DE102020200234A1 - Side channel compressor for a fuel cell system for conveying and / or compressing a gaseous medium, in particular hydrogen - Google Patents

Abstract

Side channel compressor (1) for a fuel cell system (37) for conveying and / or compressing a gaseous medium, in particular hydrogen, with a housing (3) and a drive (6), the housing (3) having an upper housing part (7) and has a housing lower part (8), with a compressor chamber (30) running around an axis of rotation (4) in the housing (3) and having at least one circumferential side channel (19, 21), with a compression chamber (3) in the housing (3) located compressor wheel (2), which is rotatably arranged around the axis of rotation (4) and is driven by the drive (6), wherein the compressor wheel (2) has on its periphery in the area of the compressor chamber (30) arranged blades (5) and with one gas inlet opening (14) formed on the housing (3) and one gas outlet opening (16), which are fluidically connected to one another via the compressor chamber (30), in particular the at least one side channel (19, 21). According to the invention, the drive (6) has a stator (11) and a rotor (17), the rotor (17) being at least almost completely enclosed by means of an encapsulation element (18) and thus in particular encapsulated from the environment.

Description

State of the art

The present invention relates to a side channel compressor for a fuel cell system for conveying and / or compressing a gaseous medium, in particular hydrogen, which is intended in particular for use in vehicles with a fuel cell drive.

In addition to liquid fuels, gaseous fuels will also play an increasing role in the vehicle sector in the future. Hydrogen gas flows must be controlled, especially in vehicles with fuel cell drives. The gas flows are no longer controlled discontinuously, as is the case with the injection of liquid fuel, but the gas is taken from at least one high-pressure tank and fed to an ejector unit via an inflow line of a medium-pressure line system. This ejector unit leads the gas to a fuel cell via a connecting line of a low-pressure line system. After the gas has flowed through a fuel cell, it is returned to the ejector unit via a return line. The side channel compressor can be interposed, which supports the gas recirculation in terms of flow and efficiency. In addition, side channel compressors are used to support the flow build-up in the fuel cell drive, especially when the vehicle is (cold) started after a certain idle time. These side channel blowers are usually driven by electric motors, which are supplied with voltage from the vehicle battery when they are operated in vehicles.

From the DE 2017 102 157 39 and the DE 10 2018 204 713 A1 a side channel compressor for a fuel cell system is known in which a gaseous medium, in particular hydrogen, is conveyed and / or compressed. The side channel compressor has a housing and a drive, the housing having an upper housing part and a lower housing part. Furthermore, a compressor chamber which runs circumferentially around an axis of rotation and has at least one circumferential side channel is arranged in the housing. In the housing there is a compressor wheel which is arranged rotatably about the axis of rotation and is driven by the drive, the compressor wheel having impeller blades arranged on its circumference in the area of the compressor chamber. In addition, the from the DE 2017 102 157 39 and the DE 10 2018 204 713 A1 Known side channel compressors each have a gas inlet opening formed on the housing and a gas outlet opening, which are fluidically connected to one another via the compressor chamber, in particular the at least one side channel.

The one from the DE 2017 102 157 39 and the DE 10 2018 204 713 A1 known side channel blowers can have certain disadvantages.

The drive consists of components that, due to their material properties, can be damaged by the anode medium, especially hydrogen, if you come into contact with them. Other substances that penetrate the drive from the environment, such as water or dirt, can also damage drive components. This can lead to an oxidation reaction, hydrogen embrittlement or further material damage. Due to the fact that the drive and also the components of the side channel compressor are at least partially in motion in the periphery of the drive, in particular in rotation, this can lead to damage to these components. This in turn can lead to failure of the drive and / or to failure of the entire side channel compressor.

Furthermore, from the DE 2017 102 157 39 and the DE 10 2018 204 713 A1 Known side channel blowers have the disadvantage that certain parts of the drive or side channel blower do not heat up quickly enough during a cold start procedure, which means that there is a risk of damage from ice bridges, which can reduce the service life of the side channel blower and / or the fuel cell system.

Disclosure of the invention

Advantages of the invention

According to the invention, a side channel compressor for a fuel cell system for conveying and / or compressing a gaseous medium, in particular hydrogen, with the features of the independent claims is provided.

