CN110346073B - Interlayer pressure measuring device and method based on metallized film capacitor - Google Patents
Interlayer pressure measuring device and method based on metallized film capacitor Download PDFInfo
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- CN110346073B CN110346073B CN201910609904.7A CN201910609904A CN110346073B CN 110346073 B CN110346073 B CN 110346073B CN 201910609904 A CN201910609904 A CN 201910609904A CN 110346073 B CN110346073 B CN 110346073B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/2206—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/225—Measuring circuits therefor
- G01L1/2262—Measuring circuits therefor involving simple electrical bridges
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/2268—Arrangements for correcting or for compensating unwanted effects
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/2268—Arrangements for correcting or for compensating unwanted effects
- G01L1/2281—Arrangements for correcting or for compensating unwanted effects for temperature variations
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- General Physics & Mathematics (AREA)
- Measuring Fluid Pressure (AREA)
- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
Abstract
The invention provides an interlayer pressure measuring device and method based on a metallized film capacitor, wherein the device comprises: the device comprises a metallized film capacitor, a first strain gauge, a second strain gauge, a third strain gauge, a fourth strain gauge, a static program-controlled strain gauge and a processor; wherein: the first strain gauge and the second strain gauge are mutually connected and are arranged on a mandrel of the metallized film capacitor; the sensitive direction of the first strain gauge is perpendicular to the sensitive direction of the second strain gauge, and the sensitive direction of the first strain gauge is parallel to the axial direction of the mandrel; the third strain gauge and the fourth strain gauge are arranged in the static program control strain gauge. Compared with the existing measuring device and method, the invention simplifies the measuring system, reduces the using amount of the strain gauge and improves the measuring precision.
Description
Technical Field
The invention relates to the technical field of pressure measurement, in particular to an interlayer pressure measurement device and method based on a metallized film capacitor.
Background
The energy storage density of the metallized film capacitor is much higher than that of the traditional oil-immersed capacitor, the metal film capacitor can realize electric field energy storage much larger than that of the oil-immersed capacitor within limited volume and weight, or has more compact volume and lighter weight under the condition of equivalent energy storage, has wide application prospect in the application fields of power transmission and distribution, pulse power and the like, and starts to replace the traditional oil-immersed capacitor under a part of application scenes, so that all capacitor manufacturers pay attention to the research and development of the high-performance metallized film capacitor. Metallized film capacitors are typically constructed of several capacitor elements mounted in series and parallel to a housing, depending on the voltage rating and capacitance values to be tolerated, and therefore the performance of the metallized film capacitor is largely dependent on the performance of the capacitor elements used. The basic structure and winding process of the capacitor element are shown in fig. 1 and 2 (in fig. 1, 1 refers to the margin of the metallized film capacitor element).
Two layers of polymer metallized films with a thickness of several mu m and a single-sided aluminum-zinc coating (the thickness is usually several nm to tens of nm) as electrodes are overlapped, then hundreds to thousands of layers of hard plastic hollow cylindrical rods with the diameter of several mm and the length of several cm are wound, and the hard plastic hollow cylindrical rods are encapsulated in a plastic shell after the processes of metal spraying, lead welding, heat setting, dipping and the like, so that a complete metallized film capacitor element is obtained.
When a certain voltage is applied to the capacitor, the electric weak point in the metallized film medium breaks down to form a discharge channel and generate local high temperature, so that the plating electrode substance near the breakdown point is evaporated, the resistance of the conductive channel is increased, the discharge cannot be maintained, and the insulation is recovered automatically. Referring to fig. 3 (in fig. 3, 2 is a metallized electrode, and 3 is a demetallized part), this process is called self-healing of the metallized film capacitor, and has an important influence on the performance of the capacitor.
