DE4244721A1 - Electrical machine with fluid-cooled semiconductor elements - Google Patents

Abstract

The proposal is for a fluid-cooled power transistor arrangement, the semiconductor component (1) of which is arranged on an especially boardlike insulating substrate (9) via a metal electrode (7). The flat side of the semiconductor component (1) away from the insulating substrate and/or the side of the insulating substrate away from the semiconductor component is in direct heat-exchange contact with a forced flow of cooling fluid in a channel (13). Here, the insulating substrate (9) or the semiconductor component (1) may form wall regions of the coolant channel (13). In order to improve the heat transfer, the wall regions to be cooled and in contact with the cooling fluid may have a surface microstructure which reduces the boundary layer thickness of the coolant flow. The improvement in the cooling action reduces the structural space required so that the electric valves may be fitted in the immediate vicinity of the electric device to be switched. This is of special advantage in electric motors in order to reduce line inductance. The electric motor and the electric valves are advantageously cooled by the same coolant circuit.

Description

The invention relates to an electrical machine fluid-cooled semiconductor valves.

To control electrical devices and machines are in large scale semiconductor valves used. Relevant for the type of valve to be used is the one Size of the power to be controlled and on the other hand the maximum operating frequency. Thyristors and triacs at mains frequency, d. H. in the order of 50 Hz, used and allow power controls up to The order of 10 megawatts. For a variety of applications cases, especially in the control of electrical Machines, however, have higher switching frequencies up to close to the mega hertz range. For use cases power transistors of this type are used. in the Frequency range around 10 kHz with powers in sizes Order between 10 and 100 kW can BIMOS power transistors and IGBT power transistors (insulated Gate bipolar transistor) can be used. To higher ones  Frequencies, but at lower powers usually used MOSFET power transistors.

Power semiconductor elements have to be cooled. in the active area of the semiconductor element, the tempe temperatures do not exceed relatively low temperatures values increase. The heat loss must not only are dissipated through the semiconductor substrate, but also through electrode plating and more layered carrier plates on which the semiconductor substrate is applied. For power transistors of the above explained type, the semiconductor substrate is at least on one side with the entire active loading overlapping of the substrate, depending on the type, the col detector or base metal forming the drain electrode provided with plating. The remaining electrodes of the Transi stors, i.e. base and emitter or gate or source Electrode, are on the opposite flat side of the Semiconductor substrate accessible. With conventional lei The transistor connects to the flat base metal plating a fluid-cooled heat sink assembly, which is the heat loss of the active area of the transistor through the semiconductor substrate and the base metal plate leads through. Because the temperature in the active Range evenly within the specified limit values must be kept, it is important that the heat sink flat arrangement with uniform heat transfer egg properties to the semiconductor substrate of the semiconductor element joins. A direct connection of the heat sink to the semiconductor substrate is given the high span voltages (1000 V and more) and high currents (for example 100 amps) usually not possible, so the half conductor substrate are applied to an insulating substrate must, over the previous power transistor arrangement against the heat loss from the semiconductor element in the  Cooling arrangement must be derived. So it is common the semiconductor element on a copper plate on both sides Apply ceramic plate and the ceramic plate with the side remote from the semiconductor element on a Bracket, for example made of steel, to be soldered. The Steel plate is in turn with an intermediate layer a thermal paste on the water-cooled, for example te cooling element attached.

Suitable heat sink arrangements are known for example from EP-A-447 835. It has However, it has been shown that the switching power capacity of Power transistors are often not completely out can be used, or it can lead to failures of lei The transistor comes when the ceramic plate with the steel plate connecting solder layer or in the Thermal paste coating inhomogeneities remain, that leads to local overheating of the semiconductor element and can lead to the destruction of the transistor.

To improve the cooling effect of power transisto ren, it is known that on the side remote from the substrate connected supply strips with heat sinks provided the cooling of the active area of the half reinforce the conductor element (EP-A-252 429 and EP-A-449 435). It is also known (EP-A-260 370) on which flat side of the semiconductor remote from the active surface elements a heat sink with cooling fins attach cohesively and the cooling fins one Suspend cooling air flow.

Finally, it is known from DE-A-41 01 205 the plate-shaped semiconductor element of a power diode or a power thyristor in a cooling fluid channel to arrange and on both sides by compliant contact to contact. The contact brushes are made in each case from a multitude of individual ones parallel to each other  Pieces of wire passing through the along the semiconductor element flowing cooling fluid to be cooled. The contact brushes However, do not allow flat heat dissipation, as for cooling the semiconductor element of a power transmission would be required. As cooling fluid in DE-A- 41 01 205 water, air, oil or a hydrocarbon term coolant proposed.

In conventional, controlled by electric valves electrical devices or machines are the electrical ones Valves usually separate from the one to be controlled electrical device arranged, and for cooling the Valves on the one hand and the device on the other are in usually separate cooling circuits are provided. This especially applies to electrical machines, d. H. electrical generators or motors too, which have elec trical valves are switched and / or commutated should. Compact high-performance electrical machines densities are required if they are used to drive driving witness, for example motor vehicles, who used the, as for example in P. Ehrhart "The electrical Gearbox of magnetic motor for cars and buses "VDI Reports No. 178, 1991, pages 611 to 622 is. Suitable motors for such applications known for example from EP-A-159 005; Control scarf Lines for such motors are in EP-A-340 686 be wrote. Such motors have, for example Power of several 100 kW at an operating voltage of about 1000 V and corresponding currents.

