US1927890A

US1927890A - Ventilation of rotor end coils of turbogenerators

Info

Publication number: US1927890A
Application number: US503429A
Authority: US
Inventors: Carl J Fechheimer
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1930-12-19
Filing date: 1930-12-19
Publication date: 1933-09-26
Anticipated expiration: 1950-09-26

Description

Sept- 1933- c. .1. FECHHEIMER 1,927,390

VENTILATION OF ROTOR END COILS OF TURBOGENERATORS Filed Dec. 19, 1930 2 SheetsSheet l WITNE E5 INVENTOR wg 9wv Carl J. fEchhe/mer (Q72 3W ATTORNEY 19, 1950 2 Sheets-Sheet 2 w 9 W m m R NQH N m E J V C T N m w w v hk M Y M aw r n d a w a C M an 9.

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1 i .hk W\. m? \N T Sept. 26, 1933. c. .1. FECHHEIMER VENTILATION OF ROTOR END COILS OF TURBOGENERATORS Filed Dec.

Patented Sept. 26, 1933 UNITED STA VENTILATION OF ROTOR END COILS OF TURBOGENERATORS Carl J, Fechheimer, Pittsburgh, Pa., assignor to Westinghouse Electric & Manufacturing Company, a corporation of Pennsylvania Application December 19, 1930 Serial No. 503,429

4 Claims.

My invention relates to high-speed or steamturbine-driven generators, commonly called turbo-generators,- and it has particular relation to the Ventilation or cooling of the long end turns of the rotor field windings of large machines of this class.

Owing to the rather long lengths that are used in the coil-ends of turbo-rotors, especially for two-pole machines, but also for large four-pole machines, and especially for the lower frequencies, such as and 60 cycles, high temperatures occur at or near the middle portions of the circumferential coil-end lengths, because the heat cannot escape otherwise than by conduction to the retaining rings or along the copper of the coilends to the core of therotor. I In the past, an attempt has been made to over come this difficulty by drilling holes through the retaining rings which surround the coil-ends and retain them against centrifugal forces. It has been found, however, that very little benefit was obtained by this expedient.

According to my present invention, I have found, by exhaustive tests, that ample cooling vcanbe obtained by reducing the volume of air that passes over the coil-ends, but greatly in creasing the .velocity'of this air, so that the amount of heat interchanged per unit area of ex- .posed'coil-ends, for each degree of temperature difference, is greatly increased, notwithstanding the reduced total volume of air.

taining ring 8.

With the foregoing and other objects in view, my invention consists in the combinations and structures hereinafter described and claimed and illustrated in the accompanying drawings, where- Figure 1 is a longitudinal sectional view of a part of a turbo-generator rotor member embodying my invention,

Fig. 2 is a transverse sectional view thereof on the plane indicated by-the line 11-11 on Fig. 1,

Fig. 3 is a partialdevelopment of the retainer ring and the coil-ends shown in the preceding figures, and

Fig. 4 is a curve diagram.

In the drawings, my invention is shown applied to a'rotor member of a turbo-alternator comprising direct-current exciting windings having a plurality of coil-ends 6 projecting out beyond the rotor core 7' and extending circumferentially around the end of the rotor member, the same being retained against centrifugal forces by a re- Some, or all, of the coil-ends,

V particularly the longest ones which have the longest circumferential distance to travel, are

spaced more than the others and are provided with blocking means of micartaboard, or the like, as indicated at 10 and 11. These blocking plates are provided with vertically extending channels 12 along their sides, which communicate with transverse channels 13 across their tops, the latter communicating with holes or perforations 15 which are drilled into the retaining ring 8'. I

The channels 12 in the side faces of the blocking plates 10 and 11 are in communication with the sides of the adjacent coil-ends 6, and provide high-velocity streams of air passing over said coil-ends'to cool the same, as hereinbefore explained. a

These channels are narrow, having a width or 7 depth (measuring axially away from the surface of the coil-end) generally of the order of one-eighth of an inch or less. As turbo-rotor windings are now constructed, it is impossible to space the coil-ends or end turns with sufii- 7 cient accuracy, and so close together, without the use of the blocking plateslO and 11. Fig.

4 shows the effects of the spacers 10 and 11 between the coil-ends 6, these effects being plotted as a function of the ratio of the area of the ventilating spaces 12 to the area of the holes 15. The area of the ventilating space is the mean cross-sectional area of the air which is flowing radially outward in the channels 12, and it is obtained by multiplying the channel width by the circumferential length of the same. The corresponding combined widths of the double channel, such as the two channels 12 of the blocking plate 10, are also plotted as abscissa.

