WO2013163994A1 - Liquid-cooled resistor - Google Patents

Description

 Liquid cooled resistor

The invention relates to a liquid-cooled resistor having at least one electrically conductive resistance element which is arranged in a cooling channel.

From DE 28 47 129 C2 a resistance element in the form of a coiled metallic wire is known, which extends between two electrical terminals and is embedded in a potting compound containing alumina. Furthermore, the embedded resistance element is cooled by a current flowing transversely to its direction of extension coolant flow.

Against this background, it was an object of the present invention to provide a liquid-cooled resistor that allows the implementation of high performance in a compact design.

This task is followed by a liquid-cooled resistor

Claim 1 and claim 2 solved. Advantageous embodiments are contained in the subclaims.

According to a first aspect, the invention thus relates to a liquid-cooled (electrical) resistor, which can be used, for example, to reduce short-term, excess electrical power. The resistor contains (at least) the following components: At least one electrically conductive resistance element through which electrical current is passed during operation. For this purpose, the liquid-cooled resistor usually further, not mentioned in detail herein components such. B. electrical external connections. The resistance element usually consists of a conventional

 Heizleitermaterial, in particular a metal or a metal alloy such as CuNi, NiCr, or AlCr. It can optionally be accommodated or embedded in an electrically insulating carrier. As a rule, the resistance element has a geometrically substantially rectilinear extent between its electrical connections, wherein it can run in a "fine structure", for example, spirally along the direction of extension in order to accommodate the largest possible line length between the terminals.

A cooling channel having a rohrformigen section through which a suitable, typically liquid coolant can be passed, wherein in the rohrformigen portion, the aforementioned resistance element (at least partially) is arranged. The term "tubular portion" is to be understood very generally as any type of geometry in which a (originally empty) space is annularly enclosed by the body of the cooling channel (possibly up to a slight opening point of the ring). In a typical embodiment, the tubular portion is in the shape of a circular cylinder. However, other cylindrical or prismatic structures with elliptical, polygonal, or other cross-sectional shapes are also conceivable. Furthermore, in the general case, the tubular section can also be built geometrically irregular.

The described liquid-cooled resistor is still characterized

characterized in that in the said tubular portion, an open cavity remains (between the resistance element and the inner wall of the cooling channel) whose thickness is not more than about 15%, preferably not more than about 10%, not more than about 8 %, not more than about 5%, or even not more is about 2% of the local diameter of the tubular portion (this condition being intended to be met at least one location, preferably more than 75% of the inner wall surface of the tubular portion, most preferably the entire tubular portion). When the tubular portion and the resistance element are both circularly cylindrical and the resistance element is arranged centrally along the axis of the tubular portion, the above-mentioned cavity is an annular gap or hollow cylinder. The "thickness of the cavity" is then identical to the wall thickness of this hollow cylinder.

The term "cooling channel" is intended to encompass both the (originally empty) space in which the resistive element and the coolant flowing through the cavity are in the finished resistor, as well as the material wall bounding this space. The material of this wall may be a metal such as e.g. Aluminum or even a plastic (for example, a thermoset or carbon fiber reinforced plastic CFK).

A liquid-cooled resistor according to a second aspect of the invention includes the following components:

At least one electrically conductive resistance element.

A cooling channel having a tubular portion in which the resistance element is arranged.

The liquid-cooled resistor according to the second aspect is characterized in that in the tubular portion, a cavity remains, whose thickness is less than about 5 mm (this condition

at least one point, preferably more than 75% of the inner wall surface of the tubular portion, more preferably in the entire tubular

Section should be fulfilled). Optionally, the thickness may be less than about 4 mm, less than about 3 mm, less than about 2 mm, or even less than 1 mm.

A liquid-cooled resistor according to the first or second aspect of the invention has the advantage that due to the relatively small thickness of the cavity in the cooling channel a dissipation of heat loss from the resistance element, which proves to be surprisingly efficient in practice. This makes it possible to implement high power losses in the liquid-cooled resistor in a compact design.

A liquid-cooled resistor according to a third aspect of the invention represents a stand-alone problem solution, and optionally may additionally include the features of the above-described liquid-cooled resistors according to the first and / or second aspects. The liquid-cooled resistor according to the third aspect includes the following components:

At least one electrically conductive resistance element.