It is an object of the invention to take up the space electrical machine, which is a generator or an engine, especially for use in a vehicle drive can act to further reduce and at the same time ver the operating behavior of the machine  improve.

Starting from an electrical machine whose field Windings on half controllable by a control circuit ladder valves, especially in the form of power transfers are connected to this goal is sufficient for the field winding to be in heat exchange contact with is a fluid cooling assembly, in their construction Cooling fluid channel integrated with the field windings the cooling arrangement a forced flow of a cooling fluid, especially a coolant, and that the Semiconductor valves also part of the assembly are the same as the cooling fluid in the cooling fluid channel if in heat exchange contact. The semiconductor valves are thus integrated in the electrical machine and are cooled together. The semiconductor valves can be more compact than usual. The spatial che proximity of the field windings to be switched to the half Conductor valves also reduce supply inductances vities considerably what the switching speed of the Semiconductor valves increased and thereby the operating behavior electrical machine.

In a preferred embodiment, the field wick form lungs of the electrical machine a stator winding and are distributed in the circumferential direction of the stator, as described for example in EP-A-159 005 is. To keep the supply lines as short as possible, the semiconductor valves on the stator in spatial after the field development associated with them or Field windings arranged.

The stator expediently a permanent magnet rotor, in particular a permanent magnet outer rotor machine comprising preferably has the field windings  load-bearing laminated core with a central recess, in the at least part of the semiconductor valves arranged is. Parts of the cooling fluid also run accordingly channel through this recess. At least part of the However, semiconductor valves can also be in the range of one axial end wall of the stator in heat exchange contact with parts of the cooling fluid channel running in this area stand. In both cases, there is already space available or already for parts of the cooling fluid channel anyway space used to accommodate the semiconductor valves be exploited. The arrangement should be so fen be that the field windings in the direction of flow of Cooling fluids behind the semiconductor valves in heat exchange contact with the cooling fluid to cool the Ensure priority for semiconductor valves.

In the semiconductor valves of the above electrical machine is preferably fluid cooled power transistor devices. To be more reliable than before for a uniform cooling of the semiconductor elements of the power transistor arrangement of the machine worry, power transistor arrangements are preferred provided which include:

• - A plate-shaped transistor semiconductor element, the on a first of its flat sides the whole Flat side covering, closed surface material cohesion sig on metal electrode connected to the semiconductor element trode and several on its second flat side Distance from each other cohesively on the semiconductor element attached connections,
• - one towards the first flat side across the half conductor element protruding, electrically insulating Insulator on which the semiconductor element with the Insulation carrier facing first flat side held  is and
• - One in heat transfer contact with at least one of the flat sides of the semiconductor element Cooling arrangement with a cooling fluid channel and means for Generating a forced flow of a cooling fluid in the Cooling fluid channel, in particular providing that the insulating support and / or the semiconductor element ment with one of its, if necessary, with a protective cover layered flat sides directly the cooling fluid Forced flow in the cooling fluid channel is exposed.

This embodiment is based on the idea of omitting the carrier plates provided in conventional power transistors for fastening to the heat sink except for the insulating carrier required for operation and instead of the insulating carrier or, if appropriate, provided with a thin protective coating, the semiconductor element directly and over its entire flat surface exposed to the cooling fluid. In this way, uniform cooling of the semiconductor element can be achieved since cohesive connections between consecutive layers of material, for example of carrier plates or the like, are limited to a minimum. The cooling fluid can be a gas, preferably a pressurized gas, such as nitrogen, or a liquid, such as water or oil, especially mineral-based or paraffin-based oil, or a synthetic oil; but it can also be a two-phase fluid, preferably a refrigerant or CO ₂ .

This idea is especially for IGBT power transistors suitable, but also for MOSFET power transistors, the services in the area at high operating frequencies of 100 kW and more and especially currents of 5-100 A  can switch at voltages of 100-1000 V.

The insulating support is used to attach the Utilized semiconductor element. With the insulating support can it is a carrier plate made of insulating material, in particular act special ceramics on which the semiconductor element its metal electrode closed surface, cohesive is appropriate. Alternatively, the insulating support can also as at least on a flat side with an iso lierschicht provided metal plate be formed, so for example as with an insulating oxide layer provided metal plate may be formed. The latter te configuration is particularly advantageous if the metal plate at the same time integrally the metal electrode forms.

The semiconductor element can completely in the cooling fluid can be arranged so that the cooling fluid both on the side of the suitably designed as a plate Insulating carrier as well as on the insulating carrier cooling side along the side of the semiconductor element flows. In a preferred embodiment with a plate-shaped insulating support is provided, however, that the insulating support forms a wall of the cooling fluid channel. This configuration is particularly useful if the insulating support has several semiconductor elements next to it each other, especially in the direction of the cooling fluid constraint flow arranged one behind the other, because this way several electrical valves, at for example in the form of one or more half or Have full bridges built in modules. Too special simple solutions can be achieved if at least two are opposite walls of the cooling fluid channel through plat ten-shaped, at least one semiconductor element load-bearing insulating supports are formed. To ensure an even  To achieve cooling and thermal expansion, the preferred two opposite insulating supports an equal number of semiconductor elements. In the simple Most configuration is sufficient if the opposing insulating carrier through sealing strips to an in Circumferential direction closed cooling fluid channel connected are.

