EP3087570B1 - Resistor and method for the production of said type of resistor - Google Patents

Description

The invention relates to a resistor, preferably a braking, discharging or high-load resistor according to the preamble of claim 1 and a method for producing such a resistor.

Braking resistors are used, for example, to dissipate excess energy in electrical drives in the event of recuperation, which cannot be used to charge a battery or a capacitor arrangement or the like, by converting these energy or voltage peaks into heat.

Braking or discharging resistors can be formed with ceramic PTC resistance elements or wire resistance elements. Braking resistors with ceramic PTC resistance elements are for example in the EP 1 225 080 B1 described by the applicant. Such braking resistors have a high level of operational reliability due to their resistance characteristic curve, which rises sharply with temperature, since they regulate themselves in the event of an overload. The disadvantage is that such PTC braking resistors are comparatively expensive.

In less demanding applications, braking or discharging resistors - also known as load resistors - are generally used, in which the resistance element is designed as a wire resistance winding that encompasses an insulating body. Cartridge-shaped designs of such wire resistance elements are for example in the DE 2 228 460 or the DE 37 03 689 C2 disclosed. However, these cartridge-shaped braking resistors have a comparatively complex structure. Solutions in which the wire resistance element has a wire winding that is wound on a flat carrier and then in one are significantly more compact a heat sink designed as a hollow profile is used. An encapsulated structure to increase safety is thus realized.

Such a solution is for example in the EP 1 711 035 A1 explained to the applicant. Accordingly, the known braking resistor has the heat sink produced as an extruded profile made of aluminum, in which the wire resistance element is inserted. Its position is positioned using Mikanit insulating plates, which keep the heating element at a distance from the peripheral wall of the extruded profile. Mikanit is the trade name of a pressed mica material that forms a solid, plate-shaped insulating material. The front side of the heat sink is sealed using a closure, whereby a connection on the power supply side is penetrated by two connecting lines. Conventionally, these closures are formed by first placing the extruded profile on an assembly device and then inserting or pressing a micanite plate into an end receptacle of the extruded profile. This micanite plate is then cast on the bottom with silicone or a suitable sealing compound, such as acid iron cement, and cured. After curing, the wire resistance element is introduced into the receiving space and filled with MgO, the filling density being increased by shaking. The MgO serves as insulation material and as a heat store. In addition, the wire resistance element and / or the position of the wire windings is fixed by the MgO. Before filling, micanite plates are used in the receiving space, which prevent direct contact of the wire resistance element with the heat sink and thus ensure the electrical insulation. A closure is then applied to this backfill and cured.

Since this manufacturing process is comparatively complex due to the two-time curing, the DE 10 2011 001 362 A1 proposed instead of using the hardening layer to insert a plate next to the filling in the heat sink, which is sealed by a sealant. A metal or ceramic sealing plate, for example, is then inserted into the heat sink adjacent to the plate and is mechanically connected to it.

In the EP 1 852 878 B1 discloses a solution in which the wire resistance winding is pressed with the carrier and the insulating plates arranged between the peripheral walls of the heat sink and the wire resistance winding, so that a filling can be dispensed with.

In the case of such wire resistance elements, the wire winding is usually wound around the two longitudinal legs of a multi-part frame-shaped micanite carrier, this winding starting from a connection-side narrow side, then extending along one longitudinal leg of the frame, in the region of another narrow side then to the other, parallel leg passes over and from there leads back to the connection-side narrow side. The manufacturing effort for the multi-part carrier and the double winding is considerable.

The publication DE 203 11 068 U1 shows a braking resistor, which is provided with a thermal sensor or switch to protect against overheating.

The publication EP 0 004 539 A2 shows a high-load wire resistor whose current flow is interrupted at overtemperature by the fact that a wire section consists of an alloy designed for the overtemperature, which - unlike the rest of the wire - melts when the overtemperature is reached.

A disadvantage of many of these solutions is that in the event of a fault, for example when an excessive voltage occurs, the wire winding can overheat, which can lead to a burnout or even a partial melting of the adjacent extruded profile. Wire resistance elements are usually provided with a protective circuit that should respond in the event of an overload - in the event of a fault, arcing can still occur and the associated problems described above. Since this arc jumps from winding to winding, so to speak, one cannot judge in advance at which point this blowout takes place.

In contrast, the invention has for its object to provide a resistance in which the operational safety is improved with little outlay on device technology. Furthermore, the invention has for its object to provide a method for producing such a resistor.

