WO2010003519A1

WO2010003519A1 - Compensated thermocouple system

Info

Publication number: WO2010003519A1
Application number: PCT/EP2009/004335
Authority: WO
Inventors: Daniel Körtvelyessy
Original assignee: Thermo-Control Körtvelyessy Gmbh
Priority date: 2008-06-16
Filing date: 2009-06-16
Publication date: 2010-01-14
Also published as: DE102009005924A1

Abstract

The present invention shows a thermocouple arrangement comprising at least one thermocouple having at least two thermocouple wires which have in each case one measurement end, and having a compensation element, associated with the thermocouple, which compensation element comprises at least one further thermocouple wire, preferably two thermocouple wires.

Description

Compensated thermocouple system

The invention relates to a thermocouple system and in particular to a Thermoelemeπtaπordπuπg, which is used together with a measuring device.

Thermocouples, also referred to below as thermocouples, have been known for a long time and are usually used in a thermocouple system or thermocouple system, i. together with a measuring device which measures the thermal voltage generated between the thermocouple wires of the thermocouple, which is almost proportional to the temperature prevailing at a measuring point.

When thermocouples are used in the field of alternating magnetic fields or moved in a magnetic field, currents or voltages are induced in the thermocouples forming thermo wires. These induced currents or voltages can influence the thermoelectric voltage generated by the temperature.

For example, occur when using thermocouples in the vicinity of a power line of a stove oven on such disturbing alternating magnetic fields. These external influences can result in up to 20% measuring errors in practice. A considerable influence on the thermo-voltage arising at the connection ends of the thermocouple with resulting measurement errors is to be expected, in particular also in the case of temperature measurement with thermocouples in the vicinity of generators or transformers. In such cases a temperature measurement with thermocouples is often not possible.

It has already been tried by means of filter circuits to reduce these magnetic fields attributable to interference. A complete reduction is rarely possible, as due to mains fluctuations, the frequency set in the filter is not 100% hit. Furthermore, these filters represent an additional component with an additional potential for error.

In EP 1881311 the possibility of a temperature measurement by means of glass fiber cable was proposed. Due to the sensitivity with this technology, however, there is a relatively expensive solution to defects in the printed conductors.

Furthermore, in the case of cooled transformers / generators, the temperature is calculated via the heat balance of the cooling fluids (see WO / 2006/050886). However, this solution does not allow an accurate and immediate and above all, but no direct measurement of the real temperature. The invention has set itself the goal of providing a thermocouple system in particular a Thermopaaranordπung or a Thermoelemeπtaπordπuπg, in a simple way without interference even in an alternating magnetic field or during the movement of the thermocouple system by a magnetic field a Temperaturmessuπg can be performed.

To solve this problem, the invention provides the use of a compensation element, which is electrically conductively connected to the temperature measuring thermocouple assembly (Figure 3), wherein the compensation element is connected against the thermocouple assembly.

Next, the invention provides that the compensation element compensates for the induced by magnetic field change in the thermocouple interference voltages or interference currents.

Preferably, the compensation element is formed by a thermocouple, which has the same physical or physical structure, as provided for the temperature measurement thermocouple. The compensation element does not generate any thermoelectric voltage when the junction of the thermocouple wires between them is heated. In this connection, reference is made to section 0.2.2.3 on pages (24) and (25) of the book by Dr. Ing. Laszlό Körtvelyessy "Thermocouple Practice", 3rd Edition This section describes copper - copper thermocouples that do not generate a thermoelectric voltage.

The invention relates to an electrical component with a thermocouple.

In the current state of the art electrical components are often used which have one or more coils. Especially at

Transformers are usually two coils, which can change the voltage higher or lower. In high power transformers, an elevated temperature may jeopardize the device, in particular the windings themselves, by relinquishing their function, thus causing a short circuit in the winding, surrounding the insulating layer surrounding the wires of the windings and being stable only up to a certain temperature range ,

To counteract this heating, the wire diameter is usually increased, so that the resistance lowers and so less heat output is generated. ,

An examination of the temperatures present in the windings could thus help in their design. Monitoring the temperatures during operation increases safety.

