WO2006069571A1

WO2006069571A1 - An electromagnetic module for a frequency converter

Info

Publication number: WO2006069571A1
Application number: PCT/DK2004/000926
Authority: WO
Inventors: Jørgen Jessen MØLLER; Preben Holst; Lasse Nielsen
Original assignee: Danfoss Drives A/S
Priority date: 2004-12-29
Filing date: 2004-12-29
Publication date: 2006-07-06

Abstract

The present invention relates to an electromagnetic module comprising a mounting cup (1) formed as a heat sink with cooling fins (2) being arranged on an exterior surface part of the mounting cup. The module further comprises at least one electromagnetic coil (8) arranged in the mounting cup, the at least one electromagnetic coil being at least partly embedded into a thermally conducting potting material (10) so as to ensure transfer of heat from the at least one electromagnetic coil to the heat sink of the mounting cup, the at least one electromagnetic coil being accessible from the outside of the mounting cup. The present invention further relates to a mounting cup for an electromagnetic module.

Description

AN ELECTROMAGNETIC MODULE FOR A FREQUENCY CONVERTER

The present invention relates to an electromagnetic module. In particular, the present invention relates to an inductive electromagnetic module to be included in a frequency converter.

BACKGROUND OF THE INVENTION

US 6,392,519 discloses a mounting apparatus for an electromagnetic device such as a transformer. The apparatus includes a generally planar metallic plate as a first heat sink, and a metallic mounting cup as a second heat sink. The mounting cup includes a cavity configured to receive the electromagnetic device, the cavity being defined by a base, and an axially-extending annular sidewall extending from the base to a flange portion of the mounting cup.

The mounting cup includes first and second passages for allowing the leads of first and second windings of the electromagnetic device to be routed out of the cavity. The cavity is filled with a polyurethane potting resin, and the mounting cup, including the potted electromagnetic device, is mounted to the plate heat sink using fasteners. The mounting cup, which surrounds the electromagnetic device, in combination with the potting resin provides improved thermal transfer to the plate heat sink, as well as providing resistance to vibration and shocks.

It is an object of the present invention to provide a replaceable inductive module for an electronic device, the replaceable inductive module being prepared for cooling.

SUMMARY OF THE INVENTION

The above-mentioned object is complied with by providing, in a first aspect, an electromagnetic module comprising

- a mounting cup formed as a heat sink with cooling fins being arranged on an exterior surface part of the mounting cup, and

- at least one electromagnetic coil arranged in the mounting cup, the at least one electromagnetic coil being at least partly embedded into a thermally conducting potting material so as to ensure transfer of heat from the at least one electromagnetic coil to the heat sink of the mounting cup, the at least one electromagnetic coil being accessible from the outside of the mounting cup.

The shape of the mounting cup may in principle be arbitrary. However, an appropriate form of the mounting would be a mounting cup having a substantially plane base plate with an axially extending sidewall from said base plate. The axially extending sidewall forms an opening opposite the plane base plate. The mounting cup is made of a heat conducting material such as aluminum, steel etc. The dimensions of the mounting cup match the size and the number of electromagnetic coils to be accommodated in the mounting cup.

The cooling fins on the exterior surface part of the mounting cup may be linear cooling fins arranged in an axial direction of the mounting cup. Alternatively, the cooling fins may be arranged essentially perpendicular to the axial direction of the mounting cup.

The thermally conducting potting material may be polyurethane potting resin. Suitable potting materials could be a combination of the SikaForce 1821 hardener and the SikaForce 2022-2 mould compound. The inductance of the at least one electromagnetic coil varies in accordance with its specific application. Thus, the inductance may in principle have any value. However, for most practical applications the at least one electromagnetic coil may have an inductance within the range 10 μH - 1000 mH, such as in the range 100 μH - 100 mH, such as in the range 200 μH - 10 mH, such as in the range 500 μH - 1 mH.

The electromagnetic module may further comprise terminal members for connecting the at least one electromagnetic coil to electronic circuits external to the electromagnetic module. The terminal members may be at least partly embedded into the potting material, each terminal member comprising a threaded portion so as to be capable of receiving a threaded bolt in order to fixate a conductor to each terminal member.

In one specific embodiment of the present invention the electromagnetic module comprises two electromagnetic coils, each electromagnetic coil being at least partly embedded into the thermally conducting potting material. The inductances of these two electromagnetic coils are preferably matched so that the two electromagnetic coils form a set of substantially identical coils. The electromagnetic coils may be wounded around the center leg of an EI core. In one embodiment of the present invention the electromagnetic coils are wounded around the same center leg of an EI core.

In a second aspect, the present invention relates to an electromagnetic module comprising

- a mounting cup being thermally conducting, and - an electromagnetic device arranged in the mounting cup, the electromagnetic device being at least partly embedded into a thermally conducting potting material so as to ensure transfer of heat from the electromagnetic device to the heat sink of the mounting cup, the electromagnetic device comprising at least three electromagnetic coils each having a set of accessible coil ends.

