GB2229323A - Electric machine with centrifugal heat-transfer tube for rotor cooling - Google Patents

Description

1 1 ELECTRIC MAC11111,51E WITH CENTRIFUGAL HEATTRANSFER TUBE POR RuTOR

COOLING The present invention relates to rotary electric ma- chines and more particularly to electric machines with a centrifugal heat- transfer tube for rotor cooling.

The invention may be used in high-torque d.c. motorsq variable-speed squirrel-cage Induction motors. as well as in phase-viound motors, highslip motors and in motors ope- rated with substantially frequent starts.

Knovin in the prior art is an electric machine (DB, A2 1,928,358) wherein the rotor is installed on a hollow shaft which is sealed eff and serves as a h--r--t-u1rFnsfer tube partially filled v.,,ith a liquid heat car- rier. A portion of the shaft mountinj, the rotor is ail evaporation zone of the heat carrier. Portions of the shaft disuosed on both sides of the rotor are zones of transfer and zones of condensation- of heat carrier vapours.The internal surface of all portions of the shaft Is made cylindrical and has ar. equal radius throughout the entire length of the shaft. In the process of operation of the electric machine the rotor gets heated. Under the action of beat the liquid heat carrier converts into vapour and moves to the condensation zones disposed at the shaft end on both sides of theevapo- ration zone. Here the vapour is condensed and the evolved heat is rejected to the environnent. Thus under the action of centrifujal forces developed durin-' rolhation of the rw rotor a closedcircult flow of the heat carrier is set up in the internal space of the shaft providing the rejection of heat on the principle of a centrifugal heat-transfer tube.

In the known construction the heat-transfer tube has a poorly extended surface both in the heat carrier conden sation zone. i.e. the internal surface of the shaft in the condensation zone and in the zone of the heat rejection to the environment, i.e. the external surface of the shaft in the condensation zone, and besides the shaft wall in the condensation zone has a substantial thickness. The disad vantages mentioned hereinbefore limit the heaIL,-transferririg. properties of the heat-transfer tube of the known electric machine.

Also knov.,,n is an electric machine with a centrifugal heat-transfer tube for rotor cooling (SU, A, 678,599), com- prising a frame vj.-.th a statuor internally accoinn,.-odatinc a rotor arranged along the centre line thereof. The rotor is installed on a hollow shaft riade in the forn. of a heattransfer tube and secured in the fralle by means of bearing supports. One of the shaft portions disposed in the vJ1- cinity of the rotor serves as an evaporation zone of the heat carrier and as, a transfer zone of vapours of the heat carrier which partially fills the heat-transfer tube. The internal surface of this portion of the shaft is made cylindrical and has a radius equal throughout the entire length thereof. Another portion of the shaft disposed outside the rotor serves as a condensation zone of heat carrier vapours and is made in the fo2ni of a truncated cone facing by its larger base the rotor and provided with fine X on the external surface. The fine are made in the form of lengthwise corruSations variable in height decreasing in magnitude from a smaller base towards the 1-arger base and are provided vilth a guide ring encompassing the external surface of the corrugations at the smaller base of the cone. In the known electric machine the condensation zone of heat carrier vapours has also a poorly extended surfaces on which the condensation takes place and the external heat exchange is accor-plisliedg and as a consequence has linalited potentia10 lities for coolin:, the rotor. As a result, the rar. 6e of povier rating of the electric machines cooled by means of the centrifugal heat-tr-,riwfe.. tube is lirilted.

The present invention aims at provid-ing an electric niachine with a centrifu.gal heat-transfer tube for rotor cooling, wherein a design embodiment of the heat-transfer tube, owing to a substantial increase in the surface on vihich vapours of a heat carrier are condensed and the external surface from which heat is rejected, will step up the cooling_ efficiency of an electric machine and will pro- vide the cooling. of electric machines of a greater power rating.

This is attained by-that in an electric machine vith a centrifugal heattransfer tube for rotor cooling, comprising a frame with a stator mointed therein and accon-mo- dating a rotor arranged along its longitudinal axis with a clearance and installed on a hollow shaft secured in the frame walls b., meens of bearing supports and made in the form of a heat-tranefer tube, one of the hollow shaft portions disposed in the vicinity of the rotor and the internal surface of w.Uch is made cylindrical servingas an evaporation zone of the heat carrier partially fillInEs the heat-transfer tube and as a transfer zone of heat carrier vapours.,, while another portion of the hollow sh., ft disposed outside the rotor serves as a condensation zone of heat carrier vapours. accordine. to the invention. the portion of the hollow shaft serving as a condensation zone of heat carrier vapours is formed by a pluralitj of pipes the ends of which at one side secured In through openings made in a disk associated with the shaft are open and face the transfer zone of heat carrier VaDOUrS, whereas the ends of the pipes at the other side are sealed off and arranged outside t.h.e frame.

