EP3169138A1 - Inductive heating device with adaptive multi-point temperature control - Google Patents

Abstract

The invention relates to an inductive heating device (1) which includes a generator (2) powered by a voltage source and at least one inductor (6), the generator (2) comprising as assemblies at least one power rectifier (62), at least one microprocessor (44). , at least one charging device (64) and at least one inverter (66a, 66b) and the assemblies of the generator (2) are housed in a generator housing (58), the generator (2) controlled by the electronic control (44) via a line connection (22a, 22b) supplying at least one inductor (6) containing at least one induction coil for attachment to an electrically conductive body (8, 10) to be heated, and due to the induction coil (56) of the inductor (56) fed with the alternating current 6) in the heated, electrically conductive body by electromagnetic induction, a current is induced, which to be heating body is heated, and in the microprocessor (44) algorithms for controlling or regulating the power of the generator (2) depending on a reference variable (T_ ext) are implemented. According to the invention, there is provided a multi-point temperature control with start mode and operating mode which causes preferably an internal temperature and / or an inductor temperature to be kept within a predetermined temperature range.

Description

The invention relates to an inductive heating device which includes a generator fed by a voltage source and at least one inductor according to the preamble of claim 1.

Such an inductive heating device is off EP 2 720 513 B1 for example, as inductive Weichen- or rail heating known. Switch and / or rail heating devices serve to keep at least a portion of a rail or a rail track consisting of two parallel rails and / or a switch free of ice and snow, in order to generally prevent ice formation on surfaces of rails or points or freezing to prevent moving elements of a switch.

Inductive heaters utilize effects of electromagnetic induction, which are followed by alternating energization of one or more coils of an inductor in the electrically conductive body, e.g. a rail or switch electrical currents are induced, through which heat the rail or switch in question and thus free from ice and snow or keep free. The inductor gives its relatively low heat loss almost in full to the rail or switch, which contributes to the saving of electrical energy. For the effect, therefore, no direct or close contact of the inductor with the rail or switch is necessary.

In the generic EP 2 720 513 B1 a two-point control is realized. The procedure is as follows; After the generator input has been connected to the AC mains, the controller independently carries out the generator startup in the context of a start mode. If this is finished, the control system automatically starts the heating process as part of the operating mode. Since the process can also take place at very low outside temperatures, it is advantageous for all semiconductors to slowly increase the load current or the heating power. This happens over a settable time during which the power is increased from a low value - practically zero - to a relatively high value. This can be a value that is above the continuous performance of the generator. Therefore, after a certain time, the power is suddenly or continuously lowered to the previously tuned continuous power. If this continuous power is not sufficient - eg during a heavy snowfall - the generator must be switched off and switched on again to get back to the benefit of the higher initial power. If the generator is switched off and on again by the higher-level controller, this is a normal sequence and not a fault mode. If the generator operated at high power for a long period of time, then a temperature switch turns off the heater, which is then in error mode. In such a case, it is necessary to find the cause of the fault, eliminate it and (as far as possible) reset the error message. However, this is cumbersome and not possible because of the remote location of the heater on the track by a control center or not immediately.

Another cause of interruptions in operation of the known heating device is also a thermal overload of the generator. In this case, a complete shutdown of the generator. Such interruptions are undesirable because they involve an active intervention of operators, but this is not or not immediately possible because of the remote location of the heater on the rail track from a control center.

Against this background, the object of the invention is to develop a heating device of the type mentioned in such a way that it has a higher availability.

This object is achieved by the features of claim 1.

Disclosure of the invention

The invention is based on the principle of electromagnetic induction, wherein in the vicinity of a conductor through which alternating current flows, in particular conductor wire windings of an inductor, an electromagnetic field is produced which in other electrical conductors, in this case the electrically conductive body to be heated, e.g. a rail or switch parts of a rail track for rail vehicles, which are within this electromagnetic field or are detected by the magnetic field lines of this electromagnetic field, causing electrical currents. These in the electrically conductive body e.g. the rail or in the switch components induced currents cause heating of the electrically conductive body. It is the well-known induction principle.

The closer the coupling between the inductor and the electrically conductive body, the smaller the stray fields and the efficiency of the transmission increases and the induced currents have clearly defined paths. The efficiency is higher, the closer the coupling between the inductor and the electrically conductive body. The induced currents are called eddy currents independent of the degree of coupling. With a larger distance, the induced current density is smaller and thus the heating is less and in addition, here a part of the field closes over the air gaps and is thus lost for the application. The heating of the electrically conductive body is based on the Joule losses.

• e) eine mit dem Mikroprozessor signalleitend verbundene Sensoreinrichtung vorgesehen ist, welche wenigstens eine im Inneren des Generatorgehäuses herrschende Innentemperatur und/oder die Induktortemperatur des wenigstens einen Induktors als Messtemperatur(en) misst und in den Mikroprozessor einsteuert, wobei
• f) in dem Mikroprozessor implementierten Algorithmen ein Temperaturbereich zwischen einem unteren Temperaturgrenzwert T_low und einem oberen Temperaturgrenzwert T_high für die Messtemperatur vorgegeben ist, wobei
• g) der elektrische Generator derart von dem Mikroprozessor gesteuert ist, dass
  • g1) im Rahmen eines Startmodus nach einem Einschalten des Generators die Leistung PW des Generators ausgehend von einer Startleistung PW Start über eine vorgegebene erste Zeitspanne t1 rampenartig auf eine demgegenüber höhere erste Leistung PW1 erhöht wird, welche kleiner oder gleich einer maximalen Leistung PW max des Generators ist, und
  • g2) diese erste Leistung PW1 über eine vorgegebene zweite Zeitspanne t2 konstant gehalten wird, und dann
  • g3) die Leistung PW des Generators sprunghaft auf eine demgegenüber niedrigere zweite Leistung PW2, die aber größer als die Startleistung PW Start ist, abgesenkt wird, und dann
  • g4) der Generator solange unter der zweiten Leistung PW2 betrieben wird, bis die Messtemperatur den unteren Temperaturgrenzwert T_low erreicht hat, und dann
  • g5) im Rahmen eines Betriebsmodus
    • g5.1) die Leistung PW des Generators rampenartig erhöht wird, bis eine vorgegebene, gegenüber der zweiten Leistung PW2 größere dritte Leistung PW3 erreicht wird, welche kleiner oder gleich in Bezug zur ersten Leistung PW1 ist, und dann
    • g5.2) der Generator solange unter der dritten Leistung PW3 betrieben wird bis die Messtemperatur den oberen Temperaturgrenzwert T_high erreicht hat, und dann
    • g5.3) die Leistung PW des Generators sprunghaft auf die zweite Leistung PW2 abgesenkt wird, und dann
    • g5.4) der Generator solange unter der niedrigeren zweiten Leistung PW2 betrieben wird, bis die Messtemperatur den unteren Temperaturgrenzwert T_low erreicht hat, und dann
    • g5.5) die Schritte g5.1) bis g5.4) zyklisch wiederholt werden.

Against this background, it is provided according to the invention that

• e) a signal device connected to the microprocessor sensor device is provided, which measures at least one prevailing inside the generator housing internal temperature and / or the inductor temperature of the at least one inductor as the measuring temperature (s) and einsteuert in the microprocessor, wherein
• f) in the microprocessor implemented algorithms, a temperature range between a lower temperature limit T_low and an upper temperature limit T_high is specified for the measurement temperature, wherein
• g) the electric generator is controlled by the microprocessor such that
  • g1) in the context of a start mode after switching on the generator, the power PW of the generator starting from a starting power PW start over a predetermined first time t1 is ramped to a comparatively higher first power PW1, which is less than or equal to a maximum power PW max of the generator is and
  • g2) this first power PW1 is kept constant for a predetermined second time period t2, and then
  • g3) the power PW of the generator is suddenly reduced to a comparatively lower second power PW2, which is greater than the starting power PW start, and then
  • g4) the generator is operated under the second power PW2 until the measurement temperature has reached the lower temperature limit T_low, and then
  • g5) under an operating mode
    • g5.1), the power PW of the generator is ramped up until a predetermined, compared to the second power PW2 larger third power PW3 is achieved, which is less than or equal to the first power PW1, and then
    • g5.2) the generator is operated under the third power PW3 until the measurement temperature has reached the upper temperature limit T_high, and then
    • g5.3) the power PW of the generator is abruptly lowered to the second power PW2, and then
    • g5.4) the generator is operated under the lower second power PW2 until the measurement temperature has reached the lower temperature limit T_low and then
    • g5.5) the steps g5.1) to g5.4) are repeated cyclically.

The microprocessor is preferably designed to control or regulate the electric power of the generator by varying the frequency f and / or the pulse width PW of the alternating current fed into the at least one inductor. Preferably, however, the frequency f is kept constant and only the pulse width PW used. For this reason, the abbreviation PW for the generator uses the same abbreviation PW as for the pulse width.

In other words, the sensor device together with the microprocessor monitor the internal temperature prevailing inside the generator housing and / or the inductor temperature of the at least one inductor as the measurement temperature (s), the microprocessor checking whether this measurement temperature (s) is within a temperature range between a lower temperature limit value T_low and an upper temperature limit T_high.