The at least three electromagnetic coils may be wounded around the same core, and constitute in combination, a common mode coil. The thermally conducting potting material may be a polyurethane potting resin.

In a third aspect, the present invention relates to a mounting cup comprising

- a bottom part formed as a heat sink, and

- a sidewall part extending away from the bottom part and forming an opening opposite the bottom part,

wherein an exterior surface portion of the bottom part comprises linearly arranged cooling fins.

Preferably, the mounting cup is fabricated as a one-piece aluminum mounting cup. The sidewall part of the mounting cup may define a center axis. The cooling fins may extend away from the exterior surface portion of the bottom part in a direction being substantially parallel with the center axis.

In a fourth aspect, the present invention relates to a frequency converter comprising an electromagnetic module according to the first and/or second aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be explained with reference to the accompanying figures, wherein

Fig. 1 shows a three-dimensional top-view of a first module according to the present invention,

Fig. 2 shows a three-dimensional view from the bottom of a first module according to the present invention, Fig. 3 shows a cross-sectional view of a first module according to the present invention,

Fig. 4 shows a three-dimensional top-view of a mounting cup according to the present invention,

Fig. 5 shows a cross-sectional view of a second module according to the present invention,

Fig. 6 shows a three-dimensional top-view of a second module according to the present invention, and

Fig. 7 shows a frequency converter comprising a first and a second module according to the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 shows a first electromagnetic module according to the present invention. The module comprises a one-piece aluminium mounting cup 1. The mounting cup has a bottom part 2 with exterior cooling fins arranged thereon. The sidewalls 3 extend from the bottom part 2 and form an opening through which electronic devices or components can enter the mounting cup. At the interface between the sidewalls 3 and the bottom part 2 a mounting flank 4 with holes 5 is provided. Upon mounting of the module in an electronic device this flank 4 abuts a corresponding flank of the housing of the electronic device, and the module is fixed to the housing with bolts inserted in holes 5. In order to obtain a waterproof interface (up to IP 66) between the mounting cup and the housing of the electronic device, a flexible seal 6 (see Fig. 2) is provided between the flank of the mounting cup and the corresponding flank of the housing.

The cooling fins 2 are provided as linear fins. However, curved or other types of non-linear cooling fins are also applicable. As seen in Fig. 2 the cooling fins are slightly angled relative to the module. This angling of the cooling fins is provided because the cooling fins also act as air guides when the mounting cup is mounted in the housing of the electronic device. Thus, the angled cooling fins of the mounting cup and cooling fins of the housing itself cooperate to obtain an effective air flow around the housing of the electronic device. Fig. 2 also shows the exterior part of an indentation 7 formed in the bottom part of the mounting cup. As discussed later this indentation is adapted to accommodate at least part of an electronic device or component mounted in the mounting cup.

Returning to Fig. 1 two electromagnetic coils 8 and 9 are mounted in the mounting cup. The coils are at least partly embedded into the thermally conducting potting material 10, see Fig. 3. The potting material is a polyurethane potting resin. Each coil is wounded around the centre leg of an EI core. The ends of the coils 11 and 12 are externally accessible via terminals 13a, 13b and 14a, 14b. Each terminal comprises a threaded portion adapted to receive a bolt for fixation of a wire or another terminal. The inductance may in principle take any value, but for most practical applications each of the coils may have an inductance within the range 10 μH - 1000 mH, such as in the range 100 μH - 100 mH, such as in the range 200 μH - 10 mH, such as in the range 500 μH - 1 mH. It should be understood that the mentioned inductance ranges are by no means limiting to the scope of protection of the present invention, since the size of the inductance is strongly coupled to the device to which the coils are connected.

Fig. 1 shows the module without the thermally conducting potting material, whereas if Fig. 3 the coils 8 and 9 are embedded into the potting material 10. As seen in Fig. 3, only the terminal 13a and 14a (13b and 14b are not shown) may be seen at the surface of the potting material.

The bottom part of the mounting cup comprises two indentations 15 and 16. These indentations are adapted to accommodate at least part of the coils 8 and 9. While parts of the coil enter the indentations the outer legs of the EI cores 17 and 18 rest on an interior bottom surface of the mounting cup. The cooling fins extend away from the bottom part in an essentially linear manner. The length of the cooling fins in the axial direction is within the range from 5 cm to 15 cm. It should be noted that the length of those cooling fins or parts of cooling fins arranged on the exterior surface part of the indentations is reduced. The number of cooling fins will vary with the size of the mounting cup. As seen in for example

Fig. 4 shows a one-piece mounting cup fabricated in aluminium. Other thermally conducting materials, such as copper, are also applicable. Also the mounting cup may be constituted by two or more sub-parts - for example a top part for housing the electronic devices or components, and a bottom part primarily constituting the cooling fans. As previously mentioned, the mounting cup has a bottom part 2 with exterior cooling fins arranged thereon, and a top part defined by the sidewalls 3. The top part forms an opening through which electronic devices or components can enter the mounting cup. Also, the two indentations 15 and 16 are also seen in Fig. 4.

