WO2006069893A1

WO2006069893A1 - Electrical machine with cooled end windings of the stator winding

Info

Publication number: WO2006069893A1
Application number: PCT/EP2005/056502
Authority: WO
Inventors: Bernd Gromoll
Original assignee: Siemens Aktiengesellschaft
Priority date: 2004-12-23
Filing date: 2005-12-06
Publication date: 2006-07-06

Abstract

The invention relates to an electrical machine (3) which comprises, inside a closed machine housing (5, 6), a rotatably mounted rotor with a rotor winding, a stationary stator with a stator winding having end windings (2) on the faces thereof, at least one thermal connecting element (10) for thermally coupling the end windings (2) to the machine housing (5, 6). Said connecting element consists of a plastic sealing compound (11) into which at least one large-surface heat-conducting element (12) from a stripe-shaped or plate-shaped material that has a poor electrical conductivity but a good thermal conductivity, especially consisting of or including carbon fiber material, is integrated, thereby increasing thermal conductivity.

Description

description

Electric machine with cooling of the winding heads of their Stän ^¬ development

The invention relates to an electrical machine that is within a closed machine housing

a rotatably mounted rotor with a rotor winding,

- A stationary stand with a stator winding, the end-side winding heads with nose-like Windungsschlau ^¬ fen has, and

- Means for thermal coupling of the winding heads to the machine housing via at least one thermal connection body containing a plastic potting compound with on or attached, the thermal conductivity increasing parts contains.

A corresponding machine is DE 1 613 297 A to entneh ^¬ men.

In machines of all performance classes, but in particular with higher performance, a considerable amount of heat is developed, which has to be dissipated by means of cooling measures with regard to improved machine efficiency and / or longer service life. For example, for larger machines such as generators, cooling of the stator and rotor with H ₂ -GaS is known (cf., for example, "Proceedings of the American Power Conferences", Vol. 39, Chicago 1977, pages 255 to 269). The H ₂ -GaS is circulated here in an encapsulated housing. Not only are complex sealing measures required, but also comprehensive safety measures have to be considered.

In addition, water-cooled generators are standard in which the water circulates in channels, in particular by the so-called stator bars or stator lamination extend. This requires the use of pumps. In addition, the water must be conditioned for corrosion protection reasons.

In addition, air-cooled machines such as motors, in particular with powers below 300 MVA, are known in which cooling takes place by means of a comparatively large air flow. This air flow can in particular be conducted through a network of fine channels (see DE 42 42 123 A1 or EP 0 823 370 A1). For some types of machines, the air flow contributes to undesirable heat generation even as a result of friction losses in the channels.

In closed machines, in which no refrigerant is supplied from the outside, which flows through the electrically active part of the machine, there is an external ventilation, as described in the magazine "Drive and Control", Issue 1, 1992, pages 10 to 12 is leading to an uneven temperature distribution in the engine. In such machines, the bearing and winding overhang of the stator winding are generally stressed below their thermal limits on the non-drive side. On the other hand, occur on the drive side higher Tempe ^¬ temperatures that claim the drive-side bearing and the drive-side winding head accordingly thermally.

For this type of machine, it is therefore state of the art to compensate for an additional air flow, the temperature differences between the two sides and thus to provide for improved cooling. One possibility is an external ventilation of the machine housing, the page on its outer ^¬ is provided with cooling fins, to which an axial air ^¬ flow is generated by means of a fan at the top ^¬ end is driven on the non-drive side of the shaft (cf. For example, DE 29 51 859 C2). Thus, although the heat from the laminated stator cores of which can generally transmit immediately enclosing outer casing, but not sufficient in the field of ketene from the Ständerblechpa ^¬ frontally outstanding windings of the Ständerwick- development. It is therefore often necessary to provide a special channel system for air cooling of the rotor and the winding heads inside the machine housing (cf., for example, DE 42 42 123 A1).

However, a large part of these losses, in particular the proportion of the winding heads protruding into the housing interior on both sides of the stator, can only be transmitted by convection to the end faces of the machine housing. To improve this convection, the rotor can be frontally with

Nubs or wings are provided, which cause an undefined turbulence of the air flow inside the housing. However, not too much heat must be transferred to the front sides of the machine housing since the temperature of the shaft bearings located there may not exceed a predetermined maximum value.