A cooling channel having a tubular portion in which the resistance element is arranged.

The liquid-cooled resistor according to the third aspect is characterized in that an electrical insulation is arranged between the resistance element and the remaining cavity of the cooling channel.

The liquid-cooled resistor according to the third aspect of the invention has the advantage that it allows the use of electrically conductive coolants, since they can not come into electrical contact with the current-carrying resistance element due to the electrical insulation. As a result, optimal cooling agents can be used under thermal aspects, which benefits the performance of the resistor.

The features of the described liquid-cooled resistors according to the first, second, and third aspects of the invention may optionally be combined with each other. Generally speaking, statements, definitions and

Explanations given for any embodiment of a resistor according to the present invention apply analogously to all other embodiments.

In the following, various advantageous embodiments of the invention will be described, which deal with both a liquid-cooled resistor according to the first, second and third aspects of the invention.

As a coolant in the liquid-cooled resistor, in particular an antifreeze such. As ethylene glycol, a corrosion inhibitor, water, deionized water, oil and / or mixtures thereof are used.

The cooling channel is preferably designed such that a coolant in the

Can flow substantially parallel to the extension direction of the resistance element through the cavity in the cooling channel. In particular, the

Connecting line between the electrical connection points of the

Resistance element substantially parallel to the connecting line between the coolant connection points of the cooling channel (where "substantially" is to mean an angle less than about 30 ° between the straight line). Additionally or alternatively, it may be required that the over the

Resistance element averaged electric current flow direction should be substantially parallel to the averaged over the cooling channel coolant flow direction.

For the geometric position or shape of the open cavity in the tubular portion are made in the general case no particular restrictions. It is conceivable, therefore, that the resistance element also bears in places on the inner wall of the cooling channel, so that the cavity here has the thickness "zero". In a preferred embodiment of the invention, however, the resistance element is in the tubular portion of the cooling channel surrounded by a cavity through which flows in the operating condition coolant. This means that the resistance element is embedded on all sides in the cavity (and thus in the coolant flow), wherein "on all sides" on the circumference relative to the electrical

Current flow direction or to the extension direction of the resistance element and excludes points for the electrical power supply and -ableitung. The embedding of the resistance element in the cavity or coolant flow has the advantage that particularly efficient dissipation heat can be dissipated by the resistance element. According to another preferred embodiment of the invention, a sheath tube is arranged between the resistance element and the inner wall of the cooling channel in the tubular portion thereof. The sheathing tube can have a circular or any other cross section. It may in particular contain or consist of metals, ceramics, metal oxides and / or metal nitrides. The jacket tube ensures a mechanically stable housing of the resistance element in the cooling channel, this tube preferably having good heat conduction properties which promote the removal of heat into the coolant flow.

According to a development of the embodiment described above, an electrical insulation is arranged between the resistance element and the jacket tube. This prevents a conductive sheath tube from participating in the conduction of electrical current through the resistive element or causing shorts.

The jacket tube may optionally have on its outside projections which increase its surface and thereby provide better heat dissipation into the coolant. The projections may be formed, for example, as extending in the longitudinal direction of the sheath tube, radially projecting ribs.

The resistive element may optionally be embedded in a mass containing inorganic fillers. Examples of such fillers are

in particular metal oxides and / or metal nitrides, for example aluminum oxides and / or aluminum nitrides. The mass is preferably electrically insulating. It then represents an example of the embodiment described above, in which the resistance element is embedded within the sheath tube in the insulating mass, so that there is no electrical contact between the resistance element and sheath tube. The use of a mass with inorganic fillers has the advantage that the resistance element can be electrically isolated from its surroundings, said fillers having a good thermal conductivity at high electrical

Have dielectric strength. The liquid-cooled resistor can be adjusted in its performance by appropriate dimensioning of the resistive element and the cooling channel to the needs. For example, a high electrical power consumption by a correspondingly long length of the cooling channel and the

Resistance element can be achieved. A high power consumption with a compact design can also be realized if the liquid-cooled resistor at least two cooling channels of the type mentioned with associated, each arranged in a tubular portion

Has resistive elements, d. H. when the simple liquid-cooled resistor is substantially multiple provided and arranged. The resistance elements can be electrically connected in series, electrically connected in parallel, or be arranged in mixed forms of these types of circuits, if they are to serve together to dissipate an electric current. If several electrical currents of different circuits are to be derived, the resistance elements usually remain electrically separate.