In this case, the invention distinguishes between a start mode and an operating mode, wherein the start mode and the temporally subsequent operating mode run automatically each time the generator is switched on or energized.

The start mode has the advantage that a relatively rapid heating of the body to be heated within the first time period t1 and the second time period t2 is achieved by him, since the then achieved first power PW1 is relatively high. The first power PW1 preferably corresponds to the maximum power PW max of the generator. The starting power PW Start, from which the power PW is increased when the generator is turned on, is for example 25 ‰ of the maximum power PWmax.

The range between the starting power PW start and, for example, half the value of the first power PW1 for the value (which can be set in this range) for the second power PW2 represents an empirical value which ensures is that the lower limit temperature T_low can be reached by the measurement temperature after some time.

During the subsequent operational mode, the first lowered to the second power PW2 power PW of the generator is then increased to the contrast greater third power PW3, which is less than or equal with respect to the first power PW _1, and then the generator while under the third power PW3 operated until the measurement temperature has reached the upper temperature limit T_high. This step ensures that the heat output is as high as possible in relation to the tolerable heat load of the generator. The value for the third power PW3 is to be determined in particular with regard to the energy consumption and the heat load of the inductor. Preferably, the third power PW _{3 is} smaller than the first power PW ₁ .

If the upper temperature limit value T_high is then reached after a certain operating time of the generator under the third power PW3, the subsequent sudden reduction to the second power PW2 ensures that damage to the generator due to excessively high temperatures is avoided.

The generator is then operated under the lower second power PW ₂ until the measuring temperature has reached the lower temperature limit T_low. By a suitable choice of the second power PW2 within said range, this can be ensured.

In order to achieve the highest possible heat output of the generator with respect to the tolerable heat load of the generator and / or the at least one inductor, in the subsequent step the power PW of the generator is ramped up starting from the second power PW2 until in turn the third power PW3 is reached becomes.

If the measuring temperature has again reached the upper temperature limit T_high during the operation of the generator under the third power PW3, then the power PW of the generator is in turn suddenly reduced to the second power PW2.

As a result, a cycle is repeatedly run in the operating mode of the generator, which ensures operation of the generator in a temperature range between the lower temperature limit T_low and the upper temperature limit T_high, in which no temperature damage to the generator and / or the at least one inductor are to be feared and / or no unwanted shutdown occurs. This cycle or operating mode is only ended after switching off the generator. Thus, an adaptive multi-point temperature control is realized, wherein the control points are formed by temperature limits.

During the start mode, therefore, the measurement temperature can be greatly increased, so that it comes to an effect similar to resistance bars, the so-called "super boost". Depending on the design of the inductors, the measuring temperature may also exceed 100 ° C. Thereafter, the control or regulation of the heater automatically goes into the operating mode and thus into the "temperature limit system". This transition can be time-dependent and / or dependent on the measurement temperature.

The inductor temperature as an additional or alternative measuring temperature with respect to the internal temperature of the generator is particularly advantageous in the "super boost" start mode, since the inductors can then reach a temperature of more than 100 ° C. The inductor temperature and / or the internal temperature of the generator is then processed by the algorithm of the microcomputer. In particular, the latter is advantageous because in the start mode, the inductor temperature rises or falls faster than the internal temperature of the generator. This would therefore result in a greater discharge of the generator.

Due to the measures according to the invention, it is no longer possible for the case described at the outset to be automatically switched off due to a single exceeding of an absolute upper temperature limit T_abs, which represents a fixed value and is provided within the scope of an overload protection of the generator and / or the inductor. As the temperature monitoring of the inductive heating device according to the invention automatically and independently and while the generator is also constantly in operation, the maintenance personnel can be freed from recommissioning due to thermal overload, which is particularly advantageous in terms of inductive Weichen- and / or rail heaters in which the generators / inductors usually far are arranged away from the next maintenance station. As a result, error messages that would lead to a shutdown of the generator, largely avoided. Overall, therefore, the maintenance of the inductive heating device according to the invention is advantageously low.

In particular, the invention operates completely independently of the lead-based control of the power of the generator, which may include complete disconnection (de-energizing) or energizing (energizing) of the generator.

Advantageous developments of the invention are the subject of the dependent claims.

Particularly preferably, the microprocessor-communicating operating device is provided, via which at least one value for the first time period t ₁ , a value for the second time period t ₂ , a value for the starting power PW start, a value for the first power PW 1, a value for the second power PW2 and / or a value for the third power PW3 can be controlled in the microprocessor. As a result, the temperature monitoring of the inductive heating device can be flexibly adapted to the respective structural design or to the ambient conditions. Furthermore, thereby the energy consumption and the thermal load of the inductive heating device can be controlled. This operating device can in particular be integral with the generator or integrated into the generator housing.

According to a preferred development, the sensor device comprises at least one temperature sensor, which detects the temperature of the at least one inverter of the generator as a measuring temperature and controls it in the microprocessor. This can for example be realized by the fact that the temperature is detected at a heat sink of the inverter, which then represents a (to be monitored) internal temperature of the generator. It has been found that in particular the inverter represents an assembly within the generator housing, which can reach a relatively high temperature during operation of the generator and therefore justifies such monitoring.

Furthermore, algorithms implemented in the microprocessor may specify an absolute upper limit temperature T_abs as a value for a temperature in the sense which may be reached at most from the measurement temperature (s). This absolute upper limit temperature Tabs is in contrast to the upper limit temperature T_high, which although given, but is variable by default, an unchangeable value and is in particular greater than the upper limit temperature T_high. If the measurement temperature (s) reaches or exceeds this absolute upper limit temperature T_abs, the microprocessor is in particular designed to generally switch off the generator.

According to a further preferred measure, the microprocessor can be designed to control or regulate the electric power of the generator by varying the frequency f and / or the pulse width PW of the alternating current fed into the at least one inductor. Preferably, however, the frequency f is kept constant and only the pulse width PW used as a reference variable of the superimposed control. For this reason, the abbreviation for the power PW of the generator also uses the same abbreviation PW as for the pulse width. It is true that a lower pulse width, i. a narrower pulse has a lower power and a larger pulse width, i. a wider pulse results in higher performance.

In the control or regulation of the electric power of the generator depending on the temperature control variables described above, the ambient temperature T_ext and / or the temperature of the body to be heated and / or the inductor temperature can preferably be used as an additional reference variable. In other words, a desired value for one or more of the variables mentioned either in the context of a characteristic map (control) or for specified an actual setpoint adjustment. These are additional reference variables, in particular at the ambient temperature T_ext. The lower temperature limit T_low and the upper temperature limit T_high are always the basic command values and can, but need not, be adjusted by the ambient temperature T_ext. Preferably, however, the services are adapted with the aid of the ambient temperature T_ext, which can lead to great energy savings. If the setting is optimal, the generator does not have to be switched off via the higher-level control, since the output power PW of the generator can be moved towards zero when the ambient temperatures T_ext increase.

In particular, the generator may include a plurality of inverters connected in parallel with respect to the charging device, each of the inverters controlling an inductor, thereby realizing a respective circle. This then parallel supply of the inductors in several parallel circuits has the advantage that each circuit is the same voltage. In this case, directly or indirectly, a temperature sensor can be arranged on or in each inverter, which controls a temperature related to the respective inverter as the measuring temperature in the microprocessor.

According to an advantageous development of this measure, the microprocessor can be programmed or designed such that it carries out a plausibility check on the basis of the values of the measurement temperatures and generates a warning signal if the values of the measurement temperatures are not plausible. In other words, in the microprocessor, the measurement temperatures obtained from the temperature sensors of the different inverters are compared with one another and the warning signal is generated in the event of significant deviations from one another. This warning signal is then visually displayed on a display of the generator and / or reported to a control center.

According to another preferred embodiment it can be provided that the sensor device has an ambient temperature sensor which measures the ambient temperature T_ext and activates it in the microprocessor, wherein the microprocessor is programmed or configured to at least adjust the lower temperature limit T_low and / or the upper temperature limit T_high and / or the first power PW1 and / or the second power PW2 and / or the third power PW3 depending on the ambient temperature T_ext. This ensures that the above values are automatically adapted to the external temperature conditions.

In order to save energy, therefore, the two temperature limits T_high and T_low can be corrected depending on the outside temperature T_ext with the aid of a correction factor. This can be done separately for both temperature limits T_low and T_high by two correction factors or together via a single correction factor. For example, in an embodiment of the inductive heating device as inductive point or rail heating, it is not necessary in heavy snowfall and an ambient temperature T_ext> 0 ° C, that the generator is operated with an equally high heating power P as at -5 ° C.

The predetermined or preset powers starting power PW start, first power PW1, second PW2 and third power PW3 are therefore preferably based on a specific value of ambient temperature T _ext , a reference ambient temperature of, for example, -5 ° C. In particular, when the inductive heating device is designed as inductive point or rail heating, it is then not necessary to further increase the heating power PW of the generator in the case of lower temperatures, since snowfall is not to be expected at lower ambient temperatures. The microprocessor is therefore designed such that the above-mentioned preset or preset powers therefore reduce with respect to the reference ambient temperature increasing ambient temperatures T_ext. In practice, this means that the maximum power PW max is preset for eg an ambient temperature of -5 ° C and heavy snowfall. But if it is then determined on the basis of weather data that no freezing or snowfall is to be expected, the inductive heating device is still switched on and is in standby mode with power output almost zero. However, as the external conditions change, the heating power automatically and continuously increases and the heater is controlled as described above. A ramp-like rise is no longer necessary here because the power increases gradually with decreasing temperature. The energy consumption is primarily dependent on the preset power values, which in turn are adjusted depending on the ambient temperature T_ext and / or on the measured air humidity. The humidity of the environment can therefore enter into the correction factor (s) in addition to the ambient temperature T_ext.

