EP3211643B1 - Current limiter and electrical assembly - Google Patents

Description

The invention relates to an electrical resistance component and an electrical assembly containing the electrical resistance component and / or system according to the preambles of the independent claims.

State of the art

In order to reduce current spikes during start-up of electric motors, resistors with negative temperature coefficients are used. Such resistors are also called NTC resistors (Negative Temperature Coefficient Thermistors) or thermistor. They have the characteristic that they have a high resistance in the cold state, for example, when no current or only a small current flows. As soon as the current flowing through the NTC resistor is increased, the resistance drops to a much smaller value due to the concomitant increase in the temperature of the resistor. Used as a current limiter during the startup of electric motors, these can reduce the initial current peak arising when the electric motor is switched on, due to the initially high resistance value. Due to the high power loss at the high starting current of the electric motor, the NTC resistor heats up quickly. The subsequent temperature-dependent adjustment of the resistance to a much smaller value results in that the power of the motor is not significantly reduced. Likewise, no unnecessary power loss is generated in the current limiter itself.

As resistance materials for thermistors, for example, pure semiconductor materials, some compound semiconductors or various metallic alloys are used. Use find, for example, sintered or pressed metal oxides of copper, nickel, iron, titanium, manganese or Cobalt. For use in, for example, electrical / electronic circuits, the NTC resistors in the form of electrical components have connection pins or wires, which are each contacted with the resistance material. The terminal pins or wires are then soldered, for example, within a circuit substrate. Bonding materials having a high electrical conductivity are generally used for the construction and connection technology, in order to keep unwanted supply resistance low. At the same time, such connecting materials have good thermal conductivity. Typical solders, such as Pb37.5-Sn37.5-In25 or In97-3Ag, have an electrical resistivity of 2.2 * 10 ^-5 Ωcm or of 2.5 * 10 ^-6 Ωcm and a good thermal conductivity of 25W / mK and 73 W / mK, respectively.

From the publication EP2902761 A1 For example, a temperature sensor is known in which a thermistor material is applied as a thin film on an insulating substrate. To ensure a trouble-free Temperature measuring function, an electrode connected to the thermistor material has a portion with a low thermal conductivity. With the help of this electrode section thermal interferences to the thermistor material are prevented by the electrode.

The publication JP2008205384 describes a thermistor element made of a thermistor material for achieving an output voltage which varies linearly with temperature.

Disclosure of the invention

The invention is based on the object to propose an NTC resistor, which shows a very high heating behavior, whereby the resistance value is quickly reduced from a high initial value to a low value. At the same time a good electrical connection should be ensured in order to keep the supply line resistance at high currents - for example, during operation of an electric motor - low. Furthermore, it is an object to effectively reduce high current peaks within an electrical module and / or system, with occurring power losses being kept low.

This object is achieved by a resistance component as well as an electrical assembly containing the resistance component as a current limiter and / or system with the characterizing features of the independent claims.

The invention is based on the idea of achieving a high heating behavior of a thermistor by thermally insulating the NTC resistance material as far as possible from its nearest environment. In this way, a low thermal mass is to be achieved, which is essentially limited to the mass of the NTC resistor material.

The invention is therefore based on a current limiter
with at least one connection contact. In this case, the resistance component comprises an NTC resistance material, which is contacted by the at least one connection contact via an electrically conductive connection material. To increase a thermal decoupling of the terminal contact of the NTC resistor material, the electrically conductive bonding material has a thermal conductivity of ≤ 20W / m K, in particular 1-10 W / mK. As soon as a current flows through the NTC resistance material in a cold state, a high power loss is generated in the current limiter due to the initially high resistance. As a result of the power loss generated, there is a build-up of heat, but due to the poor thermal conductivity of the bonding material, the heat is mainly absorbed by the thermally-isolated low mass of the NTC resistor material. Since the heat can no longer be dissipated via the next environment adjacent to the NTC resistance material, in particular the terminal contact, the NTC resistance material reaches high temperature values in a much shorter time. Because of the thermistor behavior, therefore, there are advantageously already low resistance values after a much shorter time. This ensures that high starting currents, for example when switching on electric motors or transformers, can be effectively reduced. At the same time, however, power losses are minimized due to the very fast setting of small resistance values.

The measures listed in the dependent claims advantageous refinements and improvements of the current limiter invention are possible.