In the embodiments explained above, at which the insulating support walls of the cooling fluid channel can form the semiconductor elements on the inside of the cooling fluid channel or also arranged on the outside be net, the latter design has the advantage that it can be connected more easily.

In conventional power transistors, the overlaps usually closed plate-shaped insulating supports flat the semiconductor element. In a preferred one Embodiment of the invention can be in contrast to Isolier carriers of conventional power transistors of the insulation carrier should also be designed so that it only partially with overlaps the semiconductor element, preferably just so much that the semiconductor element permanently on the insulator carrier can be attached. This has the advantage that also the flat side of the metal electrode Semiconductor element without interposing the Isolierträ gers are directly exposed to the cooling fluid flow can. Walls of the cooling fluid are thus used as insulating supports channel exploited. The insulator that it is can in turn be an insulating material plate provided with a continuous recess, at the Edges the semiconductor element is attached, and at least least with its first flat side through the recess exposed to the flow of cooling fluid. In particular the insulating support can do this transversely to the first flat side of the semiconductor element extending side walls of the Form cooling fluid channel, for example in  the form that the insulating support at least in the area of Has recess essentially U-shaped cross-section, so that on the edges of the through the U-shaped cross section formed leg sits on the semiconductor element.

It is understood that also in the design, at which of the insulating supports only partially with the Flat sides of the semiconductor element overlap, several of the Semiconductor elements on a common insulating support could be summarized in one module. This can happen, for example, in that the insulating support is designed as a profile body, the at least one or several in the direction of flow of the cooling fluid which carries arranged semiconductor elements, each of which comprises at least one power transistor. The for Formation of the cooling fluid channel used insulating carrier can in addition to those running transverse to the semiconductor element Side walls of the cooling fluid channel also parts of the in the Form plane of the semiconductor element extending walls.

In the embodiment explained above, the Semiconductor elements each for themselves and from each other be attached separately to the profile body. after the However, semiconductor elements according to conventional ones Manufacturing process in large numbers on a ge common semiconductor substrate is manufactured is in a preferred embodiment provided that each several semiconductor elements connected in one piece elements are attached to the profile body. This facilitates tern the seal of the cooling fluid channel.

A particularly simple embodiment in which more re semiconductor elements combined into a module provides that at least two oppose each other overlying walls of the cooling fluid channel in essence  chen completely by at least one semiconductor element are formed and the opposite Semiconductor elements through sealing strips to one in um direction closed cooling fluid channel connected are. The sealing strips can be formed by walls, which may be the width of the half lead in height surpass the element; it can happen with the sealing strips but also deal with comparatively flat strips.

The cooling fluid flow is forced flow to ensure adequate heat transfer guarantee. To pollution or contamination to prevent the semiconductor element or the insulating support the fluid cooling arrangement expediently comprises a closed cooling fluid circuit in which the Cooling fluid in succession through the cooling fluid channel and one Cooler, d. H. a heat exchanger that emits heat, circulates. So much for the cooling fluid, a two-phase fluid is used, the cooling fluid circuit preferably comprises an evaporator and a condenser, the cooling channel forms the evaporator. Such a kind Heat pump working arrangement allows even at low Adequate cooling of the fluid flow.

Especially with insulation supports that cover the entire surface with the Semiconductor element connected, the cooling capacity be increased if the insulating support on its the Semiconductor element facing away from the cooling fluid flow exposed side with a its heat exchange surface enlarging structure, especially ribs or front jump, is provided. As far as in the foregoing from plat ten-shaped insulating supports is said to be Structures should be included.

The use of ribs or the like for enlargement  tion of the heat exchange surfaces in cooling arrangements, such as Example heat sinks or the like is known. A Another preferred embodiment relates to measures through which the cooling capacity of the fluid cooling arrangement is increased can be. Such a fluid cooling arrangement cannot only with a power transistor arrangement of the above explained type are used, but is suitable generally given for cooling semiconductor elements if also with indirect cooling via a fluid cooled heat sink. It is provided that at least part of the wall surface of the cooling fluid channel that is exposed to the cooling fluid flow, or in a power transistor arrangement according to the previous one Art explained at least part of the surface of the insulating support or the semiconductor element with a reducing the thickness of the cooling fluid flow boundary layer Surface microstructure is provided. Here is from assumed that the cooling effect of the cooling fluid flow is greater, the smaller the thickness of the Flow boundary layer is within which the cooling fluid flow is subjected to shear and braked.

Surprisingly, it has been shown that microstructures, which reduce surface friction, an improvement in Cooling effect of a flow of cooling fluid cause it Reduce the boundary layer thickness. Microstructures that the Reduce the friction of liquids on surfaces known and became, among other things, on the skin of Haifi studied (D. Bechert and M. Bartenwerfer "The Viscous Flow on Surfaces with Longitudinal Ribs "J. Fluidmec. 1989), vol. 206, pages 105 to 129, and D. Bechert, G. Hoppe "On the Drag Reduction of the Shark Skin "AIAA Share Flow Control Conference, March 12-14, 1985, Boulder, Colorado).

