JPS6034340B2 - rotor of rotating electric machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotor of a rotating electric machine, and particularly to a structure for mitigating induced current that flows concentrated at an end of a cylindrical rotor of a turbine generator.

Generally, in a rotating electric machine such as a turbine generator, an unbalanced current flows when an accident occurs in the system or when the load is not balanced in three phases.

The unbalanced component contained in this current is generally called an anti-sequence current and creates a magnetic field that is not synchronized with the rotor speed, inducing current in the rotor conductors and causing rotor heating.
FIG. 1 is a perspective view with main parts cut away showing a rotor of a conventional turbine generator.

In this figure, the arrows indicate the outline of the path of the induced current that causes heating, and 1 is the magnetic pole surface, and 2 is a circumferential groove called a cross slot for rigidity balance. Reference numeral 3 denotes a Kaiji coil, which is inserted into a slot provided in a block of rotor iron D and is held by a number of wedges 4.

5 is teeth.

A damper bar 6 is inserted between the wedge 4 and the field coil 3, and they are short-circuited to each other by a damper ring 7 at the end. Further, at the end, the field coil 3 and damper ring 7 are robustly protected by a retaining ring 8 so as not to be damaged by centrifugal force during rotation. Now, the induced current mainly flows through the path from the damper bar 6 through the damper ring 7 and the path through the magnetic pole surface 1.

However, each conductor, such as the wedge 4, teeth 5, damper bar 6, etc., is usually not electrically insulated from other parts like the field coil 3, so the path of the induced current is also complicated. Become. In particular, as shown in Figure 1,
At the end of the rotor, the induced current ia flowing in the axial direction from the center passes through the damper ring 7 and the retaining ring 8 to i in the figure.
It flows in the circumferential direction as shown by b. For the transfer current flowing in the circumferential direction, as shown by ib in the figure, there is a damper ring 7 with a continuous path formed in the circumferential direction, as well as the holding trench 8.
As shown by ic in the figure, there is also an induced current flowing through the contact portions of the wedge 4 and teeth 5. In particular, in order for the induced current in the teeth 5 to flow circumferentially at the end of the rotor, it must pass through the wedge 4 or the retaining ring 8.

FIG. 2 is a fragmentary perspective view showing an enlarged end portion of the rotor shown in FIG. 1. FIG. The induced current on the surface of teeth 5 is
As shown by the arrow, in order to change the flow in the circumferential direction at the end of the rotor, it must flow through the contact surface between the teeth 5 and the wedge shoulder 4a, or the contact surface between the tooth step 5a and the retaining ring 8. . Incidentally, the contact surfaces between the wedge shoulder portion 4a and the teeth 5, and the contact surfaces between the wedge retaining ring 8 and the tooth stepped portions 5a play an important role in the structure of the rotor.

That is, stress due to the centrifugal force of the field coil 3 housed in the slot is applied to the contact surface between the teeth 5 and the wedge shoulder 4a.

Furthermore, since the rotor teeth 5 and the wedges 4 are made of different materials, they have different thermal elongations. For this reason,
When the machine is running and when it is stopped, the contact surfaces between the teeth 5 and the wedge shoulders 4a move, and as the machine is repeatedly started and stopped, the contact situation becomes different. Under such circumstances, if the conductive current on the teeth surface flows in all directions around the circumference, cavities and the like are likely to occur due to changes in the contact status between the teeth 5 and the wedge shoulders 4a. Once dew corrosion occurs, the contact surface between the teeth 5 and the wedge shoulder portion 4a moves due to repeated starting, stopping, etc. as described above, which further develops the haze corrosion. In particular, at the end of the rotor, the induced current from the center of the rotor is concentrated and the circumferential component of the induced current is large, and the movement of the thermal elongation of the wedge is added, which causes haze erosion. Wedge shoulder 4a has progressed significantly.
There are cracks caused by lightning erosion, which destroy the wedge 4 and cause serious accidents that impede the operation of the machine. On the other hand, a retaining ring 8 is fitted onto the teeth portion 5a.

