Method and device for non-contact detection of the temperature of a rotating component of an electric machine

Abstract

The invention relates to a method for non-contact temperature detection of a rotatable component (10) of an electric machine, which is rotatably supported with respect to a rotation axis (12), wherein a marker (18) having a fluorescent marker structure is used, and the fluorescent marker structure is arranged in at least one annular assembly (20) in a manner distributed around the rotation axis (12) on the rotatable component (10) and is thermally connected to the rotatable component; a light source (22) for exciting the fluorescent marker structure; and at least one photosensitive sensor (24) for detecting fluorescence, the fluorescence being emitted due to the excitation of the fluorescent marker structure, wherein a variable related to the temperature-dependent decay time constant τ of the material of the fluorescent marker structure is determined thereby and the temperature of the rotatable component (10) is determined by this variable. Furthermore, the invention relates to a corresponding device (14) for non-contact temperature detection of a rotatable component (10) of an electric machine.

Description

Technical Field

[0001] The present invention relates to a method and a device for non - contact detection of the temperature of a rotating component of an electric machine. Background Art

[0002] In the case of electric machines, there is often a desire to accurately - that is, accurate to a few degrees Celsius (1 - 5 °C) - determine the temperature of the rotor or other rotating components during continuous operation. In addition, accurately knowing the temperature is particularly important for monitoring purposes. It is known from the theory of electric machines that the rotor temperature can exceed the highest upper critical temperature at certain operating points. If the temperature is not monitored or determined inaccurately, it can lead to damage to the electric machine.

[0003] Document DE 10 2011 108 382 A1 describes an electric machine including a rotor and a stator, wherein at least one element arranged at the rotor and thermally connected to it is provided, and the degree of absorption of incident photons of a light source by it varies depending on the temperature, and wherein a measurement signal related to the instantaneous absorption degree of the element is obtained, and this measurement signal is a measure of the temperature of the element or the rotor temperature. Summary of the Invention

[0004] The object of the present invention is to point out a measure by means of which the temperature of the rotating components of an electric machine can be accurately determined with a suitable expenditure.

[0005] The solution of the present invention is achieved by a method having the features of claim 1. In addition, the solution of the above - mentioned task is achieved by a device having the features of claim 8. The preferred configurations of the present invention are described in the dependent claims, in the description and in the drawings, wherein other features described or shown in the dependent claims and / or in the description and / or in the drawings can represent the object of the present invention individually or in any combination (if the context does not clearly indicate the contrary).

[0006] The object of the present invention is a method for non - contact detection of the temperature of a rotatably supported rotating component of an electric machine with respect to a rotation axis, by means of a marker having a fluorescent marker structure, the fluorescent marker structure being distributed in at least one annular component arranged around the rotation axis and arranged on the rotating component and being thermally connected to this rotating component; a light source for exciting the fluorescent marker structure and at least one photosensitive sensor for detecting fluorescence, the fluorescence being emitted due to the excitation of the fluorescent marker structure, wherein a variable related to the temperature - dependent decay time constant τ of the material of the fluorescent marker structure is obtained therefrom, and the temperature of the rotating component is determined by this variable.

[0007] The core of the present invention is: by utilizing a physical effect - the decay time constant of a phosphor depends on temperature - it is possible to detect the temperature of a rotating component for a large rotational speed range (up to near standstill). Another feature of the present invention is that the temperature can be detected non - contact, and thus even very hot objects with temperatures up to 1000 °C can be thermally detected.

[0008] The rotating component is the rotating part of the motor. Generally, the motor has a rotor and a stator, where the rotating component is in particular the rotor.

[0009] By using a method or a corresponding device for non - contact temperature detection of the rotating component of the motor, the temperature can be determined with very high static accuracy. Here, the order of magnitude is approximately 1 - 5 degrees Celsius.

[0010] Thereby, the following advantages can be obtained for the application of the motor and in particular for a permanent magnet synchronous motor (PSM):

[0011] A) Reduction of total cost: The temperature class of the magnets used in the motor can be reduced because by (sufficiently) accurately determining the rotor temperature, a safety reserve is no longer required. This assumption holds if the motor can output electrical power in the order of 150 - 250 KW.

[0012] B) Power compensation: The power drop in a PSM can be compensated by current boost in the field - weakening region. The power drop is caused by a reduction in torque, which in turn is caused by a reduction in pole rotation. The reduction in pole rotation is caused by the heating of the magnets in the rotor. The reduction in pole rotation and thus the resulting torque reduction and power drop increase with increasing rotational speed (if they are not compensated). Current compensation is achieved, for example, by field - oriented control of a synchronous motor excited by permanent magnets and by boosting the stator current with power electronics.

