US1779797A - Dynamo-cooling system - Google Patents

Description

Oct. 28, 1930. F. G. BAUM DYNAMQCOOLING SYSTEM Filed May 18, 1927 2 Sheets-Sheet l ATTORN EY INVENTOR ATTORNEY 2 Sheets-Sheet 2 F. G. BAUM Filed May 18, 1927 DYNAMO COOLI NG SYSTEM Oct. 2s, 1930.

Patented Oct. 28, 1930 UNITED STATES PATENT OFFICE DYNAMo-cooLING SYSTEM Application filed May 18, 1327'. Serial My invention relates'to dynamo-electric machinery of the rotating pattern and particularly to means for the more effective cooling thereof.

The translation .of electrical energy from form to forni and from point to point is never accomplished without some loss, and the lost energy appears at the site of translation as heat. The limitation upon the capacity of any dynamo-electric machine accordingly is found to be the rate at which the heat produced by the energy loss can be removed from the machine. Transformer devices are customarily cooled for the removal of such heat by theI use of oil as a heat absorbing and circulating medium, and they are very effectively cooled thereby. It has not, however, previously been found practicable to cool rotating machinery by the use Aof oil, since submergence in oil produces prohibitive losses of energy through the churning of oil by the rotating parts, and the use of oil circulated through enclosed pipes has not been successful because of the complicated and bulky tubes and conduits required. Although some attempt has been made to prevent or minimize the loss of energy due to churning of oil, (which loss not only detracts from mechanical efficiency but represents a conversion of such energy into heat) by enclosing the rotor in a cylinder of non-magnetic material, the circulation of oil is thereby so interfered with as to make the cooling system ineffective. Accordingly, vin actual practice, as for as I am aware, only the gaseous fluids have been used for the cooling of rotatingy dynamo-electric machinery, air being the preferred fiuid because of the common occurrence thereof-and ease with which it is obtained.

My invention provides means for the utilil propriate portion of the machine. By the device of my invention I am enabled to utilize the desirably high cooling capacity of oil for the cooling of rotating machinery without the introduction of bulky conduits, Iand without the production of large energy losses from churning of the fluid. I am thus enabled to obtain a substantial and important increase in continuous rating of a dynamo-electric machine, and accordingly a greatly improved performance and a lower cost of production, from which follows a reduction in the cost of operation in the handling of electric energy.'

Other objects and structural details of my invention will be apparent from the following description when read in connection with the accompanying drawings, wherein:

Fig. 1 is a sectional view in vertical elevation of an embodiment of the device of my invention;

Fig. 2",.is a side view in vertical elevation of the same embodiment;

Fig. 3 is a sectional 'view in vertical eleva- .tion of an alternative embodiment;

Fig. 4 is a sectional view in vertical elevation of a second alternative embodiment, and

Fig. 5 is a side View in vertical elevation, partly in section, of the embodiment of Fig. 4.

It is well known that oil has a very much higher specific heat than air, and that aecordingly the cooling effect which can be obtained from it is much greater. For instance, oil has a weight of about pounds per cubic footswhile air has a Weight of about 0.08 pounds per cubic foot. The specific heat/ofY oil is about 0.5, Where that of airis about 0.237. The ratio of heat absorbing capacity of equal volumes of air and 'of oil is then given by the following equation or about 1450 times.

used. The oil is preferably applied in the form of a spray, or mist, or in relatively small drops, so that a minimum of churning effect is produced in the mixture by the movement of the rotor, andso that no single particle is suiciently large to produce unduly large impact forces when it is thrownfrom the moving rotor to the stator. The spray is formed at the outer face of the rotor. The cooling liquid is conducted to a receptacle at or' near `the periphery of the rotor where it collects in the form of aliquid in substantial quantities and thus develops the maximum centrifugal force, escaping therefrom through small openings as a spray yagainst the opposing face of the stator. The rotation of the rotor itself within the spray is thereby avoided. Another advantage of this arrangement is the fact that the centrifugal force developed in the liquid can be utilized to induce the circulation of the cooling liquid through a closed system.

