US2169017A - Damper winding for high speed salient-pole machines - Google Patents

Description

u 1939 v R. A, BAUDRY 2,169,017

DAMPER WINDING FOR HIGH SPEED SALIENT POLE MACHINES Filed April 14, 1958 K d RU Y m m m w VA T m,m H mm Patented Aug. 8, 1939 UNITED STATES DADIPER WINDING FOR- HIGH SPEED SALIENT-POLE MACHINES Rene A. Baudry, Pittsburgh, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 14, 1938, Serial No. 201,952

8 Claims.

My invention relates to dynamo-electric machines having salient-pole rotor members and damper windings disposed in the pole-face portions of the salient poles, and it has particular relation to large high-speed machines of that type.

The particular object of the invention is to provide new and improved means for taking up the centrifugal forces operating on the end rings of the damper windings and at the same time restraining, to a large extent, the distortions due to the excessive heating when the machine is being started.

With the foregoing and other objects in view,

my invention consists in the combinations, structures and methods hereinafter described and claimed, and illustrated in the accompanying drawing, wherein: Figure 1 is a fragmentary cross-sectional View of a large synchronous salient-pole machine embodying my invention, parts being broken away for clarity of illustration, the section-plane being indicated by the line II in Fig. 2,

Fig. 2 is a fragmentary longitudinal sectional view of the machine, on a somewhat larger scale than Fig. 1, showing one end of the damper winding, and

Fig. 3 is a fragmentary developed plan view of a portion of the damper-ring construction with its associated steadying ring.

The drawing shows my invention applied, by way of example, to a large synchronous machine having a primary-winding stator member I of usual construction, and a field-winding rotor member 2 having twelve salient poles 3, so that the machine operates at 600 R. P. M. on 60 cycles, which is a fairly high speed for a machine of its size (60,000 kw.) the centrifugal forces developed in the rotor member being quite high because of the large diameter, which is practically nine feet.

In the pole-face portions 4 of the salient poles 3 there are disposed damper-winding bars 5, and the bars 5 of each salient pole are joined, at each of their ends, to a damper segment 6. The twelve damper segments 6 at each end of the machine are joined by separate connectors l, which are shown as comprising two flexible strips which are bent out of a straight line, as indicated at 8 in Fig. 3, so that when they expand and contract due to heating, only a small stress will be produced in the flexible strips '1.

At each end of the machine, a strong ring 9 is mechanically associated with the segments 6 and connectors I, for taking up the centrifugal forces,

a and for resisting distortions due to the heating of the segments and connectors. These parts are mechanically held together by a large number of bolts H which are preferably provided with spacing washers I2, of relatively poor heat-conductivity, for spacing the ring 9 from the damper segments 6 and from the connectors 1, so as to retard the heat-flow to the ring 9.

The damper segments 6, and the separate connectors 1 between the segments, are of copper and are in good electrical connection with each other, so as to constitute the end-rings for the damper bars 5, which are also of copper. The supporting ring 9 is a heavy steel forging made in one piece, of a grade of steel preferably chosen for its high tensile strength. It has a considerably higher resistivity than copper, so that most of the damping-current flows through the segments 6 and connectors 1, rather than through the rings 9. The spacing washers 12 are preferably made of a material having a low-heat conductivity, such as a nickel-iron alloy, whereby the heat-transfer to the ring 9 is greatly reduced. The iron rings 9 could be completely insulated from, the current-carrying parts, but in general I find that the comparative electrical resistivities are such that practically all of the damper-winding current is kept out of the ring 9, so that it is not necessary to attempt to insulate the same.

When a machine of the size illustrated is started, the starting torque must be supplied by the damper winding 5, 6 and 1. During the starting time, which may be of the order of three minutes, the entire ultimate kinetic energy of the rotor must be transferred, in the form of heat, to the damper winding. If it were not for heat-radiation, this stored heat would raise all parts of the damper winding to a temperature of the order of 900 C. With such heat-radiation as is present, the maximum temperature of the damper bars 5 is something of the order of 400 C., which means a lengthwise expansion of some threequarters of an inch in a damper bar 5 of about eight feet in length. Similar heat effects tend to cause expansion of the damper segments 6 and end-connectors 'l, and these parts can expand somewhat circumferentially, but the iron ring 9 prevents a movement in the radial direction, which would communicate itself to the ends of the damper bars 5 which are brazed to the damper segments 6. I thus prevent the bar-ends from being bent or distorted to such an extent that breakage would occur after a certain number of startings and stoppings of the machine.

According to my invention, the damper segments 6 and the separate connectors l are firmly supported against radial expansion due to thermal and centrifugal forces, which are really quite high in a machine of this size and speed, by means of the relatively cool steel ring 9, so that the expansion of the ring 9 is quite low, resulting in a corresponding material curtailment of the possible bending stresses which can be applied to the ends of the damper bars 5.