Referring to claim 1, a side channel compressor is proposed in which a drive has a stator and a rotor, the rotor being at least almost completely enclosed by means of an encapsulation element and thus in particular encapsulated from the environment. In this way, the advantage can be achieved that the rotor is protected against contact with the anode medium, in particular hydrogen, or other substances from the environment, such as water or pollution. The encapsulation element effectively shields the rotor from contact with the surrounding medium, which increases the service life of the drive and thus of the side channel blower and thus the probability of failure due to failing components of the drive is reduced. In addition, the encapsulation of the drive and / or the rotor can be implemented in a compact design by means of the encapsulation element which at least almost completely encloses the rotor, so that no or only minimal structural changes need to be made to the drive and / or the side channel compressor. In this way, the advantageous embodiment of the invention according to the invention can be implemented in a cost-effective manner.

The subclaims relate to preferred developments of the invention.

According to an advantageous embodiment, the drive is designed as a radial internal rotor electric motor, the drive, in particular the rotor, being connected to a compressor wheel via a drive shaft, the drive shaft, the compressor wheel and the rotor being mounted rotatably about an axis of rotation and wherein the rotor and the compressor wheel are connected to the drive shaft with a form fit, material fit or force fit. In this way, inexpensive assembly of the encapsulation element can be achieved without further or at least only minor structural changes to the drive and / or to the side channel compressor being necessary. This reduces the assembly costs and thus the production costs of the side channel blower, while the probability of failure of the side channel blower can be reduced.

According to a particularly advantageous embodiment, the rotor has at least one permanent magnet and / or the encapsulation element is designed as a stainless steel cap, which has at least stainless steel. In this way, the advantage can be achieved that the failure probability of the rotor and / or the entire drive can be reduced. This can be achieved in such a way that the components of the assembly group that are particularly sensitive to hydrogen, such as the soft magnetic materials of the permanent magnet, are relocated to an internal area, while the components of the assembly group that are particularly insensitive to hydrogen, such as stainless steel, are in the external surrounding area are relocated. This offers the advantage that the service life of the drive and thus of the entire side channel compressor can be increased.

According to an advantageous embodiment of the side channel compressor, the rotor is attached to the drive shaft in such a way that it is flush with the drive shaft on the side facing away from the compressor wheel, the stainless steel cap having an opening on its side facing the compressor wheel in the area of the drive shaft and the stainless steel cap having the completely encloses the rotor applied to the drive shaft, except for the area of the opening. In this way, the advantage can be achieved that a compact design of the drive and / or the side channel compressor can be maintained or brought about.

According to a particularly advantageous development, the drive shaft and the stainless steel cap are frictionally, positively or cohesively connected to one another in the area of the opening in such a way that the rotor, in particular the permanent magnet, is encapsulated in an external area. In this way, the advantage can be achieved that an efficient encapsulation of the sensitive components and / or materials of the rotor can be achieved by means of the stainless steel cap, the only area of the stainless steel cap through which hydrogen or other substances penetrate into the inner area of the rotor and could damage the soft magnetic materials, especially the area of the opening. This advantage is achieved by a permanently encapsulating connection between the stainless steel cap and the drive shaft, which can reduce the probability of failure of the drive and / or the side channel blower.

According to an advantageous embodiment of the side channel compressor, the drive is designed as an axial field electric motor which has the stator and the rotor, the stator and the rotor being designed in the form of a disk circumferentially around the axis of rotation and the stator being arranged in the direction of the axis of rotation next to the rotor . In this way, a compact and space-saving design of the side channel blower can be achieved with the smallest possible surface in relation to the volume. This offers the advantage that only a small amount of installation space is required by the customer, for example in a vehicle. Furthermore, the compact design of the side channel blower, in particular with the smallest possible surface area in relation to the volume, offers the advantage that the side channel blower cools down more slowly at low ambient temperatures, especially in the range below 0 ° C, and thus delays the formation of ice bridges for longer can be.

According to an advantageous development, the rotor has at least the permanent magnet, a rotor hub and a fixing disk, the encapsulation element at least almost completely enclosing the rotor hub and / or the permanent magnet and thus encapsulating it to form an external area. In this way, a compact design of the drive can be achieved, in particular in the embodiment as an axial field electric motor. At least almost all components can do this of the rotor are arranged and integrated in the area of the inner diameter of the compressor wheel, including the bearing of the compressor wheel. Furthermore, the design of the side channel compressor according to the invention enables reliable encapsulation of the rotor, in particular the rotor hub and / or the permanent magnets.

