JPH077879A - Rotor of rotating electric machine - Google Patents

Abstract

PURPOSE:To prevent electrolytic corrosions and cracks from being generated in a wedge for supporting a field coil in a slot, by forming through an atomic bond accompanied by diffusion the film made of an intermetallic compound which has a low frictional quality, an arc resistance and an electric conductibility on the outer peripheral surface of the metal of the base material of the wedge. CONSTITUTION:On the surface of the shoulder part of a wedge 4 to be inserted into the slot of a cylindrical rotor, the film made of an intermetallic compound 4a' is formed through an atomic bond accompanied by diffusion. This wedge film 4a' is made to have a low frictional quality regarding its insertion into a slot tooth and an arc resistance, and to have a wear resistance capable of resisting a very small oscillation caused by its sliding contact, and further, to be an electrically good conductor. Thereby, the current flowing through the wedge which is contacted mutually with the slot tooth and a damper can be made to flow smoothly. As a result, electrolytic corrosions or cracks can be prevented from being generated on the contacting surfaces of the wedge with the slot tooth and the damper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor of a rotary electric machine, and more particularly to a structure for preventing electrolytic corrosion and cracks generated in a wedge of a rotor of a cylindrical rotor of a turbine generator.

[0002]

2. Description of the Related Art Generally, in a rotating electric machine such as a turbine generator, an unbalanced current flows in a stator when an accident occurs in the system or the load is not three-phase balanced, and an eddy current is generated on the rotor surface. . Furthermore, in recent years, a thyristor starting system has been developed, and a method of driving a generator as an electric motor to start a turbine has been studied. It is known that an eddy current is generated on the rotor surface by the harmonic current contained in the current source of this electric motor.

FIG. 1 is a cutaway perspective view showing an end portion of a rotor of a turbine generator. Reference numeral 1 is a magnetic pole surface, and 2 is a field coil, which is inserted into a slot provided in a massive rotor core 3 and held by a large number of wedges 4. Reference numeral 5 is a tooth, and the wedge 4 inserted between the teeth 5 is shortened in terms of workability in assembling. A damper bar 6 for suppressing an eddy current is inserted between the wedge 4 and the field coil 2 and short-circuited to each other by a damper ring 7 at the end. Further, the field coil 2 and the damper ring 7 are firmly protected by a retaining ring 8 at the end portion so as not to be damaged by centrifugal force during rotation.

The eddy current, as shown by the arrow in the figure, mainly passes through the damper bar 6 and the damper ring 7 and the magnetic pole surface 1.
Flow on the path. The flow is changed in the circumferential direction at the rotor end portions of the rotor surface teeth 5, and flows through the contact surface between the teeth 5 and the wedge shoulder portion 4a or the contact surface between the tooth end portions 5a and the retaining ring 8.

Here, the phenomenon of electric traces of sparks may occur on the contact surface of the wedge shoulder portion 4a due to the eddy current. Once this electrolytic surface is generated, eddy currents flow by moving from the contact surface to the normal surface of the wedge, so that the electrolytic corrosion damaged surface is further expanded, and it develops into cracks and the wedge is destroyed, and the generator There was a risk of serious accidents that hinder driving.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly reliable rotor for a rotating electric machine by preventing the electrolytic corrosion and cracks in the wedge that holds the field coil of the rotating electric machine in the slot. To do.

The occurrence of electrolytic corrosion of the wedge increases / decreases the output load in order to improve the operation efficiency of the generator, and the DSS operation (Daily Start S
Top) occurs frequently in machines that are frequently performed or machines that use the thyristor start method. That is, in the former case, the teeth and wedges of the rotor are repeatedly deformed and expanded due to heat due to the rise and fall of the temperature due to the increase and decrease of the output load, and the difference in expansion and contraction is different due to the different constituent materials. The wedge in the part causes a small friction between the contact surfaces with the teeth due to expansion and contraction.

In the latter case, the centrifugal force applied to the wedge is not sufficient in the low speed rotation region at the time of starting, and the temperature rise is low, so that the size of the gap between the teeth is large. Therefore, the wedge causes a chattering action in the circumferential direction of the rotor at the mutual contact surface with the teeth.

These phenomena open and close the flow of eddy currents at the contact interface between the teeth and the shoulders of the wedge. The reason for increasing the degree of damage due to electrolytic corrosion is as follows.

That is, the thermal expansion and contraction of the mutual contact surfaces of the teeth and the wedge surface, or chattering causes a local temperature rise and minute vibrations, which causes fatigue wear. At this time, the organic-based gas generated from the coil insulator, the insulating coating, etc. adsorbed on the respective contact surfaces is carbonized to generate powder-like wear powder. Since the abrasion powder has a low relative velocity between the mutual contact surfaces, it is not excluded from the outside of the system and is accumulated between the contact boundary surfaces, the contact resistance increases, and spark discharge is generated. The generation of sparks activates the organic gas in the surrounding area and increases the size of the sparks.

Further, the surface roughness between the teeth and the wedge is also a factor. The contact surface of both is a machined surface, which is a local contact of protrusions, and is a contact of dissimilar metals due to the difference in constituent materials, and the potential due to the Seebeck effect promotes the occurrence of rust on the local contact surface. In the same manner as described above, the abrasion of the mutual contact surfaces is promoted during the minute friction of the wedge or the chattering, and the increase of the contact resistance is increased.

The degree of this electrolytic corrosion has a great influence on the wedge portion in which the movable body is made of a metal having a low melting point. In addition, this tendency is intensified with the increase in electrical and magnetic loading accompanying the increase in the capacity of a single machine.

[0013]

SUMMARY OF THE INVENTION In view of the above, the object of the present invention is, in a wedge base metal to be inserted into a tooth, low friction, electric arc resistance and conductivity on the shoulder surface of the wedge having a contact interface with the tooth. The excellent intermetallic compound is formed by atomic bonding accompanied by diffusion of the film. Further, a similar coating is formed on the outer peripheral surface of the wedge that constitutes a part of the rotor surface, and a coating having a high electric resistivity can be formed to obtain more effective results.

The intermetallic compound coating may be, for example, a nitride,
There are alloy coatings of carbides, borides and NiAl, and coatings of these intermetallic compounds are, for example, the physical phase vapor method,
It is formed using a method such as a chemical vapor deposition method or a thermal spraying method.

[0015]

By forming the intermetallic compound film on the outer peripheral surface of the metal substrate (wedge) by atomic bonding, the bond (adhesion) between the metal substrate and the film becomes extremely good.
Specifically, the boundary between the metal base material and the coating is bonded to the surface of the metal base material such that the boundary layer is bonded to the surface of the metal base material so that it is difficult to distinguish them clearly due to the concentration gradient due to diffusion.

Further, the film formed on the surface of the wedge is a thin film, and most of the wedge is occupied by a metal base material. This metal base material may be a general-purpose metal material as a wedge, and the film also functions as a wedge material. Since it is not damaged by the presence of, and the coating itself adheres to the metal substrate with high adhesion,
It has a structure that can withstand application to high peripheral speed rotating body models.

Further, the film formation is performed by using a surface treatment technique such as a physical vapor deposition method or a chemical vapor deposition method.
Since it is possible to form a film having a very dense crystal structure,
The surface of the coating becomes smooth and the coefficient of friction of the surface can be lowered. As a result, the work of inserting the wedge into the tooth becomes easy, the gap tolerance of the mutual dimensions can be made small, and the chattering of the wedge due to the centrifugal force is small even at the low speed rotation at the time of starting the thyristor generator,
The occurrence of electrolytic corrosion can be reduced. In addition, a decrease in the contact resistance at the contact boundary portion can suppress a local temperature rise.

Further, the movement of the wedges in the damper bar and the teeth due to the thermal expansion and contraction of the wedges due to the load fluctuation of the generator is smooth, and the damage between the mutual contact surfaces is small.

Further, the formation of a highly hard and dense coating on the surface of the wedge quickly abrades the protruding contact surface with the teeth of the mating member to form a smooth surface contact, eliminating the protruding local contact. It is possible to reduce the accumulation of wear due to the generation of rust between the two.

Further, by forming a film of an intermetallic compound having a high electric resistance only on the outer peripheral surface of the wedge, the eddy current flowing in the axial direction is reduced, so that the local temperature rise of the wedge is reduced. You can

Furthermore, the coating has a high melting point and excellent arc resistance, and the degree of damage to the wedge due to spark electrolytic corrosion is small.

[0022]

The embodiment of the present invention will be described with reference to FIG.

FIG. 2 is a perspective view of a wedge incorporated in the massive rotor core of this embodiment. The wedge 4 may be any metal capable of withstanding a high centrifugal force, and its material is not particularly limited, and its appearance shape is not limited. Although not changing, a film 4a 'of an intermetallic compound, which is the gist of the present invention, is formed on the surface of the shoulder 4a of the wedge inserted into the slot by atomic bond accompanied by diffusion.

Wedge coating 4a 'formed on this portion
Must have low friction and electric arc resistance against insertion into slot teeth, have abrasion resistance that can withstand minute vibrations caused by sliding contact, and be an electrically good conductor. .

In order to meet such requirements, the intermetallic compound of the coating is preferably various nitrides, carbides and borides, for example.

As the nitride, titanium nitride (TiN),
Zirconium nitride (ZrN), hafnium nitride (Hf
N) etc. As the carbide, titanium carbide (Ti
C), zirconium carbide (ZrC), hafnium carbide (HfC) and the like. The borides include titanium boride (TiB ₂ ), zirconium boride (ZrB ₂ ), hafnium boride (HfB ₂ ), and the like.

The hardness of these nitrides, carbides and borides shows a value within the range of about Hv1500 to Hv4000, which is higher than that of the metal material of the wedge base material. Therefore, the wear resistance can be improved as compared with the case of using the conventional metal material, and the specific resistance of nitride, carbide and boride is about 6 μΩ · cm to 800 μΩ · cm.
Although it shows the range of cm and shows a value equal to or slightly higher than that of conventional metal materials, it is a good conductor. Therefore, even if a film of an intermetallic compound is formed on the surface of the wedge base material, it does not affect the performance of the generator and its function can be secured.

