DE102022201537A1 - Electric machine with hybrid excitation - Google Patents

Abstract

The present invention relates to an electrical machine (10) with a stator (12) and a rotor (14), the stator (12) comprising a stator winding (16) which interacts with the rotor (14), the rotor ( 14) hybrid excitation is such that at least two exciter modules (20, 22) are provided which are axially displaced with respect to a rotor axis (18) of the rotor (14), of which a first exciter module (20) has a supporting body (24) and one on the supporting body (24) arranged permanent magnet (26) for permanent magnetic excitation of the stator winding (16) and wherein a second exciter module (22) is designed as a claw-pole module with claw-pole fingers (28, 30) and an exciter coil (32) acting on them, the claw-pole fingers ( 28, 30) are connected to one another by a connecting element (42) and the claw pole fingers (28) are also fixed to the supporting body (24).

Description

The present invention relates to a hybrid-excited electrical machine. Furthermore, the present invention relates to a drive train that has such an electric machine and a vehicle that has at least one of the hybrid excited machine and the drive train.

Electric machines are widely known as generators and/or electric motors. The advantages of permanent magnet synchronous motors (PSM) lie in the comparatively low rotor losses and thus better efficiency compared to asynchronous machines, for example. Furthermore, permanent magnet synchronous motors can also be built with higher poles than the asynchronous machine without negatively affecting the power factor. The possible higher number of poles of the permanent magnet synchronous motors leads to better torque and power densities in the given installation space and also enables the realization of gearless drives.

A disadvantage of this concept is that the magnetic excitation depends only on the magnet temperature and that the field weakening of the machine can only be influenced via the stator current. This is particularly disadvantageous in traction machines with a wide field weakening range. This makes the design of the machine more difficult and, under certain circumstances, the use of SmCo magnets (remanence Br weaker, but less temperature-dependent) is forced instead of NdFeB magnets (remanence Br stronger, but also more temperature-dependent).

DE 10 2007 035 321 A1 describes an electrical machine, preferably a generator, with a stator core, in particular a laminated stator core and a multi-phase stator winding inserted therein, and with a rotor which interacts therewith and has hybrid excitation, consisting of at least two exciter modules with the same number of poles arranged axially next to one another on the rotor shaft, one of which Module is designed as a claw-pole module with an excitation coil for electromagnetic excitation and another module with permanent magnets for permanent magnetic excitation, wherein the electromagnetic claw-pole module consists of two axially spaced claw-pole discs with pole fingers that engage in one another on the outer circumference.

However, such solutions still have further potential for improvement.

It is the object of the present invention to at least partially overcome the disadvantages known from the prior art. It is in particular the object of the present invention to provide a solution by means of which a hybrid-excited electric machine has a simple design and/or is stable over the long term and, in addition, the field weakening can advantageously be adjusted.

The object is achieved at least in part according to the invention by an electric machine having the features of claim 1. The object is also achieved at least in part according to the invention by a drive train having the features of claim 9 and by a vehicle having the features of claim 10. Preferred embodiments of the invention are described in the subclaims, in the description or in the figures, with further features described or shown in the subclaims or in the description or in the figures, individually or in any combination, being an object of the invention if the context does not clearly indicate the opposite.

Described is an electrical machine with a stator and a rotor, the stator comprising a stator winding which interacts with the rotor, the rotor being hybrid-excited in such a way that at least two exciter modules are provided which are axially displaced with respect to a rotor axis of the rotor, of which a first exciter module has a supporting body and a permanent magnet arranged on the supporting body for permanent magnetic excitation of the stator winding, and wherein a second exciter module is designed as a claw-pole module with claw-pole fingers and an exciter coil acting on them, and wherein the claw-pole fingers are connected to one another by a connecting element and the claw-pole fingers are also connected are fixed to the supporting body.

Such an electrical machine has clear advantages over solutions from the prior art.

The electric machine described can be used or operated in particular as an electric motor. However, a function as a generator is also fundamentally covered by the present invention.

In a manner known per se, the electrical machine comprises a stator, also referred to as a stator, and a rotor, also referred to as a rotor. The stator includes a stator winding which acts on the rotor, as is known per se in a permanent-magnet synchronous machine or a permanent-magnet synchronous motor.