vTo prevent loss of oil, the circulating medium should be enclosed. The dynamo-electric machine may be provided with closed -end plates and frame with a receiver portion, and drain, at the bottom, so that as the oil spray strikes the stator, it may drain down over the hot surfaces of Ithe machine to the receiver, after which it may be cooled and recirculated. The mixture of liquid and gas may consist of a fluid, such as oil, and air, or 'it may preferably consist of a less Hammable mixture. For this purpose, it may consist of a mixture of oil spray and carbondioxide, with or without the inclusion of a small roportion of air, or .it may consist of a mixture of oil and nitrogen, also with or without the inclusion of small quantities of air, insuiicient to produce a combusti le mixture with the oil. 'f`- A preferred embodiment of the device of my invention is shown in Figs. 1 andl 2. These figures show the essential parts of la typical dynamo-electric machine to which the improvement of my -inventionfmay be advantageously applied. The machine may consist of a shaft, 1, supported in bearings, to which is attached a rotor 2. The rotor may be a rotating fieldmor a rotating armature, as desired. In the embodiment shown, it is indicated as a rotating field having salient poles, with appropriate field windings 4 thereon. AThe rotor is surrounded by a stator 5, which may consist of laminations 6, having windings 7 positioned in ap ropriate slots therein. Passages 8, for coollng iiuid, are provided through the body of the stator laminations. A suitable frame member 9 is provided for the support of the laminations formingpthe stator, and appropriate end-bell i closure members 11 and 12 are likewise provided, making a close fit about the shaft 1 and against the machine frame 9.` The rotor also has fan blades, as shown, for causinga circulation of the air or-other gas contained inthe housing 11, 12, of the machine. A clo sure member 14 is provided at the bottom of the frame 9 to form a receptacle for the cooling fluid collecting there. A drain pipe 15' is rovided, connected thereto, and led to a storage reservolr 16.

.A circulating pump 17 is provided with p the suction inlet connected to the reservoir 16. The shaft 1 is desirably provided with a passageway or duct 18 extending from one end to a point within the hub of the rotor 2, and connection is made at that point by a plurality of radial ducts 19 extending toward the surface of the rotor. At the rotor surface and between the salient poles of a plurality of liquid receptacles forming spray heads'21are provided and connected to the radial channels 19,'the channel 18, and the poles. Either construction provides a cur-L rent of iuid consisting partly of gas and partly of sprayed oil. The spray heads 21- may desirably be of a pattern to provide aV plurality of sprays of oil separated axially by a distance equal to the axial separation of the Ventilating ducts 8 in thestator.

, The current of fluidL from the spray heads 21 on the rotor isdirected towards the inner surface of the stator inthe bore thereof, and towards the inner openings of the Ventilating passages therethrough. The greatly in creased thermal. capacity of this fluid, as compared to air alone, is thus available for the cooling both of the rotor member and the stator member. A portion of the oil may be conveyed through the Ventilating channels 8 in the stator body'in the form of a spray and collect a substantial amount of heat therefrom, either by radiation or by conduction. It 'is desirable that the spray heads 21 be so positioned that the openings 22 through which the oil is discharged and sprayed are located in the planes of the Ventilating ducts 8, in order to discharge as large a portion of the oil through the Ventilating yducts as possible, and to minimize the accumulationv of iuid oil within the air gap between the rotor and stator. Accordingly While some o f the oil spray is carried freely through the lducts 8, other portions may strike the surfaces of the Ventilating ducts, and coalesce thereon into a layer of liquid. This layer may be carried radially outward along the surfaces of the Ventilating ducts by the current of mixed air and oil spray. In its passage over these surfaces, the oil layer is advantageously related thereto for the desired cooling effect, and it is enabled to absorb a substantial amount'of heat in the course of the flow. The oil is thus carried to the outersurface of the stator, through the Ventilating ducts, and it then flows downward to the receptacle 14 at the bottom of the frame, from 'which location it is conveyed by the pipe 15 to the cooler and reservoir 16 where the absorbed heat is removed and dissipated. The oil is then recirculated by the pump 17 to pass through the cycle again for the collection of further quantities of heat. By this means a very thorough and effective cooling of the dynamo machine is obtained with the handling of a minimum bulk of cooling fluid.

