DE102020114691A1 - Electromechanical energy converter with cooling of the rotor winding - Google Patents

Abstract

Current-excited electromechanical energy converter with a stator and a rotor which is rotatably mounted relative to the stator about a rotor axis running in a longitudinal direction, the rotor (1) having a rotor shaft (2) and a rotor winding carrier (4) on the rotor shaft (2) is arranged with at least one first rotor winding carrier slot and a second rotor winding carrier slot, the two rotor winding carrier slots extending in the longitudinal direction (8), with at least one rotor winding being arranged on the rotor winding carrier (8), which runs in sections in these rotor winding carrier slots and which extends in the longitudinal direction at least one end face of the rotor winding carrier (4) extends beyond this and thus forms a rotor winding head (6), characterized in that a rotor winding cooler (10) is arranged in the longitudinal direction (8) between the rotor winding head (6) and the rotor winding carrier (4), that with the Rotorwicklu ngskühler (10) a rotor winding cooler cavity (12) is formed, which extends in a radial direction (9) from the rotor winding head (6) radially inward, so that heat conduction from the rotor winding head (6) to the rotor shaft (2) is made possible.

Description

The invention is concerned with the cooling of the rotor winding, in particular the so-called end turns of the rotor winding, an electromechanical energy converter, is from the prior art and in particular from FIG DE 10 2006 022 139 A1 the active cooling of end turns of a stator winding is known.

The invention is described below on the basis of an electric drive motor for a motor vehicle, a so-called traction motor; this is not to be understood as a restriction of the invention to such an embodiment of the invention. A drive in a motor vehicle is subject to alternating operation, for which there is a requirement to achieve a high power density. In general, a high level of power output for driving can be achieved by cooling thermally stressed components. In the traction motor, the electrically active sections, in particular the windings, represent the limiting areas with regard to the design of this machine; the invention relates to a current-excited energy converter, in this case defining the temperature limit of the rotor winding in a critical design, in particular a rotor-critical design of such a machine the available continuous power and the drivable cycles of the drive.

It is an object of the invention to improve the cooling of the rotor winding in order in particular to improve the power density of the electromechanical energy converter. This object is achieved by an electromechanical energy converter according to claim 1; preferred developments of the invention are the subject matter of the dependent claims.

A basic idea of the invention is to improve the heat conduction path for dissipating heat from a rotor winding of the electromechanical energy converter and thus bring about an improvement in the heat conduction path from the radially outer rotor winding to the radially inner rotor shaft and, in particular, enable an increase in the available continuous power.

The invention relates to a current-excited electromechanical energy converter. In the sense of the invention, such an electromechanical energy converter is to be understood as an electric motor or an electric motor generator which has an electrically active part on a rotor, which therefore has a winding, so-called rotor winding, on this rotor, which in the scheduled operation of the electromechanical energy converter conducts an electric current. In particular, due to unavoidable losses, heat is generated when conducting such an electrical current. Furthermore, the electromechanical energy converter has a so-called stator and the rotor, which is mounted so as to be rotatable relative to the stator about a rotor axis running in a longitudinal direction. The rotatably mounted rotor is preferably set up to output or absorb mechanical power (speed, torque) by means of a rotor shaft.

The rotor accordingly has the rotor shaft, which is rotatably mounted about the rotor axis in scheduled operation and emits or receives mechanical power. A rotor winding carrier is arranged on the rotor shaft; it is preferably formed in one piece with the rotor shaft or is preferably connected to it in a rotationally fixed manner. The rotor winding carrier is preferably designed as what is known as a laminated rotor core or a laminated core and is used to conduct an electromagnetic field. Furthermore, the rotor winding carrier is designed to accommodate the rotor winding or the rotor windings. The rotor winding carrier is designed to accommodate the rotor winding and for this purpose has at least two (first, second), but preferably a plurality of slots, so-called rotor winding carrier slots. Furthermore, such a rotor winding carrier groove is preferably designed as a recess in the rotor winding carrier.

These rotor winding carrier grooves preferably run, at least essentially, in the direction of the rotor axis, that is to say in the longitudinal direction. In particular, the rotor winding has at least one electrical conductor which runs in the rotor winding carrier in the rotor winding carrier slot, emerges from the rotor winding carrier at one end face, describes an arc to preferably enter another of the rotor winding carrier slots at the same end face. This part of the rotor winding protruding from the rotor winding carrier can be referred to as what is known as the rotor winding head. This electrical conductor is preferably designed as a preferably enamel-insulated line and, more preferably, the rotor winding is electrically insulated from the rotor winding carrier. Such a structure of the rotor as such is also known from the prior art.