Furthermore, the rotor is hybrid-excited. This is achieved in the sense of the present invention in such a way that at least two different exciter modules are provided which are arranged axially displaced with respect to a rotor axis of the rotor.

A first excitation module comprises a support body and a permanent magnet arranged on the support body, possibly with a magnetic rotor yoke, which is used for the permanent magnetic excitation of the stator winding or the machine, which can also be referred to as the stator winding. The stator winding described above thus interacts with the permanent magnets of the first excitation module in accordance with a current flowing through it.

Furthermore, a second exciter module is provided, which is designed as a claw-pole rotor or as a claw-pole module with claw-pole fingers and an exciter coil acting on them. The electromagnetic claw-pole module comprises two axially spaced claw-pole elements with claw-pole fingers which engage in one another on the outer circumference. The claw-pole rotor combined with the permanently excited rotor is magnetized with direct current via a particularly fixed excitation coil. The DC field is converted into the north and south poles of the rotor via the geometric arrangement of the claw poles known for claw pole rotors. To be more precise, the rotating claw-pole rotor is magnetized by the DC excitation coil via two narrow air gaps. The magnetization of the claw-pole rotor can be set using the adjustable excitation current.

The excitation coil of the claw-pole module is preferably held or carried with a fixed iron yoke. Alternatively, the fixed exciter yoke can be made of another highly permeable material that is easily magnetized. Good thermal conductivity to dissipate the exciter current heat losses is advantageous. The excitation coil of the claw-pole module is particularly preferably held with a fixed iron yoke on the bearing plate of the electrical machine.

The claw pole fingers are in particular directly connected to one another by a connecting element. More precisely, a non-magnetic support structure is formed as a connecting element within the claw poles, ie between the north pole and the south pole. The support structure preferably has high strength properties. For example, it can be made of lightweight materials, such as fiber composite materials or aluminum.

Furthermore, the claw pole fingers are fixed to the support body, in particular in the axial direction. In detail, a first group of claw-pole fingers in terms of polarization, ie the claw-pole fingers functioning as the north or south pole, is preferably mechanically connected to the support body, for example fixed directly to it. Furthermore, the second group of claw-pole fingers in terms of polarization, ie the correspondingly oppositely polarized claw-pole fingers, is mechanically connected to the first group of claw-pole fingers by the connecting element, for example fixed directly thereto. As a result, the supporting body carries both groups of claw-pole fingers, even if there is only a direct connection to one group of claw-pole fingers.

Thus, the support body is part of the first exciter module, but nevertheless carries the claw pole fingers, in particular directly connected, and thus a part of the second exciter module.

By fastening the second exciter module to the first exciter module, a particularly high level of mechanical stability can be made possible, so that a particularly long-term stable configuration is possible. Furthermore, by using the first, mechanically stable excitation module, which also serves as a permanent magnet excited rotor, a conventional rotor shaft and stable rotor bearing with DE and NDE roller bearings can be used.

The hybrid-excited electrical machine described above combines the advantages of the conventional permanent-magnet synchronous machine, in particular the provision of a simple rotor with low losses, with the advantages of an adjustable current excitation of the conventional synchronous machine, without the need for complicated rotating rotor windings and exciter devices or current transmission by means of wear-prone brushes on the rotor are. The first excitation module can be applied as a simple rotor, for example with magnets sunk into the sheet metal, for example according to the IPM design, fully laminated with electrical sheets in diameter and metal pressure rings on both sides, on a simple cylindrical rotor shaft with a shrink fit. The rotor shaft can be made of steel, for example.

Because in contrast to conventional claw-pole rotors, the invention described provides a combination of permanent magnet excitation with an electrically excited, simple claw-pole rotor with a stationary excitation device, so that no excitation current transmission from the stationary part of the machine to the rotating part of the machine, for example by means of brushes, is necessary is.

In this case, the field weakening can be set particularly advantageously.