In particular, the correction factors for the limit temperatures T_high and T_low and the correction factors for the line values for the starting power PW start, the first power PW1, the second PW2 and the third power PW3 are preferably not identical. An adaptation of the power values of the generator is for example made linearly with respect to the ambient temperature T_ext.

As already described above, the inductive heating device according to the invention preferably forms an inductive point and / or rail heating device, wherein the body to be heated is formed by a rail and / or by a switch.

The invention therefore also relates to a rail network for rail vehicles, comprising at least one rail and / or a switch, which comprises at least one such inductive point and / or rail heating device.

In such a rail network, at least one inductor may be arranged on one or both side surfaces of at least one rail, in particular on a rail section located in the region of a switch.

As already indicated above, in addition to the above-described control or regulation of the heating device, depending on the lower temperature limit T_low and the upper temperature limit T_high, also a control or regulation of the electric power of the generator by varying the frequency and / or the pulse width of the fed into the at least one inductor alternating current.

This control or regulation takes place during the operation of the inductive heating device, optionally even before their commissioning by presetting the frequency and / or the pulse width by appropriate means for variable adjustment of at least one of these sizes provided means.

Thus, the operating parameters frequency and / or pulse width of the generator controlled and fed into the at least one inductor alternating current to the respective inductor or to the respective inductors in terms of their installation position, number and size are customizable.

A control by a control device can be done, for example, by a purely manual input of frequency and / or pulse width or even map-dependent, i. a certain measured ambient temperature or measurement temperature (e.g., measured rail / switch temperature) is assigned a particular value for the frequency and / or for the pulse width.

For example, the frequency is preferably set lower by the control or regulation, the larger the area to be heated (eg length of the rails / switch components) or the greater the length of the induction coils of the inductors used and possibly also the connecting lines of the inductors with each other or to Generator are. Because the greater the length of the conductor wire of the induction coils, the lower is the frequency of the excitation alternating current to set, which is necessary to generate a desired temperature in the body to be heated magnetic field and thus the necessary induction current in the heated To provide body.

The frequency therefore serves to adapt the power of the generator to the total inductance of the electrical circuit and thus to the length of the induction coils. Conversely, the smaller the surface to be heated or the volume to be heated of the body to be heated or the shorter the length of the Induction coils of the inductors and optionally the connecting lines of the inductors with each other or to the generator, the higher the frequency of the excitation alternating current can be adjusted to a necessary for generating a desired temperature in the body to be heated magnetic field and thus the necessary induction current in the to have heated body available.

The background to these considerations is that as the surface area or volume to be heated increases, the impedance increases as the length of the induction coils increases.

In particular, in the desired electromagnetic induction using periodic or aperiodic control or control functions pulses can be generated.

By the possibility of adjusting the electrical power of the generator in terms of frequency and / or pulse width of the excitation alternating current for the at least one inductor over the prior art, a significant energy saving is possible because due to a possible individual adaptation of the excitation alternating current to the respective Embodiment of the inductor or inductors the impedance, ie the resistance is customizable.

In inductive point or rail heating the inductors are preferably attached to the rails or switch components so that the generated electromagnetic fields and thus the induced currents are concentrated on the area to be heated. This concentration can be enhanced by changing polarity and / or attachment on both sides.

Fig.1

eine schematische Draufsicht auf eine als induktive Weichen- und/oder Schienenheizvorrichtung ausgeführte induktive Heizvorrichtung gemäß einer bevorzugten Ausführungsform der Erfindung;

Fig.2

eine schematische Querschnittsansicht einer Schiene mit seitlich angebrachten Induktoren der erfindungsgemäßen induktiven Heizvorrichtung;

Fig.3

eine schematische Seitenansicht von Windungen eines Induktors der erfindungsgemäßen induktiven Heizvorrichtung;

Fig.4

eine schematische Querschnittsansicht eines an einer Seitenfläche einer Schiene mittels einer abgeschirmten Befestigungsvorrichtung angebrachten Induktors der erfindungsgemäßen Heizvorrichtung;

Fig.5.1

ein Temperatur-Leistungs-Diagramm, welches sich anhand einer bevorzugten Ausführung einer Steuerung oder Regelung eines Generators der erfindungsgemäßen induktiven Heizvorrichtung ergibt;

Fig.5.2

ein Temperatur-Leistungs-Diagramm, welches sich anhand einer weiteren Ausführung einer Steuerung oder Regelung eines Generators der erfindungsgemäßen induktiven Heizvorrichtung ergibt;

Fig.5.3

ein Temperatur-Leistungs-Diagramm, welches sich anhand einer weiteren Ausführung einer Steuerung oder Regelung eines Generators der erfindungsgemäßen induktiven Heizvorrichtung ergibt;

Fig.6

eine graphische Veranschaulichung des magnetischen Flusses, welcher mittels eines Induktors der erfindungsgemäßen Heizvorrichtung in einer Schiene erzeugt wird;

Fig.7a bis d

Beispiele von Impulsfunktionen für eine beliebige zeitabhängige physikalische Größe g, die überwiegend als Hüllkurve mehrerer Pulse entstehen, worin T die Periode der jeweiligen Impulsfunktion darstellt;

Fig.8

eine schematische Gesamtdarstellung einer bevorzugten Ausführungsform des Generators der induktiven Heizeinrichtung;

Fig.9a bis c

Beispiele periodischer Schwingfunktionen in Form von symmetrischen oder asymmetrischen Sägezähnen als Einzeiwelle mit einer Periode und einer Wiederholungsrate;

Fig.10a

rechteckförmige Spannungspulse mit einer Pulsweite von 100%;

Fig. 10b

rechteckförmige Spannungspulse mit einer Pulsweite von 50%;

Fig.11a/b

trapezförmige Funktionsverläufe ohne Pulsunterbrechung, die bei einer Begrenzung der maximal zulässigen Pulsweite in den Fig.10a und 10b nach oben bei sowohl den Größen Strom als auch magnetischem Fluss entstehen;

Fig.12

einen symmetrischen Spannungsverlauf, der ein periodisches bzw. aperiodisches Durchlaufen eines beliebigen Pulsweitenbereichs bei einer Pulsweitenmodulation mit gleichbleibender Frequenz in einer ersten Betriebsart des Generators darstellt;

Fig.13

ein Zeit-Leistungsdiagramm des Generators nach dem Einschalten;

Fig.14

eine schematische Ansicht von Induktoren, welche im elektrischen Kreis derart verschaltet sind, dass sie magnetische Felder gleicher Richtung erzeugen;

Fig.15

eine schematische Ansicht von Induktoren, welche Im elektrischen Kreis derart verschaltet sind, dass sie magnetische Felder von entgegen gesetzter Richtung erzeugen.

The invention will be described below with reference to embodiments with reference to the drawings. Show it

Fig.1

a schematic plan view of a designed as inductive Weichen- and / or rail heating inductive heating device according to a preferred embodiment of the invention;

Fig.2

a schematic cross-sectional view of a rail with side-mounted inductors of the inductive heating device according to the invention;

Figure 3

a schematic side view of turns of an inductor of the inductive heating device according to the invention;

Figure 4

a schematic cross-sectional view of an attached to a side surface of a rail by means of a shielded fastening device inductor of the heating device according to the invention;

Fig.5.1

a temperature-power diagram, which results from a preferred embodiment of a control or regulation of a generator of the inductive heating device according to the invention;

Fig.5.2

a temperature-power diagram, which results from a further embodiment of a control or regulation of a generator of the inductive heating device according to the invention;

Fig.5.3

a temperature-power diagram, which results from a further embodiment of a control or regulation of a generator of the inductive heating device according to the invention;

Figure 6

a graphical illustration of the magnetic flux which is generated by means of an inductor of the heating device according to the invention in a rail;

Fig.7a to d

Examples of impulse functions for any time-dependent physical quantity g, which predominantly arise as the envelope of several pulses, wherein T represents the period of the respective impulse function;

Figure 8

a schematic overall view of a preferred embodiment of the generator of the inductive heating device;

9a to c

Examples of periodic oscillatory functions in the form of symmetrical or asymmetrical saw teeth as a one-time wave with a period and a repetition rate;

Figure 10a

rectangular voltage pulses with a pulse width of 100%;

Fig. 10b

rectangular voltage pulses with a pulse width of 50%;

11A / b

Trapezoidal function curves without pulse interruption, which in a limitation of the maximum permissible pulse width in the 10a and 10b arise upwards for both the quantities of current and magnetic flux;

Figure 12

a symmetrical voltage waveform representing a periodic or aperiodic traversing of any pulse width range in a pulse width modulation with a constant frequency in a first mode of operation of the generator;

Figure 13

a time-power diagram of the generator after power-up;

Figure 14

a schematic view of inductors, which are connected in the electric circuit such that they generate magnetic fields of the same direction;

Figure 15

a schematic view of inductors, which are connected in the electrical circuit such that they generate magnetic fields of opposite direction.