It' is not essential that the cooling liquid be conveyed to the rotor through an opening in the shaft. It may equally well be conveyed by other means, such as that shown in Fig. 3, where the oil leaves the pump 17 and is conveyed to conductors 23, which discharge the cooling oil into troughs 24 forming liquid receptacles and located at points near the periphery of the rotor. It is collected from the stationary conductors 23 which lead to the troughs 24, and is held against the frame of the rotor by centrifugal force. This construction is particularly advantageous in the case of the well known squirrel cage type of motor, in which the rotor consists of lami nations 25 having peripheral slots in which are positioned the inductor bars 26 characteristic of this type of machine. rl`he oil may be conducted through suitable channels v 27 in the rotor body from the troughs 24 to leo the rotor surface. at which point -it maybe -sprayed by any appropriate means, which may consist of jet plugs or other spray devices positioned within and near the outer ends of the channels 27. The statorcrrstruction may desirably be similar to that-indicated in Fig. 1, and may consist of laminations 6 having Ventilating ducts 8 therethrough, supported by a frame member 9 with end- bell members 11 and 12, a-bottom receptacle or reservoir 14, a drain pipe 15, and cooler and storage tank or reservoir 16. The oil is then discharged by the pump 17 through the pipes 23 into the-troughs 24 from which it passes through the ducts 27 and is sprayed thereby. The ends of the ducts 27 are desirably positioned in the plane of the Ventilating ducts 8, as previously described, and the oil spray, together with a portion of gas as previously" described, is dischargedinto them for the production of a similar cooling effect upon the structures. The cooling oil flows over the warm surfaces collecting heat and is caught in a receptacle or reservoir 14 at the bottoni of the frame member, from-which it is conveyed lto a cooler, and storage tank, and thereafter 1s recirculated as before.

By this construction usually effective and eflicient cooling means are provided for the induction type of motor, whereby much superior cooling effects, and therefore much higher load capacity, are obtainable from a p given construction.

For certain typesof machines it is not, however, necessary that a circulating pump be provided for the handling of the oil fiuid. Instead, suitable scoops and channels may be provided upon the rotor, dipping into a supply of oil fluid at the bottom of the case and frame, to convey the cooling oil to the rotor. These may consist of curved scoops,

or pipes 28, as shown in Figs. 4 and 5, fas` tened to the rotor 29, and revolving with 1t. As cach scoop revolves, it strikes the pool of oil 30 at the bottom and some of the oil passes into the scoop, to be deliveredto the annular trough 31 upon the rotor 29 from whichl it is delivered by suitable ducts 32 to spray heads as before. It is then sprayed therefrom into and against the stator 5 and the Ventilating ducts 8 therein, Where it acts,

as previously-described, for the removal ot'l cooling as that obtained by air, by the use of very much .smaller Ventilating ducts, or

"if the maximum size of Ventilating ducts are employed it is possible to producev much more effective cooling. The device of my construction thus makes it possible to increase the duty on dynamo-electric machinery, thereby considerably reducing .the cost of machinery for a given power output,since the additional parts required for the application of the device of my invention are very small items, in the cost of the machinery. Thus a direct reduction of the cost of electric power is provided.