[0013] C) Component protection: By accurately knowing the rotor temperature, improved monitoring strategies and derating strategies can be developed and implemented in the functional software. With methods for rotor temperature detection known from the technical background, derating is switched to prematurely due to a lack of (sufficiently) accurate knowledge of the rotor temperature.

[0014] D) Improvement of the functional safety concept: The torque monitoring of torque errors can be improved by accurately knowing the rotor temperature. This improvement results in a smaller error range (comparison between rated torque and actual torque). A smaller error range leads to shorter identification times and shutdown times.

[0015] E) Reducing the total software - application time: The method of determining the rotor temperature by means of a rotor temperature module (evaluation module), which is known from the background art, requires a large number of vehicle measurements and experiments in hot and cold tests. By accurately determining the rotor temperature (by means of the method given here), the software - application effort can be reduced to a considerable extent. Result: Time and costs are saved.

[0016] Preferably, in this method, it is provided that the fluorescent - marker structure is guided past the light source by the rotation of the rotating part and then past the photosensitive sensor or successively past a plurality of photosensitive sensors.

[0017] Another feature is that by means of the ingenious layout and number of the photosensitive sensors, the temperature accuracy is increased, and additionally the rotational speed and the direction of rotation can be detected.

[0018] According to a preferred configuration of the invention, the components of the fluorescent - marker structure form a code, in particular a code of the barcode type. In this way, it is also possible to determine the rotational position of the rotating part.

[0019] According to other preferred configurations of the invention, it is provided that the marker has two components extending parallel to each other, which components have different fluorescent - marker structures and the fluorescent - marker structures are jointly excited by the light source.

[0020] According to another other preferred configuration of the invention, in addition, the rotational position and / or the rotational speed and / or the direction of rotation of the rotating part can also be determined additionally from the detected fluorescence signal.

[0021] Furthermore, it is advantageously provided that the fluorescent - marker structure has ruby as the fluorescent material, in particular in the form of a ruby - powder coating.

[0022] According to other preferred configurations of the invention, it is provided that the light source is configured as a light - emitting diode or a laser diode (LED), and / or at least one photosensitive sensor is configured as a photoreceiver, in particular a photodiode (PD).

[0023] According to another other preferred configuration of the invention, a variable related to the temperature - dependent decay - time constant τ of the material of the fluorescent - marker structure is determined in advance by a reference measurement (by means of the marker, the light source and at least one photosensitive sensor).

[0024] Furthermore, the object of the present invention is a device for non - contact temperature detection of a rotatable component of an electric machine rotatably supported with respect to a rotation axis, having a marking which has a fluorescent marking structure, the fluorescent marking structure being distributed on the rotatable component in at least one annular component arranged around the rotation axis and being thermally connected to this rotatable component;

[0025] - a light source for exciting the fluorescent marking structure;

[0026] - at least one photosensitive sensor for detecting fluorescence emitted due to the excitation of the fluorescent marking structure; and

[0027] an evaluation unit, the evaluation unit being arranged to obtain a variable related to the temperature - dependent decay time constant τ of the material of the fluorescent marking structure from the detected fluorescence and to determine the temperature of the rotatable component by means of this variable.

[0028] The advantageous configurations mentioned in connection with the above - mentioned method for non - contact temperature detection of a rotatable component rotating with respect to a rotation axis apply analogously here to the device. Such a device is in particular provided for carrying out the method mentioned above.

[0029] According to a preferred configuration of the device according to the invention, a fixed spatial layout of the light source, at least one photosensitive sensor and the rotation axis is provided, in which the fluorescent marking structure of at least one component can be guided past the light source by the rotation of the rotatable component and then past the photosensitive sensor or successively past a plurality of photosensitive sensors.

[0030] According to another preferred configuration of the device according to the invention, an evaluation unit is provided which previously obtains a variable related to the decay time constant τ of the material of the fluorescent marking structure by means of a reference measurement (using the marking, the light source and at least one photosensitive sensor).

[0031] Advantageously, at least one component of the fluorescent marking structure forms a code, in particular a code of the barcode type.

[0032] According to another other preferred configuration of the device according to the invention, the rotatable component is the rotor of the electric machine or at least one rotor component. The electric machine (for its part) is in particular a permanent - magnet synchronous machine (PSM).

