HRP960562A2 - Method for replacing slip rings - Google Patents

Description

Technical area

The invention relates to the process of renewing the contact rings of synchronous electric machines.

Technological background and state of the art

The contact rings of synchronous electric machines, eg turbogenerators, normally consist of steel rings arranged in pairs. They are either wound in isolation on the contact ring sleeve or directly on the rotor shaft (see Wiedemann/Kellenberger "Construction of Electrical Machines", Springer-Verlag Berlin, Heidelberg, New York 1967, pp. 392, 393).

The contact rings of high-speed machines are necessarily subject to wear. Their replacement is relatively expensive.

Brief description of the invention

The task of the invention is to propose a procedure for renewing the contact rings which, first of all, can be easily carried out, and which, on the other hand, extends the service life and improves the properties of electric current transmission.

According to the invention, this task can be solved by the following technological operations:

a) Processing by removing the shavings of both contact rings on the shaft, removing the contact rings from the shaft, in order to obtain the contact ring sleeve, with a radius that is recommended to be 30 to 40 mm smaller than the nominal contact ring radius;

b) Heating and then putting on new contact rings made of high-strength Ce-Ni-Be alloy, on the surfaces of the clamping joint of the sleeve of the contact rings, prepared according to operation a), on the side of the machine that is not driven;

c) Re-rolling of the surfaces of the contact ring, newly drawn contact rings, to the nominal radius.

The method according to the invention provides the possibility of economical renewal of contact rings and thereby extending the service life of (new) contact rings, because they have better working properties in addition to higher current load. Here the invention provides further advantages:

- Losses in current transmission are reduced and durability of the brushes is increased.

- The load capacity of the brushes increases. In this case, the required number of brushes per polarity can be reduced. This further reduces the consumption of brushes. In addition, this increases the surface of the contact rings, not covered by the carbon brushes. As a result, the contact rings will cool better and their temperature will decrease, which again has a favorable effect on the working properties of the contact rings.

- When the contact rings work in a closed cooling circuit, due to the reduced wear of the carbon brushes, the filter becomes less dirty, and thus its durability is greater.

- In addition, due to reduced total losses, lower flue gas temperatures are achieved, and thus reduced effects of reverse cooling.

- When equipping existing plants, the invention may be able to guarantee an increased required excitation current.

Exemplary examples of the invention, as well as the advantages achieved with it, will be explained in more detail in the following text on the basis of the drawings.

Brief description of the drawing

The drawings schematically show embodiments of the invention, as follows:

Sl. 1 longitudinal section of the end of the turbogenerator shaft, non-drive side, with two steel contact rings;

Sl. 2 longitudinal section of the end of the turbogenerator shaft according to Fig. 1, non-drive side, after re-rolling of the steel contact rings and putting on new contact rings;

Sl. 3 variation of the embodiment according to Fig. 2, with contact rings consisting of two individual rings;

Sl. 4 a further change of the design according to Fig. 2, with graduated surfaces of the clamping joint, on a larger scale compared to Fig. 2;

Sl. 5 a special, recommended, embodiment of the invention, with contact rings consisting of two individual rings with different clamping joint surfaces, and which are attached to complementary, for this purpose ungraded clamping joint surfaces, on steel rings.

Methods of carrying out the invention

At the end of the shaft of the non-drive side (NS), of a turbogenerator, two steel contact rings 1, 2 are insulatingly attached via insulating foils 3, 4, i.e. pulled onto the shaft with a clamp connection 5. Electrical connection to the supply bolts of the exciter, located in the shaft bore , is omitted from the drawing for reasons of simplification; after all, they correspond to the state of the art, as it appears, for example, from the book by the authors Wiedemann/Kellenberger mentioned in the introduction. Since such contact rings are exposed to wear, they should be placed at certain intervals. Until now, for this purpose, the contact rings 1, 2 were heated to several hundreds of degrees Celsius and then removed ("stripped off") in the direction of the end of the shaft, the non-drive side. Before putting on the new contact rings, the damaged insulating foils 3, 4 were replaced during removal.

According to the invention, this is supported in another way:

The existing contact rings 1, 2 are not removed, but are re-rolled to a radius r, which is smaller than the nominal outer radius rN of the contact ring for the thickness d (usually 30 mm) of the newly applied contact ring 6 or 7. The previous contact rings now form quasi-sleeves of contact rings 8, 9, for the newly threaded contact rings 6, 7.

The newly drawn contact rings according to the invention are made of a hardening copper alloy with Ni or Be alloy additions. The alloy that appears in the trade network under the name HOVADUR CuNiBe, manufactured by Schmelzmetall AG, CH-6482 Gurtnellen/Uri (data sheet for HOVADUR CuNiBe, which is not dated), has proven to be particularly useful. This copper alloy contains alloying additions of about 1.8% Ni and about 0.4% Be. Already in its hardened "normal state", it has great hardness and thermal resistance, along with good electrical and thermal conductivity. In addition, this alloy is supplied in improved and so-called "special state". In these delivery states, this alloy reaches strength values corresponding to those of steel. However, its electrical and thermal conductivity corresponds to that of copper.

The new contact rings 6, 7 are heated to about 200°C and pulled onto the sleeves of the contact rings 8 and 9, respectively (see fig. 2). During cooling, due to the large modulus of elasticity and the high elongation limit of the copper alloy, an optimal fit of the clamping joint is obtained that can withstand all working loads. After everything, the newly tightened contact rings 6, 7 are rerolled to the nominal radius rN.