Further advantages of the device ofmy invention are found in the fact that the cooli ing system may be made completely closed,

recirculatinga given fluid as it is needed. Thus no external air need be supplied, and the conveyors and ducts which would be necessary for such supply, are saved. Like- Wise the elimination of the need for cooling air reduces the amount of dirt and moisture which would otherwise be carried into the machine by such circulating air. In consequence, the insulation condition of the machine is much improved, and the necessity for frequent cleaning to remove dirt and other obnoxious material is avoided. The presence of the oil directly adds to the insulation resistance, because of its own high Vinsulation value and Abecause of the elimination of moisture. Likewise the system makes is possible to enclose the machine in a noneombustible atmosphere, thereby greatly reducing the hazard of lires which may occur in the insulation due to overload, excess voltage, and `other factors which tend to injure the insulation. Likewise in the event that fire occurs in the insulation, it is smothered at once upon the removal of load from the machine, by the cooling effect of the large quantities of oil thrown in, and by the lack of oxygen to supportcombustion.

The device of my invention 1s particularly applicable to relatively large dynamo maV chines, such as generators, rotry converters, and large motors. It is, however, equally well adapted to application to the smaller types of industrial motors, and is also applicable to railway and other transportation motors. In such service it is particularly advantageous because when so equipped, the

motors are operating in a medium having a very high insulation resistance, as compared to operation under ordinary conditions where they are in a medium charged with moisture and other matter, tending towards a low insulation resistance.

While I have shown but three embodiments of my invention in the preceding description, they are capable of various modiications therefrom without departing from the spirit thereof, and it is desired, therefore, that only such limitations shallbe placed thereon as are required by the prior art or indicated by the appended claims.

I claim as my invention: 1. In a dynamo electric machine, comprising rotor and stator., means for spraying the interior surface of the stator at a series of points along the length of its air gap with oil.

and simultaneously directing gas currents against said surface, and means for recovering and. recirculating said oil.

2. In .a dynamo-electric machine, a rotor member and a stator member, the rotor having an internal circumferential trough within and near its periphery, openings extending through the trough in an outward direction and means v,for .circulating a cooling liquid in a closed path including said trough, anda stationary liquid feeding pipe extending over the open inner periphery of said trough. a

3. In a dynamo-electric machine, a rotor member and a stator member, the rotor having an internal circumferential trough within and near its periphery, openings extending through the 'trough in an outward direction and means for circulating a cooling liquid in a closed path including said trough, said means comprising a collecting reservoir below the axis of the rotor and a scoop rigid with the rotor and extending into the reservoir.

4. In a dynamo-electric machine, a stator,

, anl internal rotor facing the stator and having gas upon the stator in conjunction with said liquid spray.

5. In a dynamo-'electric machine, a cooling systemu com rising a stator, an internal vrotor facing the stator, as housing enclosing the same, a reservoir for holding a cooling liquid within the housing, means carried by the rotor for continuously removing liquid from the "reservoir and supplying it to the interior of the rotor, and spray means on the outer periphery of the rotor for' discharging liquid in spray form into the air gapof the machine.

6. In a dynamo-electric machine, a cooling system comprising a stator having radial passages therethrough, an internal rotor facing the stator and having a liquid receptacle at its outer face, a. housing enclosing the rotor and stator and providing a reservoir for holding a. codling liquid below the stator, means carried by the rotor and dipping into the reservoir for continuously removing liquid from the reservoir and supplying it to the said receptacle., and spray means on the outer periphery et the rotor for discharging liquid in spray form into the air gap of the machine. 7. In a dynamo-electric machine, a cooling system comprising a stator having radial passages therethrough,A an internal rotor facing the stator andhaving a liquid receptacle at its outer face, a housing enclosing the rotor and stator and providing a reservoir for holding a cooling liquid below the stator, means carried by the rotor for continuously removing liquid from the reservoir and supplying it to the said receptacle, spray means on the outer periphery of the rotor for dischar ing liquid in spray form into the air gap o the machine, and means for circulating a current ofraswithin thehousing coincident with the rota ion of the rotor.

8. The method of cooling an electric translating device comprising rotor and stator cores and windings which consists in continuously subjecting the exterior ot the rotor and interior ofthe stator in the air' gap of the machine to the cooling effect of a liquid'spray,

my signature.

` FRANK G. BAUM.

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