This object is achieved by a resistor with the features of claim 1. With regard to the method, the object is achieved by the features of the independent claim 14.

Advantageous developments of the invention are the subject of the dependent claims.

According to the invention, the resistor, which can be designed as a braking, discharging or high-load resistor, hereinafter called the braking resistor for the sake of simplicity, is designed with a wire winding element which has a wire resistance winding wound around an insulating support, the ends of which are assigned to connection elements. According to the invention, a predetermined wire section of the wire winding is better thermally insulated from the surroundings than the other wire winding, so that the wire winding element fails in this wire section in the event of a fault.

In this way, it can be structurally predetermined without reducing the wire cross section, in which area the wire winding burns out in the event of a fault, so that, with the appropriate design of this area, the risk of damage to adjacent components and a dangerous electrical contact to the housing, i.e. a body closure that can be prevented, and an "intrinsically safe exit" of the braking resistor is made possible.

• Es kommt nicht zu einem Körperschluss, dass heißt einem Durchschlagen des Stroms auf das Gehäuse. In diesem Fall wäre nicht nur das Gehäuse des Bremswiderstandes sondern auch der Motor, auf dem das System elektrisch leitend verschraubt ist unter Spannung gesetzt.
• Es bleibt ein genügend hoher Isolationswiderstand des Systems erhalten.
• Es bleibt eine genügend hohe Spannungsfestigkeit des Systems erhalten.
• Es liegt eine hinreichende thermische Sicherheit vor, also eine Sicherheit gegen Überhitzung des Systems mit einer daraus resultierenden Gefährdung von umliegenden Bauelementen.

This significantly improves the intrinsic safety of the system compared to conventional solutions. "Intrinsic safety" is defined for a wire braking resistor using the following features:

• There is no body closure, which means that the current flows through the housing. In this case, not only the housing of the braking resistor but also the motor on which the system is screwed in an electrically conductive manner would be energized.
• A sufficiently high insulation resistance of the system remains.
• A sufficiently high dielectric strength of the system is maintained.
• There is sufficient thermal security, i.e. security against overheating of the system with a resulting risk to surrounding components.

In a preferred embodiment of the invention, this wire section is at least partially surrounded by the carrier or embedded therein.

The construction of the braking resistor is particularly simple if the carrier has two carrier elements, between which the wire section runs, while the remaining wire winding runs around the two carrier elements.

It is further preferred if the wire winding extends away from a connection-side end section of the carrier towards another end section and is then returned between the carrier elements to the connection-side end section and is then connected there to a connection element. That In this variant, the wire feedthrough extends between the two carrier elements.

These are preferably plate-shaped, so that this wire return / wire passage between the plates and accordingly results in a sandwich-like structure.

Arc formation in the deflection area can be largely prevented if the winding is deflected at a distance from the other end section of the carrier in the direction of the connection-side end section. This can be effected in a relatively simple manner by this deflection taking place along a recess formed in the other end section of the carrier.

Lateral arcing can also be avoided if the wrapped region of the carrier is set back with respect to its end sections, so that they protrude beyond the winding on both sides.

In a preferred embodiment of the invention, the carrier is made of an electrically and thermally insulating material, such as e.g. Mikanit or the like.

It is particularly preferred if the wire resistor is designed as a flat wire. The distance between the wire turns should be more than 1.5 mm in one embodiment. Of course, round wire can also be used, in which case the distance is smaller, for example 0.25 mm.

The distances depend on the required total resistance of the system. A round wire is preferably used in thicknesses between 0.1 mm and 0.45 mm. With such diameters, relatively large resistance values can be achieved. If a lower resistance is required, flat wire is preferred.

The assembly of the braking resistor is particularly simple because the carrier has recesses on the connection-side end section in which the end sections of the winding can be pre-fixed.

The braking resistor is preferably formed with a heat sink, which has a receiving space which receives the wire winding element, the connecting lines extending through an end closure of the heat sink.

The electrical insulation from the heat sink is particularly effective if the wire resistance element is embedded in a filling and further insulation elements are arranged between the filling and the heat sink.

Accordingly, according to the method according to the invention, the wire resistance is first passed from the connection side between the two parts of the carrier and deflected at the opposite end section of the carrier. As a result, the resistance wire is then wrapped around the carrier, the winding direction extending toward the connection-side end section of the carrier.

In a variant of the invention, the wire winding element can also be pressed with the heat sink, wherein electrically insulating plates are provided as the insulation body between the wire winding element and the heat sink. In such a variant, the filling described can be dispensed with.