At the rotor winding head in particular, the rotor winding gives off heat to the environment during scheduled operation. It is proposed that a rotor winding cooler be arranged on at least one of the end faces, preferably on both end faces of the rotor winding carrier, in particular where the rotor winding head (s) are / are arranged. This rotor winding cooler is preferably used as a device for absorbing heat from the rotor winding and preferably from the Rotor winding head set up. Furthermore, the rotor winding cooler is preferably set up to dissipate the absorbed heat radially inward, that is to say orthogonally to the longitudinal direction, from the rotor winding to the rotor shaft. In order to enable this heat conduction in particular, a cavity is formed with the rotor winding cooler, a so-called rotor winding cooler cavity. Viewed in the longitudinal direction, the rotor winding cooler is arranged on the end face of the rotor winding carrier and the rotor winding head wraps around the rotor winding cooler so that the rotor winding cooler is arranged between the rotor winding carrier and the rotor winding head when viewed in the longitudinal direction. Furthermore, the rotor winding cooler cavity is preferably filled with a heat-conducting medium. Investigations have shown that the rotor shaft represents a heat sink compared to the rotor winding carrier when the electromechanical energy converter is in regular operation, so that by dissipating heat from at least one, preferably a large number of and preferably from all of the rotor winding heads, a higher level of operational reliability for the electromechanical energy converter can be achieved.

The rotor winding cooler cavity is preferably formed between the rotor winding cooler, in particular if it is designed, at least in sections, as a shell-like component, and the end face of the rotor winding carrier. More preferably, the rotor winding cooler cavity is formed directly in the rotor winding cooler, in particular as a recess. The rotor winding cooler is preferably materially connected to the rotor winding carrier, preferably glued to it, preferably soldered and particularly preferably welded.

In a preferred embodiment, the rotor winding cooler extends at least from the rotor winding head to the rotor shaft and, more preferably, the rotor winding cooler makes contact with the rotor shaft, preferably directly. The rotor coil cooler is preferably connected to the rotor shaft in a materially bonded manner. In particular, by making contact with the rotor shaft through the rotor winding cooler, improved heat conduction from the at least one rotor winding head to the rotor shaft can be achieved.

In a preferred embodiment of the invention, the rotor shaft is designed as a hollow shaft at least in sections, preferably at least in an area in which the rotor winding cooler contacts the hollow shaft. Furthermore, a cooling medium is preferably guided at least temporarily in this hollow shaft or in this hollow shaft section of the rotor shaft. This cooling medium is preferably to be understood as cooling water. The rotor shaft is preferably designed as an oil-cooled and preferably as a water-cooled rotor shaft. Such a design of the rotor shaft in particular enables improved dissipation of heat from the at least one rotor winding head.

In a preferred embodiment, the rotor winding cooler cavity is filled with a cooling medium. The rotor winding cooler cavity is preferably filled with a phase change material and preferably with a liquid cooling medium, preferably with cooling water or the like. The cooling medium accommodated in the rotor winding cooler cavity preferably has a higher thermal conductivity than the rotor winding cooler, or the material from which it is at least essentially formed. In particular, by designing the rotor winding cooler in this way, improved heat transfer from the rotor winding head to the rotor shaft can be achieved.

In a preferred embodiment of the invention, the rotor winding cooler has an outer cooling collar. This outer cooling collar is preferably designed to be hollow on the inside, at least in sections, this cavity of the outer cooling collar being connected in a fluid-conducting manner to the rotor winding cooler cavity, or this is a region of this rotor winding cooler cavity. The outer cooling collar preferably extends radially outside of the at least one rotor winding head, or is arranged radially outside it. The outer cooling collar preferably covers the rotor winding head at least partially or preferably completely in the longitudinal direction. The outer cooling collar preferably makes partial or complete contact with the rotor winding head. The outer cooling collar is designed in particular as a region or section of the rotor cooling body. In particular, such a configuration with an outer cooling collar can further improve the heat transport from the rotor winding to the rotor shaft through the rotor winding cooler.