In a further development of the resistance component, the connection material has an electrical resistivity of ≦ 1 * 10 ^-3 Ωcm. In particular, this is between 1 * 10 ^-5 Ωcm - 1 * 10 ^-3 Ωcm. Despite a thermal insulation of the NTC resistor material can thus ensure a sufficiently good electrical conductivity, whereby a lead resistance is kept low in an advantageous manner.

An advantageous embodiment provides that the connecting material is an electrical Leitkleb, in particular a silver conductive adhesive, which connects the electrical connection contact with the NTC resistor material via a material connection with each other. A conductive adhesive has a significantly lower thermal conductivity compared to a solder material. Thus, the NTC resistor material can be thermally insulated at a sufficient electrical connection simultaneously. The thickness of the adhesive layer allows the thermal connection of the NTC resistance material to be set to the desired performance of the resistance component. Electrically conductive adhesives have, for example, an electrical resistivity between 1 * 10 ^-4 Ωcm - 1 * 10 ^-3 Ωcm, whereas their thermal conductivity shows a value of 1-10 W / mK.

In a particular embodiment, the connecting material has a pore structure. By pore structure is meant cavity-containing structures within the electrically conductive interconnect material, which cavities do not contribute to electrical power conduction. The pore structure can be open or closed. The pores or cavities are preferably filled with air. Air shows poor thermal conductivity, so it acts as an additional thermal insulator against the NTC resistor material. In addition, the thermal mass of the bonding material is reduced by the pore structure, whereby a possible heat absorption of the heating NTC resistor material is further limited. Preferably, the bonding material is in the form of a metal foam or a metal wire mesh. The bonding material is preferably contacted via a sintered connection with the NTC resistor material and / or more preferably with the connection contact materially. As an example, the aluminum metal foam "ERG Aerospace Duocel®" called. This has an electrical resistivity of 2 - 20 * 10 ^-5 Ωcm and a thermal conductivity of about 9.7 W / mK.

In an advantageous embodiment, the at least one connection contact comprises a connection element, which preferably serves as a connection plate, a connection wire or a connecting pin, in particular with a threaded area, for electrical contacting of the current limiter is trained. As a result, a simple contacting of the current limiter, for example, within an electrical module and / or system made possible by common connection techniques. Advantageously, the shape of the connection element can be based on the application-specific requirements due to different connection options.

In a further development of the current limiter, the NTC resistance material is contacted by at least two connection contacts, so that a current flow from the one connection contact via the NTC resistance material to the other connection contact is made possible when an electrical voltage is applied. This results in the great advantage that the current-carrying NTC resistor material shows a high heating behavior due to the thermal decoupling to the terminal contacts. Such a current limiter is used to reduce current peaks during switching on and / or off of the current leading components - such as electric motors or transformers - while optimized power dissipation.

A very simple embodiment of the current limiter is characterized in that the NTC resistance material is plate-like and has an upper side and a lower side, which are contacted at least in part by a respective terminal contact. An external geometry of the plate-like NTC resistance material can be chosen arbitrarily, for example, round, square or polygonal. This results in an easy-to-implement stack construction of connecting layers, terminal contacts and the NTC resistor material in training the current limiter. A planar design of the top and bottom of the NTC resistor material also allows a surface or line contact of a respective terminal contact. As a result, the current limiter is designed to be mechanically robust overall, so ensuring high process reliability within an automated assembly and soldering on a circuit substrate can be. The connection contact can be embodied, for example, as a simple wire element or as a metallic sheet metal part, in particular a stamped or lasered sheet metal part, and at least over a section in FIG a plane of the top or bottom laterally protrude to the NTC resistor material. Beyond this section, the terminal contact, for example, by a bend, at an angle - for example, at right angles - continued to the above level.

In an advantageous development or alternative embodiment, the NTC resistance material between the top and bottom of an opening, in particular in the form of a bore. It is provided that at least one of the contact terminals comprises a connection element which penetrates the opening and which is electrically insulated from the other contact terminal. In this way, connection concepts can be realized, in which starting for at least one connection contact an axial connection option is required. For certain applications, the connection element of the at least one connection contact is designed, for example, in the form of a connection pin, which contacts the NTC resistance material at least indirectly via a force, form and / or material connection.

In principle, one or both connection contacts may comprise a carrier body, which is arranged in each case adjacent to the connection material and is connected to the connection element on a side of the carrier body opposite the connection material. By such indirect contact, the reliability of the current limiter can be improved. For example, occurring during assembly or during operation mechanical and / or thermo-mechanical force effects can be absorbed by a more homogeneous pressure distribution through the NTC resistor material. In addition, this gives the flexibility to provide the current limiter in its geometric overall shape according to the space requirements, the connection concept and the requirements of the handling ability substantially corresponding to an adapted shaping of the support body of the respective application.

