GB2279506A - Electrical power resistor - Google Patents
Electrical power resistor Download PDFInfo
- Publication number
- GB2279506A GB2279506A GB9412942A GB9412942A GB2279506A GB 2279506 A GB2279506 A GB 2279506A GB 9412942 A GB9412942 A GB 9412942A GB 9412942 A GB9412942 A GB 9412942A GB 2279506 A GB2279506 A GB 2279506A
- Authority
- GB
- United Kingdom
- Prior art keywords
- housing
- resistor unit
- electrical resistor
- accordance
- electrical
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 25
- 239000000919 ceramic Substances 0.000 claims abstract description 18
- 239000000843 powder Substances 0.000 claims abstract description 14
- 229910010293 ceramic material Inorganic materials 0.000 claims abstract description 9
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 6
- 239000000395 magnesium oxide Substances 0.000 claims description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 2
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims description 2
- 239000011347 resin Substances 0.000 claims description 2
- 229920005989 resin Polymers 0.000 claims description 2
- 238000001721 transfer moulding Methods 0.000 claims description 2
- 239000004020 conductor Substances 0.000 claims 2
- 238000010276 construction Methods 0.000 abstract description 4
- 230000000717 retained effect Effects 0.000 abstract description 2
- 229910052751 metal Inorganic materials 0.000 abstract 1
- 239000002184 metal Substances 0.000 abstract 1
- 229910052782 aluminium Inorganic materials 0.000 description 7
- 239000004411 aluminium Substances 0.000 description 7
- 239000004568 cement Substances 0.000 description 6
- 238000009413 insulation Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 239000000037 vitreous enamel Substances 0.000 description 3
- 239000003990 capacitor Substances 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 238000005056 compaction Methods 0.000 description 2
- 238000007605 air drying Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010292 electrical insulation Methods 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000010445 mica Substances 0.000 description 1
- 229910052618 mica group Inorganic materials 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G2/00—Details of capacitors not covered by a single one of groups H01G4/00-H01G11/00
- H01G2/02—Mountings
- H01G2/04—Mountings specially adapted for mounting on a chassis
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C1/00—Details
- H01C1/08—Cooling, heating or ventilating arrangements
- H01C1/084—Cooling, heating or ventilating arrangements using self-cooling, e.g. fins, heat sinks
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Details Of Resistors (AREA)
Abstract
An electrical power resistor has an electrical resistor element wound on a ceramic support (7) positioned within a cavity (6) in housing (1) of ceramic material. The space (V) between the support (7) and housing (1) is filled with a compacted aluminium oxide powder and sealed with end caps (8) retained by nuts (9a) on electrical terminals (8). The housing (1) is secured to a heat-sink by, or consistuted by, metal base (4) which has ribs (5) screwed to and/or interlockingly engaging grooves (3) in the sides of the housing (1). The construction provides high thermal dissipation for use as a snubber resistor in thyristor control circuits. <IMAGE>
Description
TITLE
Electrical Components
This invention relates to electrical components and is more particularly concerned with an encased resistor element, preferably wire wound, such as are used for dissipating substantial power through a heat-sink.
One of the main fields, but not an essential one, for the use of this invention is in thyristor snubber circuits which are used in railway traction. Other fields of application are in high voltage DC generation and transmission systems as well as electric motor drive control equipment. In thyristor snubber circuits used in AC switching and rectification over-voltage is generated each time the thyristor turns off and protection from such over-voltage is provided by a socalled "snubber" capacitor and resistor. The capacitor absorbs the energy pulse which would otherwise cause over-voltage and the resistor damps the oscillations and dissipates the power as heat.
The total loss dissipated in the resistor is not directly comparable to the power rating of conventional resistors. Conventional power rating is established assuming the loss is dissipated reasonably evenly during the cycle. Through the high switching voltages produced by the thyristor the instantaneous excursions in hot spot temperature of the resistor wire will not be negligible and the wire may burn as a fuse at an average power dissipation much lower than the rated power.
