FR2645366A1 - ELECTRICAL MACHINE HOT CENTRIFUGAL EXCHANGE TUBE FOR COOLING THE ROTOR - Google Patents

Abstract

The rotor of the electric machine is cooled by means of a centrifugal heat exchange tube, the zone of condensation of the vapors of the heat exchange agent being arranged outside the zone of the rotor and formed by a group of tubes, fixed in holes of a disc made integral with the shaft. The ends of the tubes 12 which are engaged in the disc 13 are open and oriented towards the zone 9 of transfer of the vapors of the heat exchange agent which form in the zone 8 of evaporation of the exchange agent heat provided in the area of the rotor 3. The opposite ends of the tubes 12 located outside the casing 2 of the machine are sealed. Application to high torque direct current motors and asynchronous motors with short-circuited rotor with high slip and frequent starts.

Description

ELECTRICAL MACHINE WITH CENTRIFUGAL HEAT EXCHANGE TUBE

FOR COOLING THE ROTOR

  The present invention relates to electrical machines

  and, in particular, relates to electric machines

  centrifugal heat exchange tube for cooling

rotor discharge.

  The invention can be used for

  high-torque continuous motor, short-circuit adjustable asynchronous motors as well as

  rings, high slip and frequent starts.

  An electric machine (DE-A-1 928 358) is known in which the rotor is sealingly mounted on a closed hollow shaft and made in the form of a heat exchange tube partially filled with an agent. heat exchange fluid. The section on which the rotor is fixed constitutes the

  evaporation zone of the heat exchange agent. The sections

  From the shaft, arranged on both sides of the rotor, serve as transfer zone and condensation zone vapors emitted by the heat exchange agent. The inner surface of all sections of the tree is cylindrical and its radius is constant over the entire length of the tree. During the

  operation of the electric machine, the rotor heats up.

  Under the action of heat, the liquid heat exchange agent passes into the evaporation zone in the vapor state.

  moving towards the areas of condensation arranged to the ex-

  shaft end of both sides of the evaporation zone.

  After condensation of the vapors, the condensation heat is transferred to the surrounding environment. During rotation of the rotor, a closed stream of heat exchange agent is formed under the action of centrifugal forces in the internal cavity of the rotor.

26'45366

  the shaft which thus ensures the evacuation of heat according to the

  principle of centrifugal heat exchange tube.

  In the structure envisaged above, the heat exchange tube has a poorly developed surface both in the condensation zone of the heat exchange agent (inner surface of the shaft in the condensation zone).

  that in the area where the heat is transferred to the surrounding space

  (outer surface of the tree in the condensate zone).

  tion) and, in addition, the wall of the shaft in the condensing zone.

  is very thick. These features of the heat exchange structure limit the heat transfer capabilities of the heat exchange tube of the electric machine

which releases heat to evacuate.

  We know an electric machine that is equipped with a centrifugal heat exchange tube for cooling

  rotor (SU-A-678 599), and whose stator housed in a car-

  breaks around a rotor mounted along its longitudinal axis. The rotor is mounted on a hollow shaft, in the form of a heat exchange tube and rotatably mounted in the body via the support bearings. One of the sections of

  the tree placed in the rotor zone constitutes the evapo-

  ration of the heat exchange agent and the transfer zone

  heat exchange agent vapors filling

  the heat exchange tube. The inner surface of this section has a cylindrical shape with a constant radius along its entire length. The other sector of the tree, willing to

  the outside of the rotor zone constitutes the condensing zone

  the vapors of the heat exchange agent and is

  in the form of a truncated cone whose outer surface

  rieure is provided with ribs and whose largest base is oriented towards the rotor. The ribs are made in the form of longitudinal embossings whose variable height decreases from the small base to the large base and

  they are provided with a guide ring surrounding the sur-

  outer face of the embossings of the small base. In the known electric machine, the zone of condensation of the heat exchange agent vapors is also characterized by weakly developed surfaces on which the vapors condense and on which the external exchange takes place.

  heat and, consequently, the possibilities of cooling

  Rotor deformation is limited. As a result, the power of electric machines cooled by a tube

  Centrifugal heat exchange is limited.