The energy released and the discharge duration in the self-healing process have strong relevance to the area of the evaporated electrode, the damage degree of a medium near a breakdown point and the properties and the quantity of the released reactants, so that the key performance indexes such as the service life of a capacitor element and even the whole capacitor, the energy storage density and the like are influenced. The pressure intensity between the metal film layers has obvious correlation with the energy released in the self-healing process and the discharge duration, so that the pressure intensity between the metal film layers has important influence on the performance of the capacitor, and the method has important guiding significance for exactly knowing the pressure intensity value between the metal film layers under various conditions in the process of performing quality control such as design, process improvement and even reliability on the capacitor. The interlayer pressure value cannot be obtained through accurate calculation, and can be confirmed only by carrying out actual measurement.
The metallized film capacitor element is formed by winding a metallized film, the metallized film and the metallized film are tightly adhered and mutually compacted, and tens of measuring positions need to be considered for one-time measurement. If the sensor is directly intervened between the metallized films to measure the interlayer pressure, the sensor is required to be embedded in each measuring point, the complexity of manufacturing elements is greatly increased, and the geometric dimension of the sensor elements can inevitably influence the stress distribution between the metallized films in the whole elements by embedding a plurality of sensor elements, so that the effect is difficult to achieve. And non-intrusive acoustic, electromagnetic or optical measurement means and the like are not convenient to adopt, and even if effective measurement can be realized, the cost of instruments, the complexity of a measurement system and the like are high. Therefore, the better method is only an indirect method of mechanical sensor measurement.
In the prior art, the method for indirectly measuring the pressure between the metal film layers by measuring the resistance variation of the strain gauge does not take some important error characteristics into consideration, so that the prior art has 2 important defects on the whole.
Defect 1: foil-type resistance strain gauges are strain sensors that reflect changes in the shape of an object to which a substrate is attached by changes in resistance caused by the deformation characteristics of a metal wire under stress. When the metal wire is deformed under the action of external force, the total resistance of the metal wire is correspondingly changed due to the corresponding change of the cross section area and the resistivity, and the relationship between the resistance change and the deformation is as follows:
Δr/r＝Kε
normally, the strain gauge should not be subjected to forces perpendicular to its surface when making measurements. Because the acting force perpendicular to the surface of the strain gauge can cause the metal wire to generate additional deformation, the sectional area, the length and the resistivity of the metal wire can correspondingly change under the action of compression, and further the total resistance change of the metal wire does not completely reflect the deformation change of the sensitive direction x, which is shown in fig. 4 (4 in fig. 4 is a welding point), but is doped with undesirable additional deformation change under the influence of the acting force in the perpendicular direction.
In the prior art, the strain gauge actually works in a state of having a large stress perpendicular to the surface thereof, because the extrusion of the wound metallized film to the mandrel is added to act on the surface of the strain gauge, so that the strain gauge generates an additional resistance change error in addition to sensing the circumferential deformation change of the mandrel to which the strain gauge is adhered. The strain gauge used for compensation in this scheme cannot compensate for the extra resistance deviation caused by the vertical stress because the surface has no vertical stress. If the compensation is not performed by using the die mandrel bar attached with the strain gauge, but by using the complete element manufactured under the same manufacturing process as the measured element, the vertical stress on the strain gauge of the measured element and the strain gauge in the compensation element in the initial state is the same, but after the measured element starts to remove the metalized film for measurement, the vertical stress on the strain gauge of the measured element is gradually reduced along with the removal of the metalized film, and the vertical stress on the strain gauge of the compensation element is kept unchanged, so that the compensation can not be performed. If the metalized films of the compensation element and the element to be detected are removed synchronously, the bridge cannot measure the effective output, and the output voltage U is kept to be 0 according to the bridge principle because the resistances of the two elements change synchronously. Therefore, the existing scheme lacks a deviation correction mechanism for errors generated under the action of stress vertical to the surface of the strain gauge, the errors always exist, and the error value is continuously changed along with the measurement, so that the measurement accuracy is seriously influenced.
