, collect coolant 23 in the reserve 17, project it into rain 24 on the stator 5 and the stator windings 20 and at the same time create a mist of fine droplets 25 above the reserve 17 of coolant 23. The coolant 23 consists of an electrically insulating liquid, good conductor of heat, and not corrosive to the stator windings 20 and other parts of this engine 1. This coolant 23 can be a mineral engine oil or any other suitable liquid. The rain coolant 24 sprayed onto the stator 5 and the coils 20 sneaks into the interstices thereof, and effectively removes the heat which is produced there, before falling back into the reserve 17, to leave there of the carried away heat which is evacuated through the casing 15 and the body 3, and to start another cycle while the coolant in mist 25, formed above the reserve 17, completes the action of the coolant in rain 24 and that of an evacuation by thermal conduction of rotor losses Through the shaft 9, and firstly through the projection discs 18, 19, the reserve 17 of coolant and the bodies 3 and casing 15 and secondly through the bearings or bearings 7 and 8 and the bodies 13 and casing 15, by efficiently transferring by conduction, the heat produced by the motor 1 to the bodies 3 and casing 15 of this motor 1.

 It can be seen in an electric motor 1 of the type illustrated, that the stator losses are of the order of two thirds in "Joule" losses in the stator windings or windings 20 and to twist a third in "iron" losses in stator 5, and that rotor losses are mainly losses by the Joule effect. Furthermore, in stator "Jouie" losses, approximately two thirds of these are produced in the chignon or ends of the stator windings 20.

An immersion of part of the stator 5 and the stator windings 20 in the reserve 17 of coolant 23, and a projection of coolant 23 by the discs 18, 19 in the engine 1 to form a rain 24 on the windings 20 and a mist 25 in the casing 15 allow efficient evacuation of the heat produced by the motor 1, and leave only a very small part of this heat, evacuated by conduction through the shaft 9, the bearings 7, 8 and the bodies 3 and casing 15 of the motor. As a result, the bearings or bearings 7 and 8 are subjected to a very low temperature rise and have had their life extended and that the stator 5, the rotor 10 and the stator windings 20 which are largely and effectively cooled, are not subject to thermal damage or to its destruction, encountered in known electrical machines mentioned in a previous paragraph.

 According to another characteristic, in the electric machine 1, the coolant 23 in its liquid 17, rain 24 and mist 25 forms is cooled by a stream of cooling fluid 26 coming from a source external to this machine.

 In the example illustrated, this coolant stream 26 is isolated from the coolant 23 and guided in its path inside the electric motor 1 by a tubular element which is a good thermal conductor forming a coil 27, arranged in the space between the stator 5 and the casing 15 of this motor, coaxially with the latter, and extending along this stator 5 and the stator windings 20. According to this arrangement, part of the coil 27 is immersed in the reserve 17 of liquid 23 and the other parts of this coil 27 are enveloped by coolant in rain 24 and in mist 25 projected by the projection discs 18, 19. A large thermal contact between the coolant 26 and the coolant 23 of the electric motor 1 is thus produced, through the walls which are good thermal conductors of the coil 27, which allows an efficient and intensive rapid evacuation towards the outside, of the heat. r produced by the motor 1 in operation, in parallel with an evacuation by convection, conduction through the body 3 and the casing 15 of this motor.

 The coil 27 is connected at its ends to an inlet nozzle 29 and an outlet nozzle 30 respectively formed in the casing 15 of the motor 1. The inlet nozzle 29 is provided with a filter 31 which retains solid foreign bodies possibly driven by the coolant stream 26.

 The cooling fluid 26 consists of a liquid identical to that conveyed by the pump 2.

 In the example illustrated the fluid cool 26 is water which is also a fluid conveyed by the pump 2 driven by the electric motor 1. For this purpose the inlet nozzle 29 of the coil 27 is connected to a source of water not shown while the outlet nozzle 30 is connected to the inlet of the pump 2.

 In the example illustrated, the casing 15 of the electric motor 1 comprises an air vent device 33 and an opening 34 for filling with coolant 23, closed by a device 35 which serves both as a cover and as a means of control. liquid level inside this casing 15.

 A liquid seal 36 is mounted in the hub 6 of the body 3 of the motor 1, between the two bearings or bearings 7 and 8, to isolate the enclosures of the electric motor 1 and of the pump 2 and prevent between the motor 1 and the pump 2 any leakage of liquid through this hub 6.

 To avoid problems arising from condensation of the water vapor inside the casing 15, the electric motor 1 is constructed so as to have an airtight and liquid tight enclosure. The air can then be evacuated from this enclosure and the casing 15 can be filled, above the reserve 17 of coolant 23, with a neutral gas such as nitrogen.

 According to a variant embodiment not shown, the shaft 9 of the rotor 10 is supported on the one hand by a first bearing or bearing mounted in the means 6 of the body 3 as that indicated at 7 in the example illustrated and on the other hand by a second bearing or bearing held in position by a bottom 40 of the casing 15.

Claims (10)

 1. Electric machine cooled by liquid fluid, characterized in that it comprises on the one hand in the lower part of its casing (15), a reserve (17) of a cooling liquid (23) and on the other share two projection discs (18, 19) of this coolant (23) on its stator (5) and stator windings (20), which are coaxially fixed on a shaft (9) of this electric machine, near the ends of these stator windings (20), and whose lower parts of the edges (21) are immersed in this reserve (17) of this coolant (23).  2. Machine according to claim 1, characterized in that the projection discs (18, 19) of this coolant (23) are made of a material resistant to this coolant (23) and good conductor of heat.  3. Machine according to one of claims 1 and 2, characterized in that the projection discs (18, 19) of coolant (23) have a general shape of a cup with a large turned upside.  4. Machine according to one of claims 1 to 3, characterized in that the coolant (23), in its forms of liquid (17), rain (24), mist (25), is cooled by a current of a cooling fluid (26) coming from a source external to this machine.  5. Machine according to claim 4, characterized in that the coolant stream (26) is isolated from the coolant (23) and guided in its path inside this machine, by a tubular element good thermal conductor forming a coil (27) arranged in the space between the stator (5) and the casing (15), coaxially with the latter and extending along these stator (5) and stator windings (20).  6. Machine according to one of claims 4 and 5, intended for driving a pump (2), characterized in that the cooling fluid (26) consists of a liquid identical to that conveyed by this pump (2 ).  7. Machine according to one of claims 4, 5 and 6, characterized in that the cooling fluid (26) consists of water.  8. Machine according to one of claims 1 to 7, comprising a body (3) provided with a cylindrical flange (4) intended for fixing the casing (15), and a central hub (6) intended for mounting of one or more bearings or bearings of the shaft (9) of the machine, characterized in that the enclosure of the electric machine (1) is made liquid and airtight by seals ( 14, 36) respectively mounted between the body (3) and the casing (15) and between the body (3) and the shaft (9) of the machine.  9. Machine according to claim 8, characterized in that the enclosure of the machine (1) is emptied of air and filled with a neutral gas such as nitrogen in the space above the reserve (17) of coolant (23).  10. Machine according to claim 1, characterized in that the coolant (23) is an electrically insulating liquid, good conductor of heat and non-corrosive vis-à-vis stator windings (20) and parts of the machine (1.)