In a preferred embodiment of the invention, the rotor winding cooler has an inner cooling collar which is arranged radially inside the at least one rotor winding head and which at least partially covers the rotor winding head in the longitudinal direction. Further preferably, a cavity is formed in the inner cooling collar, which is fluidly connected to the rotor winding cooler cavity. The rotor winding head also preferably makes contact with the inner cooling collar. In particular with regard to the outer and the inner cooling collar, the contacting is also to be understood as meaning that the rotor winding head is opposite the rotor winding cooler is electrically isolated. A further improvement in heat conduction from the rotor winding head to the rotor shaft can be achieved, in particular, by a configuration with an inner cooling collar.

Furthermore, a motor vehicle is provided which has, as at least one traction motor or as the one traction motor, a current-excited electromechanical energy converter according to one of the previously described embodiments, as explained, the electromechanical energy converter is designed as a traction machine. In the context of the invention, the traction machine is to be understood in particular as an electromechanical energy converter which is set up to provide drive power to overcome driving resistances such as rolling resistance, air resistance, gradient resistance, acceleration resistance and the like.

• 1: einen Teillängsschnitt durch einen stromerregten elektromechanischen Energiewandler mit Rotorwicklungskühler,
• 2: Dreidimensionale Darstellung einer Sternscheibe zur Ausbildung des Rotorwicklungskühlers.

An embodiment of the invention and individual features thereof are explained in more detail below with reference to the figures; a combination of features other than the one shown is also possible. It shows:

• 1 : a partial longitudinal section through an energized electromechanical energy converter with rotor winding cooler,
• 2 : Three-dimensional representation of a star disk for the formation of the rotor winding cooler.

In 1 is a three-dimensional partial sectional view of the rotor 1 with rotor shaft 2 shown, the rotor 1 rotatable around the rotor axis 3 is mounted in a stator (not shown). On the rotor shaft 2 is the rotor winding carrier 4th arranged. The rotor winding support 4th has a plurality of rotor winding support grooves (not shown) in which the rotor winding extends. The rotor winding occurs on the front side 5 of the rotor winding carrier from this and describes in the rotor winding head 6th an arc and re-enters a rotor winding carrier groove. The rotor winding head 6th is by means of a potting compound 7th mechanically secured and electrically isolated.

At the front 5 of the rotor winding carrier 4th is lengthways 8th between the rotor winding support 4th and the rotor end winding 6th the rotor coil cooler 10 arranged. The rotor winding head 6th is received directly on the rotor coil cooler but is electrically insulated from it by means of an electrical insulation layer. The rotor coil cooler 10 forms at the front 5 of the rotor winding carrier 4th the rotor coil cooler cavity 12th out. In the rotor winding cooler cavity 12th a heat conducting medium is added, which conducts heat from the rotor end winding 6th towards the rotor shaft 2 improved. Here is the rotor shaft 2 designed as a hollow shaft and flushed through by a further cooling medium in scheduled operation. Due to the hollow shaft construction of the rotor shaft 2 their property as a heat sink is further improved and so an improved heat dissipation is made possible.

There is also a passage of cooling medium from the rotor shaft 2 into the rotor coil cooler cavity 12th enabled, but not necessary. The rotor coil cooler has an outer cooling collar. The inner and outer cooling collar 14th , 13th cover the rotor winding head 6th in the axial direction 8th , in relation to the inner cooling collar 14th but only partially. The rotor coil cooler develops through the proposed design 10 the function of a thermosiphon and directs heat in the operation of the electromechanical energy converter from the rotor winding heads 6th towards the rotor shaft 2 away.

In 2 is a so-called star disk 15th , which is designed as a shell-like component. The star disc 15th becomes opposite to the longitudinal direction 8th to the front 5 of the rotor winding carrier 4th attached, or connected to this, so that the rotor winding cooler cavity 12th forms. In particular is the star disk 15th from the longitudinal direction 8th with a cover disk (not shown) which extends up to the centering collar 16 extends with which the star disc 15th on the rotor shaft 2 can be included, and so points the star disc 15th with a cover plate (not shown) has a hermetically sealed cavity, a so-called rotor winding cooler cavity, which is filled with a cooling medium. This cooling medium, provided that the rotor winding heads have a sufficient temperature, continuously evaporates (in the area of the rotor winding heads) and condenses (in the area of the rotor shaft) in the rotor winding cooler cavity.