Because of the heat dissipation it is usually essential to mount power resistors on a heat-sink and therefore insulation between the resistor element and the casing and between adjacent turns of the resistive element must not be liable to breakdown through the high voltage transients that may be present.
One of the main objects of this invention is to provide an electrical power resistor element which may be mounted on a heat-sink and which includes good thermal dissipation as well as high insulation resistance. A further object is to provide a construction which is more easily manufactured and which has better long term performance than known arrangements.
In accordance with this invention, there is provided an electrical resistor unit comprising an electrical resistance element wound on a ceramic support and located generally coaxially within a housing of ceramic material which is interlockingly engaged with a base forming a heat-sink, a space between the electrical resistance wire and ceramic support and the housing being filled with an insulating powder material such as aluminium or magnesium oxide.
In this construction the resistance wire is wound upon a ceramic support body which is coaxially positioned within the housing which is of a high alumina ceramic material. By the provision of aluminium oxide powder between the resistance element and the housing, excellent heat transfer is obtained as well as a very high dielectric strength. The housing is preferably interlockingly connected to the base by providing inter engaging profiled parts which may be pressed together to provide a secure connection with good thermal conductivity.
The base may be formed by strip members which connect with a chassis or with a separate heat-sink unit.
Alternatively clamp means may interlockingly engage the housing to mount same on a chassis directly.
The alumina housing and support body provides a high level of electrical insulation to the resistive element combined with good thermal conduction properties. The base, preferably of aluminium, ensures good thermal conduction to a chassis or additional heat-sink and includes accurately positioned mounting holes.
The housing is made of a high alumina ceramic material in which the wound resistive element is supported by an aluminium oxide powder which also provides a high level of inter-turn insulation. The ceramic material has a very high dielectric strength providing a great margin of safety well in excess of enduser requirements.
Preferably the wound element is held centrally inside the alumina housing mounted on a platform fitted with a tamping mechanism. The aluminium oxide powder is heated for moisture removal and is introduced, by a vibrator filling technique, into the space remaining between the housing and wound element. The powder is contained at this stage by mica washers positioned at each end. The filled assembly is then low frequency 'tamped' to further compact the powder and provide optimum element to housing thermal conductivity. The resistor element can be run at a high temperature without the risk of inter-turn insulation degradation on the element winding.
The element may be sealed in the housing by a transfer moulding technique in which resin is introduced, at high temperature and pressure, simultaneously into each end of the housing to form end caps. The opposing pressures will permit further powder infill compaction.
A temperature setting ceramic material may alternatively be used for the end caps.
The base may be in the form of an extruded aluminium section provided with housing location ribs.
A layer of air drying ceramic cement may be applied to the base of the housing which will immediately be slid into position on the aluminium base. Pressure is then applied to the location ribs which will effect a crimp joint between housing and base. This method will lock the housing in contact with the base with the ceramic cement accommodating any flatness deviation on either the base or the housing. This will ensure the intimate contact required for optimum thermal conduction.
This invention is further described and illustrated with reference to a constructional embodiments shown as examples in the drawings.
In the drawings:
Figure 1 shows a side view of a power resistor,
Figure 2 shows a plan view,
Figure 3 shows an end view.
Figure 4 shows an end view of a modification,
Figure 5 shows an end view of a second
modification,
Figure 6 shows an end view of a third modification,
and
Figure 7 shows a section on A-A of Figure 6.
Referring to Figures 1 to 3 of the drawings, a power resistor assembly comprises a housing 1 formed from a high alumina ceramic material and of elongated form with a cylindrical hollow interior 6. The base 2 of the housing is flat and at each side triangular profiled channels 3 are formed. The base 2 is arranged to be in good thermal contact with an aluminium base mount 4 which has upstanding elongated lugs 5 which define a channel into which the base 2 of the housing 1 may slide. After such sliding engagement deforming force is applied to the lugs 5 to press them against the channels 3 of the housing and thus to force the base 2 of the housing into good mechanical and thermal contact with the aluminium base 4. A ceramic cement C may be used at this joint.