In the embodiments of the current limiter, the at least one connection contact may be formed as a solder, weld, plug-in or screw contact. In the case of a plug contact, the connection contact has a corresponding plug geometry, which is complementary to a corresponding plug geometry Counter contact, such as a crimping shoe, a insulation displacement contact element, a bore or a pin is formed. The plug contact may in this case also be provided in such a way as to form a transitional or press fit in the mating contact by means of a mating operation. In the form of a screw contact, the connection contact has a thread at least over a region, which produces a screw contact in cooperation with a closure element. The screw is formed for example by a threaded pin and a threaded nut. Overall, thereby embodiments of resistance components of larger design can be performed, which pursue mechanical connection concepts.

A great advantage also results if the NTC resistor material is enclosed by an insulating protective compound and the at least one terminal contact with a terminal region protrudes from the protective compound. In this way, the NTC resistor material is well protected from external environmental and force effects. In addition, the NTC resistor material is thermally encapsulated by the protective compound, so that a heating behavior of the NTC resistor material is favored.

The invention also leads to an electrical assembly and / or system with at least one current-carrying component, which is exposed to current peaks by switching operations. Such current peaks arise, for example, during a switch-on or switch-off process by a voltage application or removal on the at least one current-carrying component. The electrical assembly and / or system also provides for the reduction of these current peaks before a current limiter. The current limiter is in this case designed as an inventive component in one of the embodiments described above. In particular, in conjunction with an electric motor and / or a transformer as the at least one current-carrying component, the advantage in an effective reduction of current peaks during the above switching operations, while simultaneously occurring power losses are minimized by setting small resistance values in a very short time. There are also other applications for use as a current limiter possible. Here are, for example, to name those in which repeated Electricity splashes reduce the life of a component, such as a battery. Likewise, such applications may be mentioned in which current peaks superimpose and distort an intended useful signal, for example in the case of a data line, as an example for a radio.

A particular embodiment provides that the electrical assembly and / or system comprises a battery with a power connector. In this case, it is advantageously taken into account that the power connection forms at least one connection element of the at least one connection contact of the current limiter. In this way, the current limiter or the resistance component according to the invention is an integral part of the battery, in particular in the form of a battery connection. As a result, a very compact design is obtained, in which a current limit in the immediate vicinity of the power source can take place and this can be effective after a short time.

In an advantageous development of the power connector is designed as a from a base, in particular a housing surface of the battery, protruding connecting pin with a threaded portion. The connection pin penetrates at least the breakthrough in the NTC resistance material and projects beyond this at least with a part of the threaded portion. This results in the advantage of a very simple structure, in which the NTC resistance material can be received by clamping between the base and a cooperating with the threaded portion closure element. In addition, further connection elements and / or carrier body of the at least one connection contact can be arranged in the clamping region. As a result, a stack structure can be held in a simple manner solely by a frictional connection. The stack construction can in this case also include no or only partially a material connection.

Brief description of the drawings

• Fig. 1: eine erste Ausführungsform eines Widerstandsbauteils in einer perspektivischen Schnittdarstellung,
• Fig. 2a: eine weitere Ausführungsform eines Widerstandsbauteils in Form eines Batterieanschlusses in einer perspektivischen Darstellung,
• Fig. 2b: das Widerstandsbauteil aus Fig.2a aus einer geänderten perspektivischen Sicht in einer geschnittenen Darstellung.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing. This shows in:

• Fig. 1 FIG. 2: a first embodiment of a resistance component in a perspective sectional view, FIG.
• Fig. 2a FIG. 2: a further embodiment of a resistance component in the form of a battery terminal in a perspective representation, FIG.
• Fig. 2b : the resistance component off 2a from a modified perspective view in a sectional view.

Embodiments of the invention

In the figures, functionally identical components are each identified by the same reference numerals.