Due to the advantageous combination of permanent magnet excitation and electrical excitation of the synchronous rotor, a good and balanced efficiency of a traction motor on the pulse-controlled inverter is achieved over the entire operating range of the machine, i.e. basic speed, field weakening and partial load operation, and also with long field weakening and constant power ranges. In the case of traction generators, the excitation can be selected within a sufficiently wide adjustment range in such a way that operation on the diode rectifier (B6 bridge) is possible as with conventional electrically excited synchronous generators. This also allows the use of NdFeB magnets in the first excitation module. Furthermore, there is no need for more expensive and complicated active rectifiers, e.g. in IGBT technology, which allows for a simpler and more cost-effective design and operation of the drive system.

Due to the possible proximity of the DC excitation device to the housing, such as the end shield, and thus for storage, the tolerances due to manufacturing, heating, etc. can be kept small, which results in two narrow air gaps between the first and second excitation module and also between the claw pole fingers and the Excitation coil allowed. The width of the air gap in turn determines the magnetization requirement of the claw pole rotor - in addition to the actual air gap between rotor and stator.

The solution according to the invention makes it possible to avoid additional current heat losses occurring in the machine, for example as a result of a field-weakening current impressed via a converter. Comparatively high start-up currents can also be avoided, which could arise in the prior art by reducing the number of stator windings depending on the length of the field weakening area. As a result, it can be largely avoided that traction inverters have to be used with the same intermediate circuit voltage with higher output currents and thus with significantly higher costs. In contrast, the present invention can thus be operated comparatively inexpensively and stably.

A claw pole finger can preferably be flanged or screwed to the support structure. In this refinement, the advantages of a simple and long-term stable construction can be made possible in a particularly effective manner. The production can also be simplified in this way.

The same applies in principle to the embodiment according to which the excitation coil acting on the claw-pole fingers is carried by a yoke or fastening yoke.

The excitation coil acting on the claw-pole fingers can also be arranged on an end shield or attached to it. The end shield is in particular part of a housing for enclosing the rotating exciter modules. Due to the proximity of the DC excitation device of the claw pole fingers to the bearing plate and thus to the bearing, which is possible in particular in this embodiment, the tolerances can be kept small, in particular as a result of production and heating, which, as indicated above, allows narrow air gaps. The width of the air gap in turn determines the magnetization requirement of the claw-pole rotor, so that this configuration has a positive effect on the magnetization of the claw-pole fingers.

If the setting range of the machine according to the invention with one claw-pole rotor is not sufficient, a structure with two claw-pole rotors on the non-drive side (NDE) and drive side (DE) is also conceivable. Accordingly, it can be advantageous that three exciter modules are provided, which are arranged axially displaced with respect to a rotor axis of the rotor, of which a first exciter module has a supporting body and a permanent magnet arranged on the supporting body for permanent magnetic excitation of the stator winding or the machine, and a second and a third exciter module are each designed as a claw-pole module with claw-pole fingers and an exciter coil acting on them, the first exciter module being arranged axially between the second and the third exciter module.

It can also be preferred that the second exciter module and optionally the third exciter module have a permanent magnet. For example, the integration of a permanent magnet in the claw-pole rotor between the claw poles near the air gap to the excitation coil or the fixed yoke may be possible, or it may also be integrated in the rotating yoke of the claw-pole rotor. Furthermore, when using permanent magnets with a low coercive field strength such as AlNiCo magnets, the integrated magnets could also be magnetized and demagnetized via the electrical excitation. The permanent magnets thus support the current excitation of the claw-pole rotor, which saves excitation energy or current heat losses. AlNiCo magnets allow the strength of the permanent magnet excitation to be adjusted, controlled via the magnetic field of the excitation coil, which can be adjusted with the excitation current. In order to change the remanence of the AlNiCo magnets, a very short excitation current is used.

With regard to further advantages and technical features of the electric machine, reference is hereby made to the description of the drive train, the vehicle, the figures and the description of the figures.

Also described is a drive train for a vehicle, in particular for a rail vehicle, the drive train comprising a motor for driving a wheel or a shaft, and the motor being an electric machine as described above.

For example, the drive train can be arranged in a rail vehicle or be part of the rail vehicle, so that good implementation in existing systems and broad applicability is given. In this case, the drive train can include an engine, a transmission connected to the engine, a wheel set shaft and an axle coupling for transmitting the drive torque from the transmission to the wheel set shaft.

The specific advantages of a drive train equipped with the motor or the electric machine can be seen in particular in the fact that an advantageous adjustability of the field weakening is made possible. Furthermore, high mechanical stability and good long-term stability can be made possible.