Description of the embodiments

Fig.1 FIG. 2 illustrates a schematic plan view of an inductive point and / or rail heating device 1 as a preferred embodiment of an inductive heating device according to the invention. This heating device 1 includes an electric generator 2, which is supplied with alternating current, for example, from a standard 50 Hz AC mains. Alternatively, it can be a 60 or 16 2/3 Hz AC grid or even a DC grid. The generator 2 is part of a plurality of electrical circuits 4, which preferably in relation to the generator 2 in parallel inductors 6 includes. This means that each of the electrical circuits 4 each include an inductor 6 and the generator 2.

The inductors 6 are preferably each arranged on an outer side surface 12 of two parallel rails 8 in the region of a switch 10, as in particular from Fig.1 . Fig.2 and Figure 4 evident. Alternatively, the inductors 6 may also be arranged both on the inner side surface 14 of the rails 8 and on the outer side surfaces 12 of the rails 8, as in FIG Fig.2 is indicated. In the present case, the mobility of the switch 10 is obtained by heating two parallel rails 8 of a rail track in the region of the switch 10 through the inductive switchpoint and / or rail heating device 1 even at low temperatures or risk of icing. Alternatively or additionally, but also parts components of the switch 10 could be heated.

For heating the rails 8 12 and / or 14 inductors 6 are preferably attached to the side surfaces thereof. The side surfaces 12, 14 are preferably side surfaces of a rail middle part 16, which seen in vertical direction or in cross section between a lower rail 18, which rests mostly on a sill and an upper rail head 20, on which the Laufund flanges of the wheels of rail vehicles unroll and also be guided sideways.

inducers

The inductors 6 can be of any desired design, they can assume flat or round shapes. For structural reasons, round shapes may be preferred. The circuit can be made in series or in parallel as required or according to the required power. Preferably, the inductors are plate-shaped, that is, they have a relatively small thickness measured on the dimension or extent of their side surfaces. The inductors 6 are arranged, for example, equidistantly with respect to the length of the rail or the rails 8 on their side surfaces 12, 14. The inductors 6 are preferably connected to one another in series by electrical connection lines 22 of the electrical circuit 4.

The plate-shaped flat design of the inductors 6 in combination with their attachment to the side surfaces 12, 14 of the rails 8 ensures that the inductors 6 can not be detected by the flanges of the wheels of rail vehicles.

How out Figure 3 As can be seen, such an inductor 8 includes an induction coil 56 with turns 24 of a conductor wire, which are arranged within a single plane, in particular in the plane of the plate. The number of spirals 24, for example spirally designed here, can be adapted by the person skilled in the art if necessary. The windings 24 are preferably cast in a plate-shaped carrier body 26, for example, wherein one end of the conductor wire of the turns 24 protrudes from the mold body 26 in order to be connected to the electric circuit 4 and to close the electric circuit 4.

The plane of the turns 24 of the conductor wire of the induction coil 56 is arranged substantially parallel to the associated side surface 12 or 14 of the rail 8. How through Figure 6 illustrated, when Wechselbestromung the conductor wire of the windings 24 of an inductor 6 in a certain direction (dots in the circle symbolize a flowing out of the plane and a cross in the circle symbolizing a flowing current in the plane) a magnetic field 28, which also detects the relevant, electrically conductive rail 8 and penetrates into this preferably substantially perpendicular to the side surface 12 and / or 14 in order to induce a current there by induction.

The inductor 6 is preferably arranged such that the magnetic flux or the magnetic field lines 28 generated by its induction coil 24 are preferably perpendicular to a surface 12 or 14 of a rail 8 or a switch component of a switch 10 (FIG. Figure 6 ).

The current induced in the rail 8 causes heating of the rail 8 in the area of the switch 10. The heating of the rail or the rails 8 in the area of the switch 10 causes between the rails and the guides the switch for the rails can not form an ice or snow layer which could block movement of the rails 8 moved by the switch 10.

Alternatively, or in addition to the rails 8 also switch components of the switch 10 could be inductively heated by inductors 6, which are arranged accordingly, so that the magnetic field lines can penetrate approximately perpendicular to surfaces of the switch components on which the inductors 6 are arranged.

The magnetic field generator is therefore preferably composed of a plurality of individual inductors 6 which are preferably connected in parallel with respect to the generator 2, each having an identical or different length of conductor wire or identical or different physical properties with respect to its conductor wire (inductance, material, diameter, number of Windings 24 etc.).

Since the physical properties of the individual inductors 6 preferably coincide partially or completely, they can be connected in parallel in a plurality of electrical circuits 4 (depending on the design, also in series or in combination) with respect to the generator 2. The individual inductors 6 can also be seen overlapping alternately left side and right side of the rail in question 8, then seen in particular in the longitudinal direction of the rail 8.

The inductors 6 can be connected in the electrical circuits 4 so that they generate the magnetic field not only in the same direction preferably perpendicular to the rare surface 12, 14 of the rail 8, but for example in the opposite direction, but again preferably perpendicular to the side surface 12th , 14 of the rail 8.

In Figure 14 an embodiment is shown in which arranged on a rail 8 inductors 6 are preferably connected in such a way in the parallel electrical circuits 4, that their magnetic fields extend in the same direction, there symbolized by the "+" in a circle.

Figure 15 shows an embodiment in which two adjacently arranged inductors 6 generate magnetic fields in opposite directions, which is symbolized there by the "+" in the circle and the "-" in the circle. In particular, according to the embodiment of Figure 15 the inductors 6 so interconnected in the electrical circuits 4, that along a rail 8 their magnetic polarity alternates. The opposite polarity of the inductors 6 results in higher temperatures in the rails 8, so that this measure brings a further energy savings.

The inductors 6 are preferably attached laterally to the rails 8 with an outer surface of their carrier body 26 directly or with a minimum distance. For this purpose, the carrier body 26 carrying the windings 24 of the conductor wire may be shaped such that its side surface facing the side surface 12, or 14 of the relevant rail conforms seamlessly to the side surface 12 or 14 of the rail 8.

The intrinsic heat of the inductors 6 is transmitted in this way directly to the rails 8 by contacting heat transfer, wherein the inductors 6 are also cooled by rails 8. The attachment of the inductors 6 to the rails 8 by any fastening devices, preferably by screws, gluing, permanent magnets or by mechanical clamping systems. The attachment of the inductors 6 to the rails 8 must be designed so that it is sufficiently resistant to the weather and mechanical stress such as vibrations.

A preferred fastening device for fastening a plate-shaped inductor on a side surface of a rail, for example, in an L-shaped elastic clip 30, with a first leg 32 at least partially embracing the rail and a holding the inductor 6 on the side surface 12 and 14 of the rail 8 second leg 34, as in Figure 4 is shown.

The first leg 32 engages around the rail 18 from below. The second leg 34 then exerts a lateral bias on the inductor 6, so that it is urged against the side surface 12 and 14 of the rail 8. Thus based the attachment of the inductors 6 on the side surfaces 12 and 14 of the rails 8 to frictional engagement, which is exerted by the bias of the legs 32, 34 of the bracket 30. The second leg 34 of such a clip 30 may be formed such that the ends of the second leg 34 each bent on the end faces of the plate-shaped inductors attack 6 and thereby fix them in the vertical direction.

In a central part of the second leg 34 may also have a convex bulge 36 seen from the inductor 6 to contact the inductor 6 and a shielding body 38, so that a lateral contact force is exerted on the inductor 6 and the shielding body 38, which first leg 32 is then supported on the rail 18. The bracket 30 is then in the cross section of Figure 4 seen burdened on bending. The clip 30 is preferably made of an electrically conductive metal.

How out Figure 4 Also shows, the second leg 34 of the bracket 30 and the inductor 6 at least one preferably plate-shaped shielding body 38 of electrically non-conductive, but magnetically conductive material such as ferrite interposed. This shielding body 38 ensures that the clamp 30 is not heated when the windings 24 of the inductor 6 are traversed by alternating current. In order to prevent or at least limit heating of the clamp 30, it is therefore preferably shielded by a ferromagnetic and non-conductive shielding body 38 from the primary electromagnetic fields.

Construction of the generator

A preferred embodiment of the generator 2 is in Figure 8 shown. The generator 2 has a generator housing 58, on the wall of which supply connections 60 for connecting an AC voltage source or a DC voltage source DC, for example, are tapped off from a catenary of a rail network. Preferably, an AC voltage source is present here.

About these supply terminals 60, a power rectifier 62 is supplied with power. The mains voltage is fed via the mains rectifier 62 in a DC intermediate circuit in a capacitor bank 64 as a charging device. By means of inverters 66a, 66b connected in parallel with respect to the capacitor battery 64, here for example transistor inverters, a square-wave voltage is generated, which is then fed into the inductor 6a, 6b of the relevant electric circuit 4a, 4b, which are connected to inductor terminals of the generator housing 58 are. Each inverter 66a, 66b therefore preferably controls an inductor 6a, 6b within an electrical circuit 4a, 4b. For reasons of clarity, only two electrical circuits 4a, 4b are shown, each with an inductor 6a, 6b. However, it is understood that more than just two electrical circuits or inductors can be present.