  It was therefore proposed to create an electric machine

  equipped with a centrifugal heat exchange tube for

  rotor cooling, in which the embodiment of the centrifugal heat exchange tube would, thanks to the significant increase of the surface on which occurs - the condensation of the heat exchange agent vapors and

  the outer surface that gives up the heat, to increase the effi-

  ciency of the cooling of the electric machine and of

  the cooling of large electric machines. The problem thus posed is solved by means of an electric machine provided with a centrifugal heat exchange tube for cooling the rotor and comprising: a stator mounted in a carcass envelope and surrounding a rotor which is housed with of play along its longitudinal axis and mounted on a hollow shaft fixed in the side walls of the casing by means of support bearings and which constitutes a heat exchange tube, one of the sections of the shaft hollow disposed in the region of the rotor and the inner surface of which is cylindrical and functions as an evaporation zone of a heat exchange medium which partially fills the heat exchange tube and the agent vapor transfer zone heat exchanger, the other section of the hollow shaft being arranged outside the zone of the rotor serving as a zone of condensation of the heat exchange agent vapors, characterized according to the invention in that the stretch of the tree creates as a zone for condensing the vapors of the heat exchange medium is constituted by a group of tubes of which

  the ends of one side are fixed in holes through

  formed in a disc made integral with the hollow shaft and are open and oriented towards the vapor transfer zone of the heat exchange medium and in that the

  ends of the tubes on the other side are closed and

outside the body.

  It is advantageous that the electrical machine comprises a perforated casing fixed on the body and receiving the open ends of the tubes arranged outside the body.

  According to one of the embodiments of the electrical machine

  each tube may have a cross-section

round or oval.

  In order to increase the transmission of heat, it is advantageous for the tubes to be made of a material

with high thermal conductivity.

  To increase the external surface from which the heat is removed, it is useful for the tubes to be provided with a group of plates or fins mounted on top of each other.

  in the direction of the length of the tubes in the sensitive planes

  perpendicular to the longitudinal axes of the tubes, each plate being provided with holes in which the tubes are

committed and fixed.

  In order to improve the conditions of entry of the heat exchange agent vapors into the inner cavities of the tubes, it is advantageous for the disc to be attached to the end of the section of the hollow shaft whose inner surface is cylindrical and serves as a vapor transfer zone

heat exchange agent.

  In order to reduce the size of the electric machine and to reduce the influence of the heat losses of the rotor on the support bearings, it is advantageous that the disk

  attached to the inside of the section of the hollow shaft which

  has a cylindrical inner surface and serves as a

  vapor transfer of the heat exchange agent.

  To eliminate the leakage of the liquid phase of the heat exchange agent from the evaporation zone into the inner cavities of the tubes, it is advantageous for the holes to be arranged on the disk along concentric circumferences and for the fixed tubes to be arranged. in these holes of the peripheral circumference are arranged at a distance from the

  inner surface of the hollow shaft.

  In order to reduce the excess condensate of the agent

  heat exchange in the tubes and to accelerate its evacuation

  out of these to the evaporation zone, it is advan-

  that the tubes are mounted on the disk so that the longitudinal axis of each tube forms with the longitudinal axis

  of the shaft at an acute angle, the ends of the tubes

  on the outside of the body being inclined with respect to the axis

mentioned above of the hollow shaft.

  The end of each tube can be closed separately but in order to reduce the influence of the non-condensable gas on the heat transfer efficiency, it is more advantageous that the ends of the tubes are closed by means of a common collector mounted thereon and which is connected by its interior cavity to the inner cavities of the

tubes.

  The invention makes it possible to increase the heat exchange area by two to three times and the transmission coefficient

  of heat up to two times. This can significantly reduce

  temperature of the rotor and stator and to raise

  the efficiency of the electric machine. The invention is advantageously applied to the cooling of the rotors and stators of electrical machines whose power is

the order of 110 to 132 kW.

  Other purposes, advantages and features of the invention

  will appear on reading the following description

  explanatory of various embodiments and made in a non-limiting manner and with reference to the attached drawing o: - Figure 1 shows in schematic section a view

  of an electric machine comprising

  both a centrifugal heat exchanger tube for cooling the rotor, according to the invention; FIG. 2 represents a disc to which tubes are attached, according to the invention; FIG. 3 shows an alternative embodiment of the electric machine according to the invention,

  in which the disc is mounted inside the

  of the hollow shaft section whose inner surface is cylindrical, and which serves as a transfer zone for the vapors of

  the heat exchange agent, according to the

  vention; FIG. 4 shows a set of heat exchange tubes comprising a condensing zone of the vapors of the heat exchange medium in which the longitudinal axis of

  each of the tubes forms with the longitudinal axis

  dinal of the tree an acute angle, according to the invention; and - Figure 5 shows a set of exchange tubes

  of heat having a condensing zone

  sation of the heat agent vapors,

according to the invention.