In other words, in the case of a rotor-critical design of a current-excited traction machine (electromechanical energy converter) known from the prior art, the temperature limit of the rotor winding defines the available continuous power as well as the drivable cycles of the drive. An improvement in the heat conduction path from the rotor winding located radially on the outside relative to the rotor to the rotor shaft located radially on the inside leads directly to an increase in the available continuous power, all the more so if this rotor shaft is active, preferably liquid-cooled.

In known electromechanical energy converters, rotor cooling takes place by cooling the overall machine, in particular by means of a water jacket arranged on the stator, or by open or closed air cooling, as well as additionally or alternatively by active cooling of the rotor shaft, in particular with oil or water (eg water lance cooling).

The rotor heat loss of an electromechanical energy converter, which is designed as a current-excited synchronous machine, occurs predominantly in the energized, i.e. electrically active, rotor winding. According to the laws of thermodynamics, the heat flows from this heat source to a heat sink, with the circumference of the rotor (heat transfer to the air gap and over the side surfaces) and the heat conduction to the, preferably liquid-cooled, rotor shaft being considered as the heat sink. In known electromechanical energy converters, the heat conduction path to the rotor shaft consists at least essentially of materials (in particular slot insulation paper, potting compound, laminated core, steel of the rotor shaft), the properties of which are essentially predetermined by their electromagnetic properties (permeability, insulation properties) or strength. For the heat dissipation of the rotor winding, its non-optimal thermal conductivity creates a bottleneck, or these have a high resistance to heat conduction, as a result of which the rotor winding is poorly cooled and the achievable continuous output of the electromechanical energy converter is limited.

One aim of the invention is to enable or improve the bridging of the thermal resistance from the rotor winding to the rotor shaft with the aid of a thermosiphon compared to the prior art, and thus to improve the heat dissipation of the rotor winding during the scheduled operation of the electromechanical energy converter. For this purpose, it is proposed to use the installation space on the end face of the rotor winding carrier, in particular by means of a so-called star disk, which can preferably be designed as a shell-like or hollow component and which has an additional shaping function for the rotor winding in the area of the rotor winding head. In addition, a rotor winding cooler can be formed with this star disk, or in connection with this star disk, which creates a thermally conductive connection between the rotor winding and rotor shaft, with the star disk and thus the rotor winding cooler in contact with both components (rotor winding, rotor shaft), in particular direct contact. The implementation of a so-called phase change cooling (rotor shaft cooler with rotor shaft cooler cavity filled with cooling medium) leads to the formation of a thermosiphon in the rotor winding cooler and offers the possibility of radial heat transport at the rotor winding heads (from the rotor winding radially inwards to the rotor shaft), this heat transport being that of a solid material for the star disc, especially aluminum, exceeds.

Preferably, a representation of the geometry of the rotor shaft cooler made of stamped / welded sheet metal (aluminum or stainless steel) is proposed, whereby the star disk is preferably closed with a cover surface opposite the end face of the rotor winding carrier and this design enables the creation of a cavity in the star disk, the so-called rotor winding cooler cavity, which is used for Increase of the radial heat transport according to the operating principle of the thermosiphon can be used.

The rotor winding cooler cavity is preferably evacuated and more preferably filled with the refrigerant, preferably with water, similar to a refrigeration cycle. The star washer constructed in this way is an essential part of the rotor winding cooler or forms it. Such a star disk is preferably turned over for dimensional accuracy, coated with electrical insulation material, at least in the area in which the rotor winding head is accommodated. In particular in the assembled state, the star washer is received on the rotor shaft, joined to the rotor winding carrier, which is preferably designed as a laminated core, and the rotor thus formed is wound or fitted with the rotor winding.

With sufficient heating of the rotor, in particular the rotor winding during operation, heat is absorbed by the rotor winding cooler, the cooling medium absorbed in the rotor winding cooler cavity will evaporate at the "warm" points, in particular in the area of the rotor winding head, i.e. radially outside under the rotor winding, and at the colder points of the Condense the rotor cooler cavity, that is, radially inward in the area of the rotor shaft, especially when it is actively cooled. In particular, due to the rotation of the rotor shaft during operation, the centrifugal force condensed, i.e. liquid cooling medium in the rotor shaft cooler cavity, due to its density, can be conveyed back radially outwards, where the warm areas of the rotor winding cooler cavity are again cooled by the phase transition enthalpy.