It is desirable that the proposed electric machine be provided with a perforated enclosure secured on the frame and encompassing the ends of the pipes arran6ed outside the f rartle.

In one of the embodiments of the electric -,..achine 20 each pipe may be made wnnular in cross-section.

In another embodiment of the electric wachine each pipe may preferably be riade oval in cross-section.

For increasing the heat transfer, it is advantageous to make the pipes of a highly heate-conductive material.

For increasing the external surface from which heat is rejected. it is desirable that the pipes be provided with a plurality of plates installed one after another throughout the length of the pipes in planes perpendicular i to lonFitudinal axes of the pipes, each plate being provided nith openings through which the pipes are passed and in whic.1a they are secured.

For improving the conditions for the flow of the heat carrier vapourS in the internal surfaces of the pipes. it is preferred that a disk is secured at the end of the hollow shaft portion the internal surface of which is made cylindrical and which serves as a transfer zone of heat carrier vapours.

For reducing the overall dimensions of an electric machine and. iinirising the effect o-." rotor heat losses on the bearin cup. orts, it.%dvmita.eous that- a disk be to LI secured inside a:)ortion of the hollow saaft the internal sur-Lc'ace of v.,hic,ll. Is, made an. serves as a transfer zone c-j"' heat carrier vapours.

For el-': natinw leaks of the I-Let:A car-rler liquid phase fron. tIle evaporation zone in the internal spaces of the pipec., it is expedient that the ope,,-nSs providing in the disú'-, be ar-an,.,ed aloi-, c)nconlur.2Le c--Lrcles.,, the pip-es se- cured in the open-LnGs of the e:?ipheral circle 'Deirie-, in- stelled a-z, a dIstance fro= t,'-,e Internal surface of the hollov.. shaf t. For reducing an ex.cessive r-:-.0u,.1.lu of the li,,-.,at car- t> rier condensate in the pipes F-n6 for fr.cilitatinl, its dis c.'Liar,se therefrom. into the evexoration Zone, it is prefer able to install the pipes on the disk so that the longi tudinal rx4Ls of each Dipe and the axis of the hollow slhaft form an actue angle, the ends of the pipes dis- posed outside the frame beinE inclined to the longitudinal axis of the liollo.., shaf t.

It is ad-vantp-,,eous that the end of each pipe be sealed off individually.

In order to reduce the effect of a permanent gas on lLhe efficlency of heat transfer, it is most advantageous C> that the ends of pipes be sealed off by way of installing a header thereon and the internal sul-face thereof be com municated the internal spaces of the pipes.

The proposet.1 invention makes iii possible to increase AL1he surface o-L" heat exchange by two-three times and the heat transfer coefficient up to tirjo time.s. This makes it pos sible to subst an't _ ally reduce the Le,.-.pera4Vure of the ro-L-,or and stator. c:,nd to increase the e..LO-L"iciency o.-LO' an, electric The invent--,t-.r, makes it possible to cool 'L-$he rojL-,or-e and stato-rs of electric.?.ac.Unes vj..Lth a power ratin:- of uP, to 110-132 k,'i- C., L 10 To enn.ble the invc!n,;U.-ion -'&,c be fully understood the erbod..-Lr, ien-,$,s thereof will no-,,j be described with, reference to 20 the accumpanyin& draviin&s, in which:

F!&. 1 is a -eneral view illustratiri.. an electric machine with a cent rif ur-al heat-transfe- tube for rotor cooling, according to the invention; Fig. 2 illustrates a dislil- ivith pipes secured thereon. 25 accor,:&illg to the.L..ivention; Fig. 3 illustrates an embodiment of the electric =achine, vibere--,-..i the disk. is insjt-,al.-L.ed inside a portion of 1 9 V4.

the hollow shaft the Internal surface of which is made cylindrical and which serves as a transfer zone of heat carrier vapour-,,, according to the invention; Fig. 4 illustrates a unit 05C the heat-transfer tube with a condensation zone of heat carrier vapours. In which the centre line of each of the pipes and the centre line of the hollow shaft form an acute angle, according to the invention; PiG-1. 5 illustrates a unit of -ALhe neat-transfer tube with a cendensation zon,-tt of heat carrier vapours. compris1n47 a hea%-'. ;er, accordin. to the invention.

