THERMOMETER

Abstract

The invention relates to a thermometer, especially for determining the winding temperature of an electric power transformer. The invention is characterised in that, in a thermometer for determining the winding temperature of an electric power transformer, an electric temperature sensor, a mechanical temperature sensor and a heating element are arranged inside a coupling part formed from a heat-conductive material, and an insulating sleeve consisting of a thermally stable material is provided between an outer wall of the coupling part and an inner wall of the housing, the housing, the insulating sleeve and the coupling part forming a coaxial structure without leaving any air gaps such that thus definable heat transfers are generated between the individual components, namely the coupling part, the insulating sleeve and the tubular housing.

Claims

1. A thermometer for determining the winding temperature of an electrical power transformer, the thermometer comprising: a tubular housing with a closed end and an open end; a coupling member inside the housing holding an electrical temperature sensor and a mechanical temperature sensor and a heating element within the tubular housing, the coupling member being made from a material with good heat conductivity; an insulating sleeve of a thermally stable material between an outer wall of the coupling member and an inner wall of the housing, the housing, the insulating sleeve and the coupling member forming a coaxial construction without an air gap such that definable heat transfers between the the coupling member, the insulating sleeve and the tubular housing, are thereby achievable.

2. The thermometer according to claim 1, wherein the coupling member is constructed as an integrally formed part having a plurality of recesses into which the mechanical temperature sensor, the electrical temperature sensor and the heating element can be pushed without leaving an air gap.

3. The thermometer according to claim 1, wherein the coupling member is produced from a material having thermal conductivity better by a multiple by comparison with the insulating sleeve.

4. The thermometer according to claim 1, wherein the coupling member is formed by an aluminum alloy.

5. The thermometer according to claim 1, wherein the insulating sleeve is made from polyetheretherketone.

6. The thermometer according to claim 1, wherein an internal thermal resistance of the material of the coupling member is significantly lower by comparison with an internal thermal resistance of the material of the insulating sleeve such that an isothermal overall arrangement of the thermometer is thereby created.

Description

[0009] The invention shall be explained in more detail in the following by way of example on the basis of figures, in which:

[0010] FIG. 1 shows an thermometer according to the invention in a side sectional illustration and a plan view and

[0011] FIG. 2 shows a thermometer according to the invention in a plan view.

[0012] The thermometer 1 according to the invention is shown in FIG. 1 in a side sectional illustration. In that case, the thermometer 1 is surrounded by an outer housing 2 of tubular construction that has an open end 3 and a closed end 4. Provided within the housing 2 is a coupling member 5 that is made of a material with good thermal conductivity and that has several recesses of precise fit, shown in FIG. 2, for receiving a heating element 6, a mechanical temperature sensor 7 and an electrical temperature sensor 8 that is equipped with two sensor elements. An insulating sleeve 9 made from a thermally stable material is tightly fitted between the inner wall of the housing 2 and the outer wall of the coupling member 5 so that ultimately no air gap can form between the housing 2, the insulating sleeve 9 and the coupling member 5. Considered overall, there thus results through the housing 2, the insulating sleeve 9 and the coupling member 5 a coaxial construction, without leaving an air gap, in such a kind that definable heat transfers between the individual components, namely the coupling member 5, the insulating sleeve 9 and the tubular housing 2, are thereby created. According to the invention an arrangement is thus provided, the thermal resistance of which within the coupling member 5 is so small by comparison with the internal thermal resistance of the insulating sleeve 9 that an isothermal overall arrangement of the thermometer 1 can be assumed. The coupling member 5 can in that case be made from, for example, an aluminum alloy, whilst the insulating sleeve 9 can be produced from, for example, polyetheretherketone, also termed PEEK. The thermal transfer resistance of the coupling member 5 relative to that of the insulating sleeve 9 and the thermal transfer resistance of the insulating sleeve 9 relative to that of the housing 2 are decisively determined by the geometric dimensions of the coaxially selected construction of the thermometer 1 and not by the air gap present therebetween, since this is kept very small, i.e. less than 0.1 millimeters, and thus negligible in consideration of the thermal equivalent circuit diagram.

[0013] FIG. 2 shows in sectional illustration the plan view of the thermometer 1 according to the invention. The coaxial construction of the thermometer 1 according to the invention, consisting of the outer housing 2, the insulating sleeve 9 connected therewith and the coupling member 5 for reception of the heating element 6, the mechanical temperature sensor 7 and the electrical temperature sensor 8, is readily evident from this illustration. These last-mentioned components 6, 7 and 8 are received in, particularly pushed into, a plurality of recesses 10, 11 and 12 provided in the coupling member 5. The simple pushing of the heating element 6, the mechanical temperature sensor 7 and the electrical temperature sensor 8 into the coupling member 5 in that case enables particularly uncomplicated exchange of these components 6, 7 and 8 in the event of a defect or maintenance operations that might arise.