Alternatively, the wire winding element can also be encapsulated with an electrically insulating material which forms a heat storage and heat transfer element. The hardened block can then be inserted into the receiving space of the heat sink. In principle, it is also possible to cast the wire winding element directly in the heat sink.

• Figur 1 eine dreidimensionale Darstellung eines erfindungsgemäßen Bremswiderstandes;
• Figur 2 den Bremswiderstand aus Figur 1 bei abgenommener Deckfläche;
• Figur 3 eine Ansicht eines Drahtwickelelementes des Bremswiderstandes gemäß den Figuren 1 und 2;
• Figur 4 eine zeichnerisch aufgebrochene Darstellung des Drahtwickelelementes gemäß Figur 3;
• Figur 5 eine Einzeldarstellung der Drahtwicklung des Drahtwickelelementes gemäß den Figuren 3 und 4 und
• Figur 6 eine Schnittdarstellung einer Variante eines Bremswiderstands.

Preferred exemplary embodiments of the invention are explained in more detail below with the aid of schematic drawings. Show it:

• Figure 1 a three-dimensional representation of a braking resistor according to the invention;
• Figure 2 the braking resistor Figure 1 with the cover surface removed;
• Figure 3 a view of a wire winding element of the braking resistor according to the Figures 1 and 2 ;
• Figure 4 a graphically broken representation of the wire winding element according Figure 3 ;
• Figure 5 a detailed view of the wire winding of the wire winding element according to the Figures 3 and 4 and
• Figure 6 a sectional view of a variant of a braking resistor.

Figure 1 shows a three-dimensional representation of a braking resistor 1 according to the invention.

The invention is explained using a resistor (braking, discharging or high-load resistor). In principle, however, the concept according to the invention can also be used as a heating resistor in a heater.

Accordingly, it has a cooling body 2 designed as an aluminum continuous casting profile, in the receiving space of which is explained in more detail below (see Figure 2 ) a wire winding element is added. The contacting of this wire winding element takes place via two connecting lines 4, 6 which pass through a closure 8 on the connection side. The heat sink 2 serves as a heat store, which absorbs the heat generated on the wire winding element. The heated heat sink is then in heat exchange with the environment.

The heat sink is designed with cooling fins 10 enlarging the heat exchange surface and has recesses 12 in the corner regions, which enable the heat sink 2 to be fastened to a housing or the like. As explained in more detail below, a bottom-side closure is formed on the end section of the heat sink 2 that is remote from the connecting lines 4, 6. At the in Figure 1 In the illustrated embodiment, the cooling fins 10 are only formed in an upper cover wall, hereinafter referred to as cover surface 14, and of course they can also be formed in the cover surface 16 below. These cover surfaces laterally protrude from the base body of the heat sink 2, so that side walls 18, 20 are formed approximately as a U-profile. Additional elements such as temperature sensors or limiters can be installed in this U-profile. Other geometries are also possible.

Figure 2 shows the braking resistor according to Figure 1 with the cover surface 14 removed so that the mentioned wire winding element 22 is visible. The layer structure shown of this braking resistor 1 is in principle from the prior art mentioned at the beginning according to the DE 10 2011 001 362 A1 known, so that only the elements essential for understanding the invention are described here. The wire winding element 22 is inserted into a receiving space 24 of the heat sink 2. This receiving space 24 is through the two U-shaped side walls 18, 20, the two top walls or top surfaces 14, 16 (top surface 14 in the illustration according to Figure 2 removed), the connection-side closure 8 and the mentioned further bottom-side closure 26 limited. The two plate-shaped closures 8, 26 can be made of metal, ceramic or glass, for example, and are preferably caulked to the heat sink 2.

A micanite plate 28 is arranged at a distance from the closure 26 and is fixed in position by means of a casting compound or the like, not shown. Pressing in the micanite plate 28 is also possible. This plate 28 is adjacent to two longitudinal micanite insulating plates 30, 32, which extend towards two connection-side plates 34, 36. These are in turn arranged at a distance from the closure 8 and held by means of a sealing compound. Like in the DE 10 2011 001 362 A1 explained, these two plates 34, 36 have mutually formed recesses which, in the assembled state, complement one another for bushings for the two connecting lines 4, 6, these bushings encompassing the circumference of the lines. Corresponding bushings 37a, 37b are also formed in the closure 8.