According to an advantageous embodiment of the side channel compressor, the encapsulation element has an at least two-layer structure, the first layer being made of an elastically deformable material, in particular an elastomer, and the second layer being made of stainless steel. In this way, on the one hand, improved encapsulation of the rotor hub and the permanent magnet can be achieved, since the elastically deformable material can flow into any area due to its material properties and / or can be better applied to the rotor hub and the permanent magnet due to its elasticity. The second layer of stainless steel, on the other hand, can give the encapsulating element better structural strength than the elastomer. The reliability of the drive and / or the side channel blower can thus be increased.

According to a particularly advantageous embodiment, the encapsulation element consists of at least one elastomer sealing element with a pressed-on stainless steel cap. In this way, the advantage can be achieved that the encapsulation element having at least two layers, which in particular has at least two materials with different properties, can be preassembled before it is attached to the drive and / or to the rotor and / or to the compressor wheel. In this way, the assembly costs and the required assembly time as well as assembly errors can be reduced. This offers the advantage of lower overall costs for the side channel blower and, due to the reduced probability of occurrence of assembly errors, a lower probability of failure of the drive and / or the side channel blower.

According to an advantageous method, in particular for starting or switching off and / or operating the side channel compressor, the stator is energized and induces inductive heating of the rotor and / or the encapsulation element, in particular the encapsulation element, which has at least stainless steel, Due to the material properties, it can be heated inductively particularly well. The material stainless steel has a high electrical conductivity, which makes it easier to heat inductively. The heating occurs as an effect due to an electrical application by means of a magnetic field, more specifically by means of eddy current losses, since the layer made of stainless steel is an electrically conductive body. In this case, the rotor is inductively warmed up when the coils of the stator are briefly energized, in particular due to the resulting power loss, which is released as thermal energy. In this way, the advantage can be achieved that when the rotating field is not present, the rotor is heated by the energization of the stator, the induction effect being used in particular for this purpose. The rotor, which consists in particular of a thermally conductive material, can be heated, which is particularly advantageous in the case of a cold start procedure for the side channel compressor and / or the vehicle. The rotor heats up and transfers the thermal energy to the compressor wheel, for example due to the high thermal conductivity of the material used. The heat energy is transferred in one flow direction into the area between the compressor wheel and a housing in which ice bridges have formed. These ice bridges can damage the side channel blower when the side channel blower is started up and / or prevent rotation of the compressor wheel in the housing by blocking. Furthermore, when the compressor wheel starts up, it can break away, releasing sharp-edged pieces of ice that can damage components behind the side channel compressor and / or a fuel cell, in particular the membrane of the fuel cell, in the conveying direction. By heating the rotor, the compressor wheel and in particular the area of the inner limiting ring and the outer annular collar, both of which form a small distance, in particular a small gap, to the housing, are heated. As a result, the ice bridges melt and the liquid changes from a solid to a liquid aggregate state and can be discharged, for example by means of a purge valve and / or drain valve present in the fuel cell system. In this way, the service life of the side channel compressor and / or the fuel cell system can be increased.

The invention is not restricted to the exemplary embodiments described here and the aspects emphasized therein. Rather, a large number of modifications are possible within the range specified by the claims, which are within the scope of expert action.

Figure list

The invention is described in more detail below with reference to the drawing.

• 1 eine schematische Schnittansicht eines erfindungsgemäßen Seitenkanalverdichters,
• 2 einen erfindungsgemäßen Teil des Seitenkanalverdichters gemäß einem ersten Ausführungsbeispiel in einer perspektivischen Darstellung,
• 3 einen erfindungsgemäßen Teil des Seitenkanalverdichters gemäß einem zweiten Ausführungsbeispiel in einer perspektivischen Darstellung.

It shows:

• 1 a schematic sectional view of a side channel compressor according to the invention,
• 2 a part of the side channel compressor according to the invention according to a first embodiment in a perspective view,
• 3 a part of the side channel compressor according to the invention according to a second embodiment in a perspective view.

Description of the embodiment

According to the representation 1 is a longitudinal section through a rotationally symmetrical to an axis of rotation 4th trained side channel compressor proposed according to the invention 1 refer to.