The inverters 66a. 66b are controlled by a microprocessor 44, which includes algorithms stored in a memory, which will be discussed later. The microprocessor 44 is controlled by an operating device 40, which setting means 42 for manually and separately setting the frequency and / or the pulse width PW of the current injected into the electrical circuits 4a, 4b and thus in the inductors 6a, 6b alternating current. These setting means 42 preferably have a display 46, on which the set values for frequency f and / or the pulse width PW are displayed. The adjusting means 42 as well as the display 46 are preferably arranged on the generator housing 58 and therefore operable or visible from the outside.

On the generator housing 58, a sensor terminal 70 is further provided, which is signal-connected to the microprocessor via an internal signal line. Connected to the sensor connection 70 here is a temperature sensor 72, which is arranged, for example, on an outer surface of the generator housing 58 so that it can measure the ambient temperature T_ext uninfluenced by the heat development of the generator 2 in operation and can control a corresponding signal in the microprocessor 44.

Furthermore, temperature sensors 74a, 74b, which measure the temperature of the inverters 66a, 66b and control corresponding temperature signals via internal signal lines in the microprocessor 44, are arranged on heat sinks of the inverters 66a, 66b, which are not explicitly shown here.

The following components or components are therefore preferably arranged in or on the generator housing 59: the supply terminals 60, the mains rectifier 62, the capacitor bank 64, the inverters 66a, 66b, the inductor terminals 68a, 68b, the microprocessor 44, the operating device 40 with the adjusting means 42 and the display 46, the inductor terminals 68a, 68b, the sensor terminal 70 and of course all internal wiring and lines.

The temperatures T_int1 and T_int2 measured by the internal temperature sensors 74a, 74b relative to the generator housing 58 preferably represent here the actual temperatures of the inverters 66a, 66b during their operation and therefore internal temperatures with respect to the interior of the generator housing 58 the temperature T_int1 corresponds to the temperature of the inverter 66a and the temperature T_int2 corresponds to the temperature of the inverter 66b. Alternatively, however, it would also be possible to measure a temperature of another component or another assembly of the generator 2 as the internal temperature of the generator housing 58.

For an optional measurement of the air humidity, a separate air humidity sensor 48 can be provided, which activates a signal corresponding to the instantaneous air humidity into the microprocessor 44. However, data about the ambient temperature Text and / or the humidity can also originate from external sources and be wirelessly controlled into the microprocessor 44 via a receiving device integral with respect to the generator 2.

Furthermore, a temperature sensor 76 is installed on at least one rail 8 and / or switch 10, which measures the temperature of the rail 8 and / or switch components in the region of a switch 10, wherein temperature signals for the actual rail / switch temperature in the microprocessor 44 is controlled become.

Manual power control

According to one embodiment, the operating parameters frequency and / or pulse width of the generator 2 are preferably manually adjustable via the adjustment means 42. Preferably, therefore, both the frequency f and the pulse width PW of the excitation alternating current can be varied by the adjustment means 42 here. Alternatively, only one of these operating variables or parameters could be varied. Therefore, since the power of the generator 2 depends on both the frequency f and the pulse width PW, the power of the generator 2 can be adjusted by adjusting the values for the frequency f and / or the pulse width PW. In this case, a higher frequency leads to a higher power and a lower frequency f to a lower power of the generator 2. Furthermore, in the context of a pulse width modulation adjustment of a larger pulse width PW (wider pulse) for a larger power and a smaller pulse width PW (narrower pulse ) for a comparatively smaller power of the generator 2.

As in Figure 8 schematically represents, controls the control device 40 with the adjustment means 42, therefore, the set values for the frequency f and / or the pulse width PW in a microprocessor 44, which in turn controls the generator 2 and its inverters 66a, 66b, which then said Set sizes in the electrical circuits 4a, 4b. The set values for frequency f and / or pulse width PW are shown on the display 46.

The manual adjustment of the frequency f and / or the pulse width PW can of course be carried out before the operation of the heater 1 or even during operation.

Line control by map

According to a further embodiment, the power P of the generator 2 by means of the microprocessor 44 by changing the pulse width PW and / or the frequency f of the excitation alternating current driven by the generator 2 depends on the ambient temperature T_ext and / or on the rail / switch temperature controlled according to at least one predetermined map. The map is stored in the microprocessor 44.

In a freely determinable ambient temperature range, in particular in a temperature range of +5 ° C to -15 ° C, the output of electrical energy, for example, over the pulse width of the exciter AC current according to a specific algorithm, for example linear as in Figure 5 , 1 controlled. For example, at an ambient temperature of + 5 ° C and above, the output by the generator 2 electric power P is driven by controlling the pulse width PW to zero, at -15 ° C and less, however, the maximum electric power is set on the generator 2, as well in Fig.5.1 shown.

Since the generator 2 preferably has no resonant or oscillatory circuit, furthermore, the frequency f of the exciter alternating current is freely adjustable with regard to the physical properties of the inductors 6. The magnitude of the induced currents is frequency (linear) and field strength dependent (up to quadratic depending on the degree of coupling). The field strength is directly proportional to the excitation alternating current flowing through the inductor 6 or the inductors 6 given the prevailing conditions.

The optimum for the energy transfer, in particular for the value of the frequency of the excitation alternating current is therefore determined by the physical properties of the inductor 6 or the inductors 6. It has been found that a particularly high efficiency is achieved in a medium-frequency range of 5 kHz to 15 kHz. The electrical energy requirement of the heating device 1 is then on average below 250 W / m but can be increased to> 600 W / m. This corresponds approximately to a magnetic field strength H of 200 A / m, which value is dependent on the inductor, and may also be less than 100 A / m. The temperature increase dT in the rail 8 / switch 10 with a constant supply of electrical energy is e.g. at 20 K, in particular between 5 K and 50 K.

power control

According to a further embodiment, the microprocessor 44 could also have the pulse width PW and / or the frequency f of the excitation alternating current controlled by the generator 2 as a function of at least one reference variable such as the ambient temperature T_ext and / or the rail / switch temperature and / or also dependent on one These temperatures in combination with the humidity regulate.

It is conceivable as an additional reference variable also a detection of other environmental parameters such as snowfall. Humidity or snowfall are important because they have an influence on the formation of ice near switches.

The output power of the generator 2, which is supplied to the inductor or inductors 6, is regulated, in turn, by changing the pulse width PW and / or the frequency f of the exciter alternating current, which flows through the inductor or inductors 6, depending on the command variable or the command variables , Corresponding control algorithms are implemented in the microprocessor 44.

The power control of the generator 2 is preferably accomplished by a continuous change of the pulse width PW. It is also possible to perform the power control by frequency modulation. However, then the efficiency is slightly worse.

An example of a power control process can also be done by Figure 5 , 1 are shown where the electric power of the generator 2 (in kW), which is proportional to the pulse width PW, depending on the ambient temperature T_ext (in ° C) is shown. As can be seen, here the power output of the generator 2 is regulated as a function of a reference variable, here for example the ambient temperature T_ext linearly between two freely settable ambient temperature limits, namely between a lower temperature limit (here eg -15 ° C) and an upper temperature limit (here eg + 5 ° C) for the ambient temperature T_ext.

Is therefore in the example of Fig . 5 . 1 the ambient temperature T_ext is less than or equal to the lower temperature limit T_u (here -15 ° C.) or greater than the upper temperature limit T_o (here eg + 5 ° C.), then a constant, but different electrical power P or pulse width PW is set. Between the two temperature limits T_o and T_u, the power output or the change in the pulse width PW, for example, runs linearly dependent on the reference variable (P controller).

According to another, in Figure 5 , 2 and Figure 5 , 3 illustrated mode, an average temperature T_av (here (here, for example, -5 ° C), which is exactly in the middle of the range between the upper temperature limit T_o (here, for example, + 5 ° C) and the lower temperature limit T_u (here, for example, 15 ° C). on the abscissa, the ambient temperature T_ext and the ordinate represents the electric power P of the generator 2 is applied again (in kW). in this mode, T be a function of the change in ambient temperature _{_EXT} starting from the mean temperature T_av either set in the direction of the upper temperature limit T_o or the lower temperature limit T_u different control algorithms for the power output of the generator 2.

By way of the setting means 42 of the operating device 40, the lower and upper temperature limit values T_o, T_u as well as the average temperature T_av can be input. These are empirical values, but these can be adapted to local circumstances if necessary.

All control operations can be linear (P control). But it is also possible to perform the control operations as PI or PID control or to combine with each other. Consequently, any control algorithms are possible.

In the example of Figure 5 , 1 is a P-control realized in which a linear range between the upper temperature limit T_o (here: + 5 ° C) and the lower temperature limit T_u (here: -15 ° C) is present. At ambient temperatures T _ext greater than _or equal to the upper temperature limit (here + 5 ° C), the generator 2 operates on the other hand with a constant minimum power output, the pulse width PW can be lowered to zero. At an ambient temperature T_ext less than or equal to the lower temperature limit (here -15 ° C), the generator 2, on the other hand, operates at maximum power.