The electric machine;.,ith a centrifugal hea'L.I-transfer tube for rotor cooling, accordin- to the invention, com prises a stato-r 1 1) instlalled in a fr,-,.-&e 2. The stator 1..,.iiternw.1.1y accomsiodates alonj: its centre line e. clearance a rotor 3 on a h J.

ollow shaft 4 P-C e n the f o =m of a heat-transfer tube. Tle shaft 4 is secure,d _in ti-ic -walls o-C the franne 2 by means of bearin& supports 5 and 6. A Poitioil 7 of the shaft 4 the inernal surface of which lls made c,ilindric,,-,.1 an,W. whIch is disposed in the vic-Ai-dty of the rotor 3 is an evaporation zone 8 of vapours of the heat car-rier partially fill-in, the heattransfer tube and is a transfer zone of heat carrier vapours. A portion lU of the shaft 4 serving as a condensa- tion zone 11 of heat carAer vapours is made up of a plurality of pipes 12 coaxially Installed in openings made. in a disk 13 disposed at the end of the portion 7 of the shaft 4. The ends of the pipes 12 secured in the disk 13 are open and face the transfer zone 9 of heat carrier vapours while the opposite ends of the pipes 12 disposed outside ttie frame 2 are sealed off, the end of each of the pipes 12 being sealed off individually. The electric machine is provided with a perforated enclosure 14 secured on the'fram 2 and ei,Ico=.pas.,-lins the ends of the pi-oes 12 diszosed outside the frame 2. The pipes 12 are provided with a plurality of plates 15 installed one after another throushout the length of the pipes 12 in planes perpendicular to centre lines of the pipes 12.

Arran,Eemenjt-o of the openings on the diell: 13 may be dif- 2U ferent. FiCs. 1 mid 2 illustrate the arran-seme,.,At of the openings along. c..-,ixcentr.-Lc ci...,cle..; of d, and d2 diameters, the pipes 12 secured in the openinge of the peripheral circle of diameter d 2 being installed at a distance from the internal surface of the hollow shaft 4.

The Dipes 12 are made of a highly Iheat-conductive material and may be annular and. oval in cross-section.

For reducins the overall dimensions. of the machine and also for rdniiuziiii; the efifect of heat losses of the rotor 3 on the bearinj Supports 6 the disk 13 (Fig. 3) is installed --'Lnside the portion 7 of the hollow shaft 4 the internal surface of which is made cylindrical between the rotor 3 and the bearing supports 6@ For reduci-l-ig an excessive amount of the condensate accu,-riulated in the Dipes 12 and for facilitating its removal th-erefror. into the evaporation zone 8 of the heat car- 1 1 rier the pipes 12 (Fig. 4) are installed so that the centre line of each pipe 12 and the centre line of the hollow shaft 4 form an acute angle ot. the sealed-off ends of the pipes 12 being inclined to the centre line of the hollow shaft 4.

For minimizing the effect of permanent gas on the efficiency of heat transfer the ends of the pipes 12 (Fig.5) are sealed off by means of a hollow header 16 one Yvall of which is provided with openings to pass the pipes 12 the internal spaces of which are communicated with the internal space of the header 16. A cone-shaped axial depression 17 is made in the opposite wall of the header 16.

The proposed electric machine with a centrifu&al heattransfer tube for rotor cooling operates in the following manner. In the process of operation of the electric machine the rotor 3 (Fig. 1) gets heated and the heat is transferred therefrom to a liquid heat carrier contained in the evaporation zone 8 of the heat- transfer tube. While absorbing the heat the heat carrier partially evaporates and tile generated vapour moving alone, the heat-transfer tube due to a pressure differential gets in the condensation zone 11 formed by the internal spaces of the pipes 12 and is condensed on the walls of the pipes 12, thereby giving up the heat thereto. Under the action of the centrifugal forces the formed condensate is collected on the portions of the internal surfnces of the pipes 12 most distant from the centre line of the shaft 4, wherefrom it flows on the cylindrical surface of the hollow shaft 4 and further is returned into the evaporation zone 8. Thus, when heat losses occur in the 1 f I- - 10 rotor 3 a closed circulating flow of the heat carrier is set up in the centrifugal heat-transfer tube.

In the case when the ends of the pipe.s 12 (Fig. 5) are sealed off by means of the header 16 permanent gas formed in the heat-transfer tube is collected in the space of the header. 6. In this case t#he entire surface of the pipes 12 is used In the heat- transfer procesn.

Intensification of an electric machine coolirW,- and expansion of the range of power ratins-s of electric machines cooled by means of a centrifugal heat-transfer tulbe are achieved due to making the condensation zone 11 (Fig. 1) of heat carrier vapours- of e. rluruli4U.,, v, of the pipes 12 of srnall diamieter providing a substantial e,.,,larc,ement of the internal surface on v..,-'.-,ich the condensr.tion of the beat carrier vapours takcc plece and the external surface from,.-.-.hich the heat is rejected, and also due increase of the coefficients of heat transfer fro.m these surfaces.