Fig. 5 and 6 show another (second) electromagnetic module 26 according to the present invention. This module forms part of a RFI-filter for a frequency converter. The module comprises a one-piece mounting cup 20 of a thermally conducting material, such as aluminium or copper, and a common-mode coil embedded at least partly embedded into a potting material. The common-mode coil is constituted by three electromagnetic coils 22, 23, and 24 each having a set of accessible coil ends. The three coils are wounded around the same core 25. Again, the thermally conducting potting material is a polyurethane potting resin.

The mounting cup 20 is formed so as to have plane and smooth exterior surface parts. These surface parts are formed to allow maximum heat to transfer from the mounting cup of the module to abutting surface parts. These abutting surface parts would typically be surface parts of a housing of a frequency converter. By ensuring heat transfer between the module and a surrounding housing the operating temperature of the common-mode coil can be kept at a level where its electrical characteristics are not heavily influenced.

Fig. 7 shows a frequency converter having a first 1 module and a second 26 module installed therein. The coils of the second module are not shown in Fig. 7. The coils of the first module constitute the coil of an intermediate circuit of the frequency converter, whereas the second module forms part of an RFI-filter of the frequency converter. The frequency converter is capable of handling power levels up to 25 kW in the three phases. The housing (not shown) of the frequency converter corresponds to an encapsulation level of at least IP 21 - meaning that the frequency converter can withstand falling water droplets. It may also be that the encapsulation level should be as high as IP55 which correspond to a completely closed encapsulation.

Claims

1. An electromagnetic module comprising

- a mounting cup (1) formed as a heat sink with cooling fins (2) being arranged on an exterior surface part of the mounting cup, and

- at least one electromagnetic coil (8) arranged in the mounting cup, the at least one electromagnetic coil being at least partly embedded into a thermally conducting potting material (10) so as to ensure transfer of heat from the at least one electromagnetic coil to the heat sink of the mounting cup, the at least one electromagnetic coil being accessible from the outside of the mounting cup.

2. An electromagnetic module according to claim 1, wherein the thermally conducting potting material is polyurethane potting resin.

3. An electromagnetic module according to claim 1 or 2, wherein the at least one electromagnetic coil has an inductance within the range 10 μH - 1000 mH, such as in the range 100 μH - 100 mH, such as in the range 200 μH - 10 mH, such as in the range 500 μH - 1 mH.

4. An electromagnetic module according to any of claims 1-3, further comprising terminal members (14a, 14b) for connecting the at least one electromagnetic coil to electronic circuits external to the electromagnetic module.

5. An electromagnetic module according to claim 4, wherein the terminal members are at least partly embedded into the potting material, each terminal member comprising a threaded portion so as to be capable of receiving a threaded bolt in order to fixate a conductor to each terminal member.

6. An electromagnetic module according to any of claims 1-4 comprising two electromagnetic coils (8, 9) and four terminal members (13a, 13b, 14a, 14b), each electromagnetic coil and each terminal member being at least partly embedded into the thermally conducting potting material.

7. An electromagnetic module according to claim 6, wherein each of the electromagnetic coils is wounded around the center leg of an EI core.

8. An electromagnetic module according to claim 7, wherein the electromagnetic coils are wounded around the same center leg of an EI core.

9. An electromagnetic module comprising

- a mounting cup (20) being thermally conducting, and

- an electromagnetic device arranged in the mounting cup, the electromagnetic device being at least partly embedded into a thermally conducting potting material so as to ensure transfer of heat from the electromagnetic device to the mounting cup, the electromagnetic device comprising at least three electromagnetic coils (22, 23, 24) each having a set of accessible coil ends.

10. An electromagnetic module according to claim 9, wherein the at least three electromagnetic coils are wounded around the same core (25), and constitute in combination, a common mode coil.

11. An electromagnetic module according to claim 9 or 10, wherein the thermally conducting potting material is polyurethane potting resin.

12. A mounting cup comprising

- a bottom part (2) having an outer portion being formed as a heat sink, and

- a sidewall part (3) extending away from the bottom part and forming an opening opposite the bottom part,

wherein the outer surface portion of the bottom part comprises a number of substantially linear cooling fins.

13. A mounting cup according to claim 12, wherein the mounting cup is fabricated as a one- piece aluminum or copper mounting cup.

14. A mounting cup according to claim 12 or 13, wherein the sidewall part defines a center axis, and wherein the cooling fins extend away from the outer surface portion of the bottom part in a direction being substantially parallel with the center axis.

15. A mounting cup according to claims 12-14, wherein an inner portion of the bottom part comprises a number of indentations, each indentation being adapted to receive at least part of an electromagnetic device, such as a coil.

16. A frequency converter comprising an electromagnetic module according to any of claims 1-11.