But it is also possible to set a freely selectable temperature-dependent correction factor via the adjusting means 42 of the operating device 40. For example, the correction factor indicates a percentage of the power output per ° C set for the mean temperature T_av. The regulation then refers to the mean temperature T_av and alters the power output, e.g. between zero and maximum allowable power output. Here, too, advantageously two different correction factors for both directions can be determined, starting from the average temperature T_av up to the upper temperature limit and down to the lower temperature limit.

Operating modes of the heater

According to one operating mode, the inductive heating device 1 is remotely switched on or off as required by a railroad station (energizing, discharging the generator), in which case an operation, for example, with previously set constant operating parameters (frequency f, pulse width PW), during the operation map-controlled or manually varied operating parameters (frequency f, pulse width PW) as well as regulated is possible.

According to another mode, the inductive point and / or rail heating device 1 continuously over a predetermined heating period (eg from October to March of each year in the northern hemisphere) with constant (electric) power P, with variable manual or map-controlled power PW or operated with regulated power PW.

Since the temperature rise rate in the rail 8 / turnout 10 depends directly on the output (electric) power PW of the generator 2, the power of the generator 2 according to another mode immediately after switching on the generator 2 or an activation of the heater 1 for a increased and then back to an operating value be driven, as will be explained later in the context of the operating modes of the generator.

Operating modes of the generator

For the generation of the electromagnetic field by the inductors 6, these are preferably excited only by periodic oscillation functions of the excitation alternating current. Quadrilateral voltage pulses automatically generate symmetrical trapezoid-shaped current pulses with freely adjustable ratio between a dynamic and a static component. For a process flow can be selected by means of the operating device 40 which controls the microprocessor 44, between modes of a constant mode, a frequency mode and a pulse width mode. Furthermore, there is also a basic mode according to which the characteristics of the excitation alternating current are not changed. These operating modes or modes of the generator 2 are stored as control software in the microprocessor 44 and can be adjusted via the operating device 40.

The control software for the generator 2 for generating alternating magnetic fields implemented in the microprocessor 44 preferably includes a combination of higher frequencies, preferably frequencies in the kHz range, with a superimposed one. Modulation in the low-frequency range such that preferably only oscillating or alternating functions (and thus no pulse or pulse functions) with a rectangular voltage curve and trapezoidal current waveform arise.

Thus, these curves from a frequency range of, for example, 5 kHz to 60 kHz, preferably 5 kHz to 15 kHz continuously modulate through freely selectable periods of time, wherein the higher-order modulation is preferably in a range between 0.1 to 10 Hz. In practical terms, this results in a higher-level modulation of 0.5 Hz for a section time of one second, a higher-level modulation of 5 Hz for a section time of 100 ms, and so on. The frequency values are changed according to the clock of the microprocessor 44, for example a thousand times per second. This procedure is applicable to all the above operating modes. The low frequency range of preferably 0.1 Hz to 10 Hz, by having the superordinate modulation, can advantageously enhance the effects of the resulting electromagnetic field changes on the rail / shunt.

According to a basic mode of the generator 2, the frequency f as well as the pulse width PW of the exciting AC current are kept constant.

According to a first operating mode of the generator 2, the pulse width PW of the excitation alternating current is continuously changed while the frequency f of the exciter alternating current remains constant. In the realization of the continuous pulse width change, for example by means of MOSFETs or IGBTs, these can advantageously operate in low-loss switching operation. Further advantageously, the information to be displayed is contained in a continuous pulse width ratio instead of in a binary manner.

According to a second mode of operation of the generator 2, the frequency f of the exciter alternating current is continuously changed while the pulse width remains constant. Although this second mode of operation is possible in principle, it is preferably not used. The generator control in the microprocessor 44 is constructed so that said modes are freely programmable and storable. It is also advantageous if limit values for all operating modes are freely adjustable. This ensures that application-related limit values can be reliably met. It is also advantageous if time constants required for the individual operating modes are all freely adjustable. This improves the controllability of the generator 2 and thus of the electromagnetic field to be generated.

As detailed above, a frequency and / or pulse width modulation is performed for the power control or power control of the generator 2.

In outdoor generators 2, it may not be advisable for thermal reasons, for example, at ambient temperatures during a very cold period T_ext of -20 ° C and less to turn on the full generator power abruptly. It is then more advantageous to ramp up the power of the generator 2. In the context of a start mode of the generator 2, the generator power P is preferably set, controlled or regulated by varying the pulse width PW at a constant frequency f. This is the case when a switch-on signal comes from a higher-level controller, for example in a control panel.

The diagram of Figure 13 shows a preferred course of the power PW of the generator 2 in a start mode and in this subsequent operating mode after turning on the generator 2 at a constant frequency f and variable pulse width PW. Since the power P of the generator then depends directly on the pulse width PW, the ordinate represents the pulse width PW representative of the power P.

In the algorithms implemented in the microprocessor 44, a temperature range between a lower temperature limit T_low and an upper temperature limit T_high is specified here, in each case for the temperatures of the inverters 66a, 66b, which are measured by the temperature sensors 74a, 74b and referred to below as measurement temperatures, as internal temperatures, see Figure 8 , The values for the lower temperature limit value T_low and the upper temperature limit value T_high are input to the generator 2 via the setting means 42 of the operating device 40, for example.

• Im Rahmen des Startmodus nach einem Einschalten des Generators 2 (Bestromen) wird die Leistung PW des Generators 2 ausgehend von einer vorgegebenen Startleistung PW Start am Punkt P1 über eine vorgegebene erste Zeitspanne t1 rampenartig auf eine demgegenüber höhere erste Leistung PW1 erhöht, welche kleiner oder gleich in Bezug auf eine maximale Leistung PW_max des Generators 2 ist. Unter der maximalen Leistung PW_max des Generators 2 wird die maximale Leistung PW des Generators 2 verstanden, die dieser aufbringen kann. Die vorgegebene erste Zeitspanne t1 wird ebenfalls zuvor über die Einstellmittel 42 der Bedieneinrichtung 40 in den Generator 2 eingegeben.

The electrical generator 2 or, in particular, its inverters 66a, 66b are then controlled by the microprocessor 44 on the basis of implemented algorithms, preferably as follows:

• In the context of the start mode after switching on the generator 2 (energizing), the power PW of the generator 2 is ramped from a predetermined starting power PW start at point P1 over a predetermined first time t1 to a higher first power PW1 which is smaller or equal with respect to a maximum power PW_max of the generator 2. Below the maximum power PW_max of the generator 2, the maximum Power PW understood by the generator 2, which can muster this. The predetermined first time period t1 is also previously input via the adjusting means 42 of the operating device 40 in the generator 2.

This first power PW1 is then kept constant for a predetermined second time period t2. The predetermined second time interval t2 is also previously input via the adjusting means 42 of the operating device 40 in the generator 2.

Then, when the point P2 is reached after the lapse of the second time period t2, the power PW of the generator 2 is abruptly lowered to a comparatively lower second power PW2, which is in a range between the starting power PW start and, for example, half the value of the first power PW1 lies.

Then, the generator 2 is operated under the second power PW2 (until the point P4) until the measurement temperatures have reached the lower temperature limit T_low. This completes the start mode and automatically connects to the (continuous) operating mode at point P4.

As part of the operating mode, the power PW of the generator 2 is then ramped up until at point P5 a predetermined, compared to the second power PW2 larger or higher third power PW3 is achieved, which is less than or equal to the first power PW1.

Then, the generator 2 is operated under the third power PW3 until the measurement temperatures have reached the upper temperature limit T_high. This point is in Figure 13 designated P6.

Then, the power PW of the generator 2 is abruptly lowered to the second power PW2 (point P7), and then the generator 2 is operated under the lower second power PW2 until the measurement temperatures reach the lower temperature limit T_low, which is in Figure 13 is symbolized by the point P8.

Subsequently, as part of the operating mode, the ramp-up of the power from the second power PW2 to the third power PW3, the holding of the third power PW3 to T_high is reached, and the sudden lowering from the third power PW3 to the second power PW2 cyclically repeated as long as the generator is in operation or is energized.

As a result, a cycle is repeated in the operating mode of the generator 2, which ensures operation of the generator 2 in a temperature range between the lower temperature limit T_low and the upper temperature limit T_high, in which no temperature damage to the generator 2 and / or the inductors 6 are to be feared. This cycle or the operating module is terminated only after switching off the generator 2.

Thus, an adaptive multi-point temperature control is realized, wherein the control points are formed by the lower temperature limit T_low and the upper temperature limit T_high.

The average power Pav delivered to the rail is dependent on how fast after the jump from PW1 (or PW3) the lower limit temperature T_low can be reached. By additional cooling measures (such as "active cooling" through the use of fans), the average power Pav can be significantly increased, so that the use in high mountains would be readily possible, so-called "supper boost".

During the start mode, therefore, the temperatures at the inductors 6 are greatly increased, so that there is an effect similar to resistance bars, the so-called "super boost". Thereafter, the control or regulation of the heater 1 is automatically in the operating mode and thus in the "temperature limit system" on.

In particular, the above and in Figure 13 The multi-point temperature control described above is the control of the size-based control or regulation of the power of the generator 2. The management-based control or regulation of the power of the generator 2 is therefore preferably juxtaposed to the multi-point temperature control.

Both controls therefore have their own reference variables. The control / regulation has as reference variable (s) the ambient temperature T_ext and / or the humidity and / or an occurrence of snowfall and / or the temperature of the rail / switch and controls the generator 2 by switching the generator 2 on and off Control / regulation can not prevent turning off the generator 2 due to a high internal temperature of the generator 2, whereby the problems described above occur. The further control / regulation (adaptive multi-point temperature control) has the task by suitable power control to protect the generator 2 against overheating and to prevent unwanted switching off and to improve the power output. The reference variables of this further control / regulation (adaptive multi-point temperature control) are here exclusively the temperatures described above (lower temperature limit T_low, upper temperature limit T_high, or T_ext).

By means of the operating device 40 communicating with the microprocessor 44, via which, for example, at least one value for the first time period t1, a value for the second time interval t2, a value for the starting power PW start, a value for the first power PW1, a value for the Second power PW2 and / or a value for the third power PW3 is controlled in the microprocessor 44, the temperature monitoring of the inductive heating device 1 can be flexibly adapted to the respective structural design and to the environmental conditions. Furthermore, thereby the energy consumption and the thermal load of the inductive heating device 1 can be controlled.

Furthermore, algorithms implemented in the microprocessor 44 may specify an absolute upper limit temperature T_abs as a value for a temperature in the sense which may be reached at most from the measurement temperature (s). This absolute upper limit temperature T_abs, in contrast to the upper limit temperature T_high, which, although predetermined, but can be varied by default, represents an invariable value and is in particular greater than the upper limit temperature T_high. If the measurement temperature (s) this absolute upper Limit temperature T_abs reaches (reach) or exceeds (exceed), so the microprocessor 44 is designed in particular that it generally turns off the generator 2 (de-energized). This case only occurs when the control should not work at the upper limit temperature T_high. The functionality of the control is monitored by a plausibility check described below.

As above, in the above-described start mode and operation mode, the microprocessor 44 controls the electric power PW of the generator 2 by varying the pulse width PW of the AC power supplied to the inductors 6. Preferably, therefore, the frequency f is kept constant and only the pulse width PW used as a reference variable of the superimposed control.

The microprocessor 44 is preferably designed such that it carries out a plausibility check on the basis of the values of the internal temperatures T_int1 and T_int2 and, if the values of the internal temperatures T_int1 and T_int2 are not plausible, generates a warning signal, which is displayed on the display 46, for example. In other words, in the microprocessor 44, the measurement temperatures obtained from the temperature sensors 74a, 74b of the different inverters 66a, 66b are compared with one another and the warning signal is generated in the event of significant deviations from one another.

Furthermore, here the microprocessor 44 is preferably designed such that it adapts at least the lower temperature limit value T_low and / or the upper temperature limit value T_high and / or the first power PW1 and / or the second power PW2 and / or the third power PW3 depending on the ambient temperature T_ext , This ensures that the above values are automatically adapted to the external temperature conditions.

To save energy, therefore, the two temperature limits T_high and T_low can be corrected depending on the outside temperature T_ext with the aid of a correction factor. This can be done separately for both temperature limits T_low and T_high by two correction factors or together via a single correction factor. For example, it is in heavy snowfall and At an ambient temperature T_ext> 0 ° C, it is not necessary for the generator to be operated with an equally high heating power P as at -5 ° C.

The predetermined or preset powers starting power PW start, first power PW1, second PW2 and third power PW3 are therefore preferably based on a specific value of ambient temperature T_ext, a reference ambient temperature T_ext_Bezug of eg -5 ° C. It is then not necessary in contrast to lower temperatures to increase the heat output PW of the generator 2 on, since at lower ambient temperatures T _{ext is} not expected to snowfall. The microprocessor 44 is therefore designed such that the abovementioned preset or preset powers are therefore reduced at increasing ambient temperatures T_ext with respect to the reference ambient temperature T_ext_Bezug. In practice, this means that the maximum power PW max is preset for eg an ambient temperature T_ext of -5 ° C and heavy snowfall. However, if it is then determined on the basis of weather data that no freezing or snowfall is to be expected, the inductive heating device 1 will not be switched on, for example. However, as the external conditions change, the inductive heater 1 is turned on and controlled as described above. The energy consumption is primarily dependent on the preset power values, which in turn are adjusted depending on the ambient temperature T_ext and / or on the measured air humidity. The humidity of the environment can therefore go into the or the correction factor (s) in addition to the ambient temperature T_ext.

In particular, the correction factors for the limit temperatures T_high and T_low and the correction factors for the line values for the starting power PW start, the first power PW1, the second PW2 and the third power PW3 may preferably not be identical. An adaptation of the power values of the generator 2 is carried out, for example, linearly with respect to the ambient temperature T_ext.

Physical background

Some examples of pulse functions for any time-dependent physical quantity g, here the excitation alternating current of the induction coils 56, which arise predominantly as the envelope of several pulses are in the FIGS. 7a to 7d where T represents the period of the respective impulse function.

Furthermore, methods are known in which periodic oscillatory functions in the form of symmetrical or asymmetrical saw teeth are used as a single wave with a period of eg 10 ms (T1, corresponding to 100 Hz) with a repetition rate of 100 ms (T2, corresponding to 10 Hz). Examples of such periodic oscillatory functions are in FIGS FIGS. 9a to 9c shown.

If, in the following, a function is referred to as "pulse" or "pulse", it is always a function course during a half-period. This is followed by a pulse with the opposite sign. In the case of a voltage curve, the positive and negative pulses take place with a zero phase between the two half-waves; in the case of a current profile and / or a field profile, this sequence is uninterrupted. In this case, the two half-waves form a periodic alternating function.

The magnetic flux Φ is directly proportional to the electric current I causing it. The proportional constant is called inductance L and represents the characteristic size of an inductor: $$\mathrm{\Phi }=\mathrm{L}\times \mathrm{i}$$

The above equation states at the same time that the course of the magnetic flux in linear systems faithfully follows the course of the current. If the current i increases linearly, the flux Φ also increases linearly; if the current i is constant, the flux Φ also assumes a constant value.

wobei die induzierte Spannung $$\mathrm{u}=-\mathrm{d\Phi }/\mathrm{dt}$$

ist. Je höher die Frequenz f ist, desto höher ist auch die induzierte Spannung u. Allerdings ist auch eine hohe Feldstärke Φ notwendig, d.h. es wird dazu ein größerer Strom i benötigt. Strom i und Feldstärke Φ zusammen bestimmen den Arbeitsbereich (Spannung und Frequenz) an den Induktoranschlüssen 68a und 68b des Generators 2.Since these are linear systems and time-dependent curves, ie alternating currents, the equation can be differentiated by time: $$\mathrm{d\Phi }/\mathrm{dt}=\mathrm{L}\times \mathrm{di}/\mathrm{dt}$$

the induced voltage $$\mathrm{u}=-\mathrm{d\Phi }/\mathrm{dt}$$

is. The higher the frequency f, the higher the induced voltage u. However, a high field strength Φ is also necessary, ie it requires a larger current i. Current i and field strength Φ together determine the working range (voltage and frequency) at the inductor terminals 68a and 68b of the generator 2.

Particularly advantageous is a perpendicular to a surface of the rail 8, in particular to a side surface 12, 14 of the rail 8 extending direction of the field lines shown (see Figure 6 ). The magnetic field strength or the induction of the magnetic field produced by the induction coil 56 is controlled by means of a frequency and / or a pulse width modulation.

As explained above, a control or regulation of the power P of the generator 2 by means of a pulse width modulation is referred to as a first operating mode, a control or regulation by means of a frequency modulation as a second operating mode.

It is preferred to use exclusively periodic oscillatory functions which assume both positive and negative values, without these having to be in a defined relationship to one another. A periodic function satisfies the equation: $$\mathrm{f}\left(\mathrm{t}+\mathrm{T}\right)=\mathrm{f}\left(\mathrm{t}\right)$$

In the limiting case, the oscillating functions are transformed into alternating functions, whereby the positive and negative areas bounded by the voltage curve are identical within one period.

Both positive and negative voltage pulses are rectangular. In Figure 10a is the pulse width PW at 100%, in 10B shown with 50%. The control signals for the current and thus also for the course of the current are generated in such a way that there is no interruption in both, independently of the respective pulse width PW comes. If the maximum permissible pulse width PW is limited to the top - for example, with 75% - arise in the current uninterrupted trapezoidal similar waveforms without pulse interruption, as in the Figures 11a and 11b shown.

The first operating mode or pulse width mode preferably used here allows a periodic or aperiodic passage through an arbitrary pulse width range at a constant frequency f via corresponding control specifications. This corresponds to one in Figure 12 shown pulse width modulation: $$\mathrm{PW\_mode\; at\; f}=\mathrm{const}\mathrm{,}$$

The first operating mode (pulse width mode) results in a current change and thus also in a flux change. Both quantities can be continuous, i. be changed in a ramp, or jump between two freely selectable limits.