In the Fig. 1 a first embodiment of a current limiter 100 is shown in a perspective sectional view. The resistance component 100 comprises an NTC resistance material 10, which has a high resistance value at low temperatures, while the resistance values at high temperatures are greatly reduced. Accordingly, the resistance value is subject to a temperature dependency. The current limiter 100 is designed as a thermistor or NTC resistor. For this purpose, the resistance component 100 has two connection contacts 30 which are made laterally from a protective compound 40 which completely encloses or encapsulates the NTC resistance material 10. The protective compound 40 is formed, for example, as a housing. The connection contacts 30 are each designed, for example, as a wire element or a sheet metal part, for example a sheet metal stamped part. The current limiter 100 can be contacted electrically within an electrical circuit, for example as part of an electrical assembly and / or electrical system 200, via the connection contacts 30 projecting laterally out of the housing 40. For this purpose, each of the laterally guided out of the housing 40 connecting contacts 30 at least one connection region, which is preferably designed for electrical contacting of the current limiter 100 as a solder contact, welding contact or plug contact. Within the housing 40, the connection contacts 30 are connected to the NTC resistance material 10 in a material-locking manner via a connection material 20. The NTC resistor material 10 is preferably plate-like, so that the one terminal 30 a top 11 and the other terminal contact 30 a bottom 12 of the NTC resistor material 10 at least part of the surface, preferably the entire surface connects. Overall, therefore, results in the interior of the housing 40, a stack structure of terminal contacts 30, the NTC resistor material 10 and between the terminal contacts 30 and the top 11 and bottom 12 of the NTC resistor 10 arranged connection material 20. The connecting material 20 has a conscious low thermal conductivity. As a result, the NTC resistance material 10 is to be thermally insulated from the connection contacts 30. Good thermal insulation is exhibited when the thermal conductivity of the bonding material is 20 ≦ 20 W / mK. A particularly good thermal insulation is present at values between 1 and 10 W / mK. At the same time, the bonding material 20 has a low specific resistance, in particular ≦ 1 × 10 ^-3 Ωcm, preferably between 1 × 10 ^-5 Ωcm-1 × 10 ^-3 Ωcm. As a result, a lead resistance of the resistance component 100 is kept sufficiently low. Conductive adhesives are particularly suitable as connecting materials, with silver-conducting adhesives preferably being used. By applying a voltage between the connection contacts 30, a current can flow from one connection contact 30 via the respective connection material 20 and the NTC resistance material 10 to the other connection contact 30. As a result of the described stack construction within the housing 40, the connection contacts 30 are offset in a plane parallel to the NTC resistance material 10. With respect to a longitudinal extent, they pass out of the housing 40 in the opposite direction. On the other hand, depending on the application, one of the connection contacts 30 within the plane can be rotated in relation to the other connection contact 30 at an angle of less than 180 ° to 0 °.

In the Fig. 2a and 2 B a further embodiment of the current limiter 100 is shown. Unlike the execution in Fig. 1 the NTC resistor material 10 is now contacted via two differently shaped connection contacts 30. In this case, both connection contacts 30 basically have a carrier body 32, which are materially connected via the connection material 20 to the upper side 11 or lower side 12 of the NTC resistance material 10. The carrier body 32 are each on a the Connecting material 20 opposite side of the support body 32 connected to a connecting element 31. The connection element 31 of one connection contact 30 is in the form of a connection plate 31 "with a connection region 31a". Furthermore, the connection region 31a "is formed, for example, as a tab protruding toward a base surface of the connection plate 31 ', wherein the connection region 31a" can additionally have one or more bends in the tab section. The connection element 31 of the other connection contact 30 is designed essentially as a connection pin 31 ', which has a threaded area at its at least one end, The other end can in turn be connected to a base of a contact partner via a form, force or material connection, for example The connecting pin 31 'penetrates the stack structure formed from at least the NTC resistance material 10, the two carrier bodies 32, the arranged connecting materials 20 and the one connecting plate 32 "and projects beyond this at least with a partial section it threaded area. For this purpose, the individual elements forming the stack structure 10, 20, 32, 31 "each have a recess, in particular in the form of a bore, which are respectively aligned coaxially with respect to a common axis S and form a passage in the stack structure In this case, the clamping connection results from the fact that the present stack construction is accommodated in a clamping manner between the abovementioned base area of a contact partner and a closure element 35, for example a threaded nut, brought into operative connection with the threaded area of the connecting pin 31 ' For the electrical insulation of the connection pin 31 'having terminal contact 30 with respect to the other terminal contact 30, in particular with respect to the terminal plate 31 ", within the passage in the stack structure at least partially an insulating material, for example in Shape of an insulating sleeve 30, arranged electrically separating. In addition, a further metal sleeve 37 can be received within the insulating sleeve 36 in order, for example, to mechanically support the stack structure and the clamping closure. In addition, the stack construction may have further elements supporting the terminal closure. So can For example, on the side of the closure element 35, a washer 34 adjacent to the carrier body 32 complete the stack construction. On the then opposite side of the stack structure, a further disc, for example a spring washer 38, can also be accommodated within the stack structure and support the maintenance of the clamping closure.