The ceramic housing 1 has a central cylindrical passageway 6 which is adapted to receive a ceramic support 7 which includes a helically wound metallic resistance wire (not shown). The resistance wire has axial terminations 8 which may also serve to initially position and support the assembly within a housing 1.
The space V left between the resistor wire support 7 and the inner surface of the ceramic housing 1 is filled with an inorganic powder material which is then compacted and tamped using vibration and pressure. After this process end caps 9 may be applied, these, for example, comprising a settable ceramic material. If it is necessary to provide for the interchanging of the housing 1 and the base 4, then locking screws 10 may be positioned through the lugs 5 to contact the channel 3 in the housing 1. For example, three locking screws may be provided on each side as shown. The base 4 will include suitable apertures 11 for mounting on to a chassis.
The shape and configuration of the aluminium base 4 may be varied according to the thermal resistance characteristics required and operating temperature, power requirements and resistance configuration needed in a particular application. Thus, the particular dimensions of the base can be selected according to the normal temperature required in actual use. A larger heat-sink could be used as a base in order to increase the power rating of the resistance unit. Several housings 1 could be mounted in line on the same elongate aluminium base 4 and connected together in series or as required.
The various materials used for the ceramic support 7, the infill powder material in space V and the housing 1 will be chosen for good mechanical properties and in particular will be materials having a high thermal conductivity.
Referring to Figures 4 and 5 of the drawings, like parts have been denoted by like reference numerals where applicable. In Figure 4 the form of lugs 5 has a different configuration and these are specifically adapted to be pressure rolled from a lateral direction to provide firm attachment through the profiled channels 3.
In Figure 5, the base mount 4 is formed by two separate rails, each of which incorporates the lugs 5 and which may be secured to a chassis or heat-sink 4a by means of attachment screws 4b. The mounting holes through which screws 4b pass in the flanges 4 may be elongated, thus allowing the unit 1 to be easily positioned with the flanges thereafter pressed from the sides into good engagement.
Referring now to Figures 6 and 7, these show a modified construction and here again, like references have been used to indicate like parts already described in conjunction with Figures 1 to 5. The resistive element is wound onto the ceramic support 7 and thereafter given a primary protection by way of a precoat of a ceramic cement or impervious vitreous enamel.
The electric element and support 7 is then assembled inside the case 1 and retained in position by means of the end caps 9 which, in this embodiment, are in the form of plugs which enter the passageway 6. The terminations for the resistive element 8 are in the form of threaded rods which project from each end of the casing and the end caps 9 are secured by stainless steel lock nuts and washers 9a. Both of the end caps 9 are sealed into the case 1 using vitreous enamel, ceramic cement or other suitable material. The filling material Af is filled
V into the spaceLbetween the casing 1 and resistive elemen-t by mounting the assembly vertically on a platform fitted with a vibrating and tamping mechanism with a pre-heated mineral powder material being introduced into the space V through suitable holes in one of the end caps 9. After completion, compaction and tamping of the filling, the filling hole or holes in the end cap 9 are sealed using ceramic cement or vitreous enamel.
Claims (11)
1. An electrical resistor unit comprising an electrical resistance element wound on a ceramic support and located generally coaxially within a housing of ceramic material which is interlockingly engaged with a base forming a heat-sink, a space between the electrical resistance wire and ceramic support and the housing being filled with an insulating powder material such as aluminium or magnesium oxide.
2. An electrical resistor unit in accordance with Claim 1, wherein the housing is a high alumina ceramic.
3. An electrical resistor unit in accordance with Claim 1 or 2, wherein the housing is interlockingly connected to the base by providing inter engaging profiled parts which may be pressed together to provide a secure connection with good thermal conductivity.