The total surface of the condensation zone 11 formed by the Internal spaces of a multitude of the pipes 12 of a small diameter may be several times (2-3 times) larger than the surface of one cylinder of a large diameter in the cross-section plane of which they may be inscribed.

The use of the heat-transfer tube of such a construction in a squirrelcage induction motor of 55 kW power rating made it possible to reduce the temperature of the stator winding by 300C, the squirrel-cage rotor by 900C and at the same time to Increase the efficiency by 0,5%.

1 f

Claims (13)

CLAIMS:

1. An electric machine with a centrifugal heat-transfer tube for rotor cooling, comprising a frame with a stator mounted therein and accommodating a rotor arranged along Its longitudinal axis with a clearance and installed on a hollow shaft secured in the frame walls through the agency of bearing supports and made in the form of a beattransfer tube. one of the hollow shaft portions which Is disposed in the vicinity of the rotor and the internal surface of which is made cylindrical serving as an evaporation zone of the heat carrier partially fillin6 the heat-transfer tube and as a transfer zone of heat carrier vapours, while another portion of the hol- low shaft disposed outside the rotor serves as a condensation zone of heat carrier vapours and is formed by a plurality of pipes the ends of which at one side secured in through openings made in a disk associ.ated with the shaft are open and face the transfer zone of heat carrier vapo- urs, whereas the ends of the pipes at the other side are sealed off and arranged outside the frame.

2. An electric machine with a centrifugal heat-transfer tube for rotor cooling, as claimed in Claim 19 waich Is provided with a perforated enclosure secured on the frame and encompassing the ends of the pipes disposed outside the frame.

3. An electric machine with a centrifugal heat-transfer tube for rotor cooling. as claimed in Claim 19 where- in each pipe is annular in cross-section.

4. An electric machine with a centrifugal heat-transfer tube for rotor coolingg as claimed in Claim 1, wherein each pipe is oval In crosssection.

5. An electric machine with a centrifugal heat-transfer tube for rotor coolingg as claimed In Claim 19 wherein the pipes are made of a highly beat-conductive material.

6. An electric machine with a centrifugal heat-trans- fer tube for rotor cooling, as claimed in Claims 1 to 5, wherein the pipes are provided with a plurality of plates installed one after another throughout the length of the pipes in planes perpendicular to longitudinal axes of the pipes, each plate being provided with openings through which the pipes are passing and in which they are secured.

7. An electric machine with a centrifugal heat-transfer tube for rotor cooling, as claimed in Claims 1 to 6, wherein a disk is secured at the end of a shaft portion whose internal surface is made cylindrical and servesxas a transfer zone of heat carrier vapours. 20

8. An electric machine with a centrifugal heat-transfer tube for rotor cooling, as claimed in Claims 1 to 79 wherein the disk is secured inside a shaft portion whose internal surface is made cylindrical and serves as a trans fer zone of heat carrier vapours.

9. An electric machine with a centrifugal heat-trans fer tube for rotor cooling as claimed in Claims 1 to 8, wherein the opening provided in the disk are arranged along concentric circles, the pipes secured in the openings of i 1 the peripheral circle being installed at a distance from the internal surface of the hollow shaft.

10. An electric machine with a centrifugal heat-trans- fer tube for rotor cooling, as claimed in Claims 1 to 9, wherein the pipes are secured on the disk so that the lonsitudinal axis of each pipe and the longitudinal axis of the hollow shaft form an acute angle, the ends of the pipes disposed outside the frame being inclined to the longitudinal axis of the shaft.

11. An electric machine with a centrifugal heat-transfer tube for rotor cooling, as claimed in Claims 1 to 101 wherein the end of each pipe is sealed off individually.

12. An electric machine with a centrifugal heat-transfer tube for rotor cooling, as claimed in Claims 1 to 10, wherein the ends of the pipes are sealed off through the agency of a header installed thereon and one of the walls thereof is provided with openings for the pipes to pass, the inner space of the header bein6 in communication with the internal spaces of the pipes.

13. An electric machine with a centrifugal heattransfer tube for rotor cooling constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Published 1990 at The PatentMee, State House. 8671 High Bolborn. LondoziWC1R4TP. Further copies may be obtatnedfrorn The Patent office9Wes Branch, St Mary Cray. Ozlib4wn. Kent BM M. Printed by Multiplex WChWquu ltd, St Mary Crigy. Kent, Con. I W