To improve the dissipation of heat from the end windings it is also known, these high thermal conductivity, such as in a powder of alumina (Al2O3) or boron nitride (BN) einzu ^¬ beds (see FIG. WO 2004/055957 Al). Instead, then also the thermal coupling of the winding heads to the Maschinenge ^¬ housing via a plastic potting compound make (see DE 199 43 446 Al). However, known potting materials have a relatively low thermal conductivity which is generally in the range of 1 to 3 W / m * K. For larger distances of the winding heads of the respective housing wall therefore larger temperature differences would be required. For these reasons, 1613297 A, in the known electrical machine according to the aforementioned DE Ver ^¬ the casting compound and the thermal conductivity enhancing fillers, and in particular metal powder-based possess. It turns out, however, that problems with partial discharges can occur with such fillers.

From DE 1 204 316 B it is known to provide adapted to the winding heads of a stator winding of an electric machine heat transfer rings, for example, from a copper cast. In addition, the free stand space can be filled with an embedding mass, which consists of an electrically insulating material with good thermal conductivity, of an insoluble silicone resin with a filler of finely divided powdered alumina.

Also in other electrical machines, it is known to provide a heat removal from the area of winding heads of a stator winding body of a potting compound, in or on the thermal conductivity increasing parts of electrically non-conductive materials such as Al ₂ O ₃ or AlN one or are attached.

Object of the present invention is to design the machine with the features mentioned in that on the one hand to realize a good thermal connection of the winding heads to the machine housing and on the other hand to limit the risk of partial discharges.

This object is achieved with the features of the main claim ge ^¬. In this case, at least one large-area, strip-shaped or plate-shaped heat-conducting body made of an electrically non- or poorly-conductive material should be provided in or on the potting compound, whose thermal conductivity is greater than 100 W / mK,

- whose electrical conductivity is less than 0.5 Sm / mm ²

- And the smallest distance (a) between the machine housing (5, 6) and the respective associated winding head by at least 50%, preferably at least 80% bridged, wherein the at least one heat-conducting body in between adjacent nose-like windings of the respective winding head (2) formed intermediate space protrudes at least a little way. In this case, a strip or plate shape should be understood to mean any structure having a shape that is pronounced in two dimensions.

The problems associated with this embodiment of the machine main advantages are to be seen in that in the attached ^¬ given dimensions across the material of the or the large-area heat conducting the heat with much smaller temperature differences (between the outer housing and the winding head) can dissipate it as if no action such Wärmeleitkör ^¬ per. The heat-conducting body is a quasi-large "cooling flag".

Because of the high thermal conductivity, which is well above that of conventional filling materials such as Al ₂ O ₃ with about 30 W / mK, there is also the advantage that due to this passive heat dissipation at low temperature differences correspondingly high power densities and a long service life by lower Operating temperatures are possible. In addition, this type of heat dissipation is inexpensive because it is passive, ie no air cooling for the winding heads required, and because it is also maintenance-free.

In addition, since the at least one heat-conducting body in the between adjacent nose-like winding loops of the respective winding head formed gap at least a little protrudes, preferably as far as possible, a correspondingly good heat transfer between the winding loops of the winding head and the heat-conducting body is to achieve.

Finally, since the material of the heat conducting only a very low electrical conductivity below 0.5 Sm / mm ² (at 2O ⁰ C), preferably of less than 0.1 Sm / mm ² , and preferably is practically electrically insulating, are unwanted elekt ^¬ preclude ripples or partial discharges at the windings. Advantageous embodiments of the machine according to the invention will become apparent from the dependent claims.

Thus, advantageously from the at least one heat conducting the greater part, that is to be covered more than 50%, the area occupied by the respective subordinate to ^¬ nose-like Windungsschlaufe of the respective winding head surface. In this manner, a large-area heat transfer is between the angular extension loop of the winding head and the heat-conducting body to ge ^¬ währleisten.

In addition, advantageously, the at least one heat-conducting body can make up at least 20%, preferably at least 30%, of the volume of the thermal connection body. With the relatively high proportion of Wärmeleitkörpers then a correspondingly good heat BUS between the machine housing and the associated respective winding head is to be formed.

Preferably, the thermal conductivity of the at least one Wärmeleitkörpers should be greater than that of the copper (of about 380 W / m-K). The heat dissipation from the winding head area is then particularly effective.

It is particularly advantageous if the at least one heat conducting body ^¬ at least partially is made of carbon fiber material be ^¬. Corresponding, particularly suitable materials can have very high thermal conductivities of more than 500 W / mK, which are thus greater than that of copper. They are also electrically good insulating. Corresponding bodies are also commercially produced in strip or plate form. The material combines well with the potting ^compound .

The at least one heat-conducting body can be advantageously UNMIT ^¬ telbar connected to the machine housing, so that it then effectively a cooling fin or a cooling finger of the housing represents and thus ensure a correspondingly good heat transfer to the housing.