In Figure 12 a symmetrical voltage curve is shown. The corresponding current profile then results analogously to 11B ,

All defaults can be set via any arbitrary time or pulse rate constants either manually (by means of a keyboard, for example) or automatically (for example, by means of the control or the control).

As described above, the inductive heating apparatus 1 includes a generator 2 having at least one inductor 6 with at least one induction coil 56 for generating an electromagnetic field with alternating current.

The voltage present at the output of the generator 2 is preferably generated in the form of quadrilateral pulses. The current flowing through the induction coil 56 preferably assumes a symmetrical trapezoidal shape. The trapezoidal-shaped current pulses are preferably generated as individual pulses without additional frequency modulation. The freely adjustable frequency range is preferably between 5 kHz and 15 kHz.

The limit values for all operating modes are freely adjustable via the operating device 40. All time constants required for the individual operating modes are likewise freely adjustable via the operating device 40. The gradients are symmetrical. The processes can be carried out with a variable number of pulses or with a constant number of pulses. For this purpose, the generator 2 has a control / regulation freely programmable by the operating device 40 or the adjusting means 42. This programmable controller is implemented in a microprocessor 44.

Therefore, a generator 2 controlled by the microprocessor 44 as described above is preferably used to supply AC power to inductors 6 provided in an inductive heater 1 for attachment to a rail 8 or shunt 10, the one controlled or controlled by the microprocessor 44 Generator 2, the frequency f and / or the pulse width PW of the excitation alternating current of the inductors 6 changed.

In other words, an in Figure 8 in summary, shown inductive heating device with at least one of an example AC voltage source fed generator 2, a line connection 22 between the generator 2 and at least one at least one induction coil 56 containing inductor 6 for supplying the at least one induction coil 56 with generated by the generator 2 alternating current, and with a control or regulating device 44 for controlling or regulating the electric power of the generator 2 by varying the frequency f and / or the pulse width PW of the alternating current fed into the induction coil 56 is preferably used as an inductive point and / or rail heating, wherein the at least one Inductor 6 is arranged on a rail 8 and / or on a switch 10 of a rail network and in which due to the supplied with the AC induction coil 56 in the rail 8 and / or in the switch 10 by electromagnetic induction inducing a current is decorated, which heats the rail 8 and / or the switch 10.

Of course, instead of heating switches / rails, the inductive heater may be used to heat any other electrically conductive one Body can be used. The multi-point temperature control described above serves to protect the generator of the inductive heating against overheating while optimizing performance and can be applied to all inductive heating regardless of application and cooling (convection, forced ventilation, water cooling, ...). It is therefore applicable to all continuous or quasi-continuous inductive heating processes.

LIST OF REFERENCE NUMBERS

1

contraption

2

generator

4a, b

electrical circuits

6a, b

inducers

8th

rail

10

switch

12

outer side surface

14

inner side surface

16

Rail middle part

18

rail

20

railhead

22

interconnectors

24

turns

26

support body

28

magnetic field lines

30

clip

32

first leg

34

second leg

36

bulge

38

shielding

40

operating device

42

adjustment

44

microprocessor

46

display

48

Humidity Sensor

56

induction coil

58

generator housing

60

supply connections

62

Mains rectifier

64

capacitor bank

66a / b

inverter

68a / b

inductor terminals

70

sensor connection

72

Ambient temperature sensor

74a / b

Tempertursensor

76

temperature sensor

Claims (14)

An inductive heating device (1) which includes a generator (2) powered by a voltage source and at least one inductor (6), wherein a) the generator (2) as modules at least one power rectifier (62), at least one microprocessor (44), at least one charging device (64) and at least one inverter (66a, 66b) and the assemblies of the generator (2) in a generator housing (58) are housed, b) the generator (2) controlled by the electronic control (44) via a line connection (22) at least one inductor (6) containing at least one induction coil (56) for attachment to an electrically conductive body (8, 10) to be heated ) supplied with alternating current, and c) due to the induction coil (56) of the inductor (6) fed with the alternating current, a current is induced by electromagnetic induction in the electrically conductive body (8, 10) to be heated, which heats the body (8, 10) to be heated, and d) in the microprocessor (44) algorithms for controlling or regulating the power of the generator (2) are implemented as a function of a reference variable (T _ext ), characterized in that e) a sensor device (72; 74a, 74b; 76) which is signal-connected to the microprocessor (44) and which has at least one internal temperature (T_int1, T_int2) prevailing in the interior of the generator housing and / or the inductor temperature of the at least one inductor (6). measures as measuring temperature (s) and enters the microprocessor (44), wherein f) in the microprocessor (44) implemented algorithms a temperature range between a lower temperature limit (T_low) and an upper temperature limit (T_high) is specified for the measurement temperature, wherein g) the electric generator (2) is controlled by the microprocessor (44) such that g1) in the context of a start mode after switching on the generator (2) the power (PW) of the generator (2) starting from a starting power (PW _start ) over a predetermined first time period (t1) ramped to a comparatively higher first power (PW1) which is less than or equal to a maximum power (PW max) of the generator (2), and g2) this first power (PW1) is kept constant for a predetermined second period of time (t2), and then g3) the power (PW) of the generator (2) is abruptly lowered to a comparatively lower second power (PW2), which is greater than the starting power PW Start, and then g4) the generator (2) is operated under the second power (PW2) until the measurement temperature has reached the lower temperature limit (T_low) and then g5) under an operating mode g5.1), the power (PW) of the generator (2) is ramped up until a predetermined, compared to the second power (PW2) larger third power (PW3) is achieved, which is less than or equal to the first power (PW1) is, and then g5.2) the generator (2) is operated under the third power (PW3) until the measurement temperature has reached the upper temperature limit (T_high) and then g5.3) the power (PW) of the generator (2) is suddenly reduced to the second power (PW2) and then g5.4) the generator (2) is operated below the lower second power (PW2) until the measurement temperature has reached the lower temperature limit (T_low) and then g5.5) the steps g5.1) to g5.4) are repeated cyclically. Inductive heating device according to claim 1, characterized in that an operating device (40, 42) communicating with the microprocessor (44) is provided, via which at least one value for the first period (t1), a value for the second period (t2), a value for the starting power (PW Start), a value for the first power (PW1), a value for the second power (PW2) and / or a value for the third power (PW3) in the microprocessor (44) is einsteuerbar. Inductive heating device according to one of the preceding claims, characterized in that the sensor device (72; 74a, 74b; 76) comprises at least one temperature sensor (74a, 74b) which has a temperature (T_int1, T_int2) of the at least one inverter (66a, 66b) of the generator (2) detected as a measuring temperature and in the microprocessor (44) einsteuert. Inductive heating device according to one of the preceding claims, characterized in that in the microprocessor (44) implemented algorithms an absolute upper limit temperature (T_abs) is predetermined, wherein if the measurement temperature (T_int1, T_int2) this absolute upper Limit temperature (tabs) reached or exceeded, the microprocessor (44) is designed to turn off the generator (2). Inductive heating device according to one of the preceding claims, characterized in that the microprocessor (40) for controlling the electric power of the generator (2) by varying the frequency (f) and / or the pulse width (PW) of the at least one inductor (6) fed AC is formed. Inductive heating device according to one of the preceding claims, characterized in that an additional reference variable is the ambient temperature (T_ext) and / or the temperature of the body to be heated (8, 10) and / or the inductor temperature of at least one inductor (6). Inductive heating device according to one of the preceding claims, characterized in that the generator (2) includes a plurality of inverters (66a, 66b) connected in parallel with respect to the charging device (64), each of the inverters (66a, 66b) having an inductor (6a, 6b) is connected. Inductive heating device according to claim 7, characterized in that on or in each inverter (66a, 66b) directly or indirectly, a temperature sensor (74a, 74b) is arranged, which on the respective inverter (66a, 66b) related temperature (T_int1, T_int2 ) in the microprocessor (44) einsteuert as the measuring temperature. Inductive heating device according to claim 8, characterized in that the microprocessor (44) is designed to perform a plausibility check based on the values of the measurement temperatures (T_int1, T_int2) and generates a warning signal if the values of the measurement temperatures (T_int1, T_int2) are not plausible. Inductive heating device according to one of the preceding claims, characterized in that the sensor device (72; 74a, 74b; 76) has at least one ambient temperature sensor (72) which measures the ambient temperature (T_ext) and drives it into the microprocessor (44), the microprocessor (44) is designed such that it has at least the lower temperature limit value (T_low) and / or the upper temperature limit value (T_high) and / or the first power (PW1) and / or the second power (PW2) and / or the third power (PW2 ) depending on the ambient temperature (T_ext). Inductive heating device according to one of the preceding claims, characterized in that it forms an inductive Welchen- and / or rail heating device, wherein the body to be heated (8, 10) is formed by a rail and / or by a switch. Rail network for rail vehicles, comprising at least one rail (8) and / or a switch (10), characterized in that it comprises at least one inductive Welchen- and / or rail heating device (1) according to claim 11. Rail network according to claim 12, characterized in that the at least one inductor (6) is arranged on one or both side surfaces (12, 14) of at least one rail (8). Rail network according to Claim 13, characterized in that the at least one inductor (6) is arranged on the rail (8) in a rail section located in the region of a switch (10).

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