The retaining ring 8 is the most mechanically difficult part of the rotor, where stress due to the centrifugal force at the end of the field coil 3 is concentrated.
Therefore, if corrosion due to induced current or cracks due to lightning corrosion occur on the contact surface between the tooth stepped portion 5a and the retaining ring 8, these will progress significantly and there is a possibility that a serious accident will occur that will hinder the operation of the machine. There is. These are the biggest factors that significantly reduce machine reliability, and this tendency is especially
It is becoming stronger as the electric and magnetic loading increases with the increase in single machine capacity.

An object of the present invention is to provide a highly reliable rotor for a rotating electric machine by preventing dew and cracks from occurring on the contact surfaces of the various parts of the rotor end.

In order to achieve this object, the present invention provides grooves in the teeth of the massive rotor core to guide the current flowing in the axial direction along the teeth to the damper bar via wedges, thereby reducing the current flow at the end of the rotor. It is characterized by preventing the concentration of Hereinafter, the present invention will be explained in detail based on illustrated embodiments. FIG. 3 is a fragmentary perspective view of a main part of the rotor end of a turbine generator according to an embodiment of the present invention.

A slot is provided in the rotor core 9, and the field coil 3 and damper bar 6 are inserted into the slot.

The retaining ring 8 is shrink-fitted to the tooth stepped portion 5a. The wedge 4 is manufactured to an appropriate length and is inserted using the guide grooves 5b provided in the teeth 5. It is inserted at the top of the tube. A co-directional groove 10 having an axial width of 8 is provided in the teeth 5 corresponding to the joining portion 11 of the wedge 4A and the wedge 4B. The circumferential groove 10 has a circumferential direction sub 6 which is made larger than the gap 6w of the wedge joint portion 11. Furthermore, the radial depth h of one circumferential groove is made to be the same as the radial inner circumferential surface of the wedge 4. The current ia induced on the surface of the teeth 5 of the rotor or the surface of the wedge 4 flows through the teeth 5 and the wedge 4 as shown in FIG. 3.

The induced current ia that has flowed through the teeth 5 is influenced by the circumferential grooves 10 provided in the teeth 5 near the circumferential grooves 10, and flows toward the inner diameter side through the vertical groove end faces 5c.
Then, it flows into the damper bar 6 through the contact portion with the wedge 4. On the other hand, the induced current flowing through the wedge 4 changes its flow inward at the wedge end surface 4b and flows into the damper bar 6 through the damper bar upper surface 6a. In this way, the current flowing into the damper bar 6 flows in the axial direction inside the damper bar 6, and finally passes through the damper ring 7.
It flows in the circumferential direction as shown by ib in FIG. In general, the specific resistance of the damper bar material is about 1/1 of the specific resistance of the rotor village and wedge material that constitute the teeth, and as described above, , by providing circumferential grooves 10 in the teeth 5 and guiding the induced current in the teeth 5 to the vicinity of the damper bar, the current flows through the damper bar 6 and is concentrated on the teeth 5 and the wedge shoulder 4a, or on the tooth step 5a and the retaining ring 8. It is possible to reduce the circumferential component of the induced current that was flowing.

That is, in FIG. 3, the circumferential groove 10 provided in the teeth 5 is
Although only one circumferential groove is shown in the axial direction, by providing a plurality of similar circumferential grooves along the axial direction, the induced current in the teeth portion is sequentially passed through the damper bar 6, and the circumferential current at the end of the rotor is reduced. It is possible to alleviate the concentration in the teeth portion and reduce the current flowing to the tooth step portion 5a.

Although the axial width 6 of the circumferential groove 10 is drawn large for the sake of explanation in FIG. 3, in reality, since the gap 6w of the wedge joint portion 11 is very small, the value of 6 is also small, and the tooth The mechanical strength of No. 5 is not significantly reduced.

As described above, according to this embodiment, one circumferential groove 10 or a plurality of circumferential grooves 10 are provided at appropriate intervals in all directions of the axis, and the induced current flowing on the surface of the teeth is transferred to the teeth 5. By guiding the induced current toward the inner bulge side and sequentially transferring it to the damper bar 6, concentration of the circumferential component of the induced current at the end of the rotor can be alleviated.

Therefore, the induced current flowing in the contact surface between the tooth 5 and the wedge shoulder 4a or the tooth step 5a and the retaining ring 8 can be significantly reduced. Therefore, the occurrence of lightning strikes caused by induced currents on these touch-enhancing surfaces is significantly reduced, and cracks that occur in wedges or retaining rings due to this can be eliminated, resulting in a highly reliable rotor for rotating electric machines. be able to. FIG. 4 shows another embodiment of the invention.