Of course, the at least one heat-conducting body can have an anisotropy of the thermal conductivity. In such a case, such a design and arrangement of the Wärmeleitkörpers is advantageous that the greater thermal conductivity has at least approximately in the direction of the smallest distance. Thermal conductors with thermal anisotropy can be constructed in particular with fiber material.

Further advantageous embodiments of the machine according to the invention are apparent from the above-not addressed to ^¬ claims and the drawings.

Hereinafter, a preferred embodiment of an electric machine according to the invention will be explained with reference to the drawings. In this case, the single figure shows in a schematic representation only the area of a winding head of this machine with the thermal coupling to the housing with the parts essential for the invention. In the electric machine according to the invention, of known types of medium and higher power range such. of generators or low-voltage motors (see the cited publications). All other parts, not shown, at least largely correspond to those known machines.

In the figure, a portion of a winding head 2 with a single nose-like winding loop of a stator winding of an electric machine 3 is illustrated. The specific execution of such winding heads is well known (see, eg, the book by G. Müller: "Electrical Machines", 6th edition 1985, VDE-Verlag Berlin, pages 201 to 209) 5 a machine housing ^¬ , with 6 a frontal housing cover this hous ^¬ ses 5, with 7 generally the engine compartment and with A the axis about which a rotor is rotatably mounted with a rotor winding. For thermal coupling of the winding head 2 to the radially outer part of the machine ^housing 5, 6 is provided a common ^¬ designated 10 thermal connection body.

This connecting body 10 surrounds the protruding from the stator core 4 winding head 2 and its nose-like Windungsschlaufen and extends to the machine housing 5, 6. For this purpose, a potting compound 11 of a known plastic material such as a ^¬ hardenable resin is provided for the connecting body.

According to the invention, at least one special heat-conducting body 12 should preferably be integrated or embedded in the potting compound 11. The potting material does not have to completely cover the heat conducting body ^¬. Thus, the heat ^¬ conductive body also laterally adjacent to the potting compound. The scope of this Wärmeleitkörpers is indicated in the figure by a dashed line. That is, the heat-conducting body should be designed over a large area, wherein it covers on one side preferably the largest part of the nose-like winding loop of the winding head 2 in a longitudinal section through the axis A of the machine occupied area F. By a "Cover B ^¬ CKEN" the projection of the Windungsschlaufe be understood to the plane of the heat conducting case. Accordingly extends the heat conducting far into the space formed between adjacent nose-like Windungsschlaufen space or in a corresponding formed on a Windungsschlaufe neighboring space inside. Here, the heat conducting element 12 should have such an axial extension or length 1 that Wenig ^¬ least 50%, preferably at least 80%, of the maximum axia ^¬ len extension of the wrapping head 2 and the respective Windungsschlaufe outside of the stator core 4 of the Wär ^¬ meleitkörper 12 be detected. In With regard to a sufficiently good dissipation of heat loss from the winding head 2 to the machine housing 5, the smallest distance a of the part of the winding head 2 which is the farthest from the machine housing should also be at least 50%, preferably at least at least 80%, be bridged by the heat-conducting body 12. Preferably, the heat-conducting body 12 can protrude directly on the housing 5 on the side opposite the winding head and in particular can be anchored to it over a large area. In this way, thermal resistances can keep entspre ^¬ accordingly small. This results in the representation of the figure, a heat-conducting body 12 in the form of a large-scale cooling lug. The loss heat which can be given off via the machine housing 5 in a known manner radially outwards to air or to a cooling medium such as water is indicated in the figure by swept lines, generally designated W.

With regard to a sufficiently good heat transfer of the at least one heat conducting body to hen consist of a material on the one hand a sufficiently good electrical insulators having ^¬ tion property. For this purpose, the electrical Leitfä ^¬ ability to the at least one heat conducting body 12 is less than 0.5 Sm / mm ² (at 2O ⁰ C), preferably less than 0.1 Sm / mm ^2, and since ^¬ with significantly below that of electrically low-conductive Me - Tallen as eg of zirconium (with 2.3 Sm / mm ² ) are. On the other hand, the thermal conductivity should be greater than 100 W / mK and thus, for example, above that of iron (with 40-60 W / mK). In addition, from the point of view of good heat dissipation, the at least one heat-conducting body 12 should make up at least 20% of the volume of the entire thermal connection body 10 composed of the potting compound 11 and heat-conducting body 12, preferably at least 30%.

In this case, a strip or plate form should be understood to mean any shape with a pronounced two-dimensional shape, which moreover does not necessarily have to consist of a solid material (with 100% density). Thus, structures such as fabrics, felts, fleeces or mats made of fiber or fibrous material or also composite structures made of a plurality of different materials are also suitable for the heat-conducting body.