In the area between the wire winding element 22 and the lower cover surface 16 and in Figure 2 removed upper cover surface 14 of the heat sink 2, at least one micanite base plates are provided on each side, between which the wire winding element 22 is then arranged. Accordingly, these two micanite base plates, the longitudinally arranged insulating plates 30, 32 and the small plates 28, 34, 36 arranged on the end face form a closed insulating body which encompasses the wire winding element 22 in a box-shaped manner. The receiving space 24 is filled with a sand filling, which is partially solidified by shaking, so that the wire winding element 22 is reliably positioned in the receiving space 24 and is also effectively thermally coupled to the heat sink. The wire is also positioned.

The structure of the wire winding element 22 is evident from the Figures 3 to 5 , The Figures 3 and 4 show an individual representation of the wire winding element 22 according to Figure 2 , The wire winding element 22 has a carrier 38 made of micanite, which according to the broken illustration in FIG Figure 4 in principle consists of two micanite support elements 40, 42, of which in the illustration according to Figure 3 only the support element 42 is visible. This covers the in Figure 4 support element 40 located above.

The two substantially congruent carrier elements 40, 42 have a connection-side end section 44 and an end section 46 remote therefrom, which are widened on both sides with respect to a winding section 48 arranged between them. On the connection-side end section 44, two connection areas 50, 52 are provided, each of which is formed by a welding bridge, to which the two connection lines 4, 6 are punctured or connected in some other way. The carrier 38 carries the actual wire winding. The resistance wire 54 used here is formed in the illustrated embodiment as a flat wire with a rectangular cross section and is made of a heating wire alloy. The winding distance W is preferably more than 0.5 mm. As explained at the beginning, a round wire can also be used instead of a flat wire. In this case, the wire diameters are usually in the range between 0.1 mm and 0.45 mm.

During the winding process, the in Figure 3 below and in Figure 4 Above end 56 of the wire 54 can be contacted with the connection area 52 of the connection line 4. In a subsequent operation, the wire 54 is then passed between the two carrier elements 42, 44 to a recess 58 formed on the other end section 46 of the carrier 38 and deflected there. This deflection area of the wire is in Figure 4 provided with the reference number 60. The wire 54 is then guided from this deflection area 60 to the adjacent area of the winding section 48 and then the carrier 38 is wrapped until the wire 54 again reaches the end section 44 on the connection side. The corresponding end 62 of the wire is then contacted with the connection area 50 and thus with the connection line 6. A pre-fixation of the wire winding is possible in that the respective ends 56, 62 are clamped in two recesses 64, 66, so that contact can then be made with the connecting lines 4, 6 after assembly.

The wire section 68 passed through between the two carrier elements 40, 42 is opposite the external winding by the two plate-shaped micanite carrier elements 40, 42 thermally insulated. In the event of a fault, the wire section 68 lying between the carrier elements 40, 42 will heat up significantly more than the outside winding cooled by the heat sink 2, so that the burnout also takes place in the region of this passage. The burnout takes place in such a way that an interruption point is formed which is so far that an arc that is formed is quickly interrupted. This way the element becomes intrinsically safe, in particular a body connection (electrical connection to the housing) is impossible.

Damage to other components due to thermal overheating is therefore reliably excluded.

Figure 5 shows an individual representation of the wound wire 54. The wire section 68 running between the two carrier elements 40 and 42 can be seen, which extends through the interior of the winding and is contacted with its end 56 with the connection 52. This wire section 68, which runs somewhat obliquely to the winding axis, is deflected in the region of the deflection 60; the actual winding then extends back to the right in Figure 5 and ends in the slightly inclined end 62, which can be contacted with the further connection 50.

In the exemplary embodiment described above, the wire winding element 22 with the micanite plates forming an insulating body is inserted into the receiving space 24 of the insulating body 2, the remaining cavity being filled with a filler, for example MgO, in order to position the wire winding element 22 in the receiving space 24. This backfilling is comparatively complex. Figure 6 shows an embodiment in which the wire winding element 22 according to the invention with internal feedback and the surrounding micanite insulating plates, of which here the longitudinally arranged insulating plates 30, 32 and the two bottom plates 70, 72 are visible, inserted into the receiving space 24 and then as in the EP 1 852 878 B1 described are pressed together. During this pressing, the side walls 74, 76 shown are drawn inwards in the manner shown, so that the wire winding element 22 with the associated insulating body is reliably positioned. During this pressing, the windings of the wire are pressed into the carrier 38 and / or the base plates 70, 72, so that a very good heat transfer is guaranteed. Furthermore, the intimate contacting of the wire with the carrier 38 and the electrically insulating plates of the insulating body results in good heat storage capacity.

