US1930994A - System and method for heating dynamo-electric machines - Google Patents

Description

Get. 17, 1933. 5 BROWN 1,930,994

SYSTEM AND METHOD FOR HEATING DYNAMO ELECTRIC MACHINES Filed Dec. 24, 1929 2 Sheets-Sneet 1 3 /n1 /e/7/or fr/c Bro wn E. BROWN Oct. 17, 1933.

SYSTEM AND METHOD FOR HEATING DYNAMO ELECTRIC MACHINES Filed Dec. 24. 1929 2 Sheets-Sheet 2 quick full-load application thereon.- Y

Patented Oct. 17, 1933 SYSTEM AND METHOD FOR HEATING DYNAMO-ELECTRIC MACHINES Eric Brown, Baden, Switzerland; assignor to Aktiengesellschait Brown Boveri &,Cie., Baden, Switzerland,a joint-stock company of Switzere land:

Application December 24, 1929, Serial No.

, 416,307, and in Germany December 24, 1928 5 Claims. v(o1. 171-252) This invention relates to improvements in electriccurrent generators and, particularly, to means for maintaining large generators incon'clition for substantially instantaneous starting at full load. Large generators cannot be placed under full load immediately upon starting for the reason that the several portions'of the generator heat up at different'ratesthereby causing; stresses and strains in the generator structure. The copper portions embedded in the iron of the rotor heat up more quickly than the ironypartly because of the heat-insulating qualities of the coverings of the copper. Such action,especially when fre quently repeated, materially shortensthe life of the copper insulation. A furtherjdifierence in the heating efiect is likewise apparent when large generators are quickly started, in that the circumference of the rotor reaches the full load operating temperature before the core thereof has'been materially heated. Such difference in temperature-conditions; causes stresses in the materials and may even cause bending of the shaft, thereby giving rise todestruc'tivevibrations.

Itis, therefore, among the objects of'thepresent invention to provide means for maintaining generators, and particularly large generators, in such condition'as will permit quick-starting Another objector the present invention is to provide means for maintaining generators in such heatedcondition as to permit full-load operation thereof substantially immediately after starting.

- Another object of the invention is to provide means for preheating and automatically maintaining generators at the proper temperature for full-loadoperation immediately upon starting by the" use of portions of the generator structure itself'in combination with exterior heat sources. @bjects and advantages, other than thoseabove set forth, will be apparent from the following de scription and the accompanying drawings, in 1. 9 3

Figure 1 shows a side elevation of one embodie ment of the/invention using a ,heat source 'external to the generatorjor maintaining the temperatu l ereoi, L y

Iig} 2 shows a modified form of the invention,

haw Fig- 1 Fig. 3 is a modified embodiment of the inven-v tion in which portic n s of the generator tobe hea e a e utili e s he t; s ur maddition tome'ansior supplying heat from external sources thereto, and

also in Side elevation, which similar to. that Fig. 4 illustrates one manner of using portions of the generator as a supplemental heatsource,

Referring more particularly to the drawings by characters'of referencathe reference numeral 6 indicates a generator which is enclosed in a sub;

stantially gas-tight manneryand to which are connected supply conduits '7, 8 having a common portion and connecting with the generatoro at the ends thereof. A discharge conduit 9 is connected with the generator structure at'substan tially the central portion thereof. The supply conduits '7, 8 and the discharge conduit 9 are con;-

nected by means of a blower 11 driven by a suit-- able source of power, such as a motor 12, for the purpose of maintaining the heat-carrying medium within the'supply conduits 7, 8, within the gen- 'erator' housing and within the discharge com; duit 9; in circulation. The gases circulating'i through the generator and thevarious conduit connections therewith are heated by means of a.

heat-exchanger 13 or aheating resistance '1 ar ranged in the "common portion of the supply con-' duits 7, 8. The heat-exchanger 13 may be supplied for heating purposes with steam or hot water;

or any suitable heat-carrying medium"-from-'a suitable'source. It will, of course, be understood thatboth oreither the heat-exchanger 13 or the heating resistance 14 may be connected to provi e;

forltransmission of heat'to the gasesci'rcula through the supply conduits, the generator,"

and

the discharge conduit circuit under the ac'tibiifer the blower 11, as above set forth.

If it is desired to provide means for manate cally maintainingthe generator G at a 'p'rdetermined temperature, a branch pipe'16 is'connected with the common portion of the supply; conduits '1, 8,; immediately behind thefhe'atexchanger '13 and the heating resistance'fi. "The branch pipe 16 is connected witha blower 17*, operated by a' suitable source of powersuch "as asteam'turbine 18, for maintaining the gases within the generatorin constant circulatio nby discharging the same through a discharge pipe 19 connecting with the discharge conduit 9. A heat ing' resistance 21 is shown arranged within the discharge pipe 19, and is connected-by means or a suitable switch 22 to a regulating rheostat23.

The amount of the rheostatresistance connected into the heating circuit is determined by the operation ofta suitable-thermostatic element 24' within, the by-pass pipe 25 between'the branch pipe 16and thedischarge pipe 19.

' Intcase' it is desired to utilize the exhaust steam from the turbine 18 as the heating medium; a thermostatically-operated valve, indicated at 26,

I of the generator 6 are connected with a suitable is connected with the exhaust line 27 from the turbine 18 and. the heating resistance 21 is replaced by a heat-exchanger of any suitable character.

It will be seen that the above embodiment of the invention provides means for maintaining the gases circulated about the stator and rotor of a generator in a preheated condition either by manual operation of the heat-exchanger 13 or the heating resistance 14,or by thermostatic operation of the heating resistance 21 or a heatexchanger inserted in the discharge line 19 in place thereof.