While I have described my invention in a form of embodiment which is at present preferred, I wish it to be understood that such embodiment is intended only for illustrative purposes, and not by way of limitation. the appended claims shall be accorded the widest scope of interpretation permitted by the prior art and by the language of the claims.

I claim as my invention.

1. A dynamo-electric machine having asalient pole rotor, damper-winding bars in the 'poleface portions of the salient poles, a damper segment for the bars at each end of each salient pole, separate connectors between the several segments at each end of the machine, a strong ring at each end of the machine for taking upthe centrifugal forces and for resisting distortions due to heating of the segments and connectors, and means for mechanically associating the rings with their respective segments comprising connecting-means for preventing an easy direct heattransfer between the rings and their respective segments.

2. A dynamo-electric machine having a salient-pole rotor, damper-winding bars in the poleface portions of the salient poles, a damper segment for the bars at each end of each salient pole, separate connectors between the several segments at each end of the machine, a strong ring at each end of the machine for taking up the centrifugal forces and for resisting distortions due to heating of the segments and connectors, and means for mechanically associating the rings with their respective segments and connectors comprising connecting-means forvpreventing an easy direct heat-transfer between the rings and their respective segments and connectors.

3. A dynamo-electric machine having a salient-pole rotor, damper-winding bars in the poleface portions of the salient poles, a damper segment for the bars at each end of each salient pole, separate connectors between the several segments at each end of the machine, a strong ring at each end of the machine for taking up the centrifugal forces and for resisting distortions due to heating ofthe segments and connectors, and means for mechanically associating the rings with their respective segments comprising connecting-bolts between the connected parts, and spacing washers of a relatively poor heat-conductivity associated with said bolts between said connected parts.

4. A dynamo-electric machine having a salient-pole rotor, damper-winding bars in the poleface portions of the salient poles, a damper segment for the bars at each end of each salient pole, separate connectors between the several segments at each end of the machine, a strong ring at each end of the machine for taking up the centrifugal forces and for resisting distortions due to heating of the segments and connectors, and means for mechanically associating the rings with their respective segments and connectors comprising connecting-bolts between the connected parts, and spacing washers of a relatively poor heat-conductivity associated with said bolts between said rings and said connected parts.

5. A dynamo-electric machine having a salient-pole rotor, damper-winding bars in the poleface portions of the salient poles, a damper segment for the bars at each end of each salient pole, separate connectors between the several seg- I desire, therefore, that,

ments at each end of the machine, a strong ring at each end of the-machine for taking up the centrifugal forces and for resisting distortions due to heating of the segments and connectors, and means for mechanically associating the rings with their respective segments comprising connecting-means for preventing an easy direct heattransfer betweenvthe rings and their respective segments, the rings having a higher resistance than the segments and connectors whereby most of'the dampingwinding current flows through the segments and connectors rather than the rings.

6. A dynamo-electric machine having a salient-pole rotor, damper-winding bars in the poleface portions of the salient poles, a damper segment for the bars at each end of each salient pole, separate connectors between the several segments at each end of the machine, a strong ring at each end of the machine for taking up the centrifugal forces and for resisting distortions due to heating of the segments and connectors, and

means for mechanically associating the rings with their respective segments and connectors comprising connecting-means for preventing an easy direct heat-transfer between the rings and their respective segments and connectors, the rings having a higher resistance than the segments and connectors whereby most of the damping-winding current flows through the segments and connectors rather than the rings.

'7. A dynamo-electric machine having a salient-pole rotor, damper-winding bars in the poleface portions of the salient poles, a damper segment for the bars at each end of each salient pole, separate connectors between the several segments at eachlend of the machine a strong ring at each end of the machine for taking up the centrifugal forces and for resisting distortions due to heating of the segments and connectors, and means for mechanically associating the rings with their respective segments comprising connecting-bolts between the connected parts, and spacing washers of a relatively poor heatconductivity associated with said bolts between said connected parts, the rings having a higher resistance. than the segments and connectors whereby most of the damping-winding current flows through the segments and connectors rather than the rings. 7

8. Aldyna'mo-electric machine having a salient-pole rotor, damper-winding bars in the poleface portions of the salient poles, a damper segment for lthe barsat each end of each salient pole, separate connectors between the several segments at each end of the machine, a strong ring at each end of the machine for, taking up the centrifugalforces and forrresisting distortions due to heating of the segments and connectors, and means for mechanically associating the rings with their respective segments and connectors comprising-connecting-bolts between the connected parts, and spacing washers of a relatively poor heat-conductivity associated with said bolts between said rings and said connected parts, the

ringshaving a higher resistance than the seg- RENE A. BAUDRY.

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