Defect 2: in order to make the resistance strain gauge work normally, the bridge must be connected, and a certain voltage must be applied to the two ends of the resistance strain gauge, so that joule heat is generated as a resistance element strain gauge, the temperature of the metal wire can be changed due to the joule heat, the temperature change can cause the metal wire to generate extra expansion or contraction deformation, and the deformation can cause extra change of the resistance of the strain gauge to disturb measurement. In general, in order to counteract the error caused by the joule heat of the strain resistor, it is necessary to provide the strain gauge to be measured with a corresponding compensation plate, as in the prior art. This method has significant drawbacks. In the existing scheme, the compensation strain gauge and the measured strain gauge are in different thermal balance states, the compensation gauge directly contacts with air to dissipate heat to achieve thermal balance, the measured gauge is pressed by the metallized film to achieve a thermal balance state with the metallized film, and as the metallized film is stripped, the extrusion stress between the metallized film and the measured gauge is gradually reduced, and the extrusion stress has influence on heat conduction, so that as the measurement is carried out, the thermal balance state of the measured gauge is in a continuously changing process, the static compensation gauge can not reflect the temperature compensation state of the measured gauge at all, and therefore the effect can not be achieved, and the measurement accuracy is influenced.
In summary, the prior art does not correctly consider the problem to be considered for the foil-type resistance strain gauge to work normally, the measured strain gauge is under the action of the constantly changing vertical stress and the constantly changing thermal balance, and an additional, unpredictable and constantly changing additional resistance variation is generated, so that the deformation measurement also generates a corresponding error, and the error cannot be compensated and corrected by the compensation strain gauge in the prior art, and the compensation strain gauge and the compensation element cannot play an effective role.
Disclosure of Invention
In view of this, the invention provides an interlayer pressure measuring device based on a metallized film capacitor, so as to more accurately measure the interlayer pressure of the metallized film capacitor
In order to achieve the purpose, the invention adopts the following scheme:
in one embodiment of the invention, the interlayer pressure measuring device based on the metallized film capacitor comprises: the device comprises a metallized film capacitor, a first strain gauge, a second strain gauge, a third strain gauge, a fourth strain gauge, a static program-controlled strain gauge and a processor; wherein:
the first strain gauge and the second strain gauge are mutually connected and are arranged on a mandrel of the metallized film capacitor; the sensitive direction of the first strain gauge is perpendicular to the sensitive direction of the second strain gauge, and the sensitive direction of the first strain gauge is parallel to the axial direction of the mandrel;
the third strain gauge and the fourth strain gauge are arranged in the static program control strain gauge;
one end of the first strain gauge is connected with one end of the second strain gauge, one end of the third strain gauge is connected with one end of the fourth strain gauge, the other end of the first strain gauge is connected with the other end of the fourth strain gauge, and the other end of the second strain gauge is connected with the other end of the third strain gauge; two ends of a power supply in the static program control strain gauge are respectively connected between the first strain gauge and the fourth strain gauge and between the second strain gauge and the third strain gauge;
the first strain gauge and the second strain gauge are the same strain gauges, and the third strain gauge and the fourth strain gauge are the same strain gauges;
the processor is connected with the static program control strain gauge and used for calculating the interlayer pressure of the metallized film according to the deformation quantity of the mandrel and the elastic modulus of the mandrel, which are measured by the static program control strain gauge.
In one embodiment of the present invention, the number of wound layers of metallized film of the metallized film capacitor is 500 to 2000.
In one embodiment of the invention, the dimensions of the first strain gage and the second strain gage are 36mm × 41 mm; the dimensions of the third strain gauge and the fourth strain gauge are 37mm × 43 mm.
In one embodiment of the invention, the metallized film capacitor is a cylindrical wound capacitor.
