JPH0427785B2 - - Google Patents

Description

Claim 1: A pressure wedge abutting against a stator bar of a rotating electric machine; a curl wedge having both ends abutting the respective pressure wedge; and a curl wedge abutting a central portion of the curl wedge and engaging a stator core slot. a mating dovetail wedge, the dovetail wedge being pressed against the slot by the spring action of the curling wedge, and the pressure wedge being pressed against the stator bar; The dovetail wedge is comprised of a coiled laminate including at least two epoxy glass sheets and one woven aromatic polyamide sheet, the at least two epoxy glass sheets interleaved with each other. 2. A wedging device characterized in that the wedging device is coiled closely and together with the polyamide woven sheet such that the polyamide woven sheet is on the outside of the glass sheet.

BACKGROUND OF THE INVENTION This invention relates to large rotating electrical machines and stator wedge apparatus, and more particularly to an improved dovetail wedge for retaining conductor bars within stator core slots.

Large rotating electrical machines, such as generators, use laminated stator cores to transmit induced voltages through stator conductor bars to generator terminals. Iron cores are typically made by assembling pre-slotted stamped plates or laminated plates into an annular housing for later housing the generator rotor. The slotted stamping plate, when assembled, defines an axially extending radial slot that terminates at the radially inner circumference of the stator annulus. Stator bars or conductors are disposed within these radial slots and a wedging device is used to hold the bars in place against electromagnetic forces generated during operation of the rotating electrical machine. If the wedging device is not effective, the resulting vibrations will destroy the conductor insulation and ultimately lead to generator failure.

U.S. Patent Application No. 307,007, filed September 30, 1981, discloses a new and improved wedging device for a stator core of a rotating electrical machine. This wedging device includes a pressure wedge 27, a curl wedge 31 and a dovetail wedge 41 that cooperate to hold the stator bar as shown in FIG. It is a device that applies holding pressure directly to the stator bar by coming into contact with the stator bar (via), and has a shape as shown in the figure, and a "curl wedge" is a pressure wedge that It comes into contact with the stator core and presses it, and has an elongated shape as shown in the figure.Furthermore, the "dovetail wedge" fits into the stator core slot (specifically, the dovetail slot provided there). 17) and abuts against the curling wedge to press (i.e. apply pressure) on the curling wedge, thus pressing on the pressure wedge and thus holding the stator bar, as shown. It has a shape like this.

Hereinafter, in this specification, the terms "pressure wedge", "curl wedge", and "dovetail wedge" refer to wedges having the above-mentioned functions and shapes. This new wedging device increases the radial force exerted on the conductor bar, thereby providing a higher performance wedging device than previously available in the art. While the machine under operating conditions generates bar forces on the order of 5 to 20 pounds per inch, the new wedging device as described in the above patent application resists bar forces on the order of 30 to 100 pounds per inch. Generates a radial force. In other words, this new wedging device provides an anti-bar force that is 5 to 6 times the magnitude of the bar forces encountered during machine operation. For this reason, the present invention was developed to ensure the performance and long life of the stator wedge.

The dovetail wedge shown in U.S. Pat. No. 4,200,818, issued April 29, 1980, consists of two separate parts. That is, the glass fiber core is surrounded on at least two sides by facing layers of fiber mat, ie Kevlar®, sold by DuPont, both parts impregnated with resin. The fiber mat provides a protective and lubricating interface between the stator core laminates and the stator slot wedges. Each stator core laminate has an electrically insulating coating,
If this coating is interrupted or subjected to some other disturbance, a short circuit will occur, resulting in localized overheating within the rotating electrical machine.

One of the requirements for the stator wedge is that it be able to withstand radial forces without cracking. According to the patent, a typical phenolic kraft paper slot wedge has a strength on the order of 1500 pounds per inch of length. A wedge made in accordance with said patent has a strength of 3510 pounds per inch of length. The wedge disclosed below and manufactured in accordance with the present invention is an improvement over the prior art and has a strength of 9100 pounds per inch of length, which is approximately a 260% improvement over the prior art. be.

SUMMARY OF THE INVENTION The present invention provides a wedging device that includes a pressure wedge, a curl wedge, and a dovetail wedge, the dovetail wedge being a laminate that includes at least two epoxy glass sheets and one woven aromatic polyamide sheet. It is formed from a structure whose body is coiled (i.e., spirally). This configuration significantly increases the strength of the wedge.

OBJECTS OF THE INVENTION One object of the present invention is to provide an improved slotted wedge with increased load carrying capacity.

Another object of the present invention is to provide a new fabrication method for forming stator core slot wedges.

The novel circumstances believed to be characteristic of the invention are set forth in the appended claims.

However, the invention itself, as well as other objects and advantages of the invention, will be better understood by reference to the following description taken in conjunction with the drawings.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a part of a stator core showing an environment in which the present invention is actually applied, and FIG. 1A is a side view of a wedging device applied to a slot of the stator core.

FIG. 2 is an end view of the stator core wedge of the present invention.

FIG. 3 is a perspective view showing the preferred arrangement of parts prior to fabrication.

FIG. 4 is a diagram showing the structure of the present invention before being placed in a mold.