[0033] Finally, the present invention also relates to an electric machine having a rotatable component rotatably supported with respect to a rotational axis and the device described above for non - contact temperature detection of the rotatable component. The rotatable component 10 is in particular the rotor of the electric machine. The electric machine itself is in particular a permanent - magnet synchronous machine (PSM). Description of the Drawings

[0034] The present invention will be illustrated in the drawings according to preferred embodiments and will be described in detail below. Among them:

[0035] Figure 1 A device for temperature detection of a rotatable component of an electric machine according to a first embodiment of the present invention is shown;

[0036] Figure 2 A graph of the corresponding optical signals for each fluorescent - marker structure is shown;

[0037] Figure 3 A graph of relevant variables when determining a variable related to the temperature - dependent decay - time constant τ of the material of the fluorescent element is shown, and

[0038] Figure 4 A device for temperature detection according to a second embodiment of the present invention is shown. Detailed Description of the Embodiment

[0039] Figure 1 The rotatable component 10 of the electric machine is shown, which is rotatably supported with respect to a rotational axis 12, and a device 14 for non - contact temperature detection of the rotating rotatable component 10. The rotatable component 10 is in particular the rotor 16 of the electric machine.

[0040] The device 14 for non - contact temperature detection of the rotatable component 10 includes:

[0041] A marker 18 having a fluorescent - marker structure, which is distributed on the rotatable component 10 arranged in at least one annular assembly 20 around the rotational axis 12 and is thermally connected to this rotatable component; a light source 22 for exciting the fluorescent - marker structure; at least one photosensitive sensor 24 for detecting the fluorescence emitted due to the excitation of the fluorescent - marker structure; and an evaluation unit 26, which is arranged to determine a variable related to the temperature - dependent decay - time constant τ of the material of the fluorescent - marker structure from the detected fluorescence and to determine the temperature of the rotatable component 10 from this variable.

[0042] The association between the variable related to the temperature - dependent decay - time constant τ of the material of the fluorescent - marker structure and the temperature is stored, for example, in a database (not shown) of the evaluation unit 26.

[0043] The spatial layout of the light source 22, the photosensitive sensor 24, and the axis of rotation 12 of the rotating part 10 is determined within the motor such that the fluorescent structure is guided past the light source 22 by the rotation of the rotating part 12 and then successively past the photosensitive sensor 24 (arrow 28). For this purpose, the light source 22 and the photosensitive sensor 24 are arranged / fixed at the machine-fixed part of the motor - such as at the housing or at the stator corresponding to the rotor 16 (not shown in detail).

[0044] In the example here, the light source 22 is configured as a light-emitting diode or a laser diode (LED), and the photosensitive sensor 24 is configured as a photoreceiver - more precisely, as a photodiode (PD). The fluorescent structure has ruby as the fluorescent material, especially in the form of a powder coating.

[0045] Figure 2 A diagram showing the corresponding optical signals, in which the signal intensity (here specified as the power P related to the area) with respect to time t is shown respectively. The upper diagram shows the constant signal of the light source 22. The middle diagram shows the fluorescence signal of one of the fluorescent structures, and the lower three diagrams show the discrete signals of the photosensitive sensor 24. These discrete signals are triggered by the corresponding positions of the fluorescent structure with reference to the light source 22 and the photosensitive sensor 24.

[0046] Figure 3 Two diagrams showing the relevant variables when determining the variables related to the temperature-dependent decay time constant τ of the material of the fluorescent element and the temperature are shown.

[0047] The variable related to the decay time constant τ of the material of the fluorescent element is obtained from the fluorescence intensity detected by the photosensitive sensor 24 and the time difference between the signals detected by different sensors 24 (left diagram), and the temperature of the fluorescent structure and the rotating part 10 thermally connected thereto is determined from the temperature dependence of this variable and the decay time constant τ.

[0048] In Figure 3 the current situation, for example, for the first and third photosensitive sensors 24, it applies that:

[0049]

[0050] In a specific example, that is, τ = 6ms / ln(0.58 / 0.115) = 3.7ms

[0051] By means of the relationship given in Figure 3 the second diagram, the temperature is obtained as 7°C.

[0052] Figure 4Shows an alternative configuration of the device 14 for temperature detection. The light source 22 operates in a pulsed excitation mode and illuminates the entire marker 18. In this embodiment, this marker 18 has two components 20 of parallel-extending, different fluorescent marker structures, each of which constitutes a bar code. More precisely, in this particular case, it is two components 20 of parallel-extending fluorescent marker structures, which are identically constructed but aligned in an anti-parallel manner.

[0053] The photosensitive sensor 24 is implemented in the form of a CCD sensor 30 or a CCD optoelectronic element, and is optically coupled to the fluorescent marker structure of the marker 18 at the corresponding "reading position" through an optical guiding element 32. In the stationary state and during each rotation, the position is determined by means of the photosensitive sensor 24 by reading the code position. The rotational speed is determined mathematically by differentiation from the position. The resolution is variable and depends on which bar code is used. For example, a resolution of 9 bits (0.70°) can be achieved either by means of a 512-bit code or by means of interpolation.

[0054] To measure the temperature, the sum signal of the photosensitive sensor / photodiode is used, and the two annular components 20 are always scanned by means of the CCD optoelectronic element 30.

