JPS5983548A - Magnetic pole structure for rotary electric machine - Google Patents

Abstract

PURPOSE:To reduce a dovetail stress by composing so that the contacting surface of a cock with a dovetail and the line for connecting the root of the dovetail to the inside center of the dovetail become perpendicular. CONSTITUTION:A magnetic pole 1 has a flared projection 4 formed toward the inside called ''a dovetail'', and a rotor ring 3 has a dovetail groove 5 of similar shape to the dovetail 4. The pole 1 is secured to the rim 2 by inserting the dovetail 4 into the groove 5 of the rim 2 and press-fitting a cotter 3 into the air gap produced between the dovetail 3 and the groove 5. At this time, the angle beta formed between the contacting surface of the cotter 3 with the dovetail 4 and the line for connecting the root of the dovetail 4 and the inside center of the dovetail is 90 deg.. In this manner, the dovetail stress can be reduced, thereby improving the buckling strength.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a magnetic pole mounting structure for a rotating electrical machine, and particularly to a magnetic pole mounting structure suitable for improving the buckling strength of a high-speed, large-capacity machine such as a pumped water turbine generator.

A conventional magnetic pole mounting structure is shown in FIG. 1, and its stress generation mechanism is shown in FIG. As shown in Figure 2, the conventional magnetic pole mounting structure has the disadvantage that excessive compressive stress, which can cause L6 bending accidents, is likely to occur in the center area of the inner circumferential side of the magnetic mounting protrusion called a dovetail. was there.

An object of the present invention is to provide an entire magnetic pole mounting structure that prevents buckling failure by sufficiently reducing dovetail stress, and that can be manufactured within the same number of man-hours as conventional dovetails.

In recent years, the power demand in Japan has a significant difference between day and night, and hydroelectric power generation facilities have been increasing in capacity in order to supply peak power and effectively utilize surplus power distributed at night.

Large-capacity pumped storage power generation facilities such as those in the 1990s have been made faster in order to improve economic efficiency, and recently, 700 rpm class is being planned, compared to the conventional 300 rpm class. In this way, as speed increases, unprecedented problems arise in terms of the strength of the equipment. One such phenomenon is the buckling phenomenon of the magnetic pole mounting structure, which is the object of the present invention. FIG. 3 is an elevational cross-sectional view showing a conventional magnetic pole mounting structure, and FIG. 4 is a cross-sectional view perpendicular to the axis of FIG. 3.

In FIG. 4, the magnetic pole 1 has a protrusion 4, which is called a dovetail, on the inner circumferential side of -7 and widens toward the inside. On the other hand, the rotor rim 2 has a dovetail 5 having a similar shape to the dovetail 4 on its outer periphery. Magnetic pole 1 connects dovetail 4 to rotor rim 2
The cock 3 is inserted into the dovetail groove 5 of the rotor rim 2, and the cock 3 is fully press-fitted into the gap formed between the dovetail 4 and the dovetail groove 5.

1 The magnetic pole centrifugal force F caused by the rotation of the coater rim is
The scattering of the magnetic poles is suppressed by vectorial balance with the rim reaction force P. The entire vector relationship between F and P is shown in FIG.

This structure has the following drawbacks regarding buckling of the magnetic pole dovetail, which is an obstacle to increasing speed. below,
Let me explain this.

FIG. 1 shows an enlarged view of the magnetic pole mounting structure. Kotsuta reaction force P
is decomposed into a force Fi perpendicular to the stone and a force Ff parallel to the cross section of interest. The stress state caused by these forces is shown in FIG.

F@ compresses the cross section ABi as shown in a) of the same figure, thereby generating a compressive stress σ. On the other hand, pr is the cross section AB
A bending moment M=Ii'', Xe is generated for
As shown in Figure b), bending stress noise occurs. The maximum bending stress occurs at both ends of the cross section, i.e., the root A of the dovetail and the center B on the inner circumference of the dovetail, and from the direction of the bending moment, the stress is compressive at point B, and the stress at point A is tensile. It becomes stress.

Furthermore, the FT of FIG. 1 generates a shear stress τ as shown in FIG. 2C).

Eventually, these y&: stresses occur in the AB cross section. In particular, compressive stress σ and bending stress σb have a large influence. From this point of view, the composite result of σゎ and σb is
Shown in Figure d). At point A, σ and σb are in opposite directions, so they cancel each other out and the value becomes smaller, whereas at point 13, σ,
Since both σ1 and σ1 are compressed, they overlap and become even larger values.