FIG. 5 is a diagram showing a mold used for processing the present invention.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows the lower part of a stator core 11 of a rotating electrical machine, and FIG. 1A shows the placement of the wedging device within the core slot. A rotating electrical machine has a rotor (not shown) and a stator core, and the stator core is an annular structure that surrounds the rotor when the rotor is installed in the rotating electrical machine. The stator core is assembled by pressing a number of slotted punched plates or laminates 13 together in a well known manner and mounting them on a key rod (not shown). The stator core is formed with a plurality of radial slots 15 (only one shown) spaced circumferentially along its annular inner periphery, and these slots 15 extend along the axial length of the stator core. and terminating at its radially inner portion as a dovetail slot 17, which are well known in the art. The conductors 19 consist of lightly insulated conductor strands (not shown) each comprising a radially inner bar 19a and an outer bar 19b. The conductor or conductor bar includes an electrical insulator 21 wrapped around its periphery.

A backing plate 23 extends in the axial direction (lengthwise direction) along the slot radially inward from the bar 19a. A number of pressure wedges 25 are introduced into the slot 15 and are spaced apart along the axial length of the slot 15 to bear against the insulating caul plate 23. The pressure wedge 25 is provided with opposing sloped surfaces 27 to facilitate assembly of the stator bar wedge arrangement. Wedge 2
The material No. 5 is preferably a high-strength insulating material that can be cut or molded into the shape shown in the drawings. The wedge may be formed from a resin compound with suitable fillers to increase its strength, or from a number of commercially available materials, such as "Textolite" (registered trademark of General Electric Company). It can be made from. In addition to the above, the wedging device includes a number of curling wedges 31, each curling wedge 31 having a longitudinally extending elongated body portion, each end of which meets the sloped surface 27 of the pressure wedge. Abutting inclined surface 35
Terminates with. Curl wedge 31 is 1007 Scotchply available from 3M Company or G-11 available from Spaulding Company.
Preferably, it is made from glass.

In accordance with the present invention, dovetail wedges 41 are used to retain the wedging device within the stator core slot. The dovetail wedge in place straddles the curl wedge at notch 43 and further includes an angled surface 45 that engages dovetail slot 17 in stator core slot 15. This dovetail wedge will be further explained using FIG. 2. Figure 2 shows the complex nature of the wedge. The slot wedge is a laminate of at least two resin-impregnated epoxy glass sheets 47 and one woven aromatic polyamide sheet 49 wound into a coil. An aromatic polyamide completely surrounds the epoxy glass, as further described in connection with the remaining figures.

FIG. 3 is a perspective view showing the initial stacking of materials to make the stator wedge. In the preferred embodiment, two sheets 47 of impregnated epoxy glass material, such as Scotchiply 1009-36, are precisely mated with one woven sheet 49 of aromatic polyamide, such as Kevlar 49. For a 6-inch mold length, cut the material into a rectangle approximately 6.5 inches by 9 inches. Scotchiply 1009
The -36 sheets are high strength tapes of unidirectional non-woven crossply E-glass filaments pre-impregnated with epoxy resin, each sheet being approximately 0.016 inch thick. The Kevlar 49 tape is approximately 0.013 inches thick.

After first stacking the materials together, the three sheets are rolled into a roll cake to form a laminated coil wrap as shown in FIG. It should be noted that the aromatic polyamide sheet 49 completely surrounds the glass sheet layer 47 and is present throughout the entire wedge cross section. This winding operation is done by hand and all that is required is that the laminate roll can be fitted into the mold. One way to facilitate this fit is to approximate the shape of the wedge to the mold cavity by preshaping the wedge into a concave-convex shape before inserting the wedge into the mold cavity.

FIG. 5 is a sectional view of a press mold 50 used for manufacturing the wedge of the present invention. press mold 5
The upper template 52 of 0 has a protrusion 54 which is used to form a notch 43 in the wedge. A cavity 58 is formed in the lower template 56 of the press mold.

After putting the composite coil-wound laminate into the mold,
A pressure of 125 psi is applied for 1 hour at a temperature of 160°C. After this processing, the formed wedges are removed from the mold cavity and post-fired in a furnace at 160° C. for 8 hours.

Additional information regarding wedge forming is shown in Table 1. That is, the table shows the weight percentages of the wedge material in both the cured and uncured states.

Table 1 Uncured Composition Cured Composition 56% by weight Glass 65% by weight Glass 12% by weight Kevlar 14% by weight Kevlar 32% by weight Epoxy resin 21% by weight Epoxy resin As can be seen from the above, stator wedges were manufactured. The method to do this is extremely simple and is as follows. In a preferred embodiment, two pre-impregnated epoxy glass tapes and a woven aromatic polyamide sheet are laminated such that at least two sides of the glass tape are in intimate contact with each other. The three sheets are coiled so that the woven aromatic polyamide sheet surrounds the epoxy glass tape. The thus wound laminate is preformed into a crescent shape so that it can be inserted into a mold. The preformed laminate is placed in a mold and the wedge is cured for 1 hour at a pressure of 125 psi and a temperature of 160°C. wedge
Post-cure at 160°C for 8 hours.

Although what is presently believed to be the preferred embodiment of the invention has been disclosed, other modifications will readily occur to those skilled in the art. The present invention encompasses all such modifications.