  The electrotechnical or electromotive machine provided with a centrifugal heat exchange tube comprises a stator 1 (FIG. 1), mounted in a casing 2. A rotor 3 is housed with clearance in the stator I along its longitudinal axis and is mounted on a hollow shaft 4 serving as a heat exchange tube. The shaft 4 is fixed in the side walls of

  the casing or casing 2 by means of intermediate bearings

  5 and 6. A section 7 of the shaft 4, with an inner surface

  re cylindrical and which is disposed in the region of the rotor 3, serves as zone 8 of evaporation of the heat exchange agent, partially filling the heat exchange tube and

  zone 9 for transferring the heat exchange agent. A section

  10 of the shaft 4 serving as zone 11 for condensing the vapors of the heat exchange medium is formed by a group of tubes 12 coaxially mounted in holes made in a disk 13 which closes the end of the section 7 of

the tree 4.

  The ends of the tubes 12 fixed on the disc 13 are open and oriented towards the vapor transfer zone 9

  of heat exchange agent while the opposite ends

  The tubes 12, which are arranged outside the body 2, are closed off. The end of each of the tubes 12 is closed separately. The electric machine is provided with a perforated housing 14 fixed on the casing 2 and surrounding the ends of the tubes 12 disposed outside the casing 2. The tubes 12 are provided with a group of plates or fins 15, successively mounted one behind the other in the direction of the length of the tubes 12 in planes perpendicular to the longitudinal axes of the tubes 12. The holes may be arranged on the disc 13 of

  different ways. Figures 1 and 2 show an arrangement

  according to the diameters of the circumferences

  d1 and d2, the tubes 12 being fixed in the holes provided

  circumferential circumferences are mounted to

  distance from inner surface of hollow shaft 4.

  The tubes 12 are made from a material with

  high thermal conductivity and may have a

  round cross section but also oval.

  To reduce the size of the machine and reduce the influence of the thermal losses of the rotor 3 on the bearing bearings 6, the disk 3 (FIG. 3) is mounted inside the section 7 of the hollow shaft 4. whose inner surface is

  cylindrical between the rotor 3 and the bearings 6.

  In order to reduce the accumulation of condensate in the pipes 12 and to accelerate its evacuation out of these tubes towards the evaporation zone 8 of the heat exchange medium, the tubes 12 are mounted (FIG. position as

  the longitudinal axis of each tube 12 forms, with the longitudinal axis

  tudinal of the hollow shaft 4, an acute angle a, the closed ends of the tubes 12 being inclined with respect to the axis of

the hollow shaft 4.

  To reduce the loss of efficiency of heat transfer

  caused by the uncondensed gases, the extremes

  12 of the tubes 12 (FIG. 5) using a hollow collector 16 in one of the side walls of which holes are made.

  in which tubes 12 are engaged, the space of which

  It is connected to the internal cavity of the collector 16. A conical axial cavity 17 is formed in the wall

opposite of the collector 16.

  The machine according to the invention equipped with an exchange tube

  Centrifugal heat pump for cooling the rotor

  as follows. During rotation, the rotor of the motor 3 (FIG. 1) heats up under the effect of the electrical losses that develop therein and its heat is transmitted to the liquid heat exchange agent in the

  zone 8 of evaporation of the heat exchange tube. In absorbing

  In addition to the heat, the heat exchange medium evaporates partially and the vapor, which then forms, moves towards the heat exchange tubes 12 due to the difference between the pressure prevailing in the zone 8 and that prevailing in the condensing zone 11 formed by the inner cavities of the tubes 12 and the exchange agent is condensed on the walls of the tubes 12 by yielding thereto its heat of vaporization. Under the action of centrifugal forces, the condensate that forms

  accumulates on the sections of the interior surfaces of

  tubes 12 furthest from the longitudinal axis of the shaft 4 where it flows towards the cylindrical surface of the hollow shaft 4 and returns to the evaporation zone 8. Thus, a closed cycle of circulation of the heat exchange agent is

  form for evacuating heat losses in the rotor 3.

  In the case where the ends of the tubes 12 (FIG. 5)

  are closed with the aid of the collector 16, the non-condensed gas

  sand entrained in the heat exchange tube accumulates in the cavity of the collector 16. In this embodiment, the entire surface of the tubes 12 is used in the

heat transfer process.