For a particular application, the current limiter 100 is part of an electrical assembly / or plant 200 with live components, in particular an electric motor and / or a transformer. In this case, the electrical assembly and / or system 200 is charged by switching on and / or off operations on the current-carrying components caused current spikes. To reduce the current peaks current limiter 100 is used as a current limiter circuitry. If, as a part of the electrical assembly and / or installation 200, there is also a power source, for example a battery, with a power connection, the design can be followed Fig. 2a and 2 B as battery terminal 200 'integrally provide. In this case, the power connection is then to be provided as the connection pin 31 ', whereas, for example, a battery housing surface or other surface offers the counter surface necessary for the clamping connection.

In principle, in all embodiments of the current limiter 100, the connecting material 20 may be designed in the form of a metal foam, for example an aluminum metal foam, or a metallic wire mesh. A connection to the NTC resistance material 10 is then carried out, for example, by a sintered connection. In terms of the execution according to the Fig. 2a and 2 B Alternatively, a simple support contact is sufficient, which can be permanently maintained by a frictional connection due to the present terminal closure.

Claims (12)

1. Current limiter (100) having at least one connecting contact (30), wherein the current limiter (100) comprises an NTC resistance material (10), which is contacted by the at least one connecting contact (30) via an electrically conductive connecting material (20), wherein to increase thermal decoupling of the connecting contact (30) from the NTC resistance material (10), the electrically conductive connecting material (20) has a thermal conductivity of ≤ 20 W/mK, in particular 1 - 10 W/mK.
2. Current limiter (100) according to Claim 1,
   characterized in that
   the connecting material (20) has an electrical resistivity of ≤ 1*10^-3 Ωcm, in particular between 1*10^-5 Qcm - 1*10^-3 Ωcm.
3. Current limiter (100) according to either of Claims 1 and 2,
   characterized in that
   the connecting material (20) is an electric conductive adhesive, in particular a silver conductive adhesive, which connects the electric connecting contact (30) to the NTC resistance material (10) via an integral connection.
4. Current limiter (100) according to one of the preceding claims,
   characterized in that
   the connecting material (20) has a pore structure, preferably in the form of a metal foam or a metal wire braid.
5. Current limiter (100) according to one of the preceding claims,
   characterized in that
   the at least one connecting contact (30) comprises a connecting element (31, 31', 31"), which is preferably formed as a connecting metal sheet, a connecting wire or a connecting pin, in particular having a threaded region, for making electric contact with the resistance component (100).
6. Current limiter (100) according to one of the preceding claims,
   characterized in that
   the NTC resistance material (10) is contacted by at least two connecting contacts (30), so that when an electric voltage is applied, a flow of current from the one connecting contact (30) via the NTC resistance material (10) to the other connecting contact (30) is made possible, wherein the NTC resistance material (10) through which current flows exhibits a high heating behaviour because of the thermal decoupling relative to the connecting contacts (30).
7. Current limiter (100) according to Claim 6,
   characterized in that
   the NTC resistance material (10) is plate-like and has an upper side and an underside (11, 12), which, at least over some of the area, are contacted by respectively one connecting contact (30) .
8. Current limiter (100) according to Claim 7,
   characterized in that
   the NTC resistance material (10) has an aperture between the upper side and underside (11, 12), in particular in the form of a bore, wherein at least one of the contact connections (30) comprises a connecting element (31'), which penetrates the aperture and which is insulated electrically relative to the other contact connection (30).
9. Current limiter (100) according to one of Claims 5 to 8,
   characterized in that
   the at least one connecting contact (30) comprises a supporting body (32), which is arranged adjacent to the connecting material (20) and is connected to the connecting element (31, 31', 31") on a side of the supporting body (32) that is opposite the connecting material (20).
10. Current limiter (100) according to one of the preceding claims,
    characterized in that
    the at least one connecting contact (30) is formed as a solder, welding, plug-in or screw contact.
11. Current limiter (100) according to one of the preceding claims,
    characterized in that
    the NTC resistance material (10) is enclosed by an insulating protective compound (40), and the at least one connecting contact (30) projects out of the protective compound (40) with a connecting region (31, 31', 32").
12. Electric assembly and/or system (200) having at least one current-carrying component which is subjected to current peaks by switching operations, in particular during a switching-on or switching-off operation, by the application or removal of voltage on the at least one current-carrying component, and having a current limiter according to one of Claims 1 to 11 for reducing these current peaks.

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