A particularly compact design with efficient cooling results when the liquid-cooled resistor has at least two cooling channels with corresponding resistance elements, wherein the cooling channels are connected to a common manifold for supplied coolant and / or to a common collector for coolant to be derived. The liquid-cooled resistor then requires only a single supply line for coolant or only a single outflow for coolant.

The above-mentioned distributor and / or the collector are advantageously designed so that when operating in the connected cooling channels an approximately equal flow of coolant - and thus an equal cooling capacity - sets. For example, the geometry of the distributor may be such that in operation there is approximately the same dynamic pressure at all inputs of cooling channels.

A particularly advantageous construction of a liquid-cooled resistor with at least two cooling channels and associated resistances results, when these cooling channels and resistance elements are arranged geometrically parallel to each other.

Preferably, a plurality of existing cooling channels are formed in a one-piece block, so that a close thermal coupling is formed.

Inequalities in the generation of heat loss can then be balanced across the block, so that all the cooling channels are involved in approximately equally in the dissipation of heat loss. The block may contain, for example, metal, plastic or ceramic or consist of these materials.

The resistor may optionally include means for directing a flow of coolant in the cooling passage, such as ribs or vanes, with which the flow of the coolant can be influenced. In particular, the

Steering means be designed so that they produce a twist, d. H. a helical flow of the coolant around the resistance element. Said means may preferably be arranged on the inner wall of the cooling channel and / or on the outer wall of a sheath tube.

In the following the invention will be explained in more detail by way of example with the aid of the figures. Showing:

Fig. 1 is a longitudinal section through an inventive

 liquid cooled resistor;

2 shows a cross section through the resistor of Figure 1 along the

 Line II-II;

Fig. 3 shows the resistance of Figure 1 with coolant connections in one

 perspective exploded view;

Fig. 4 shows a cross section through a jacket tube with radial ribs.

The liquid-cooled resistor 100, shown partially schematically in the figures, represents an exemplary embodiment of the present invention. It contains the following components: A number of (here six) similar resistance elements 101, which are arranged geometrically parallel to each other. The resistance elements 101 are formed by electrical conductors, which are shown in the figures cylindrical. In detail, however, the resistive elements 101 may have a "fine structure" not shown in detail, according to which they are z. B. can be wound spirally along the extension axis.

A corresponding number of sheath tubes 103, such as copper tubes, each sheath tube 103 surrounds one of the aforementioned resistive elements 101 without contacting it.

In order to ensure a mechanically stable, electrically insulating, and thermally well-conducting housing of the resistance elements 101 in the cladding tubes 103, the resistance elements 101 are embedded in the cladding tubes in an electrically insulating potting compound 102. This potting compound may contain or consist of inorganic fillers, for example, aluminum oxide or aluminum nitride.

A corresponding number of cooling channels K, which are formed in the example shown in a common one-piece block 104 made of metal or plastic. The cooling channels K each comprise a tubular (in this case circular-cylindrical) section which extends in a straight line through said block 104. In each of the cooling channels K is centrally one of said sheath tubes 103 with the therein

embedded resistive element 101, wherein the resistive elements 101 typically protrude slightly beyond the two ends of the channels K so as to be electrically connectable (eg, in series or parallel) (not shown).

A distributor 105 and a collector 106 which cover the ends of the cooling channels K at the block 104 and via which a coolant (eg an ethylene glycol / water mixture) can be supplied or removed. The distributor 105 ensures a uniform distribution of the Coolant in the cooling channels K. Similarly, the collector 106 provides for the capture of the escaping refrigerant and its common discharge.

For a uniform distribution of the flow of the manifold 105 and / or the collector 106 may be provided, for example, in the flow direction from channel branch to channel branch decreasing cross sections (or smaller constrictions). As a result, the same dynamic pressure can be built up in channels located further back as in the case of front channels.

Figure 3 shows the case that the line connections of manifold 105 and collector 106 are on the same side (top). However, they may also be located on different sides (i.e., diametrically opposite) or generally located at other positions.

The manifold 105 and / or the collector 106 may be made of metal (e.g.

 Aluminum) or plastic.