With regard to further advantages and technical features of the drive train, reference is hereby made to the description of the electric machine, the vehicle, the figures and the description of the figures.

A vehicle is also described, the vehicle having at least one of an electric machine and a drive train as described above.

For example, the vehicle can be a rail vehicle, since corresponding drive trains or electrical machines are particularly suitable for such vehicles. Rail vehicle drive systems often have very long constant power ranges. If the field weakening range (shown above the driving speed or engine speed) is almost the same as the constant power range, the result is an advantageous design of the motor pulse-controlled inverter and good utilization of the power semiconductors. For example, Si-IGBT or SiC-MOSFET (Metal Oxide Semiconductor Field-Effect Transistors) are used as power semiconductors.

The advantages described above are also relevant for a vehicle described, so that an advantageous adjustability of the field weakening is made possible. Furthermore, high mechanical stability and good long-term stability can be made possible.

With regard to further advantages and technical features of the vehicle, reference is hereby made to the description of the electric machine, the drive train, the figures and the description of the figure.

• 1 eine Schnittansicht einer elektrischen Maschine gemäß einer Ausgestaltung der vorliegenden Erfindung von der Seite;
• 2 Schnittansichten durch einen Rotor für eine elektrische Maschine gemäß der Ausgestaltung nach 1;
• 3 eine Schnittansicht einer elektrischen Maschine gemäß einer weiteren Ausgestaltung der vorliegenden Erfindung von der Seite; und
• 4 weitere Schnittansichten durch einen Rotor für eine elektrische Maschine gemäß einer weiteren Ausgestaltung der vorliegenden Erfindung.

Further details, features and advantages of the subject matter of the invention result from the dependent claims and from the following description of the figures. In the figures show:

• 1 a sectional view of an electric machine according to an embodiment of the present invention from the side;
• 2 Sectional views through a rotor for an electrical machine according to the embodiment 1 ;
• 3 a sectional view of an electrical machine according to a further embodiment of the present invention from the side; and
• 4 further sectional views through a rotor for an electrical machine according to a further embodiment of the present invention.

In the 1 an embodiment of an electrical machine 10 is shown. The electric machine 10 can, in particular as a motor, be part of a drive train of a vehicle, such as in particular a rail vehicle.

The electrical machine 10 has an even number of poles between six and 24, advantageously pole numbers of six, eight, twelve and 16 (pole pair numbers: 3,4,6 and 8).

The electrical machine 10 includes a stator 12 and a rotor 14 , the stator 12 including a stator winding 16 which interacts with the rotor 14 . The rotor 14 is also hybrid excited.

For this purpose, at least two excitation modules 20, 22 are provided which are arranged axially displaced with respect to a rotor axis 18 of the rotor 14. The rotor axis 18 runs through a shaft 34 of the rotor 14.

A first exciter module 20 comprises a supporting body 24 and a permanent magnet 26 arranged on the supporting body 24, possibly a magnetic rotor yoke, for the permanent magnetic excitation of the stator winding 16 and the synchronous machine. The support body 24 is attached to the shaft 34 and can be designed, for example, as a laminated core.

A second exciter module 22 is designed as a claw-pole module with claw-pole fingers 28, 30 and an exciter coil 32 acting on them. It is also shown that the excitation coil 32 acting on the claw pole fingers 28, 30 is carried by a yoke 36. FIG. The yoke 36 can be formed of iron, for example. Furthermore, the yoke 36 can be fastened to a bearing plate 38 as part of a housing, so that on the other hand the excitation coil 32 acting on the claw-pole fingers 28, 30 is also arranged on the bearing plate 38 or is fixed to it via a support 39 of the bearing plate 38 and thereby fixed. The shaft 34 or the rotor 14 is mounted in the end shields 38 via bearings 40 . That in the 1 The right bearing 40 shown, which is located adjacent to the first exciter module 20, is the drive-side bearing 40, whereas the opposite bearing 40 is the non-drive-side bearing 40.

In the 1 is also shown that the claw pole fingers 28, 30 are connected to one another by a connecting element 42, which forms a support structure and can be made of a lightweight material. Furthermore, the claw pole fingers 28, 30 are fixed to the support body 24.

