JPS6240935B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a salient pole rotor for a rotating electric machine, and particularly to a coupling structure between a rotor rim and magnetic poles.

In recent years, there has been a significant difference in electricity demand in Japan between day and night, and as a result, pumped storage power generation facilities have been increasing in capacity to supply peak electricity and effectively utilize surplus electricity at night. In order to improve economic efficiency, such large-capacity pumped storage power generation facilities have been made to rotate at high speeds.
In contrast to the conventional 300rpm class, recently a 700rpm class is being planned.

As pumped storage power generation equipment increases in capacity and rotates at high speeds, various problems arise regarding the strength of the equipment.
There is a risk that buckling may occur in the dovetails of the magnetic pole attachment parts of the salient pole rotor of the generator (which becomes a synchronous motor when pumping water).

That is, in this type of rotating electrical machine, the magnetic poles 1 of the salient pole type rotor engage the dovetails 1a provided at the base with the dovetail grooves 2a of the rotor rim 2, and the magnetic poles 1 have a dovetail groove 2a between the dovetail inclined side surface and the dovetail groove side wall. By press-fitting 3, it is firmly attached to the outer periphery of the rotor rim 2. Note that 4 is a field coil wound around the magnetic pole 1. The centrifugal force F _P generated on the magnetic pole 1 due to the rotation of the salient pole rotor is supported by the counterforce P applied from the side wall of the dovetail groove 2a of the rotor rim 2 via the rotor 3, and The protrusion is suppressed. The balance state of this force is shown in FIG.

By the way, when the dovetail joint is enlarged, as shown in Fig. 4, the reaction force P from the cotter 3 is
is decomposed into a radial component force F _R and a perpendicular component force F 〓. Due to these two component forces, a compressive stress as shown by the arrow in Figure 5a is generated due to the component force F on the radial cross section XX passing through the midpoint B of the dovetail tip surface. However, the component force F _R generates a bending stress as shown by the arrow in FIG. 5b, and the resultant stress is as shown by the arrow in FIG. 5c.

The stress distribution state in Fig. 5 is simplified to aid understanding, but when the dovetail in Fig. 4 with the ratio of dimensions S and T is 1:2 is analyzed using a finite element method using an electronic computer, the following results are obtained. As shown in FIG. 6, the stress distribution on the X-X cross section shows that the stress σ _c occurring at point B at the tip of the dovetail 1a is maximum. Therefore, the tip of the dovetail 1a tends to buckle and cannot withstand large centrifugal force F _P , making it difficult to design and manufacture a salient pole rotor for a large-capacity, high-speed rotating electric machine.

SUMMARY OF THE INVENTION An object of the present invention is to provide a salient pole rotor for a rotating electrical machine that has a large capacity and can withstand high-speed rotation by increasing the buckling strength against compressive loads of the dovetails at the dovetail joints of magnetic poles.

In order to achieve this object, the present invention provides that the reaction force P applied to the dovetail from the radial center of the contact surface of the dovetail and the dovetail is directed from the radially outer end of the contact surface of the dovetail and the dovetail in the circumferential direction of the dovetail tip surface. By applying the force to the center of the straight line leading to the midpoint, the compressive load distribution acting on the dovetail is averaged and the maximum load (stress) is reduced, thereby making the dovetail less likely to buckle. Features.

According to Ka´rma´n, regarding buckling of a rectangular plate, the maximum compressive load that can actually be applied is when the stress distribution in the cross section perpendicular to the load direction is maximized at the center of the cross section. , it has been revealed that the value is larger than the maximum compressive load obtained by the buckling calculation formula for a rectangular plate. That is, Fig. 7a,
As shown in b, the thickness is equal, and the vertical dimension e,
When loads W ₁ and W ₂ are applied to rectangular plates with the same lateral dimension l at the positions shown, the maximum load that can be applied is W ₁ > W ₂ (TV Ka′rma′n Trans.
ASME′54 (1932), 53The Strength of Thin
Plate in Compression). The present invention utilizes this principle to create a reaction force P acting from the kotsuta to the dovetail.
The maximum stress is generated at the center of the radial cross section at the circumferential center of the dovetail.

The present invention will be explained in detail below based on illustrated embodiments.

FIG. 8 shows a dovetail joint according to one embodiment of the invention. By making the bottom surface of the dovetail groove 2a of the rotor rim 2 a trapezoidal concave surface, and making the tip surface of the dovetail 1a of the magnetic pole 1 a trapezoidal protruding surface with a height L (≈S/3), the rotor 3 and the dovetail inclined side wall A straight line passing through the radial midpoint C of the contact surface and perpendicular to this surface intersects the center E of the straight line from the radial outside A of the contact surface to the circumferential midpoint B of the tip surface of the dovetail 1a. is configured to do so.
Note that the dimensions S and T are equal to the dimensions (ratio) of a conventional dovetail joint, and therefore the shaded portion is different from the conventional structure.