Particularly suitable for improving cooling performance  have shown microstructures that act as a rib pattern with langge in the flow direction of the cooling fluid flow stretched out, essentially parallel micro-ribs are formed, especially when the micro ribs at least approximate to a cutting edge have young backs. The height of the ribs and their cross distance is suitably in the order of Boundary layer thickness or is smaller than the boundary layer thickness. The cooling fluid is conveniently a single-substance system.

The following are exemplary embodiments of the invention explained in more detail using a drawing. Here shows:

Figure 1 is a partially sectioned perspective view of a fluid-cooled power transistor arrangement.

Fig. 2 to 4 sectional views of variants of Lei stung transistor arrangement according to Fig. 1;

Fig. 5 is a perspective view of a ren fluidge cooled module with several Leistungstransisto;

Fig. 6 is a sectional view of the module, seen along a line VI-VI in Fig. 5;

FIG. 7 shows a sectional view of a variant of the module from FIG. 5;

Fig. 8 is a sectional view of a multi-module assembly;

Fig. 9 is a schematic representation of a liquid cooling arrangement for a power transistor;

FIG. 10 is a schematic diagram of a refrigerant cooling arrangement for a power transistor;

Fig. 11 is a schematic representation of a cooling arrangement with gaseous cooling fluid for a power transistor;

Fig. 12 is a perspective view of a surface microstructure for improving the cooling performance of a fluid-cooled electric valve;

Fig. 13 is a variant of the surface microstructure,

Fig. 14 is a sectional view through the surface microstructure, seen along a line XIV-XIV in Fig. 13;

Fig. 15 is a schematic partial section controlled by a fluid-cooled electric valves of electrical machine, and

Fig. 16 and 17, partial sections through variants of the electric machine.

Fig. 1 shows in a representation in which the thickness-ratios of the individual components are not to scale, a power transistor module, here an IGBT module, circuit having a first chip or semiconductor element 1 having a plurality of power transistors comprehensive transistor and a second chip or Semiconductor element 3 , which contains the control electronics and protective circuit for the power transistors and is connected via connecting lines 5 to the first semiconductor element 1 . The semiconductor elements 1 , 3 are firmly bonded to a metal plating 7 , for example eutectically produced, in particular consisting of copper.

The metal plating 7 forms the collector of the power transistors of the semiconductor element 1 and, like the semiconductor element 1, is connected with a ceramic insulating plate 9 in a material, flat and homogeneous manner. The insulating plate 9 is partially held edge in rails 11 of a circumferentially-closed coolant channel 13, in such a way that both of the insulating plate 9 facing away from the flat side of the semiconductor element 1 and the the semiconducting terelement 1 facing away from the flat side of the insulating plate 9 a direction indicated by arrows 15. Cooling fluid flow is exposed. Control lines 17 in the form of thin wires and busbars 19 in the form of copper strips connect the circuits of the semiconductor elements 1 , 3 to connections 21 arranged on the outside of the cooling channel 13 . Of the two semiconductor elements, at least the semiconductor element 1 is essentially directly exposed to the cooling fluid flow 15 as far as the heat transfer is concerned, so that it is cooled over the entire surface from both sides. Despite compact dimensions, a high power density can be achieved in this way. Since only the metal plating 7 remains between the semiconductor element 1 and the insulating plate 9 as a single intermediate layer, can be with reasonable certainty a homo genetic material connection between the semiconductor element 1 and insulating plate 9 achieve what the temperature stability and reliability of the IGBT module benefits. The rail 11 is preferably elastic and insulating (z. B. made of silicone rubber).

In the cooling channel 13 , a plurality of IGBT modules can be arranged one behind the other in the direction of flow 15 on a common insulating plate, as indicated at 23 . It is understood that the cooling fluid does not have to be gelei tet on both sides of the insulating plate 9 through the cooling channel 13 . In individual cases, it may be sufficient if a cooling fluid flows through only on the side facing away from the semiconductor elements 1 , 3 between the insulating plate 9 and the cooling channel 13 . Alternatively, only that part of the cooling channel 13 which covers the semiconductor elements 1 , 3 can also be present or used for the cooling fluid flow. It goes without saying that instead of IGBT modules, the semiconductor elements 1 , 3 can also be implemented with other types of power transistors, for example bipolar power transistors or MOSFET power transistors with or without driver stages or protective circuitry. The control circuit provided on the semiconductor element 3 can optionally be replaced by an external electronic circuit.

Fig. 2 shows a variant of the IGBT module, which differs from the structure of Fig. 1 only in that the cohesive and all-over the metallization 7 a attached to the ceramic insulating plate 9 a, again plate-shaped semiconductor elements 1 a, 3 a except for the contact points of the control lines or the contact strips 19 a are coated with a thin protective layer 25 , which protects the active zone of the semiconductor elements 1 a, 3 a from contamination with the cooling fluid. The protective layer 25 can be, for example, a coating made of silicone rubber, which is covered on the outside by a metal foil. For further explanation, here, as in the exemplary embodiments described below, reference is made to the preceding figures and their description, reference numerals from the previous figures being used to designate components having the same effect, but with the addition of a different letter.