The stated requirements can be met, in particular, if the at least one strip mark to be used is the plate-shaped heat conducting body 12 consists of a carbon fiber material of high thermal conductivity or with ei ^¬ nem such material in combination with at least one other material, which serves as a carrier matrix for the carbon fibers, for example. Correspondingly designed materials are generally available. Preference is given to using those carbon fiber materials whose thermal conductivity is above 500 W / mK, for example with the trade name "Thornel K-800X" or "Thornel K-1100"("Cytec Industries Inc.", US). from such carbon fibers, plate-shaped parts, eg by means of pressing and Wärmebehandlungsschrit ^¬ ten manufactured, the NEN particularly as corresponding Kühlfah ^¬ are suitable for the connector body 10 degrees. as a concrete embodiment has a corresponding plate cm- the dimensions 20.3 33.0 cm-0.79 cm (called "Cytec Ind. Inc.", trade name "ThermalGraph 6000X"). In addition, said fiber material is practically electrically insulating.

Plate or strip structures, such as the known carbon fiber plate, can exhibit pronounced anisotropy in their thermal conductivity. In such a case, the structure should be arranged within the connecting body 10 so that the greater thermal conductivity at least approximately in the direction of the shortest distance line a between the winding head 2 and the nearest part of the

Machine housing 5, 6 points. Thus, at Wärmeleitkörpern 12 made of carbon fiber material at least the greater part of Fa ^¬ fibers in this direction.

Outside the range of the heat-conducting body 12, of course, other parts of the machine may also be located in the potting compound 11. So least a ring-like electrical connection line 13 are indicated for the stator winding in the figure parts of Minim ^¬.

Claims

claims

1.Electrical machine (3), which within a closed machine housing (5, 6) - a rotatably mounted rotor with a rotor winding,

- A stationary stator with a stator winding, the end-side winding heads (2) with nose-like Windungs ^¬ loops, and

- Means for a thermal coupling of the winding heads

(2) to the machine housing (5, 6) with at least one thermal connection body (10), which has a plastic potting compound (11) with incorporated or attached, the heat conductivity increasing parts, characterized in that in or at the casting ^¬ mass (11) than the heat conductivity enhancing parts Wenig ^¬ least a large-surface heat conducting body (12) is provided from an electrically non- or poorly-conductive material in strip or plate form,

- whose thermal conductivity is greater than 100 W / m-K,

- whose electrical conductivity is less than 0.5 Sm / mm ²

- And the smallest distance (a) between the machine housing (5, 6) and the associated winding head (2) by at least 50%, preferably at least 80%, bridges over ^¬ , wherein the at least one heat conducting body in a between adjacent nose-like Windings of the respective winding head (2) formed gap protrudes at least a little way.

2. Electrical machine according to claim 1, characterized in that of the at least one heat-conducting body (12) of the larger part of an associated nose-like winding loop of the respective winding head (2) occupied area (F) is covered.

3. Electrical machine according to claim 1 or 2, characterized in that the at least one heat-conducting body (12) at least 20 vol .-%, preferably at least 30 vol .-% of the thermal connection body (10).

4. Electrical machine according to one of the preceding claims, characterized by a thermal conductivity of the at least one heat conducting body (12) which is greater than that of the copper.

5. Electrical machine according to one of the preceding Ansprü ^¬ che, characterized in that the at least one heat ^¬ conductive body (12) consists at least partially of carbon fiber material of high thermal conductivity.

6. Electrical machine according to claim 5, characterized by a carbon fiber material of its at least one ^{Wärmeleitkör} pers ^¬ (12) with a thermal conductivity of at least 500 W / mK.

7. Electrical machine according to one of the preceding claims, characterized in that the at least one heat ^¬ conducting body (12) has an anisotropy of the thermal conductivity.

8. Electrical machine according to claim 7, characterized by a design and arrangement of the at least one Wärmeleit ^¬ body (12) such that the greater thermal conductivity ^¬ speed at least approximately in the direction of the smallest distance (a) has.

9. Electrical machine according to one of the preceding Ansprü ^¬ che, characterized in that of the at least one heat-conducting body (12) at least 50%, preferably at least 80%, of the maximum axial extent (1) of the winding head (2) are detected.

10. Electrical machine according to one of the preceding Ansprü ^¬ che, characterized in that the at least one heat ^¬ conductive body (12) is directly connected to the machine housing (5).

11. Electrical machine according to one of the preceding Ansprü ^¬ che, characterized by an electrical conductivity of the at least one heat-conducting body (12) of less than 0.1 Sm / mm ² .