The obvious task would therefore be to incorporate one or more thermocouples in the winding. Unfortunately, this obvious task is not feasible with the current state of the art. The choice of technologies for temperature measurement are diverse but have disadvantages that do not allow a specific application or only very limited.

The following explains the main groups and how they can be used.

The simplest technology would be the use of metallic thermometers, as disclosed for example in DE 102005004835 B4. One of them is the group of thermocouples, consisting of at least two thermo legs, which are made of different materials, such as NiCr and NiAl. The other group is that of resistance thermometers, for example PtIOO.

Both types of thermometers are used in tens of thousands in many applications and are correspondingly inexpensive and proven in practice. In terms of the task, the disadvantage of these thermometers is their sensitivity to the alternating magnetic fields prevailing in the transformer. These fields cause an induced voltage, which falsifies the measuring voltage and thus does not allow a correct measurement. Accordingly, this technology is a solution.

The next technology would be an optical measurement, for example with infrared laser or glass fiber, as disclosed in EP 1881311. These technologies are not sensitive to the magnetic fields, but have the disadvantage that only the externally visible surface of the transformer can be checked. In addition, the technology is relatively sensitive to the surface texture. Especially at temperatures below 600 ^c C, the measurement signal is very weak. So here is only partially an application feasible. In power generation transformers, additional cooling by air or liquid media is required. Here WO / 2006/050886 discloses the control over the heat flow of the cooling medium. This method has the weakness that only the transformer is detected as a complete component and not local points can be measured.

The invention solves the above-mentioned problems by using for measurement a metallic thermocouple having a compensation element. It contains at least two. Further . Wires consisting of one of the thermocouple materials. This thermocouple arrangement will be explained with reference to FIGS. 6 and 7.

Since this thermocouple assembly is insensitive to magnetic fields and can also be made from inexpensive materials, it can be installed at critical points in the machine.

An embodiment is shown in Figures 6 and 7.

Further advantages, objects and details of the invention will become apparent from the description of Ausführuπgsbeispieleπ with reference to the drawing; in the drawing shows:

1 shows a thermocouple system according to the prior art; FIG. 1 a shows a side view, FIG. 1 b shows a plan view of the connection point, and FIG. 1 c shows a section of the plane A - A in FIG. 1 a;

Figure 2 shows schematically a detail of Figure 1 and that of the thermocouple wires of the thermocouple shown in Figure 1;

FIG. 3 shows a schematic circuit diagram of an exemplary embodiment of a thermocouple system according to the invention, consisting of a measuring device and a thermocouple arrangement according to the invention;

Figure. 4 shows a schematic circuit diagram of an embodiment of a thermocouple system according to the invention, in which the occurring voltages are plotted;

Figure 5 is a schematic representation of an advantageous embodiment of the invention in section, consisting of the thermocouple, the compensation element and the measuring device j

Figure 6 shows a simple transformer (801) as prior art. This transformer has a primary winding (802) and a secondary winding (03) and a metallic core (04). In both windings between core and winding (807, 808, 809, 810), in the middle (811, 812) and at the edge (813, 814, 815, 815) each incorporated a thermocouple in the described thermocouple assembly; and

Figure 7 shows the embodiment of a thermocouple assembly consisting of the positive thermo leg (826) and the negative thermo leg (818). 1 shows a Thermoelemeπtsystem according to the prior art (DE 30302010) with two thermocouples and a separate empty protective tube (08). This conduit (08) allows the verification of existing thermocouples during operation, without disturbing this by lowering the temperature. It shows an embodiment with a Anschlußk ^' sacrifice (01), a metallic protective tube (02), three 0 5mm thin ceramic protective tubes. side by side (03) and the pressure bushing of the passage (04) of the compensation line and the Ausgleichsleituπg (13) itself. In the connection head (01) (hereinafter referred to as connection point (19)) are further two terminals (05) and (06) and an opening (05) is provided, which allows access to the empty pipe (08). The described prior art is mainly used in vacuum ovens with a quenching pressure of up to 20 bar. The enlarged section A - A in Figure 1c shows the three ceramic protective tubes (10a, 10b and 08). Of these, a tube is empty (08), in which the review of the two thermocouples, each consisting of a capillary (09) and a positive thermo wire (12) and a negative thermo wire (11) passing through a junction, preferably at the measuring point eg welding or soldering, forming a thermocouple. DE 3045652 discloses the use of differently thick thermo wires by which an advantageous behavior towards drifting thermocouples is achieved with the same thermowire diameters. Due to the small distances of the thermo wires (11, 12), this design is already less susceptible to magnetic interference. FIG. 2 schematically shows a thermocouple (14) from FIG. 1 in detail.

It has a Thermoscheπkel in particular a positive thermo wire (15) and a thermo leg in particular a negative thermo wire (16). The

Thermal wires (15) and (16) are connected at a connection point (17), which is also referred to as a solder joint, weld or measuring point. In the following, reference is made to the connection point (17) as the measuring point (18). In FIG. 2, reference numeral 19 designates the connection point which is at the "cold" end of

Thermocouple (14), i. is provided at the connection or measuring ends (21) and (21). In this connection point (19) via the Aπschlussklemmen (05) and (06), the compensation line (13), consisting of the thermo wires (25) and (26), and connected via the compression fitting (04) from the connection head

(01) to the terminals (22) and (23) of the measuring device (24) out.

The thermocouple system (3.1) according to the invention is shown in FIGS. 3 and 4, namely a measuring device (24) and a thermocouple arrangement (34). The thermocouple assembly (34) has a thermocouple 14 and a compensation element (35).

The thermo-wire (15) is made of NiCr, for example, and is called a "plus" pole thermo-wire or a positive thermo-wire (15) .The second thermo-wire (16) of the thermocouple is connected to the positive thermo-wire (15) at the junction (17). welded, for example, has a negative pole at a connecting or connecting point (30). The second thermal wire (16) consists, for example, of Ni and is used as a negative pole thermo-wire or as a negative thermo-wire (16). designated. For the thermo wires (15, 16) further materials / alloys can be used, such as platinum rhodium (PtRh) - platinum (Pt).

The compensating element (35) is formed by two thermo wires (28) and (29), one of the thermo wires, e.g. Thermodrome (28), at the so-called cold end (30) of the thermocouple (14) z ^ B. weld through a joint. In the exemplary embodiment, the two thermo wires (28) and (29) of Kompensatioπselements (35) are made of the material of the negative thermo wire 16. Figure 5 shows an advantageous embodiment of the arrangement of the four

Thermal wires (15, 16, 28, 29) of the above thermocouple assembly (34) in cross section and the connected measuring device (24). The thermocouple wires are surrounded by an insulating layer (37) and are enclosed in a jacket (36). From Figure 5 it can be seen that the distances of the thermocouple wires to each other are as small as possible. The advantageous embodiment has the property that the counter circuit of the compensation element completely compensates even these small induced voltages.

The terminal ends (20) and (21) of the thermocouple wires (15) and (29) are optionally connected in the connection point (19) with a compensation line (13) consisting of a positive thermo-wire (25) and a negative thermo-wire (26). wherein the materials used of the compensating leads are made of lower quality alloys than the thermocouple wires (15) and (16). The

Compensation line (13), consisting of the thermo wires (25, 26), is connected via the connection contacts (22) and (23) to the measuring device (24). Considering the economic factors, the embodiment of Figs. 3 and 4 may also have a reverse polarity in which the compensating element (35) is made of the positive thermo-wire (15) and in this case at the terminal end of the positive thermo-wire (15 ) enters a connection point.

Thus, FIG. 3 and also FIG. 4 show a thermocouple arrangement (34) in which a thermocouple (14) formed by a positive thermo-wire (15) (eg ^' NiCr) and a negative thermo-wire (16) (eg Ni) has a thermoelectric voltage and a compensation element (35), formed by two negative or two positive thermo wires (28, 29), which can not generate a thermoelectric voltage, since the thermocouple wires (28, 29) of the compensation element (35) consist of two identical materials.

Preferably, the thermocouple wires (28) and (29) are made of one or the other material of the thermocouple wires (15) and (16).

In FIG. 4, the total voltage U _tot at the plus and minus terminals (20, 21) of the thermocouple arrangement (34) at the connection point (18) is given by:

U _ges = Uu ₁ + 0

In order to do this, the thermoelectric voltage generated between the thermocouple (15) and (16) and tapped off at the connection point (18) and 0 is the non-developing one Thermospanπung between the existing of the same material thermo wires (28, 29) of Kompensatioπselementes (35).

By moving this thermocouple arrangement (34) (see FIG. 3) through a magnetic field which is generated, for example, by a north pole (32) and a south pole (33), the thermocouple wires (15, 16) and (28 , 29) the same Wechselspanπung | U, _n | induced.

By the shown suitable circuit of the compensation element (35) whose induced voltage is set against that of the thermocouple (14) and it applies:

^• U _g es = Uu, + U _1n + 0 - U _1n = U _1n

This voltage U _tot occurs, as shown in Figure 4, on the terminals (20) and (21).

According to the invention, the thermocouple (14) against the compensation element (35) - as shown - connected.

Preferably, the thermocouple wires (15) and (16) or (28) and (29) are electrically insulated from each other and electrically connected only at the connection points (17, 27) and (30).

Thus, the inventive thermocouple assembly (34) is immune to any magnetic field movements and field strength changes, since the induced voltages are always the same and cancel each other out. The thermocouple assembly (34) thus provides the unadulterated thermal voltage. It can also be said that a parallel connection of the two elements (14, 35) would not be technically correct, since the compensation element (12) causes a short circuit in the measuring device (24), so that the temperatures at the connection terminals (22) and (23 ) and not that of the measuring point (18) would be measured. Likewise, a series circuit would double the Störspaπnungen.

As mentioned in the introduction, a compensation line (13) must often be provided between the measuring device (24) and the thermocouple arrangement (31). ^'The usually two conductors, the compensation line can have a considerable length, for example, (20) m or more, and consist of a less expensive material than. the material that must be used for the thermocouple wires. The compensation line (13) has a similar characteristic at low temperatures as the thermocouple wires. As alloys, for example, nickel / copper, copper alloys are used. The equalizing line (13) should be outside the magnetic field. If this is not the case, that is, the compensation line (13) is also located within a magnetic field (eg in the vicinity of a transformer or a power line), so in the compensation line (13) induced disturbances can be compensated in the same way that of the thermocouple assembly (31).

Figure 7 shows the embodiment of a thermocouple assembly consisting of the positive thermo leg (826) and the negative thermo leg (818) which at the measuring point via a connection (817) electrically conductive with each other are connected. Via a connection (821), a compensation element, in the example consisting of two negative thermo legs (822) and (824), which are electrically conductively connected to one another at the measuring point via a connection (823), is connected in opposite directions with the thermocouple. The positive thermo leg (826) and the return line of the compensation element (824) are here connected to a measuring instrument (825). This connection can also be made via an equalizing line consisting of a negative equalizing line wire (827) and a positive equalizing line wire (828).

This incorporation according to FIG. 6 can take place, for example, during winding of the coil, since the thermocouple on FIG. 7 can have a design which fits into the intermediate spaces of the winding. With the help of these ten thermocouples, a complete recording of the temperatures in the transformer can be carried out with a measuring recorder. Alternatively, the measurement signals can also function as triggers to trigger an alarm above a certain value.

In power generation due to power fluctuations of the turbine, the performance of the transformers is also fluctuating. Here the control of the temperature can contribute to the safety of the system.

Claims

claims

1 Thermopaaranordπung (31) having at least one thermocouple (14) which at least two each having a measuring end (20, 30) possessing thermocouples (15, 16) and with a thermocouple (14) associated Kompensationselemeπt (35) consisting of at least one other Thermal wire (28, 29), preferably of two thermo wires (28, 29).