In order to facilitate the threading of the inner contact ring 7 over the sleeve of the contact ring 8, the outer contact ring 6, it is recommended to re-roll the outer contact ring 1 to a radius smaller by the measurement δ and, accordingly, to increase the thickness of the newly threaded contact ring 6 by this difference δ ( see Fig. 2). A difference δ of 1 to 2 mm is sufficient.

The contact rings of medium and large turbogenerators have an axial width of the order of 200 to 400 mm. Narrow rings of the aforementioned copper alloy - normally made from raw material by forging processes and can be produced more economically than wide rings; they can be manipulated more easily during assembly. For this reason, it is expedient that the (new) contact ring consists of a larger number of identical individual rings 6a, 6b, or 7a, 7b, as shown in Fig. 3 for a contact ring consisting of two individual rings.

Here too, it is expedient that the radius r of the outer sleeve of the contact ring 8 is smaller by the measure δ than the radius of the inner sleeve 9 of the contact ring, and therefore the thickness of both parts of the ring 6a, 6b should be increased by the measure 5.

In the embodiment shown in Fig. 4, the surfaces of the clamping joint on both sleeves of the contact rings 8, 9, and accordingly the corresponding surfaces of the clamping joint on the inner circumference of the contact rings 6, respectively 7, are made stepwise. The radii in question are marked r1, r2, r3, r4, where it is valid that r1 > r2 > r3 > r4, so that the inner contact ring 7 could be pulled over the outer contact ring 8. This graduation represents an additional securing of the contact rings 6, 7 in in the axial direction, and thus the installation is also facilitated, because the graduation provides an axial stop when pulling.

The embodiment according to Fig. 4 can also be transferred to individual rings 6a, 6b or 7a, 7b, as clearly shown in Fig. 5. In this case, the individual rings 6a, 6b, or 7a, 7b fit on the graduated surfaces of the clamping joint of radii r1, r2, r3, or r4, where again r1 > r2 > r3 > r4 applies.

The invention, of course, is not limited to restoring contact rings directly clamped onto the rotor shaft. It can of course also be applied to contact ring designs in which the steel contact ring is pulled onto the sleeve of the contact ring or onto the ring of the pre-clamping joint, as shown in the book by Wiedmann/Kellenberger, on p. 392, Fig. 386 or Fig. 388, mentioned in the introduction.

List with markings and names of parts

1 outer contact ring made of steel

2 inner contact ring made of steel

3.4 insulating films

5 shaft

6 outer contact ring made of Cu-alloy

6a,6b outer individual rings

7 inner contact ring made of Cu-alloy

7a,7b inner individual rings

8 outer sleeves of contact rings

9 inner sleeves of contact rings

d the thickness of the new contact ring 7

d+δ thickness of the new contact ring 6

NS shaft termination that is not on the drive side

r the radius of the sleeve of the contact ring

rN nominal radius

r1, .. the radii of the graduated sleeves of the contact rings

δ difference of radii of 8 and 9

Claims (5)

1. The process of renewing the contact rings of synchronous machines, characterized by the following technological operations: a) Processing by removing the shavings of the contact rings on the shaft, without removing the contact rings from the shaft, in order to obtain the sleeve of the contact rings (8, 9) with a radius that is 30 to 40 mm smaller than the nominal radius of the contact rings; b) Heating, and then putting on new contact rings (6, 7; 6a, 6b, 7a, 7b) made of high-strength Cu-Ni-Be-alloy, on the surfaces of the clamping joint of the sleeve of the contact rings (8, 9), on the side non-power machine (NS), prepared according to operation a); c) Re-rolling the surfaces of the contact rings, newly drawn contact rings, to the nominal radius (rN). 2. The procedure according to claim 1, characterized by the fact that in operation a) the contact ring on the non-drive side is brought to a smaller diameter, it is recommended to be 2 to 3 mm smaller than the second contact ring (2). 3. The method according to claim 1, characterized by the fact that in operation b) several individual rings (6a, 6b, 7a, 7b) are applied per one contact ring, which lie right next to each other. 4. The procedure according to claim 2, characterized by the fact that in operation a) the processing by removing the shavings is carried out in such a way that on the remaining sleeves of the contact rings (8, 9) graded surfaces of the clamping joint of different radii (r1 r2, r3 and r4 respectively) are formed and that the contact rings (6, 7) threaded with a clamping joint have a supplementary graded inner surface, whereby the outer diameter of the larger surface of the clamping joint on the sleeve (8) of the contact ring, on the non-drive side, is smaller than the outer diameter of the smallest surface of the clamping joint on the adjacent sleeve ( 9) contact ring. 5. The procedure according to claim 3, characterized by the fact that in operation a), the processing by removing chips is carried out so that on the remaining bushings (8, 9) of the contact rings, the graduated surfaces of the clamping joint have different radii (r1 r2, r3, r4), and that the individual rings (6a, 6b, 7a, 7b) that are tightened with a clamping joint represent supplementary internal surfaces, whereby the outer diameter of the larger surface of the clamping joint on the side of the sleeve (8) of the contact ring, which is not driven, is smaller than the outer diameter of the smaller surface of the clamping connection, on the adjacent sleeve of the contact ring (9).