The side channel blower 1 has a compressor wheel 2 on, in particular as a closed disc-like compressor wheel 2 is formed and around the horizontally extending axis of rotation 4th rotatable in a housing 3 is stored. A drive is used for this 6th , especially an electric drive 6th , as a rotary drive 6th of the compressor wheel 2 . The drive 6th can, according to a first exemplary embodiment, be a radial internal rotor electric motor 6th be designed or according to a second embodiment as an axial field electric motor 6th be executed. Furthermore, the drive 6th several cooling fins 33 exhibit. The case 3 comprises a housing upper part 7th and a lower housing part 8th that are connected to each other. Between the two housing parts 7, 8 a can be around the axis of rotation 4th circumferential sealing element, which encapsulates a compression chamber 30th of the side channel blower 1 causes, in particular against contamination or moisture from the outside. According to the first embodiment, the compressor wheel 2 non-rotatably on a drive shaft 9 arranged and is from the upper part of the housing 7th and the lower part of the housing 8th enclosed. According to the second embodiment, the compressor wheel 2 in particular indirectly via a rotor hub 29 (shown in 3 ) and at least one warehouse 27 be mounted on a journal, for example in the upper part of the housing 8th is located.

In the first embodiment, the compressor wheel 2 an inner compressor wheel hub 10 on, with the compressor wheel hub 10 has a recess through which the drive shaft 9 is plugged in and the compressor wheel hub 10 in particular by means of a press fit with the drive shaft 9 connected is. The compressor wheel hub 10 is also revolving on the axis of rotation 4th remote side by a hub foot 12th limited. In addition, in this exemplary embodiment, at least one is around the axis of rotation 4th circumferential seal 23 on the outside diameter of the drive shaft 9 arranged, in particular axially to the axis of rotation 4th between the hub foot 12th and the drive 6th and radial to the axis of rotation 4th between the drive shaft 9 and the upper part of the housing 7th .

From the hub foot 12th outwards from the axis of rotation 4th away forms the compressor wheel 2 a rotating circular hub disc 13th out. It also forms the compressor wheel 2 one on the outside of the hub disc 13th subsequent at least one delivery cell 28 out. This at least one delivery cell 28 of the compressor wheel 2 runs circumferentially around the axis of rotation 4th in the rotating compressor room 30th of the housing 3 . Furthermore, in 1 in the area of the conveyor cell 28 the cut contour of an airfoil 5 to see. This shovel blade 5 can have a V-shaped contour. Furthermore, the respective delivery cell 28 in the direction of rotation of the compressor wheel 2 of two shovel blades 5 limited, being a number of airfoils 5 all around the axis of rotation 4th on the compressor wheel 2 radial to the axis of rotation 4th are arranged.

Furthermore, the housing 3 , especially the upper part of the housing 7th and / or the lower part of the housing 8th , in the area of the compressor room 30th at least one circumferential side channel 19th , 21 on. The at least one side channel runs here 19th , 21 such in the case 3 in the direction of the axis of rotation 4th that this is axially to the delivery cell 28 runs on one or both sides. The at least one side channel 19th , 21 can at least in a partial area of the housing 3 all around the axis of rotation 4th run, in the sub-area in which the at least one side channel 19th , 21 in the housing 3 is not formed, a breaker area 15th in the housing 3 is trained.

In the first embodiment, the drive shaft is 9 by means of at least one bearing 27 , which are rolling bearings 27 can act, in particular to ball bearings 27 , in the housing 3 stored. The drive 6th can with the housing 3 of the side channel blower 1 be connected, in particular with the upper part of the housing 7th by the drive 6th with at least one end face on one end face of the housing 3 axial to the axis of rotation 4th is present.

Furthermore, the housing forms 3 , especially the lower part of the housing 8th , a gas inlet port 14th and a gas outlet port 16 out. Here are the gas inlet opening 14th and the gas outlet port 16 , in particular via the at least one side channel 19th , 21 , fluidically connected to each other. This increases as the circulation progresses from the gas inlet opening 14th to the gas outlet opening 16 in the direction of rotation of the compressor wheel 2 the compression and / or the pressure and / or the Flow rate of the gaseous medium in the delivery cell 28 , especially in the conveyor cells 28 of the compressor wheel 2 and in the side channels 19th . The gaseous medium is released through the gas outlet opening after it has passed through 16 of the side channel blower 1 diverted and flows in an outflow direction, in particular in the direction of a jet pump 41 a fuel cell system 37 , out. Through the breaker area 15th a separation of a pressure side and a suction side is effected, whereby the suction side is in the area of the gas inlet opening 14th and the pressure side is in the area of the gas outlet opening 16 is located.