4. An electrical resistor unit in accordance with any preceding claim, wherein the base is formed by strip members which connect with a chassis or with a separate heat-sink unit.
5 An electrical resistor unit in accordance with Claim 1, 2 or 3, wherein clamp means interlockingly engage the housing to mount same on a chassis directly.
6. An electrical resistor unit in accordance with any preceding claim, wherein aluminium oxide powder is heated for moisture removal and is introduced, by a vibrator filling technique, into the space remaining between the housing and wound element.
7. An electrical resistor unit in accordance with Claim 6, wherein the powder is compacted by tamping preferably using low frequency vibration.
S. An electrical resistor unit in accordance with any preceding claim, wherein the resistor element is sealed in the housing by a transfer moulding technique in which resin is introduced, at high temperature and pressure, simultaneously into each end of the housing to form end caps.
9. An electrical resistor unit in accordance with any preceding claim, wherein the ceramic support has opposed axial threaded conductors connected to each end of the resistance element, end caps closing the housing being secured by nuts engaging said conductors.
10. An electrical resistor unit according to any preceding claim, wherein the housing has grooves on opposed sides, the base having spaced opposed projections engaging one with each groove.
11. An electrical resistor unit constructed and arranged to function as herein described and exemplified with reference to the drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB939313511A GB9313511D0 (en) | 1993-06-30 | 1993-06-30 | Electrical components |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9412942D0 GB9412942D0 (en) | 1994-08-17 |
| GB2279506A true GB2279506A (en) | 1995-01-04 |
Family
ID=10738052
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB939313511A Pending GB9313511D0 (en) | 1993-06-30 | 1993-06-30 | Electrical components |
| GB9412942A Withdrawn GB2279506A (en) | 1993-06-30 | 1994-06-28 | Electrical power resistor |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB939313511A Pending GB9313511D0 (en) | 1993-06-30 | 1993-06-30 | Electrical components |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB9313511D0 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001037288A1 (en) * | 1999-11-16 | 2001-05-25 | Abb Research Ltd. | An arrangement for electrically insulating a high voltage component |
| US6771487B1 (en) | 1999-04-21 | 2004-08-03 | Epcos Ag | Power electronics component with improved thermal properties |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1196385A (en) * | 1967-09-22 | 1970-06-24 | Vitrohm G M B H & Co K G Deuts | Wire-Wound Power Resistor |
| US3795046A (en) * | 1972-04-05 | 1974-03-05 | Sprague Electric Co | Method of making a heat sinked resistor |
| GB2079533A (en) * | 1980-06-27 | 1982-01-20 | Hayashi Denko Kk | Resistance thermometer element |
| GB2210206A (en) * | 1987-09-18 | 1989-06-01 | C G S Resistance Co Ltd | Improvements in electrical resistors |
-
1993
- 1993-06-30 GB GB939313511A patent/GB9313511D0/en active Pending
-
1994
- 1994-06-28 GB GB9412942A patent/GB2279506A/en not_active Withdrawn
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1196385A (en) * | 1967-09-22 | 1970-06-24 | Vitrohm G M B H & Co K G Deuts | Wire-Wound Power Resistor |
| US3795046A (en) * | 1972-04-05 | 1974-03-05 | Sprague Electric Co | Method of making a heat sinked resistor |
| GB2079533A (en) * | 1980-06-27 | 1982-01-20 | Hayashi Denko Kk | Resistance thermometer element |
| GB2210206A (en) * | 1987-09-18 | 1989-06-01 | C G S Resistance Co Ltd | Improvements in electrical resistors |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6771487B1 (en) | 1999-04-21 | 2004-08-03 | Epcos Ag | Power electronics component with improved thermal properties |
| WO2001037288A1 (en) * | 1999-11-16 | 2001-05-25 | Abb Research Ltd. | An arrangement for electrically insulating a high voltage component |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9313511D0 (en) | 1993-08-11 |
| GB9412942D0 (en) | 1994-08-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |