JPH08168197A - Rotor for electric rotating machine - Google Patents

Abstract

PURPOSE: To protect a wedge for holding the field coil of an electric rotating machine in a slot against electrolytic corrosion or cracking by making a slit at a wedge shoulder part touching a ties obliquely to the ties face thereby discharging organic substances deposited on the border face into the slit. CONSTITUTION: A slit 9 is made on the surface at the shoulder part 4a of a wedge 4 touching a ties 5. Slip takes place repeatedly on the contacting face due to thermal deformation, expansion/contraction or chattering and an insulation layer applied to the contact face also slides together with the ties 5 and. The insulation layer is stripped at the part of slit 9 and carried, in the form of abrasive powder, into a recess 9' in the spiral slit 9. In other words, excessive substances adhering to the border face is cut at the part of the slit 9 to expose the metal material, composing the wedge 4 and the ties 5, continuously thus reducing the contact resistance between them.

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 rotating electric machine, and more particularly to a cylindrical rotor of a turbine generator, in which an electrolytic corrosion is generated in a tooth portion and a wedge portion of a rotor core.
It relates to a rotor for preventing cracks.

[0002]

2. Description of the Related Art A rotor having a cylindrical block magnetic pole rotating field type is applied to a turbine generator or the like.
It is well known that in the case of harmonic load operation, asynchronous operation, etc., an induced current is generated on the rotor surface to heat the surface.

FIG. 1 is a 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 divided into short pieces in consideration of workability of assembly or thermal expansion. A damper bar 6 for suppressing an induced 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.

Here, the path of the induced current mainly flows through the path from the damper bar 6 to the damper ring 7 and the path of the magnetic pole surface 1 as shown by the arrow in the figure. Then, the induced current in the tooth 5 portion flows in the wedge 4 or the retaining ring 8 at the end portion of the rotor because it flows in the circumferential direction. That is, as indicated by the arrow shown in FIG. 2, it flows into the retaining ring 8 through the contact surface between the shoulder 4 a of the wedge 4 and the tooth 5.

Here, the contact surface between the wedge shoulder portion 4a and the tooth 5 has different thermal expansion due to the difference in material. Therefore, the contact surface between the tooth 5 and the wedge shoulder 5a moves between when the machine is operating and when it is stopped, and the contact surface changes due to repeated start and stop of the machine. When the induced current on the tooth surface flows in the circumferential direction in such a state, electrolytic corrosion is likely to occur on the contact surface between the tooth 4 and the wedge shoulder portion 4a. In particular, when used as a variable speed electric motor from a low speed range such as a thyristor starting type generator, sparks are generated in the gap part due to movement of wedges in the teeth at low speed rotation, or thyristor power supply is used. Phenomena such as welding due to local heating of the contact surface due to the contained harmonic induced current are likely to occur. The degree of damage due to this electrolytic corrosion has a great influence on the wedge portion of the movable body, which uses a metal having a lower melting point than the teeth.

Once this electrolytic corrosion surface is generated, the induced current flows through the contact surface to the normal surface of the wedge, so that the electrolytic corrosion damage surface is further expanded, and it develops into a crack and the wedge is destroyed, There was a risk of serious accidents that hinder the operation of the generator.

[0007]

The occurrence of electrolytic corrosion on the wedge causes an increase / decrease in output load, D in order to increase the moving efficiency of the generator.
The frequency of occurrence is high in machines that frequently perform SS operation (Daily Start Stop) or in machines used as variable speed electric motors in the low speed range by 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 or decrease of the output load, and the difference in expansion and contraction occurs due to the different constituent materials. The wedge of the short movable body causes minute friction due to expansion and contraction between the contact surfaces with the teeth.

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 chattering in the circumferential direction of the rotor at the mutual contact surface with the teeth.

These so-called fretting phenomena cause an electrolytic corrosion surface to open and close the flow of the induced current at the contact boundary surface between the tooth and the shoulder portion of the wedge, but the extent of damage is increased as follows. There are reasons.

That is, because of the fretting fatigue of the metal forming the teeth and the wedge, the metal oxide wear layer intervenes at the contact boundary surface and the following organic material layer is formed. Organic chemicals used in power generators, such as organic gas slightly remaining in coil insulation coatings and paints, gradually increase in concentration in a sealed atmosphere, causing teeth and wedges to Adsorb to the contact surface. In this state, the temperature rise and the spark discharge due to the thermal expansion and contraction, the chattering, etc. as described above cause the adsorbed gas to be carbonized and become wear powder to adhere to the contact surface to form a wear layer. Since the abrasion powder has a low relative velocity between the contact surfaces, it is not discharged to the outside of the system and is deposited on the contact boundary surface. That is, the contact surface is covered with the insulating layer film.

As a result, the contact resistance between the teeth and the shoulder portion of the wedge increases remarkably, and the induced current conducts electricity to the boundary layer, which causes electric breakdown of the insulating layer or slight current concentration on the metal conductive surface. Therefore, the spark erosion or the melting of the metal forms an electrolytic surface. Then, since the conductive point moves to a surface having a lower contact resistance than the electrolytic corrosion surface, the above phenomenon gradually expands.

It is an object of the present invention to provide a highly reliable rotor of a rotating electric machine by preventing electrolytic corrosion and cracking of a wedge that holds a field coil of the rotating electric machine in a slot.

[0014]

In order to achieve the above object, the present invention provides a wedge to be inserted into a tooth, in which the wedge shoulder contacting with the tooth is provided with a slit groove oblique to the tooth surface. The organic matter deposited on the contact interface was discharged.

[0015]

With the above structure, the metal oxide wear powder generated by fretting between the teeth and the wedge, or the organic matter deposited on the contact boundary surface such as the coil insulating coating and the paint, may cause minute friction or vibration such as chattering. Since it moves along with it and is carried into the spiral groove of the wedge, the contact resistance is reduced and the frequency of spark discharge can be reduced.

[0016]

EXAMPLE An example of the present invention will be described with reference to FIG.

FIG. 3 is a perspective view of a wedge incorporated in the tooth of this embodiment, in which a slit groove 9 which is the gist of the present invention is formed on the surface of the shoulder portion 4a of the wedge 4. The surface of the wedge shoulder 4a comes into contact with the tooth 5, and both of them repeatedly deform, expand and contract due to heat, or slip due to chattering, and the insulating layer interposed on this surface also forms the tooth 5.
It moves with and makes sliding contact. Then, the insulating layer is peeled off at the slit groove 9. In particular, since the moving distance of the contact surface between the two at the time of starting and stopping the generator is large, the action is also large.
The peeled insulating layer is carried as abrasion powder into the recess 9 ′ of the spiral groove 9. That is, since the excessive adhered matter existing on the contact boundary surface is scraped off at the slit groove 9 and the metal base material forming the wedge and the tooth is kept exposed, the contact resistance between both surfaces is reduced. Significantly reduced.

Here, the slit groove 9 of the wedge shoulder portion 4a
May have a spiral shape 9a as shown in FIG. 4 or a crossed shape 9b with slit grooves 9 as shown in FIG.
In short, it is effective if the groove that contacts the tooth is as long as possible.

[0019]

According to the present invention, the circulating current flowing through the teeth and the wedge which are in contact with each other can be smoothly passed. 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 sectional view of a wedge and a tooth portion.

FIG. 3 is a perspective view showing a wedge of the turbine generator according to the embodiment of the present invention.

FIG. 4 is a perspective view of a wedge showing another embodiment of the present invention.

FIG. 5 is a perspective view of a wedge showing another embodiment of the present invention.

[Explanation of symbols]

2 ... field coil, 3 ... massive rotor core, 4 ... wedge,
4a ... wedge shoulder, 5 ... teeth, 6 ... damper bar,
7 ... Damper ring, 8 ... Retaining ring, 9 ... Slit groove.

Front page continued (72) Inventor Yasuomi Yagi 3-1-1, Sachimachi, Hitachi, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Ie Miyagawa 3-chome, Saiwai-cho, Hitachi, Ibaraki No. 1 Stock company Hitachi Ltd. Hitachi factory

Claims (1)

[Claims] 1. A lumped 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 in the slots. A damper ring for short-circuiting the end of the damper bar; and a retaining ring closely fitted to the end of the massive rotor core for holding the end of the winding coil and the damper ring against centrifugal force. A rotary electric machine rotor according to claim 1, wherein slits are formed on the outer peripheral surface of the wedge.