Although the above is shown as an analytical formula for explanation, the actual stress distribution has a complicated shape. This distribution state can be determined using a finite element method program using an electronic computer. FIG. 5 shows, as an example, the results of finite element method calculation of a dovetail having a conventional standard size ratio. The stress at both ends is large and the direction is opposite, and the direction is the same as the direction of the bending moment shown in FIG. 2b). This shows that in the conventional dovetail, bending stress occupies a large proportion. Therefore, the first step to improving buckling strength is to reduce bending stress.

The magnitude of bending stress σb is the length t of the AB cross section (Fig. 1)
is inversely proportional to the square of That is, FIG. 6 shows the stress distribution of the AB section based on the finite element method calculation when the section length t is changed under the same load and boundary conditions as in FIG. 5. Figures 6a) and 5 show the same thing. In Figure 6, the stress at point B is a
) is the largest, and decreases rapidly as the cross section t increases. However, as shown in FIG. 6d), the maximum value of the normal stress σ3·ntax tends to become larger. The reason for this is that the direction of the bending moment acting on the AB cross section is opposite in FIGS. 6a) and 6d). FIG. 7 shows the stress generation mechanism of FIG. 6d). The direction of the net compressive stress due to Fl is the same in FIG. 2a) and FIG. 7a), whereas the direction of the bending moment is opposite in FIG. 2b) and FIG. 7b). This is because the positional relationship of the non-cross-sectional midpoint C with respect to the line of action of the rotor rim reaction force P is reversed.

From the above, in Figure 2 d), the stress σ at point A and σ
b cancel each other out, resulting in a small resultant stress, whereas in FIG. 7, on the contrary, they overlap in the same direction.

This is the reason why the maximum value σ,·n1aX of the normal stress is large. As described above, the conventional structure has the drawback that even if the dovetail cross section is increased, the stress cannot be reduced below a certain level. In order to eliminate this drawback, the present invention is an attempt to improve the conventional stress generating mechanism without a cross section. That is, as described above, in the conventional structure, bending stress and shear stress occur simultaneously in the K1 cross section. The present invention
Of these stresses, the net compressive stress σ, (see Figure 2 a))
Eliminate the occurrence of In principle, the line of action of the rotor rim reaction force P in FIG. 1 is parallel to the AB section.

Based on this principle, the component force F of P on the AB section becomes zero, and only stress remains on the line surface of the AB section. As mentioned above, according to the beam theory of materials mechanics, bending stress is inversely proportional to the square of AB cross-sectional length t, so by increasing tf, compression in region B, where conventionally excessive compressive stress has occurred, is reduced. The total stress can be kept sufficiently small.

FIG. 8 shows an embodiment of the magnetic pole mounting structure of the present invention. show. According to the principles of the present invention, β=90.

Therefore, the component force of the rotor rim reaction force P on the AB section becomes zero, and only the shear stress τ due to P and the bending stress σ due to the bending moment M=PXe are generated on the AB cross section.

Here, as mentioned above, the bending stress σb is 2 of AB cross-sectional length t.
The total stress can be reduced by increasing t'z, ie by decreasing the angle α in FIG. 8. Therefore, this embodiment has the effect of preventing buckling of the dovetail.

According to the present invention, of the bending compressive stress and the pure compressive stress that conventionally occur at the same time in the inner peripheral area of the dovetail, the generation of the pure compressive stress can be completely prevented, so the total dovetail stress can be reduced, and the dovetail stress can be reduced. It has the effect of improving bending strength.

[Brief explanation of drawings]

Figure 1 is an enlarged view of the conventional magnetic pole mounting structure, Figure 2 a) to d
) is a diagram of the stress generation mechanism in a conventional magnetic pole, FIG. 3 is a vertical cross-sectional view of a conventional generator, FIG. 4 is a cross-sectional view taken along the ■-■ arrow in FIG. 3, and FIGS. 5 and 6 a) - d) are stress distribution diagrams obtained by the conventional dovetail finite element method, and Fig. 7 a) - C) are
Figure d) is a diagram of the stress generation mechanism, and Figure 8 is a diagram of the magnetic pole structure of an embodiment of the present invention. 4... Dovetail. 1st mouth 0 'i43 figure'#7 [￥1 8th m

Claims (1)

[Claims] 1. A magnetic pole in which a dovetail groove is provided on the outer periphery of the rotor rim, a dovetail is cut and disposed on the inside of the magnetic pole, and in an assembled state, the magnetic pole is fixed to the rotor rim by driving a stud into the gap created between the dovetail and the dovetail groove. A magnetic pole structure for a rotating electric machine, wherein the structure is such that a contact surface between the cock and the dovetail, a line connecting the root of the dovetail and an inner center of the dovetail are perpendicular to each other.