In order to solve the above technical problems, the present invention further provides a metallized film capacitor-based interlayer pressure measurement method applied to a metallized film capacitor-based interlayer pressure measurement apparatus, comprising:
respectively measuring deformation quantities of the mandrel before and after the metallized film is stripped from the metallized film capacitor according to the resistances of the first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge;
and calculating the pressure intensity between the metallized films according to the deformation quantity and the elastic modulus of the mandrel.
In one embodiment of the present invention, measuring the deformation amount of the mandrel before and after peeling the metallized film from the metallized film capacitor based on the resistances of the first strain gauge, the second strain gauge, the third strain gauge, and the fourth strain gauge, respectively, includes:
respectively measuring the resistance variation of the first strain gauge and the resistance variation of the second strain gauge before and after the metallized film is stripped from the metallized film capacitor by utilizing the Wheatstone bridge principle according to the initial resistance of the first strain gauge and the second strain gauge and the resistance of the third strain gauge and the fourth strain gauge;
calculating the difference of the resistance variation of the first strain gauge and the second strain gauge caused by the deformation of the mandrel according to the resistance variation of the first strain gauge and the second strain gauge before and after the metallized film is stripped from the metallized film capacitor;
and calculating the deformation amount of the mandrel according to the difference of the resistance variation amounts of the first strain gauge and the second strain gauge generated by the deformation of the mandrel.
In one embodiment of the present invention, the first strain gauge resistance variation amount includes: the resistance variation of the first strain gauge caused by the deformation of the mandrel, the resistance variation caused by the stress of the first strain gauge and the resistance variation of the first strain gauge caused by the temperature change.
In one embodiment of the present invention, the second strain gauge resistance variation amount includes: the resistance variation of the second strain gauge caused by the deformation of the mandrel, the resistance variation caused by the stress of the second strain gauge and the resistance variation of the second strain gauge caused by the temperature change.
In one embodiment of the present invention, the output of the static program-controlled strain gauge is zeroed to obtain the initial deformation amount of the first strain gauge and the second strain gauge.
In one embodiment of the invention, the metallized film is peeled from the metallized film capacitor 10 to 100 layers at a time.
The invention relates to an interlayer pressure measuring device based on a metallized film capacitor and a matched measuring method thereof.A single-chip vertical double-grid-region foil type resistance strain gauge and a matched measuring circuit are creatively designed, external element compensation in the prior art is changed into compensation in a measured element, so that the additional error resistance variable quantities of two grid regions of the resistance strain gauge which is extremely sensitive to pressure and temperature in the vertical direction are subtracted, the error caused by the subtraction is completely counteracted in principle, and only the normal resistance variable quantity generated by the strain gauge driven by the deformation of a mandrel is reserved, so that the measuring precision is greatly improved (the external compensation mode cannot compensate the additional resistance change caused by the pressure and temperature change in the process of removing a film, and the error cannot be eliminated). Meanwhile, because the single strain gauge is adopted for internal compensation, an additional capacitor element used for external compensation is omitted, a measuring system is simplified, the number of the strain gauges used for detecting one element is reduced from 2 to 1, and the cost is saved. Therefore, compared with the existing measuring device and method, the invention simplifies the measuring system, reduces the using amount of the strain gauge and improves the measuring precision.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts. In the drawings:
FIG. 1 is a schematic diagram of a metallized film capacitor element;
FIG. 2 is a schematic view of the winding of a metallized film capacitor element;
FIG. 3 is a schematic diagram of a self-healing process of a metal film capacitor;
FIG. 4 is a schematic diagram of a foil-type resistive strain gage;
FIG. 5 is a schematic structural diagram of an interlayer pressure measuring device based on a metallized film capacitor according to an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of a vertical dual-gate foil-type resistance strain gauge according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of the measurement circuit connections of one embodiment of the present invention;
FIG. 8 is a schematic flow chart of a method for interlayer pressure measurement based on a metallized film capacitor in an embodiment of the present invention;
FIG. 9 is a schematic diagram I illustrating the principle of measuring the pressure between the metallized films by mandrel deformation according to an embodiment of the present invention;
FIG. 10 is a schematic diagram of a second principle of measuring pressure between metallized films by mandrel deformation according to an embodiment of the present invention;
FIG. 11 is a flowchart illustrating a step 100 according to an embodiment of the present invention;
FIG. 12 is a flow chart illustrating an exemplary embodiment of the present invention;
fig. 13 is a graph showing the relationship between the pressure of the metallized films and the number of layers of the metallized films in the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.