From the drive 6th becomes a torque on the compressor wheel 2 transfer. Thereby the compressor wheel 2 set in rotation and the conveyor cell 28 moves in a rotational movement around the axis of rotation 4th through the compressor room 30th in the housing 3 in the direction of a first direction of rotation. A is already in the compressor room 30th gaseous medium present through the pumping cell 28 moved with it and thereby promoted and / or compressed. In addition, there is a movement of the gaseous medium, in particular an exchange of flow, between the delivery cell 28 and the at least one side channel 19th , 21 instead of. Furthermore, the side channel blower is 1 via the gas inlet opening 14th and the gas outlet port 16 with the fuel cell system 37 connected, the gaseous medium, which is in particular an unconsumed recirculation medium from a fuel cell, via the gas inlet opening 14th in the compressor room 30th of the side channel blower 1 one and / or the side channel blower 1 is supplied and / or is from the area that the gas inlet opening 14th is upstream, sucked. The gaseous medium is released through the gas outlet opening after it has passed through 16 of the side channel blower 1 derived.

2 shows a part of the side channel compressor according to the invention 1 according to a first embodiment in a perspective view, wherein the drive 6th as a. It is shown that the drive 6th as a radial internal rotor electric motor 6th is executed and a stator 11 and a rotor 17th having. Thereby the rotor 17th by means of an encapsulation element 18th at least almost completely enclosed and thus in particular encapsulated from the environment. The drive 6th , especially the rotor 17th , is about the drive shaft 9 with the compressor wheel 2 connected, the drive shaft 9 , the compressor wheel 2 and the rotor 17th rotatable around the axis of rotation 4th are stored and each of the rotor 17th and the compressor wheel 2 form fit, material fit or force fit with the drive shaft 9 are connected. In this case, by way of example, the drive shaft 9 by means of two bearings 27 which are located on both sides of the compressor wheel 2 located, is stored.

It is also shown that the rotor 17th at least one permanent magnet 25th has and / or the encapsulation element 18th than a stainless steel cap 18th is executed, which has at least stainless steel. Here is the rotor 17th so on the drive shaft 9 applied that he was on the the compressor wheel 2 remote side is flush with this, with the stainless steel cap 18th on your the compressor wheel 2 facing side in the area of the drive shaft 9 an opening 22nd having. The stainless steel cap also encloses it 18th the one on the drive shaft 9 applied rotor 17th completely, except for the area of the opening 22nd . Furthermore is the drive shaft 9 and the stainless steel cap 18th in the area of the opening 22nd are connected to one another in a non-positive, positive or material manner that the rotor 17th , especially the permanent magnet 25th is encapsulated to an external area.

In 3 is a part of the side channel blower according to the invention 1 according to a second embodiment shown in a perspective view. Here is the drive 6th than an axial field electric motor 6th is carried out, which is the stator 11 and the rotor 17th having, the stator 11 and the rotor 17th disc-shaped circumferentially around the axis of rotation 4th are formed and wherein the stator 11 in the direction of the axis of rotation 4th next to the rotor 17th is arranged. Furthermore, the rotor 17th at least the permanent magnet 25th , the rotor hub 29 and a fixing washer 31 having, wherein the encapsulation element 18th the rotor hub 29 and / or the permanent magnets 25th at least almost completely encloses and thus encapsulates to form an external area. The encapsulation element 18th has an at least two-layer structure, the first layer being made of an elastically deformable material, in particular an elastomer, and the second layer being made of stainless steel. In an exemplary embodiment, the encapsulation element 18th consists of at least one elastomer sealing element with a pressed-on stainless steel cap, which enables simplified assembly.