Fig. 3 shows a variant of an IGBT module, the semiconductor elements 1 b, 3 b on one of the function after the metallization 7 corresponding metal plate 7 b, in play as a copper plate, closed surface, are integrally fixed. The metal plate 7 b is provided outside the areas of the semiconductor elements 1 b, 3 b, but at least on the flat side facing away from the semiconductor elements 1 b, 3 b with an insulating layer, for example a thin oxide layer 9 b. In addition to the electrode function, the metal plate 7 b takes over the fastening function of the insulating plate 9 from FIG. 1.

Fig. 4 shows a variant in which the semiconductor elements 1 c, 3 c are arranged over the entire area on a metallization 7 c, which also has an electrode function. The insulating plate 9 c, however, is provided with a continuous, at least by the semiconductor element 1 c containing the power transistors overlapped recess 27 , through which the cooling fluid is in direct heat exchange contact with the metallization 7 c and thus the semiconductor element 1 c, which can occur Heat dissipation is facilitated. The recess 27 overlaps the semiconductor element 1 c essentially completely. The semiconductor element 1 c is supported only in the edge region of the recess 27 on the insulating plate 9 c. As indicated in Fig. 4 by a dashed line 13 c ge, the cooling channel together with the insulating plate 19 c also have the shape of a profile tube, here a possibly one-piece rectangular tube, on which the semiconductor elements 1 c, 3 c subsequently and be attached from the outside. It is understood that Derar term cooling channel constructions can also be used in the variants of FIGS . 1 to 3.

Fig. 5 shows an embodiment that allows several IGBT modules, each of which, as in the examples explained above, forms an electric valve to valve modules, in particular in the form of half bridges or full bridges, partly in parallel or series connection, if appropriate also to combine several of these bridges. The module generally designated 29 comprises two mutually parallel, made of ceramic material insulating plates 9 d, which are connected along their longitudinal edges by preferably elastic sealing strips 31 to a circumferentially closed cooling channel 13 d. Arrows 15 d again indicate the direction of flow of the cooling fluid. Each of the two insulating plates 9 d carries on its flat side, which is remote from the channel, a plurality of semiconductor elements 1 d arranged one behind the other in the direction of flow 15 d, each of which forms a separate IGBT valve. The number of semiconductor elements 1 d on each of the two insulating plates 9 d is the same. The semiconductor elements 1 d are, as can be seen in FIG. 6, in turn, metallizations 7 d on the insulating plates 9 d applied positively over the entire surface. The connections can be seen at 19 d. Semiconductor elements with control circuits or the like can be present, but are not shown. It is understood that the variants of FIGS. 2 to 4 can also be used with the module 29 .

In Fig. 5, the semiconductor elements 1 d of each valve are separated from each other and spaced 9 th on the Isolierplat. Since semiconductor elements of the type in question are usually produced in the same design several times next to each other on semiconductor substrate wafers, several of the semiconductor elements 1 d can optionally also be connected in one piece, as is indicated in FIG. 5 at 33 .

Fig. 7 shows a further variant, which is based on integrally interconnected semiconductor elements 1 e. The semiconductor elements 1 e of several electrical valves are cut out together from the above-mentioned substrate disk and provided with a metallization 7 e. The semiconductor element plates 1 e are arranged parallel to one another and are connected to one another via sealing spacer strips 31 e. Together with the spacer strips 31 e, the semiconductor element plates 1 e limit a cooling channel 13 e closed in the circumferential direction. The connections of the valves are indicated at 19e.

FIG. 8 shows schematically how several of the modules 29 according to FIGS. 5 to 7 can be combined to form one structural unit. The modules 29 f are held in a common housing 35 parallel to one another in elastic rails 37. Their cooling duct 13 f is connected at one end to a common cooling fluid supply duct 39 and at the other end to a common cooling fluid discharge duct 41 . The modules 29 f are assigned in the module level arranged support webs 43 which are provided with connecting members 45 . The connecting members 45 are used to connect the control lines and busbars and are, as indicated by lines 19 f, connected to the semiconductor elements 1 f of the modules 29 f.

The cooling fluid can be a gas under atmospheric pressure, for example nitrogen, a liquid, such as water, or an oil, specifically a mineral-based oil, a paraffin-based one, or a synthetic oil. However, two-phase fluids, such as refrigerants or CO _2, are also suitable. The cooling fluid is circulated through the cooling channel in a forced flow.

Fig. 9 shows an embodiment of a Kühlanord voltage with a liquid as the cooling fluid. The Kühlflüs liquid is supplied by a pump 47 via a cooler or heat exchanger 49 to the cooling channel 13g in the circuit.

The cooling arrangement comprises a temperature control circuit 51 , which measures the temperature of the indicated at 1 g, in heat exchange contact with the cooling liquid semiconductor element by means of a temperature sensor 53 and in example by means of a fan 55 , which affects the cooling performance of the cooler 49 , the semiconductor temperature to one holds at 57 adjustable setpoint. For the sake of completeness, a compensation tank for cooling liquid is indicated at 59 .