A further possibility of dispensing with a filling which is complex in terms of production technology is to encapsulate the wire winding element 22 according to the invention, which is designed with an internal return line, with a heat storage and transmission element. This means that the wire winding element 22 is cast with a hardening material, which can consist, for example, of a mixture of MgO and water glass and harden under an inert gas atmosphere and temperature. This electrically insulating potting material surrounds the wire winding element 22, so that it can be inserted as a "block" into the receiving space 24 of the heat sink 2. The attachment can be done, for example, by pressing or pressing. In principle, it is also possible to cast the wire winding element directly in the receiving space 24, so that it acts practically as a casting mold. In this case, the insulating micanite plates could even be dispensed with.

Disclosed is a resistor, preferably a braking, discharging or high-load resistor and a method for producing such a resistor, in which a wire section of a wire winding is thermally insulated from the other wire winding, so that the wire section fails in the event of a fault.

Reference symbol list :

1

braking resistor

2

heatsink

4

connecting cable

6

connecting cable

8th

Lock on the connection side

10

cooling fins

12

recess

14

cover surface

16

cover surface

18

sidewall

20

sidewall

22

Wire winding element

24

accommodation space

26

shutter

28

Tile

30

insulation

32

insulation

34

Tile

36

Tile

37a

execution

37b

execution

38

carrier

40

support element

42

support element

44

end

46

end

48

winding section

50

terminal area

52

terminal area

54

resistance wire

56

The End

58

recess

60

deflection region

62

The End

64

recess

66

recess

68

wire section

70

baseplate

72

baseplate

74

sidewall

76

sidewall

Claims (14)

1. A resistor, preferably a braking resistor, discharge resistor or high power resistor including a wire winding element (22) having a wire resistor winding wound around a carrierr (38), the ends (56, 62) of which are connectable to connection areas (50, 52), a wire section (68) by contrast with the remaining wire coil, being thermally insulated in an improved manner against the environment, so that in the event of an error the wire winding element (22) fails in that wire section (68), characterized in that the carrier (38) has recesses (64, 66) on a terminal side end portion (44) for prefixing the ends (56, 62).
2. The resistor according to claim 1, wherein the wire section (68) is surrounded by the carrier (38) at least in sections.
3. The resistor according to claim 1 or 2, wherein the carrier (38) has two carrier elements (40, 42) between which the wire section (68) runs, whereas the remaining wire winding substantially runs around carrier elements (40, 42).
4. The resistor according to claim 3, wherein the wire winding extends away from the terminal side end portion (44) of carrier (38) to another end portion (46) and is conducted between carrier elements (40, 42) to the terminal side end portion (44).
5. The resistor according to claim 3 or 4, wherein the carrier elements (40, 42) are formed in the shape of a plate.
6. The resistor according to claim 4 or 5, wherein the passthrough at a distance from the other end portion (46) of the carrier (38) is redirected toward the terminal side end portion (44) or the winding.
7. The resistor according to claim 6, wherein redirection (60) takes place along a recess (58) formed in the other end portion (46).
8. The resistor according to any of the preceding claims, wherein a winding portion (48) of the carrier (38) is relocated vis-à-vis the end portions (44, 46).
9. The resistor according to any of the preceding claims, wherein the carrier (38) consists of micanite.
10. The resistor according to any of the preceding claims, wherein the wire is formed as a flat wire.
11. The resistor according to any of claims 1 to 9, wherein the wire is executed as a round wire.
12. The resistor according to any of the preceding claims including a heat sink (2) having a receiving space (24) receiving the wire winding element (22), the terminal lines (4, 6) extending through a closure (8).
13. The resistor according to claim 12, wherein the wire winding element (22) is embedded in an insulating filling or crimped with the heat sink or cast in a heat transfer and storage element.
14. Method for the production of a resistor according to any of the preceding claims, comprising the steps of

    - preparing a carrier (38) of at least two parts;

    - conducting one end (56) of a wire between carrier elements (40, 42) of carrier (38) from one terminal side end portion (44) toward another end portion (46);

    - redirecting the wire in the section of the other end portion (46) and winding the wire around the carrier (38) toward the terminal side end portion (44);

    - prefixing the ends (56, 62) on recesses (64, 66) of the carrier (38) located on the terminal side end portion (44).

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