FIG. 9 is an analysis of the stress distribution state of the dovetail 1a shown in FIG. 8 according to the finite element method. The maximum value σ _n of the compressive stress is near the center of the cross section of the dovetail 1a (X-X cross section in FIG. 9), and
Its size is approximately 60% of that of a conventional dovetail, and the stress value at the tip surface (point B) is extremely small. Therefore, such a dovetail 1
A is resistant to buckling and facilitates the design and manufacture of salient pole rotors for large-capacity rotating electric machines.

FIGS. 10a to 10d show stress distribution states when the radial dimension (length) H of the dovetail 1a is varied, and other conditions are the same, and analysis is performed according to the finite element method. FIG. 10a is the same as FIG. 6, and FIG. 10c is the same as FIG. 9. 1st
It can be seen from Figures 0 a to d that the maximum value σ _n of the generated stress once decreases and then increases as the H dimension increases. Also, the maximum stress σ _n is the smallest at the 10th
As a result of examination, this is the reaction force P of Kotta 3.
It is almost consistent that the bending moment of the cross section A-B of the dovetail 1a caused by It was also found that the straight line (the straight line in the acting direction of the Kotta reaction force) almost coincides with intersecting at the center E of the A-B cross section.

Therefore, if the dimension H of the dovetail 1a is determined so that the bending moment of the cross section A-B generated in the dovetail 1a due to the reaction force P given by the roller 3 is minimized, the bending moment generated in the dovetail 1a will be Compressive stress can be minimized and buckling strength can be increased.

11 and 12 show a dovetail joint according to another embodiment of the invention. In the embodiment shown in FIG. 11, the dovetail slanted side surface is moved so that the midpoint C of the contact surface between the cotter 3 and the dovetail 1a is brought closer to the base of the dovetail 1a so that the reaction force P acts on the center E of the cross section A-B. A relief notch 1b that does not come into contact with the cotter 3 is provided on the tip side, and in the embodiment shown in FIG. 12, a similar escape notch 3a is provided on the cotter 3 side. Therefore, according to each of these embodiments, the same effects as the embodiment shown in FIG. 8 can be obtained without particularly increasing the length H of the dovetail.

As explained above, according to the present invention, the reaction force P applied to the dovetail from the radial midpoint of the contact surface between the dovetail and the dovetail is transmitted from the radially outer end of the contact surface between the dovetail and the dovetail to the circle of the tip surface of the dovetail. Since the force is applied to the center of the straight line leading to the midpoint in the circumferential direction, the compressive load distribution acting on the dovetail is averaged, reducing the maximum load and increasing the buckling strength of the dovetail, improving its reliability. can be improved. Moreover, the shape of the dovetail joint for this purpose is not particularly complicated and is comparable to that of conventional products, which is advantageous in terms of design and manufacturing.

[Brief explanation of the drawing]

Figure 1 is a longitudinal cross-sectional side view of a conventional salient pole rotor, Figure 2 is its end view, Figure 3 is a vector diagram of the centrifugal force and Kotta reaction force generated in the magnetic poles, and Figure 4 is a conventional salient pole rotor. Figures 5 a to c are stress distribution diagrams of this dovetail, Figure 6 is a composite stress distribution diagram, Figures 7 a and b are compressive stress distribution diagrams of a rectangular plate, Fig. 8 is an end view of a dovetail joint of a salient pole rotor according to an embodiment of the present invention, Fig. 9 is a stress distribution diagram of this dovetail, and Figs. 10 a to d show cases in which the length of the dovetail is changed. FIGS. 11 and 12 are end views of dovetail joints of salient pole rotors according to other embodiments of the present invention. 1...Magnetic pole, 1a...Dovetail, 1b...Escape notch, 2...Rotor rim, 2a...Dovetail groove, 3...Kotta, 3a...Escape notch, 4...
...Field coil, P...Kotuta reaction force, A...Radially outer end of the contact surface of the dovetail and the dovetail, B...Midpoint of the dovetail tip surface, C...Radial midpoint of the contact surface of the dovetail and the dovetail, E ... Central part of cross section A-B.

Claims (1)

[Claims] 1. A rotor rim having a dovetail groove on its outer periphery;
A salient pole for a rotating electrical machine, comprising: a magnetic pole attached to the rotor rim by engaging the dovetail with the dovetail groove; and a clasp that is press-fitted between the dovetail inclined side surface and the dovetail groove side wall and fastens the dovetail into the dovetail groove. In the type rotor, a straight line that passes through the radial midpoint of the contact surface between the rotor and the dovetail and is perpendicular to the contact surface extends from the radial outer end of the contact surface to the circumferential midpoint of the dovetail tip surface. A salient pole type rotor for a rotating electrical machine, characterized in that the rotor intersects with the central part of the rotor. 2. A salient pole rotor for a rotating electric machine according to claim 1, characterized in that an escape notch is provided on the tip side of the dovetail inclined side surface. 3. A salient pole rotor for a rotating electric machine according to claim 1, characterized in that an escape notch is provided on a surface corresponding to the tip side of the dovetail inclined side surface of the rotor.