More precisely, it is shown that a first group of claw-pole fingers 28 in terms of polarization, in particular the claw-pole fingers 28 magnetized as the south pole, is mechanically connected to the supporting body 24 . This can be done, for example, by means of a screw connection or a flange and/or using a fastening element 41 which engages over the claw-pole fingers 28 and the supporting body 24 and is fastened to the claw-pole fingers 28 and the supporting body 24 . A second group of claw-pole fingers 30 in terms of polarization, in particular the claw-pole fingers 30 magnetized as the north pole, is mechanically connected to the first group of claw-pole fingers 28 by the connecting element 42 .

Furthermore, the 1 a plurality of cooling channels 48, 50 through which effective cooling is to be allowed.

In principle, when using the electric machine 10 as a traction motor, it is advantageous to provide an encapsulated machine 10 in which the active part, i.e. the stator 12 and rotor 14, does not have cooling air flowing directly through it from the outside in order to minimize the effects in the event of a fault causing damage to the stator winding limit outside of the machine 10. However, if the electrical excitation in proportion to the permanent magnet excitation is high, this possibility of field weakening can limit the fault current in the defective stator winding 16 and thus the effect on the outside. The direction of action of the DC excitation current in the claw-pole excitation device or in the excitation coil 32 can also be reversed, so that a very high effect of the field weakening is achieved compared to the permanent magnet excitation. In this case, the encapsulation can be dispensed with and the active part can be directly ventilated and efficiently cooled with outside air. Accordingly, it can be fundamentally advantageous that the electrical machine 10 is of open design and is cooled through ventilation.

• - Offen oder gekapselt;
• - Eigenbelüftet oder fremdbelüftet;
• - Wassermantelkühlung;
• - Bei Kapselung mit und ohne Innenkühlkreislauf.
• - Spaltrohrmaschine mit Direktkühlung des Ständers beziehungsweise Stators 12 über ein isolierendes Kühlöl, wie etwa Transformatoröl, und Luftkühlung des Rotor 14.

If the electrical machine 10 is used as a traction generator, in principle a ventilation can be selected, since the operation in the event of a fault is short in time, and a diesel engine may run on for a few minutes. Thus, in principle, all types of cooling that occur in traction machines can be considered for the electric machine 10, such as:

• - Open or encapsulated;
• - Self-ventilated or externally ventilated;
• - water jacket cooling;
• - For encapsulation with and without internal cooling circuit.
• - Canned machine with direct cooling of the stand or stator 12 via an insulating cooling oil, such as transformer oil, and air cooling of the rotor 14.

In the 1 an encapsulated arrangement is shown. In this case, the cooling channel 48 forms an outer circuit that is supplied with cooling air via external ventilation. Also shown are cooling channels 50 which are part of an inner circuit. The connecting element 42 or the supporting structure between the north pole and the south pole is also axially permeable, so that the rotor cooling air flow can flow well through the entire rotor 14 . The inner circuit can be operated by an inner fan 52, for example. 1 thus shows an encapsulated, externally ventilated machine with an internal cooling circuit.

In the 2 FIG. 14 is a view of the rotor 14 of the embodiment of FIG 1 shown where the 2a shows a plan view and wherein 2 B shows a corresponding longitudinal section. In the 2 the shaft 34 is shown, around which the fixed yoke 36 and the excitation coil 32 are arranged with a corresponding gap. The claw-pole fingers 28, 30, which are magnetized in the north pole and south pole, are also shown at a distance from the exciter coil 32 via gaps 44, 46 a first group of claw pole fingers 28 are magnetized as the south pole and a second group of claw pole fingers 30 are magnetized as the north pole.

3 shows a further embodiment of an electrical machine 10, which essentially as to 1 executed is designed.

Essential in the design according to 3 is that a further excitation module 54 is provided. It is shown in detail that three exciter modules 20, 22, 54 arranged axially displaced with respect to a rotor axis 18 of the rotor 14 are provided, of which a first exciter module 20 has a supporting body 24 and a permanent magnet 26 arranged on the supporting body 24 for the permanent magnetic excitation of the stator winding 16 and a second and a third exciter module 22, 54 are each designed as a claw-pole module with claw-pole fingers 28, 30 and an exciter coil 32 acting on them. The first exciter module 20 is arranged axially between the second 22 and the third 54 exciter module.