In the 1 seal shown 23 can be superfluous in the second exemplary embodiment, since here there is a fluidic separation, in particular in the form of an intermediate wall, between the space of the stator 11 and the space of the rotor 17th , in the housing 3 is trained. In addition, there is no drive shaft here either 9 for torque transmission from the drive 6th on the compressor wheel 2 needed because in this embodiment the rotor 17th as a disc-shaped element directly in the compressor wheel 2 is located.

For each of the first and second exemplary embodiments of the side channel blower 1 can by energizing the stator 11 inductive heating of the rotor 17th and / or the encapsulation element 18th causes, in particular the encapsulation element 18th , which has at least stainless steel, allows rapid heating due to the material properties, in particular due to a high inductive resistance.

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 201710215739 [0003, 0004, 0006]
• DE 102018204713 A1 [0003, 0004, 0006]

Claims (10)

Side channel compressor (1) for a fuel cell system (37) for conveying and / or compressing a gaseous medium, in particular hydrogen, with a housing (3) and a drive (6), the housing (3) having an upper housing part (7) and has a housing lower part (8), with a compressor chamber (30) running around an axis of rotation (4) in the housing (3) and having at least one circumferential side channel (19, 21), with a compression chamber (3) in the housing (3) located compressor wheel (2), which is arranged rotatably about the axis of rotation (4) and is driven by the drive (6), wherein the compressor wheel (2) has on its periphery in the area of the compressor chamber (30) arranged blades (5) and with one gas inlet opening (14) formed on the housing (3) and one gas outlet opening (16) which are fluidically connected to one another via the compressor chamber (30), in particular the at least one side channel (19, 21), characterized in that, that the drive (6) has a stator (11) and a rotor (17), the rotor (17) being at least almost completely enclosed by means of an encapsulation element (18) and thus in particular encapsulated from the environment. Side channel compressor (1) according to Claim 1 , characterized in that the drive (6) is designed as a radial internal rotor electric motor (6), the drive (6), in particular the rotor (17), being connected to the compressor wheel (2) via a drive shaft (9) , wherein the drive shaft (9), the compressor wheel (2) and the rotor (17) are rotatably mounted about the axis of rotation (4) and the rotor (17) and the compressor wheel (2) in each case form-fitting, materially or non-positively with the drive shaft (9) are connected. Side channel compressor (1) according to Claim 2 , characterized in that the rotor (17) has at least one permanent magnet (25) and / or the encapsulation element (18) is designed as a stainless steel cap (178) which has at least stainless steel. Side channel compressor (1) according to Claim 3 , characterized in that the rotor (17) is applied to the drive shaft (9) in such a way that it is flush with the side facing away from the compressor wheel (2), the stainless steel cap (18) facing towards the compressor wheel (2) Side in the area of the drive shaft (9) has an opening (22) and wherein the stainless steel cap (18) completely encloses the rotor (17) attached to the drive shaft (9), with the exception of the area of the opening (22). Side channel compressor (1) according to Claim 3 or 4th , characterized in that the drive shaft (9) and the stainless steel cap (18) in the area of the opening (22) are so positively, positively or materially connected that the rotor (17), in particular the permanent magnet (25) to an external area is encapsulated. Side channel compressor (1) according to Claim 1 , characterized in that the drive (6) is designed as an axial field electric motor (6) which has the stator (11) and the rotor (17), the stator (11) and the rotor (17) rotating in a disk-shaped manner the axis of rotation (4) are formed and wherein the stator (11) is arranged in the direction of the axis of rotation (4) next to the rotor (17). Side channel compressor (1) according to Claim 6 , characterized in that the rotor (17) has at least one permanent magnet (25), a rotor hub (29) and a fixing disk (31), the encapsulation element (18), the rotor hub (29) and / or the at least one permanent magnet (25) at least almost completely encloses and thus encapsulates to form an external area. Side channel compressor (1) according to Claim 7 , characterized in that the encapsulation element (18) has an at least two-layer structure, the first layer being made of an elastically deformable material, in particular an elastomer, and the second layer being made of stainless steel Side channel compressor (1) according to Claim 8 , characterized in that the encapsulation element (18) consists of at least one elastomer sealing element with a pressed-on stainless steel cap. Method according to one of the preceding claims, characterized in that energizing the stator (11) induces inductive heating of the rotor (17) and / or the encapsulation element (18), in particular the encapsulation element (18), which is at least Stainless steel has, due to the material properties, in particular due to a high inductive resistance, favors rapid heating.

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