  Improved cooling of the electric machine

  that and the increase of the power of the electric machines cooled by means of a centrifugal heat exchange tube is obtained because the zone 11 of condensation of the heat exchange agent vapors is constituted by a great

  number of tubes 12 of small diameter which ensure an increase

  noticeable difference in the inner surface over which -

  The vapors of the heat exchange medium condense together with the external surface which gives up the heat to the environment and also because of the increase in the coefficient.

  heat transmission of these surfaces.

  The total area of the condensing zone 11 formed by the inner cavities of the plurality of tubes 12 of

  small diameter can be several times (2 to 3 times) higher than

  than the large diameter cylinder in the plane

  transversal of which they could be inscribed.

  The application of a heat exchange tube produced according to the invention has an asynchronous motor of 55 kW has reduced the temperature of the stator winding of 30 C and

  reduce the short-circuit rotor by 90 C while increasing

  both simultaneously yield of 0.5%.

  Of course, the present invention is not limited to the embodiments described and shown but it is capable of numerous variants accessible to the man of

  art without departing from the spirit of the invention.

Claims (12)

  1.- Electric machine equipped with a central exchange tube   heat pump for cooling the rotor and   both: a stator mounted in an envelope or carcass and   a rotor which is housed with play along its longitudinal axis and mounted on a hollow shaft fixed in the side walls of the casing by means of bearing bearings and which constitutes a heat exchange tube, one of the sections of   the hollow shaft, arranged in the region of the rotor and whose   inner side is cylindrical, acting as an evaporator   a heat exchange agent which partially fills the heat exchange tube and the vapor transfer zone of the heat exchange medium, the other section of the hollow shaft being disposed at the outside the rotor zone serving as a condensing zone for the heat exchange medium vapors, characterized in that the section (7) of the hollow shaft (4) serving as zone (11) for condensing the vapors the heat exchange medium is constituted by a group of tubes (12) whose ends on one side are fixed in through-holes in a disc (13) connected to the hollow shaft (4) and are open and oriented towards the zone (9) for transferring the vapors of the heat exchange medium and in that the ends of said tubes on the other side are closed off   and disposed outside the body (2).   2. An electric machine according to claim 1, characterized   characterized in that it comprises a perforated housing (14) fixed on the body (2) and receiving the open ends of the   tubes (12) disposed outside the body (2).   3.- electric machine according to claim 1 or 2, characterized in that the cross section of each tube (12) is round.   4.- electric machine according to claim 1 or 2, characterized in that the cross section of each tube (12) is oval.   5.- Electric machine according to any one of the   1 to 4, characterized in that the tubes (12) are   made of a material with high thermal conductivity.   6.- Electric machine according to any one of the   1 to 5, characterized in that the tubes (12) are   equipped with a group of plates or fins (15) superbly mounted   in the direction of the length of the tubes (12) in planes substantially perpendicular to the longitudinal axes of the tubes (12), the plates being provided with holes in which   the tubes (12) are engaged and fixed.   7.- Electric machine according to any one of the   1 to 6, characterized in that the disc (13) is attached to the end of the section (7) of the hollow shaft (4), which has a cylindrical inner surface and serves as a transfer zone (9) vapors of the heat exchange agent.   8.- Electric machine according to any one of the   1 to 6, characterized in that the disk (13) is fixed inside the section (7) of the hollow shaft (4), which has a cylindrical inner surface and serves as a transfer zone (9). vapors of the heat exchange agent.   9.- Electric machine according to any one of the   1 to 8, characterized in that the holes are   on the disk (13) according to concentric circumferences   the tubes (12) fixed in the holes of the peripheral circumference being mounted at a distance from the inner surface of the hollow shaft (4).   10.- Electric machine according to any one of   Claims 1 to 9, characterized in that the tubes (12)   are mounted on the disc (13) so that the longitudinal axis of each tube forms, with the longitudinal axis of the hollow shaft (4), an acute angle (a) and in that the ends of the tubes (12) ) disposed outside the body (2) are inclined   with respect to said axis of the hollow shaft (4).   11.- Electric machine according to any one of   claims 1 to 10; characterized in that the end of   each tube (12) is closed separately.   12.- Electric machine according to any one of   Claims 1 to 10, characterized in that the ends   tubes (12) are closed by means of a common collector (16), mounted on said tubes and having on one of its side walls, orifices and through which   the tubes (12) are engaged, the internal cavity of the   common core (16) being connected to the inner cavities of the tubes (12).