Fig. 10 shows a variant in which a two-phase refrigerant is used for cooling the semiconductor elements 1 h. In the manner of a heat pump, the refrigerant compressed by a compressor 61 is cooled and liquefied in a capacitor 63 , for example by means of a fan 65 . The cooling channel 13 h forms an evaporator in which the liquid refrigerant is introduced via a nozzle 67 or the like and is evaporated by absorbing heat. The use of the refrigerant as the cooling fluid allows the cooling arrangement to be made more compact.

Fig. 11 for completeness shows a closed-end coolant circuit for a gaseous cooling fluid that is compressed by a compressor 69, before it subsequently in a cooler or heat exchanger 71 abge cooled and then the cooling passage 13 clock-i for the Wärmetauschkon with the semiconductor element 1 i is supplied. It goes without saying that the variants of FIGS. 10 and 11 can also be temperature-controlled.

The heat transfer from the surfaces to be cooled Semiconductor elements or the closed surface and fabric metal connected to the semiconductor elements plating and insulating plates can be especially for liquids as cooling fluid through surface micro  improve structures that limit the boundary layer thickness of the Reduce cooling fluids. The boundary layer is concerned the area of the cooling fluid flow in which the Flow rate through the friction and Fluidhaf tion on the wall surface is reduced. It has shown that "shark skin" like surface structure not only the fluid friction on the wall surface reduce, but also reduce the boundary layer thickness. As the boundary layer thickness decreases, the Distance of the heat emitting surfaces to the currents the areas of the heat-absorbing cooling fluid.

Fig. 12 shows an example of such, the boundary layer thickness-reducing surface microstructure. The microstructure consists of a plurality of ribs 72 which are parallel to one another and run in the flow direction 15 k of the cooling fluid and whose side flanks taper in a wedge shape to form a cutting-like back 73 . The ribs 72 merge into one another in concavely curved grooves. The height of the ribs and their distance from one another is preferably less than the boundary layer thickness.

The rib shape shown in FIG. 12 has proven to be expedient; however, other rib shapes are also useful, for example ribs with a rounded back or trapezoidal ribs or the like.

13 and 14 show further boundary layer-reducing surface structures . These figures show a plan view of diamond-shaped knobs or elevations 75 which rise in a wedge-shaped manner in the direction of flow 15 l of the cooling fluid running perpendicular to the surface to be cooled. The roof surfaces formed by the elevations 75 can be flat or also be provided with microrip pen similar to FIG. 12, which is indicated at 72 l. Instead of the diamond-shaped contour shown in FIG. 13 in plan view, the elevations 75 can also have other, generally polygonal contours. Triangular shapes are also suitable, which have 15 l with one of their corners in the direction of flow. Also in the embodiment of FIGS . 13 and 14, the dimen sions of the elevations 75 are in the order of the limit layer thickness.

A major advantage of the valve structure according to the invention ren is that the space required due to the verbes total cooling can be reduced overall. The electrical valves can thus be better than before in close proximity to the electri to be controlled accommodate devices. This is special Advantage in electrical machines, such as elec with electric motors or through the electric valves to be switched field windings, because the field windings then have very short leads can be connected. By shortening the allowance the circuit inductance can be reduced and thus who shortens the response time of the electric valves the.

Fig. 15 shows an electrical machine with a stator 77 and a rotatable around a rotation axis 79 rotor 81st The machine can be a generator or a motor. The stator 77 comprises, in a conventional manner, a soft iron laminated core 83 which bears windings 85 on a large number of circumferentially distributed poles, not shown in more detail. The rotor 81 encloses the laminated core 83 with a plurality of permanent magnets 87 which are alternately poled in the circumferential direction. The laminated core 83 and the windings 85 are accommodated in a stator housing 89 made of plastic, which in turn is held on a stationary, for example plate-shaped suspension 91 . Electrical machines of this type are known, for example from EP-A-159 005, and are therefore not to be described further.

Since electrical machines of the type mentioned can be dimensioned for very high powers of, for example, 100 kW with a comparatively small space requirement, the windings 85 are arranged in one or more chambers 93 , which are connected via a supply connection 95 and a discharge connection 96 to the cooling fluid circuit of a cooling arrangement are. The cooling arrangement can be a cooling arrangement according to FIGS. 9 to 11.

The laminated core 83 encloses a central recess 97 in which the stator housing 89 forms a further chamber 99 . The chamber lies in the cooling fluid flow circuit of the cooling arrangement between the supply connection 95 and the chamber 93 of the winding 85 , so that the cooling fluid flows through it before it heats up on the winding 85 . In the chamber 99, the winding 85 associated electrical valves 101 located in close proximity to the to be switched winding 85th The electrical valves can be conventional power transistors, but are preferably fluid-cooled power transistors of the type explained with reference to FIGS . 1 to 8. The connecting lines between the electrical valve 101 and the winding 85 run directly through the stator housing 89 and are preferably directly connected to the valves 101 without detachable terminals or the like, for example welded or soldered on. It can also be considered to weld the wire ends of the windings 85 directly to the semiconductor elements of the valves.

FIG. 16 shows a variant of the electrical machine with a stator 77 m and a rotor 81 m rotating about an axis of rotation 79 m, which differs from the electrical machine of FIG. 15 essentially only in that the electrical valves 101 m do not are arranged inside the chamber 99 m of the stator housing 89 m through which the cooling fluid flows, but are separated therefrom by a partition 103 . This ensures that the electrical valve's 101 m also come into direct contact with the cooling fluid in heat exchange contact, preferably before the heat exchange contact takes place with the winding.