In a preferred embodiment, webs are arranged in the rotor winding cooler cavity, which are set up in particular to increase the strength (support of the evacuated rotor winding cooler cavity). These webs are preferably designed in such a way that they preferably guide the liquid or vapor transport of the cooling medium in the rotor winding cooler cavity or preferably evenly distribute or particularly preferably enable both.

The use of a thermosiphon (evaporation in the warm outer area of the rotor coil cooler, condensation in the radially inner area) is advantageous because the vapor / condensate is separated in the cooling medium and the condensed cooling medium is transported back by centrifugal force due to the rotor shaft rotation. This transport mechanism can be more efficient than the transport mechanism of other cooling concepts. In a further preferred embodiment, the rotor winding cooler cavity is at least partially or completely coated on one or both sides with porous sintered material or preferably this is provided with grooves on the wall at least partially, which effect a capillary return of the cooling medium. In particular, by means of such a configuration, the rotor winding cooler can also function when the rotor is at a standstill in accordance with the mode of operation of a so-called heat pipe (also called a heat pipe).

Further preferably, the use of several tubular thermosiphons is proposed, which are integrated into the star disk, i.e. the rotor winding cooler or running outside the same, dip deeper into the rotor winding carrier groove of the rotor winding and contact the rotor shaft on the other side, i.e. the opposite end face of the rotor winding carrier.

List of reference symbols

1

rotor

2

Rotor shaft

3

Axis of rotation

4th

Rotor winding support

5

Front side of 4

6th

Rotor winding head

7th

Potting compound

8th

Longitudinal direction

9

Radial direction orthogonal to 8

10

Rotor coil cooler

11th

Insulation layer

12th

Rotor winding cooler cavity

13th

Outer cooling collar

14th

Inner cooling collar

15th

Star disc

16

Centering collar

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102006022139 A1 [0001]

Claims (8)

Current-excited electromechanical energy converter with a stator and a rotor which is rotatably mounted relative to the stator about a rotor axis running in a longitudinal direction, the rotor (1) having a rotor shaft (2) and a rotor winding carrier (4) on the rotor shaft (2) is arranged with at least one first rotor winding carrier slot and a second rotor winding carrier slot, the two rotor winding carrier slots extending in the longitudinal direction (8), with at least one rotor winding being arranged on the rotor winding carrier (8), which runs in sections in these rotor winding carrier slots and which extends in the longitudinal direction at least one end face of the rotor winding carrier (4) extends beyond this and thus forms a rotor winding head (6), characterized in that a rotor winding cooler (10) is arranged in the longitudinal direction (8) between the rotor winding head (6) and the rotor winding carrier (4), that with the Rotorwi cklungkühler (10) a rotor winding cooler cavity (12) is formed, which extends in a radial direction (9) from the rotor winding head (6) radially inward, so that heat conduction from the rotor winding head (6) to the rotor shaft (2) is made possible. Current excited electromechanical energy converter according to Claim 1 , characterized in that the rotor winding cooler (10) makes contact with the rotor shaft (2). Current-excited electromechanical energy converter according to one of the preceding claims, characterized in that the rotor shaft (2) is designed at least in sections as a hollow shaft and that a cooling medium is guided at least temporarily in the hollow shaft. Current-excited electromechanical energy converter according to one of the preceding claims, characterized in that the rotor winding cooler cavity (12) is filled with a cooling medium. Current-excited electromechanical energy converter according to one of the preceding claims, characterized in that the rotor winding cooler (10) has an outer cooling collar (13) which is arranged radially outside the at least one rotor winding head (6) and which at least partially covers this in the longitudinal direction (8) . Current excited electromechanical energy converter according to Claim 5 , characterized in that the rotor winding cooler cavity (12) extends into the outer cooling collar (14). Current-excited electromechanical energy converter, characterized in that the rotor winding cooler (10) has an inner cooling collar (14) which is arranged radially inside the at least one rotor winding head (6) and which at least partially covers this in the longitudinal direction (8). Motor vehicle with an energized electromechanical energy converter according to one of the Claims 1 until 7th , wherein this electromechanical energy converter is designed as a traction machine of the motor vehicle.

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