The between the inner wall of the channels K and the outer wall of the

Ummantelungsrohre 103 remaining cavity is here a hollow cylinder or annular gap RS. It preferably has a small thickness Δ, which is smaller than about 10% of the diameter of the cooling channel at the corresponding location. As shown, when the diameter of a cooling passage K is denoted D and the diameter of the associated shroud tube 103 is d, the above condition is expressed as the formula:

Δ = (D-d) / 2 <D-10/100

For more general geometries, refer to a point on the

Inner wall of the cooling channel (K), the sizes used are defined as follows: The "thickness Δ of the cavity" can be measured as the

Diameter of the largest (imaginary) sphere, which lies entirely in the cavity (RS) and contains the point considered. The "local diameter D of the tubular portion" can be measured as the diameter of the largest (imaginary) sphere, which lies entirely in the tubular section and contains the point considered.

In absolute terms, the thickness (Δ) of the cavity is preferably less than about 2 mm.

Through the cavity RS, during operation of the resistor 100, a coolant can be conducted essentially parallel to the extension direction of the resistance element 101 (see block arrows in FIG.

With the described construction, a liquid-cooled resistor is provided, which allows efficient dissipation of high power losses in a compact design. In particular, the design can be carried out so that relatively high currents can be passed through the resistor elements, for example, currents of about 250 A or more.

FIG. 4 shows a cross-section through an alternative embodiment of a sheath tube 103 ', which may optionally be substituted for that described above

Sheath tube 103 could be used. In contrast to the latter, it has on its outside projections V to increase the surface and thus to improve the heat dissipation. The projections V can

be configured, for example, distributed over the circumference, radially projecting ribs. In the longitudinal direction (i.e., perpendicular to the plane of the drawing of Figure 4), the projections V may be straight and parallel to the axis of the

Sheath tube 103 'extend. Alternatively, they may also orbit spirally about the axis of the sheath tube 103 'to impart a corresponding twist to the coolant.

Claims

claims 1 . Liquid cooled resistor (100) containing:  at least one electrically conductive resistance element (101), a cooling channel (K) with a tubular section in which the resistance element (101) is arranged, wherein in the tubular section a cavity (RS) remains whose thickness (Δ) does not exceed approx 15% of the local diameter (D) of the tubular section. 2. Liquid-cooled resistor (100), in particular according to claim 1, comprising:  at least one electrically conductive resistance element (101), a cooling channel (K) with a tubular portion in which the resistance element (101) is arranged, wherein in the tubular portion a cavity (RS) remains whose thickness (Δ) is less than about 5 mm. 3. Liquid-cooled resistor (100) according to at least one of the other claims, comprising: at least one electrically conductive resistance element (101), a cooling channel (K) with a rohrformigen section in which the resistance element (101) is arranged, wherein between the resistance element (101) and the remaining cavity (RS) of the cooling channel (K) an electrical Insulation (102) is arranged. 4. Liquid-cooled resistor (100) according to at least one of the other claims,  characterized in that the resistance element (101) in  tubular portion of the cooling channel (K) is surrounded by a cavity (RS). 5. Liquid-cooled resistor (100) according to at least one of the other claims,  characterized in that in the tubular portion a  Sheath tube (103, 103 ') between the resistance element (101) and the inner wall of the cooling channel (K) is arranged. 6. Liquid-cooled resistor (100) according to claim 5,  characterized in that the sheathing tube (103 ') has on its outside projections (V). 7. Liquid-cooled resistor (100) according to at least one of the other claims,  characterized in that the resistive element (101) is embedded in a mass (102) containing inorganic fillers,  in particular metal oxides and / or metal nitrides. 8. Liquid-cooled resistor (100) according to at least one of the other claims,  characterized in that it comprises at least two cooling channels (K) with resistance elements (101) connected to a common Distributed manifold (105) for supplied coolant and / or to a common collector (106) are connected for discharging coolant. 9. Liquid-cooled resistor (100) according to at least one of the other claims,  characterized in that it comprises at least two cooling channels (K) with resistance elements (101) formed in a one-piece block (104). 10. Liquid-cooled resistor (100) according to at least one of the other claims,  characterized in that it comprises means (V) for steering a  Coolant flow in the cooling channel (K) contains, in particular for generating a spiral flow.