In this embodiment, the circumferential grooves 10 provided on the teeth 5 are offset in the axial direction with respect to the wedge joint portion 11. Therefore, the induced current i flowing on the surface of the teeth 5
In the vicinity of the circumferential groove 10A, the flow flows inward in the vertical direction, as shown by the ■ mark, and as shown below by the dotted line, it flows inside the damper bar (not shown) under the wedge 4, and then flows into the rotor. At the end, it flows circumferentially through a damper ring (not shown) provided below the retaining ring 8. In particular, in this example,
The axial position of the wedge joint portion 11A where the concession current i-rail flowing on the surface of the wedge 4 transfers to the damper bar, and the circumferential position of the circumferential groove 10A where the induced current iat flowing through the teeth 5 transfers to the damper bar. Because of the difference in the damper bar, the current flowing through the damper bar increases smoothly.

FIG. 5 shows still another embodiment of the present invention, and shows a cross section corresponding to the section 1-1 in FIG. 4.

Strictly speaking, the positions of the damper bar 6, the field coil 3, and the insulating layer 12 of the field coil are shifted, but for the sake of explanation, they are shown on the same surface. In this embodiment, the circumferential grooves 10A, l of the teeth 5 are
The depth h in the vertical direction of OB, IOC, and 10D is changed respectively.

That is, the depth of the circumferential groove 10A on the center side in the axial direction of the rotor is the shallowest, and the depth of the circumferential groove 10D at the end of the rotor is the deepest. Therefore, the transfer current iat on the tooth surface is sequentially transferred to the damper bar 6 by the circumferential grooves 10A, 1OB, 10C, and 10D. As described above, according to the present invention, it is possible to significantly reduce the current flowing through the contact surfaces between the teeth and the wedges or between the teeth and the retaining ring at the end of the rotor.

As a result, the reliability of this type of rotor can be improved by preventing lightning corrosion or cracks from occurring on each of these contact surfaces.

[Brief explanation of drawings]

Fig. 1 is a cutaway perspective view of a main part showing a rotor of a conventional turbine generator, Fig. 2 is a cutaway perspective view of a main part showing an enlarged end of the rotor shown in Fig. 1, and Fig. 3 4 is a fragmentary perspective view showing an end of a rotor of a turbine generator according to an embodiment of the present invention, and FIG. 4 is a perspective view showing an end of a rotor of a turbine generator according to another embodiment of the present invention. The developed view, FIG. 5, is a sectional view corresponding to the 1-1 section in FIG. 4, showing the end of the rotor of a turbine generator according to still another embodiment of the present invention. 3...Kaiji Coil, 4,4A,4B...Wedge, 5...Tease, 6...Dan/Gubar, 7...
Damper ring, 8... Retaining ring, 9...
Block rotor core, 10, 10A, 10B, 10C, 10
D... Circumferential groove, 11, 11A... Wedge joint portion. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A block rotor core having a plurality of winding insertion slots and teeth formed between these slots, a winding coil, a damper bar, and a coil holding wedge inserted into the slots. , a damper ring that shorts the ends of the damper bar, and a retaining ring that is closely fitted to the end of the massive rotor core and holds the end of the winding coil and the damper ring against centrifugal force. A rotor for a rotating electrical machine, characterized in that the teeth are provided with grooves that guide current flowing in the axial direction along the teeth to the damper bar via the wedges. 2. The rotating electric machine according to claim 1, wherein the radial position of the bottom of the groove is approximately equal to the radial position of the inner circumferential surface of the wedge, or is located further inward than the radial position of the inner peripheral surface of the wedge. rotor. 3 In claim 1, a plurality of the grooves are provided at intervals in the axial direction, and the depth of each groove becomes shallower from the end in the axial direction toward the center. A rotor for a rotating electrical machine characterized by: 4. The rotating electric machine according to claim 1, wherein the wedge is divided in the axial direction, and the axial position of the joint portion of the wedge is approximately equal to the axial position of the groove. Child. 5. The rotation according to claim 1, wherein the wedge is divided in the axial direction, and the axial position of the joint portion of the wedge and the axial position of the groove are different from each other. Electric machine rotor.