Fig. 17 shows a double motor which can be used in particular as a vehicle drive and which axially carries a stator 77 n on both sides of a suspension plate 91 n, to which a permanent magnet 81 n rotating around a common axis of rotation 79 n is assigned. The electrical valves 101 n which are not shown in detail but which are arranged according to FIG. 15 are arranged in the region of the axial end faces of the stators 77 n, again in the immediate vicinity of the windings to be switched by them. The valves 101 n are in the embodiment of FIG. 17 separated by a partition with the cooling fluid circuit of the Kühlan arrangement of the windings in heat exchange contact. According to the arrangements in FIGS. 1 to 3, the dividing wall can be insulating supports of semiconductor elements; however, the electrical valves or semiconductor elements can also be arranged analogously to FIG. 15 within a chamber lying in the cooling fluid flow path. It goes without saying that the electrical machine can comprise electrical valves arranged in accordance with FIGS. 15 and 16 as well as in FIG. 17.

Claims (33)

1. Electrical machine, the windings ( 85 ) of which are connected to controllable semiconductor valves ( 101 ), in particular in the form of power transistors, characterized in that
that the windings (85) are in heat exchange contact with a fluid cooling arrangement, in which a Bauein unit with the windings (85) combined cooling fluid channel (93, 99), the cooling arrangement comprises a forced flow of a cooling fluid, in particular a cooling liquid, generated
and that the semiconductor valves ( 101 ) are also part of the assembly and are also in heat exchange contact with the cooling fluid in the cooling fluid channel ( 93 , 99 ). 2. Machine according to claim 1, characterized in that the windings ( 85 ) form a stator winding and are arranged distributed in the circumferential direction of the stator ( 77 ) and that the semiconductor valves ( 101 ) on the stator ( 77 ) in spatial proximity to the verbun with them which winding ( 85 ) or windings are arranged. 3. Machine according to claim 2, characterized in that the stator ( 77 ) is associated with a permanent magnet rotor ( 81 ), in particular a special permanent magnet outer rotor surrounding the stator ( 77 ). 4. Machine according to claim 2 or 3, characterized in that the stator ( 77 ) has the windings ( 85 ) carrying laminated core ( 83 ) with a central cut-out ( 97 ; 97 m) and that at least some of the semiconductor valves ( 101 ; 101 m) are in heat exchange contact with an area ( 99 ; 99 m) of the cooling fluid channel ( 93 , 99 ) running in the recess ( 97 ). 5. Machine according to one of claims 2 to 4, characterized in that at least a part of the semi-conductor valves ( 101 n) with an axial end wall of the stator ( 77 n) brought up region of the cooling fluid channel is in heat exchange contact. 6. Machine according to one of claims 1 to 5, characterized in that the windings ( 85 ) of a cooling fluid channel ( 93 , 99 ) forming housing ( 89 ) are closed and in direct heat exchange contact with the cooling fluid in the cooling fluid channel ( 93 , 99 ) stand. 7. Machine according to one of claims 1 to 6, characterized in that the windings ( 85 ) in the flow direction of the cooling fluid behind the semiconductor valves ( 101 ) are in heat exchange contact with the cooling fluid. 8. Machine according to one of claims 1 to 7, characterized in that the semiconductor valves form the power transistors have:

• - A plate-shaped transistor semiconductor element ( 1 ) which on a first of its flat sides covering the entire flat side, cohesively with the semiconductor element ( 1 ) connected metal electrode ( 7 ) and on its second flat side several cohesively at a distance from each other Semiconductor element attached connections ( 5 ) carries,
• - In the direction of the first flat side over the semiconductor element ( 1 ) projecting, electrically insulating insulating support ( 9 ; 7 b, 9 b), on which the semiconductor element ( 1 ) with the insulating support ( 9 ; 7 b, 9 b) facing the first flat side is held
• - And a in heat transfer contact with at least one of the flat sides of the semiconductor element ( 1 ) standing fluid cooling arrangement with a Kühlfluidka channel ( 13 ) and means for generating a forced flow ( 15 ) of a cooling fluid in the cooling fluid channel ( 13 ), the insulating support ( 9 ; 7 b, 9 b) and / or the semiconductor element ( 1 ) with at least one of its flat sides is directly exposed to the cooling fluid forced flow in the cooling fluid channel ( 13 ).