When the automatic apparatus is used for controlling the temperature, some of the air from the outlet side of the blower 11 takes the path to the right through the branch pipe 16, through the blower 1'7, and thence by way of the discharge pipe 19 to the heating resistance 21, whereupon it mingles with the air being discharged from the generator 6 and passes with this air through the blower 11. The amount of air passing through this circuit, and the amount of heat imparted thereto by the resistance 21,

.aresufficient to maintain the air, circulated through the generator, at the required temperature. The air passing through the by-pass pipe 25 subjects the thermostatic element 24 to substantially the temperature of the air as it is forced into the generator, and this element operates to efiect variation of the temperature of the vheating resistance 21 inversely proportionally to variations in the air temperature at this P int.

, Figure 2 shows a modification of the present invention in which a generator 28, driven by a turbine 29, is heated to maintain the generator in such condition as to be available as a reserve machine for instantaneous starting. In this em- ;bodiment, a heat-exchanger 31, supplied with a heating medium from a suitable source, is connected with the generator 28 and with a blower 32 for the purpose of circulating a heat-carrying medium therethrough.

Connections are made with the pipe leading from the generator 28 to the inlet of the blower 32- for discharging part of the heat-carrying medium through a second generator 33, also driven by turbine 29, for the purpose of 'maintaining this generator also in the proper heated condition necessary for instantaneous full-load operation upon starting. Connections are so arrangedthat the heat-carrying medium is supplied to the generator 33 at one or more points,

;and is abstracted therefrom at a different point by means of a circulating blower 34 connected between the inlet and outlet connections between the generator 33 and the circulatory system connected with the generator 28. This method of maintaining both generators in a heated condition is particularly valuable for use in centraloperated stations, or for ships which are provided with electrically operated power transmission, inasmuch as the rotors of the generators are usually slowly rotated so that the same are maintained in a uniformly heated condition which permits the application of the full load thereon immediately upon starting.

The arrangement shown in Fig. 3 is similar to that shown in Fig. 1, with the exception that the windings of the rotor itself are utilized as heating resistances to aid in maintaining the temperature of the generator at the predetermined value. For this purpose,.the slip rings 36 source of current such as a generator '37 driven by a suitable source of power, such as a turbine 38. The amount of current supplied to the windings of the rotor is determined by means of a regulating resistance 39 controlled, in dependence on the temperature of the gases circulating within the generator housing, by means of a thermostatic element 41 operating a system of levers 42 for the purpose of cutting resistance into or out of the circuit. For the purpose of facilitating the connection of the windings of the rotor for use as heating resistances, the ends of the several phases 46 and 47 are brought out in such manner that they may be connected in series by means of switches 48.

It will be seen that the present invention provides means whereby a generator may be maintained at substantially the operating temperature for the purpose of making it possible to bring the same to full-load immediately after starting. According to the present invention, this result is attained either by the use of external heat sources for transmitting heat to gases circulated through the generator, or by a combination of such external heat sources with the use of the rotor windings as heating resistances. It will likewise be seen that the temperature of the generator may be regulated either manually or auto matically in the case of either the use of an external heat source or the combination of the external heat source with the rotor windings as heating resistances.

Although but a few embodiments of this invention have been illustrated and described, it will be understood that various other embodiments are possible, and that various changes may be made without departing from the spirit of the invention or the scope of the appended claims. 7

The invention claimed is:

1. In a system for maintaining an electric current generator in immediately operative condition, a supply conduit connected with the generator, a discharge conduit connected with the generator, means for circulating a heat-carrying medium through said conduits, a source of heat for heating the heat-carrying medium, and thermostatic means for controlling the amount of heattransmitted to the heat carrying medium from said heat source.

2. In the art of operation of a dynamo electric machine, the method of maintaining the temperature throughout the machine structure substantially constant, during non-operation thereof, at substantially the temperature developed during normal operation; said method comprising supplying a heat-carrying medium to the machine structure, and increasing the temperature of said medium when the temperature throughout the machine structure decreases from substantially the temperature developed during normal operation of the machine.

3. In a system of the character described, a dynamo electric machine, means for supplying a heat-carrying medium to said machine comprising a closed circuit including the machine, means operable independently of said machine for causing said medium to circulate around said circuit, means operable independently of. the condition of operation of said machine for imparting heat to said medium, and means for controlling said medium-heating means responsive to variations in the temperature of said medium, at a given point in said circuit, from a predetermined degree of temperature.

4. In a system of the character described, a heat-carrying medium to said machine comprisdynamo electric machine, means for supplying a ing a closed circuit including the machine, means heat-carrying medium to said machine comprisoperable independently of said machine for causing a closed circuit including the machine, means ing said medium to circulate around said circuit,

5 operable independently of said machine for causand means comprising an electrical resistor and ing Said medium to circulate around Said C cu operable independently of the condition of operaand means comprising an electrical resistor and tion of said machine for imparting heat to said Operable independently the conditifln 0f opermedium, said resistor being embodied in said ation of said machine for imparting heat to said machine and forming at least part of the operat- 10 medium. ing windings thereof. 5. In a system of the character described, a ERIC BROWN. dynamo electric machine, means for supplying a 20 J I V Y Y I v v r i I V i so p g I I V v v as V i v t a I g I i v I a g I 40 g V Q i V g p v i i I 45 I v 1 i I 7' I e co g p i a g I Y i g I v I a i r a 7 1 25 1 55 I I g p i I v V so l l V v I p g I v c5 7 V i g a g g 7 v 3 i I v p I 14c 70 g j I I g g I I a I 75 V A i i c a 15o

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