[0055] Below, in addition to the core of the present invention, the advantages of the present invention and the "optimal mode" should be described again in other terms:

[0056] The core of the present invention lies in that by using the physical effect - the decay time constant of the phosphor is temperature-dependent - the temperature, rotational speed, rotational direction and even the position can be detected in a non-contact manner at the rotating part. By means of this method / this device, temperature measurement can be carried out for the entire rotational speed range (even when stationary).

[0057] By using the device 14 for non-contact detection of the temperature of the rotating part 10 of the motor, the temperature can be determined with very high static accuracy. Here, the order of magnitude is approximately 1 - 5 degrees Celsius.

[0058] By means of the measurement principle described here, a so-called composite sensor (Kombi-Sensor, English: Smart Sensor) can be constructed, by which up to 4 physical measurement variables can be determined. This composite sensor can be particularly advantageously used in the application conditions of motors and especially in the application conditions of permanent magnet synchronous motors (PSM). Detailed advantages: reduction of the total cost, increase of the power, improvement of the functional safety scheme and component protection.

[0059] List of reference numerals

[0060] 10 Rotating part

[0061] 12 Axis of rotation

[0062] 14 Device

[0063] 16 Rotor

[0064] 18 Mark

[0065] 20 Annular marking structure component

[0066] 22 Light source

[0067] 24 Photosensitive sensor

[0068] 26 Evaluation unit

[0069] 28 Arrow

[0070] 30 CCD sensor

[0071] 32 Light guide element

[0072] T Temperature of the rotating part

[0073] τ Decay time constant.

Claims

1. A method for non - contact temperature detection of a rotatable component (10) rotatably supported with respect to a rotation axis (12) of an electric machine, wherein by means of - a marker (18) having a fluorescent marker structure, the fluorescent markers being distributed in at least one annular component (20) arranged around the rotation axis (12) on the rotatable component (10) and being thermally connected to this rotatable component; - a light source (22) for exciting the fluorescent marker structure, and - At least one photosensitive sensor (24) for detecting fluorescence emitted due to excitation of the fluorescent marker structure, wherein, a variable related to the temperature - dependent decay time constant τ of the material of the fluorescent marker structure is determined therefrom and the temperature of the rotatable component (10) is determined by this variable, wherein at least one component (20) of the fluorescent marker structure forms a code, in addition, the rotational position and / or rotational speed and / or rotational direction of the rotatable component (10) is determined from the detected fluorescence signal.

2. The method according to claim 1, wherein The fluorescent marker structure of the component (20) is guided past the light source (22) by the rotation of the rotatable component (10) and then past the photosensitive sensor (24) or successively past a plurality of photosensitive sensors (24).

3. The method according to claim 1 or 2, characterized in that, At least one component (20) of the fluorescent marker structure forms a code of the barcode type.

4. The method according to claim 1 or 2, characterized in that, The marker (18) has two components (20) with parallel - extending, different fluorescent marker structures, which are excited together by the light source (18).

5. The method according to claim 1 or 2, characterized in that, The fluorescent marker structure has ruby as the fluorescent material.

6. The method according to claim 1 or 2, characterized in that, The fluorescent marker structure has ruby as the fluorescent material in the form of a ruby powder coating.

7. The method according to claim 1 or 2, characterized in that, A variable related to the temperature - dependent decay time constant τ of the material of the fluorescent marker structure is determined in advance by a reference measurement using the marker (18), the light source (22) and at least one photosensitive sensor (24).

8. A device (14) for non - contact temperature detection of a rotatable component (10) rotatably supported with respect to a rotation axis (12) of an electric machine, having - a marker (18) having a fluorescent marker structure, the fluorescent markers being distributed in at least one annular component (20) arranged around the rotation axis (12) on the rotatable component (10) and being thermally connected to this rotatable component; - a light source (22) for exciting the fluorescent marker structure; - at least one photosensitive sensor (24) for detecting fluorescence emitted due to the excitation of the fluorescent marker structure; and - an evaluation unit (26) arranged to determine a variable related to the temperature - dependent decay time constant τ of the material of the fluorescent marker structure from the detected fluorescence and to determine the temperature of the rotatable component (10) by this variable, Among them, wherein at least one component (20) of the fluorescent marker structure forms a code, in addition, the rotational position and / or rotational speed and / or rotational direction of the rotatable component (10) is determined from the detected fluorescence signal.

9. The device according to claim 8, characterized in that, The fixed spatial layout of the light source (22), at least one photosensitive sensor (24), and the axis of rotation (12), in which the fluorescently labeled structure of the assembly (20) is guided past the light source (22) by the rotation of the rotating member (10) and then past the photosensitive sensor (24) or successively past a plurality of photosensitive sensors (24).

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