9. Machine according to claim 8, characterized in that the semiconductor element ( 1 ; 1 a; 1 d) with its metal electrode ( 7 ; 7 a; 7 d) closed surface cohesive sig on a carrier plate ( 9 ; 9 a; 9 d) made of insulating material, in particular ceramic, is attached and at least the carrier plate ( 9 ; 9 a; 9 d) is exposed to the cooling fluid forced flow. 10. Machine according to claim 8, characterized in that the insulating support is designed as at least on a flat side with an insulating layer ( 9 b) provided metal plate ( 7 b). 11. Machine according to claim 10, characterized in that the metal electrode and the metal plate ( 7 b) are integrally formed. 12. Machine according to one of claims 8 to 11, characterized in that the insulating support ( 9 ; 9 d) is designed as a plate and a wall of the cooling fluid channel ( 13 ; 13 d). 13. Machine according to claim 12, characterized in that the insulating support ( 9 ; 9 d) carries several Semiconductor elements ( 1 ; 1 d) side by side, in particular in the direction of the cooling fluid forced flow ( 15 ; 15 d) arranged one behind the other. 14. Machine according to claim 12 or 13, characterized in that at least two opposite walls of the cooling fluid channel ( 13 d) are formed by plate-shaped, each having at least one semiconductor element ( 1 d) de insulating carrier ( 9 d). 15. Machine according to claim 14, characterized in that the two opposite insulating supports ( 9 d) carry an equal number of semiconductor elements ( 1 d). 16. Machine according to claim 14 or 15, characterized in that the opposite Isolierträ ger ( 9 d) are connected by sealing strips ( 31 ) to a circumferentially closed cooling fluid channel ( 13 d). 17. Machine according to one of claims 8 to 11, characterized in that the insulating carrier ( 9 c) formed in particular as an insulating material carrier plate has a continuous recess ( 27 ) covered by the semiconductor element ( 1 c), at the edges of which the semiconductor element ( 1 c) is attached, and that at least the first flat side of the semiconductor element ( 1 c) is exposed through the recess ( 27 ) through the cooling fluid flow. In that the insulating support (9 c) transversely (c 1) forms 18. Machine according to claim 17, characterized in that the first flat side of the semiconductor element extending side walls of the coolant channel (13 c). 19. Machine according to claim 18, characterized in that the insulating support ( 13 c) is formed as a profile body, the at least one or more preferably integrally connected, in the flow direction of the cooling fluid arranged one behind the other semiconductor elements ( 1 c) carries, of which each comprises at least one power transistor. 20. Machine according to claim 8, characterized in that at least two opposite walls of the cooling fluid channel ( 13 e) essentially exclusively by at least one, preferably by several integrally connected, in the flow direction of the cooling fluid one behind the other arranged semiconductor elements ( 1 e) , each of which comprises at least one power transistor, are formed and the opposing semiconductor elements ( 1 e) are connected by sealing strips ( 31 e) to a circumferentially closed cooling fluid channel. 21. Machine according to one of claims 8 to 20, characterized in that the fluid cooling arrangement comprises a closed cooling fluid circuit ( 13 g, 47 , 49 ; 13 h, 61 , 63 ; 13 i, 69 , 71 ) in which the cooling fluid successively circulated through the cooling fluid channel ( 13 g; 13 h; 13 i) and a cooler ( 49 ; 63 ; 71 ). 22. Machine according to claim 21, characterized in that the cooling fluid circuit comprises an evaporator and a condenser ( 63 ) and that the cooling channel forms the evaporator ( 13 h). 23. Machine according to one of claims 8 to 22, characterized in that the cooling fluid is a gas, in particular gas under atmospheric pressure, preferably N ₂ , or a liquid, preferably water or oil, especially mineral-based or paraffin-based oil or a synthetic oil, or a two-phase fluid, preferably a refrigerant or CO ₂ . 24. Machine according to one of claims 8 to 23, characterized in that the insulating support ( 9 ; 7 b, 9 b) is exposed to the cooling fluid flow and on its side facing away from the semiconductor element ( 1 ; 1 b) with a structure which enlarges its heat exchange surface, in particular ribs ( 72 ) or projections ( 75 ) is provided. 25. Machine according to one of claims 8 to 24, characterized in that the semiconductor element ( 101 ), the cooling channel ( 99 ) and an electrical device to be controlled by means of the semiconductor element ( 101 ), in particular a field winding ( 85 ) of an electrical machine a unit are combined and that the elec trical device is also in heat exchange contact with the fluid cooling assembly for cooling. 26. Machine according to claim 25, characterized in that the electric device is directly connected to the semiconductor element (101) and / or at a contact portion of the semiconductor element (101) supporting the insulating support (103). 27. Machine according to one of claims 8 to 26, characterized in that at least a part of the cooling fluid flow exposed wall surface of the cooling fluid channel ( 13 ) and / and the insulating support ( 9 ; 7 b, 9 b) and / or the semiconductor element ( 1 ) is provided with a surface microstructure ( 72 ; 75 ) which reduces the thickness of the cooling fluid flow boundary layer. 28. Machine according to claim 27, characterized in that the microstructure is designed as a rib pattern with in the flow direction ( 15 k) of the cooling fluid flow elongated, substantially parallel micro-ribs ( 72 ). 29. Machine according to claim 28, characterized in that the micro-ribs ( 72 ) at least approximately to a cutting edge ( 73 ) have tapered backs. 30. Machine according to claim 28 or 29, characterized in that the height of the ribs ( 72 ) and their transverse distance is of the order of magnitude or less than the boundary layer thickness. 31. Machine according to one of claims 27 to 30, characterized in that the microstructure comprises a plurality of micro-surveys preferably arranged in a grid ( 75 ). 32. Machine according to claim 31, characterized in that the micro elevations ( 75 ) have a polygonal shape in the top view, in particular triangular or quadrangular shape. 33. Machine according to claim 31 or 32, characterized in that the micro elevations ( 75 ) seen in a direction extending in the flow direction ( 15 l) rise in a wedge shape perpendicular to the surface.