Two sets of curves are shown in Fig. 4. Curves 9o 21 and 22 show the variation in the amount of heat transferred, for a given exposed area of the coil and for a given temperature difference between the coil and the air, for the diiferent ratios of areas, the upper curve 21 being for a machine 05 having a three-inch coil depth and the lower curve 22 being for a machine having a seven-inch coil depth. The other two

curves

23 and 24 show the variation in the volume of air, under the same conditions.

It would be theoretically desirable to have the ratio of areas and the width of ventilating space or channels so small that the maximum heat transfer would be obtained, but reference to Fig. 4 will show that these values of ratio and width 106 together are so small that it isnot, at present, considered to be safe practice to approach such dimensions very closely, because of the danger of such minute channels becoming quickly clogged with dirt, and because ofthe physical p0 lating air in the ventilating spaces or channels.

The mean velocity of this air should be more than one-tenth of the peripheral velocity of the outer surface of the retaining ring and, preferably, it should be at least of the order of about one-fifth of said peripheral velocity. Thus, in a four-pole 60-cycle machine, of 100,000 K. V; A. capacity, the peripheral velocity of a fifty-eightinch retaining ring is 27,300 feet per minute, and

the velocity of the air in the channels 12 is something of the order of 5000 to 6000 feet per minute.

It is important to note that the end-coil surfaces which are directly cooled by high-velocity air-streams are defined by blocks or spaces 10 and 11, and that those portions of the end-coil surfaces which are notdirectly cooled by the airstreams are only slightly warmer than the cooled parts, as the distance that theheat flows from the one to the other is short.

Tests have indicated that the introduction of my spacing blocks 10 and 11 has resulted in a reduction of the hot-spot temperature-rise, in testing for a considerable overload, from 275 C. to 67 C., with a corresponding large reduction in the average temperature of the winding.

While I have shown my invention in a single form of construction Which is, at present, the preferred form, it is obvious that I am not limited to any one precise detail of construction. I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language and the prior art.

I claim as my invention:

1. A rotor member for a dynamo-electric machine, said rotor member comprising windings having end turns, at least some of the end turns being spaced from each other to provide channels for the flow of air, solid metal retainer rings surrounding said end turns for retaining them against centrifugal forces, said retainer rings being perforated to permit the escape of ventilating air for said end turns, the sizes of the channels and perforations being such that at least some of the air that flows in said channels past the end turns and out through the retainer-ring perforations associated therewith has a mean cross-sectional area, in said channels, which is less than four times the area of the associated perforations.

2. A rotor member for a dynamo-electric machine, said rotor member comprising windings having end turns, solid metal retainer rings surrounding said end turns for retaining them against centrifugal forces, said retainer rings being perforated to permit the escape of ventilating air for said end turns and characterized further by narrow channels between certain of said end turns, said narrow channels having such restricted width that the mean velocity of the ventilating air therein is more than one-tenth, and of the orderof one-fifth, of the peripheral velocity of the outer surface of the retainer rings.

3. A rotor member for a turbo-dynamo-electric machine, said rotor member comprising windings having end turns, at least some of the end turns being spaced from each other, solid metal retainer rings surrounding said end turns for retaining them against centrifugal forces, said retainer rings being perforated to permit the escape of ventilatingair for said end turns and characterized further by spacers between at least some of the spaced sides of said end turns, said spacers having channels in their sides, adjacent to the respective end turns, the relative sizes of the channels of the spacers and the perforations of the retainer ring being such that at least some of the air that flows in said channels past the end turns and out through the retainer-ring perforations associated therewith has a mean crosssectional area, in said channels, which is less than four times the area of the associated perforations.

4. A rotor member for a turbo-dynamo-electric machine, said rotor member having windings with end turns, at least some of the end turns being spaced from each other, solid metal re tainer rings surrounding said end turns for retaining them against centrifugal forces, said retainer rings being perforated to permit the escape of ventilating air for said end turns, and characterized further by spacers between at least some of the spaced sides of said end turns, said spacers having channels in their sides, adjacent to the respective end turns, said channels being of such restricted cross-section that the mean velocity of the air in said channels is at least of the order of about one-fifth of the peripheral velocity of the outer surface of'the retainer rings.

CARL J. FECHHEIMER.