2. Thermopaaranordπung according to claim 1 which compensates for a generated at the measuring ends of the thermocouple (14) by a changing magnetic field in the thermocouple (14) generated interference voltage.

3. thermocouple assembly according to claim 1 wherein the compensation element is physically constructed as the thermocouple to be compensated (14) and thermocouple wires (28, 29), which are made of the same materials.

4. thermocouple assembly according to claim 1 or 3 with a thermocouple (14) consisting of two different materials which form a positive pole and a negative pole and with at least one identical further thermo-wire, consisting of at least one negative pole or positive pole

A thermocouple assembly as claimed in any one of the preceding claims, wherein the assembly is moved by a magnetic field generating an induced voltage in the thermocouple and the further thermo wire.

6. Thermopaaranordπung according to one of the preceding claims, wherein the arrangement is exposed to an alternating magnetic field.

7. thermocouple assembly according to any one of the preceding claims, wherein all the ends of the thermocouple (14) and the further thermo-wire at the measuring point (18) form an electrical contact.

8. thermocouple assembly according to one of the preceding claims, wherein the thermocouple (14) except for the connection points (17, 27) and (30) electrically from the. other parts, the thermocouple assembly (34) is isolated.

9. thermocouple assembly according to any one of the preceding claims, wherein the thermocouple (14) of a positive thermo-wire (15) and a negative thermo-wire (16) is constructed, and the compensation element (35) of two positive or two negative thermo wires (28, 29) is constructed, and wherein the thermocouple (14) with the compensation element (35) is preferably connected in series (in series).

The thermocouple assembly according to claim 8, wherein the positive thermo-wire (15) is made of a platinum-rhodium (PtRh) alloy, and the negative thermo-wire (16) is made of platinum.

11. Thermocouple arrangement according to one of the preceding claims, wherein the thermocouple wires (15, 16) of the thermocouple (14) and the thermocouple wires (28, 29) of the compensation element (35) are arranged side by side extending.

12. thermocouple assembly according to any one of the preceding claims, wherein the thermocouple wires (15, 16) of the thermocouple (14) and the thermocouple wires (28, 29) of the compensation element (35) are arranged stranded or tightly wound around each other.

13. A thermocouple assembly according to any one of the preceding claims, wherein thermocouple (14) and Kompensationselemerrt (35) via a compensation line (13) with a measuring device (24) are connected.

14. Thermocouple assembly according to one of the preceding claims, wherein the thermocouple wires (25, 26) of the compensation line (13) are stranded.

15. Thermocouple assembly according to one of the preceding claims, wherein the thermocouple wires (25, 26) of the compensation line (13) are stranded.

16. Thermocouple assembly according to one of the preceding claims, wherein the compensation line (13) may also have a compensation element when it is also exposed to a magnetic field and wherein the compensation line in this case, as far as the thermo-electrical properties, as the thermocouple or the Thermocouple is formed. ^'

17. Electrical component with at least one winding in which at least one Thermopaaraπordnuπg is inserted. Wherein the thermocouple assembly is composed of at least one Thεrmopaar consisting of a positive thermo leg and a negative thermo leg and a compensation element. The compensation element is formed from two thermo legs of the same material of a thermo leg, which is electrically connected in opposition to the thermocouple.

18. Electrical component according to claim 17, characterized in that at least the thermocouple assembly is incorporated in the intermediate space of the windings.

19. Electrical component according to claim 17, characterized in that at least one thermocouple assembly is attached from the inside to the core.

20. Electrical component according to the preceding claims, characterized in that at least one thermocouple assembly is guided from the outside into the winding.

21. Electrical component ^na ch the previous claims, characterized in that one of the coils is designed as a permanent magnet.

22. Electrical component according to claim 21, characterized in that the thermocouple is attached to the permanent magnet.

23. Electrical component according to claim 21 _; characterized in that the Thermopaaranordπung is incorporated in the permanent magnet.