The coating is not limited to the above-mentioned ones, but NiAl coating, for example, is also applicable.

Thus, the film on the wedge shoulder 4a 'is
In particular, it is important that the wedge surface is formed by atomic bond with diffusion.

There are various methods of surface treatment for forming a coating film. In this embodiment, however, the material of the coating film to be formed is nitride, carbide, boride, etc. of intermetallic compound, and therefore chemical vapor deposition. Method (Chemical Vapor Deposition, CVD
Method), physical vapor deposition (Physical Vapor Deposition, P
VD method), thermal spraying method, or the like.

As for the thickness of the intermetallic compound coating formed by these methods, the thicker it is, the more preferable it is in consideration of abrasion as long as it is a thickness that does not cause peeling. Generally, it is about 100 μm or less.

The above is the wedge shoulder 4 in contact with the teeth.
In the case of forming a conductive coating 4a 'on the surface a, the coating having a high electric resistivity is applied to the outer peripheral surface 4b where a part of the wedge is exposed. The current is suppressed and more effective results are obtained.

In FIG. 2, the outer peripheral surface 4b of the wedge 4 is shown.
In addition, various nitrides, carbides and oxides are used as the intermetallic compound coating, and the treatment method for forming the coating is the same as described above.

Silicon nitride is a nitride having a high electric resistivity.
(Si ₃ N ₄ ), alumina nitride (AlN), silicon carbide (SiC) as carbide, and alumina oxide (Al as oxide).
₂ O ₃ ), titania oxide (TiO ₂ ) and the like.

Since the wedge surface 4b electrically forms a high resistance coating, the flow of the eddy current in the axial direction is suppressed, and particularly in the case of the thyristor starting method, the eddy current loss due to the current distortion of the power source causes a local loss. Temperature rise is reduced.

By using the conductive coating 4a 'of the intermetallic compound on the shoulder portion of the wedge 4 and the coating 4b having a large electric resistivity on the outer peripheral surface, the eddy current smoothly flows into the damper bar and the occurrence of electrolytic corrosion is further enhanced. It can be effectively prevented.

It is also possible to form a composite film of an intermetallic compound formed on the surface of the wedge base material. In particular, in the thermal spraying method, a material having so-called solid lubrication characteristics, such as molybdenum disulfide or boron, which can improve friction characteristics at the time of sliding contact of the contact interface between the powder, which is a nitride, carbide, or boride powder, is used. By mixing with nitride, graphite, etc., it is possible to obtain a texture structure in which these solid lubricating elements are dispersed in the coating.

[0038]

According to the present invention, the electric current flowing through the wedges that are in mutual contact with the teeth and the damper bar can be made to flow smoothly. As a result, the occurrence of electrolytic corrosion or cracks on these contact surfaces can be prevented.

[Brief description of drawings]

FIG. 1 is a perspective view of an essential part showing an enlarged end portion of a rotor of a turbine generator.

FIG. 2 is a perspective view showing a wedge of the turbine generator according to the embodiment of the present invention.

[Explanation of symbols]

2 ... field coil, 3 ... massive rotor core, 4 ... wedge,
4a ', 4b ... Wedge coating, 5 ... Teeth, 6 ... Damper bar, 7 ... Damper ring, 8 ... Retaining ring.

Front page continuation (72) Inventor Haruo Obaraki 1-1-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi Research Laboratory, Hitachi, Ltd. No. 1 Stock company Hitachi Ltd. Hitachi factory

Claims (6)

[Claims] 1. A massive rotor core having a plurality of slots for inserting windings and teeth formed between the slots, and a winding coil inserted in the slots.
A damper bar and a coil pressing wedge, a damper ring that short-circuits the end of the damper bar, and a close fitting to the end of the massive rotor core, and the end of the winding coil and the damper ring against centrifugal force. In the one provided with a retaining ring for holding, it is possible to form a film of an intermetallic compound having low friction characteristics and excellent arc resistance on the outer peripheral surface of the metal base material of the wedge by atomic bonding accompanied by diffusion. The rotor of the rotating electric machine that features. 2. The rotor of a rotating electric machine according to claim 1, wherein the film of the intermetallic compound is made of any one of nitride, carbide, boride and oxide. 3. The rotor of a rotary electric machine according to claim 1, wherein the film of the intermetallic compound is a film of NiAl. 4. The rotor of a rotating electric machine according to claim 1, wherein the intermetallic compound coating film is formed by any one of a physical vapor deposition method, a chemical vapor deposition method and a thermal spraying method. 5. The rotor of a rotating electric machine according to claim 1, 2, 3 or 4, wherein the coating film of the intermetallic compound has a high electrical resistivity for suppressing an eddy current flowing in the wedge of the rotor. 6. The rotor of a rotating electric machine according to claim 1, 2, 3 or 4, wherein the film of the intermetallic compound contains a solid lubricant for improving frictional characteristics against wedge insertion.