Just as the second exciter module 22 is attached to the first exciter module 20, the third exciter module 54 is also attached to the first exciter module 20 in accordance with the description above.

In the 4 is again shown a view of the rotor 14, wherein the 4a shows a plan view and wherein 4b shows a corresponding longitudinal section. Basically, the design corresponds to 4 according to the design 2 .

According to 4 however, provision is made for the second excitation module 22 to have one or a plurality of permanent magnets 56 . In particular, the permanent magnets 56 are arranged on an annular yoke 58 which is in contact with the claw pole fingers 30 functioning as the north pole. The claw pole arrangement 28 (south pole) can also be designed with permanent magnets 56 in this form.

Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Reference List

10

electric machine

12

stator

14

rotor

16

stator winding

18

rotor axis

20

excitation module

22

excitation module

24

body

26

permanent magnet

28

claw pole fingers

30

claw pole fingers

32

excitation coil

34

Wave

36

yoke

38

bearing shield

39

support

40

camp

41

fastener

42

fastener

44

gap

46

gap

48

cooling channel

50

cooling channel

52

indoor fan

54

excitation module

56

permanent magnet

58

yoke

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited 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 102007035321 A1 [0004]

Claims (11)

Electrical machine (10) with a stator (12) and a rotor (14), the stator (12) comprising a stator winding (16) which interacts with the rotor (14), the rotor (14) being hybrid-excited in such a way that at least two excitation modules (20, 22) are provided, which are arranged axially displaced with respect to a rotor axis (18) of the rotor (14), of which a first excitation module (20) has a supporting body (24) and a permanent magnet arranged on the supporting body (24). (26) for permanent magnetic excitation of the stator winding (16) and wherein a second excitation module (22) is designed as a claw-pole module with claw-pole fingers (28, 30) and an excitation coil (32) acting on them, characterized in that the claw-pole fingers (28, 30) are connected to one another by a connecting element (42) and the claw pole fingers (28) are also fixed to the supporting body (24). Electrical machine (10) after claim 1 , characterized in that a first group of claw pole fingers (28) in terms of polarization is mechanically connected to the supporting body (24) and a second group of claw pole fingers (30) in terms of polarization is connected to the first group of claw pole fingers (28) by the connecting element ( 42) are mechanically connected. Electrical machine (10)) after claim 1 or 2 , characterized in that the excitation coil (32) acting on the claw pole fingers (28, 30) is fixed. Electrical machine (10) according to one of Claims 1 until 3 , characterized in that the excitation coil (32) acting on the claw pole fingers (28, 30) is carried by a yoke (36). Electrical machine (10) according to one of Claims 1 until 4 , characterized in that the excitation coil (32) acting on the claw pole fingers (28, 30) is arranged on a bearing plate (38). Electrical machine (10) according to one of Claims 1 until 5 , characterized in that three with respect to a rotor axis (18) of the rotor (14) arranged axially displaced exciter modules (20, 22, 54) are provided, of which a first exciter module (20) has a support body (24) and one on the support body ( 24) arranged permanent magnet (26) for permanent magnetic excitation of the stator winding (16), and a second (22) and a third (54) excitation module each designed as a claw-pole module with claw-pole fingers (28, 30) and an excitation coil (32) acting on them are, wherein the first exciter module (20) is arranged axially between the second (22) and the third (54) exciter module. Electrical machine (10) according to one of Claims 1 until 6 , characterized in that the second exciter module (22) and optionally the third exciter module (54) has a permanent magnet (56). Electrical machine (10) according to one of Claims 1 until 7 , characterized in that the electrical machine (10) is designed to be open and cooled through ventilation. Drive train for a vehicle, in particular for a rail vehicle, the drive train comprising a motor for driving a wheel or a shaft, characterized in that the motor is an electric machine (10) according to one of Claims 1 until 8th is. Vehicle, characterized in that the vehicle has at least one of an electrical machine (10) according to one of Claims 1 until 8th and a drive train claim 9 having. vehicle after claim 10 , characterized in that the vehicle is a rail vehicle.

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