Fig. 5 is a schematic structural diagram of an interlayer pressure measurement device based on a metallized film capacitor according to an embodiment of the present invention. As shown in fig. 5, the measuring apparatus includes: metallized film capacitor 1, strain gauge 2, strain gauge 3, strain gauge 4 and strain gauge 5, static program-controlled strain gauge 6 and processor (not shown in the figure); wherein:
the strain gauge 2 and the strain gauge 3 are mutually connected and are arranged on a mandrel 7 of the metallized film capacitor; the sensitive direction of the strain gauge 2 is vertical to the sensitive direction of the strain gauge 3, and the sensitive direction of the strain gauge 2 is parallel to the axial direction of the mandrel 7; it can be understood that the sensitive direction of the strain gauge 2 may also be perpendicular to the axial direction of the mandrel 7, as long as it is ensured that the sensitive direction of one of the strain gauges 2 and 3 is perpendicular to the axial direction of the mandrel 7, and the sensitive direction of the other strain gauge is parallel to the axial direction of the mandrel 7. In addition, the structure can ensure that the strain gauge 2 and the strain gauge 3 are synchronously under the action of the same vertical pressure, and the temperature balance states of the strain gauge 2 and the strain gauge 3 are completely consistent, so that the problem that the strain measurement generates extra resistance change errors due to the fact that the strain gauge is under the action of the continuously-changed pressure vertical to the surface direction of the strain gauge and the heat balance state is continuously changed along with the test is solved.
In one embodiment, the strain gauges 2 and 3 can be integrated into the structure shown in fig. 6, i.e. a vertical dual-gate foil-type resistance strain gauge, and it can be understood that with this structure design, the number of strain gauges used for detecting one component is reduced from 2 to 1, which saves cost and simplifies the measurement system.
The strain gauge 4 and the strain gauge 5 are both arranged in the static program control strain gauge;
the strain gauges 2 and 3 are the same strain gauges (at least the size and the resistance are the same), the strain gauges 4 and 5 are the same strain gauges (at least the size and the resistance are the same), and the strain gauges 2 and 3 and the strain gauges 4 and 5 may be the same or different.
Referring to fig. 7, one end of a strain gauge 2 is connected with one end of a strain gauge 3, one end of a strain gauge 4 is connected with one end of a strain gauge 5, the other end of the strain gauge 2 is connected with the other end of the strain gauge 5, and the other end of the strain gauge 3 is connected with the other end of the strain gauge 4; one end of a power supply in the static program control strain gauge 6 is respectively connected between the strain gauge 2 and the strain gauge 5, and the other end of the power supply is connected between the strain gauge 3 and the strain gauge 4; it can be understood that, by adopting the connection mode, the resistance strain gauge which is extremely sensitive to the pressure and the temperature in the vertical direction subtracts the extra error resistance variation of the two grid regions, thereby completely offsetting the error from the extra error resistance variation, only keeping the normal resistance variation generated by the strain gauge driven by the deformation of the mandrel, and greatly improving the measurement precision. If the strain gauges 2 and 3 can be integrated into the structure shown in fig. 6, they need to be connected by a connection method indicated by a broken line in fig. 7.
The processor is connected with the static program control strain gauge and used for calculating the interlayer pressure of the metallized film according to the deformation quantity of the mandrel and the elastic modulus of the mandrel, which are measured by the static program control strain gauge.
In one embodiment, the number of the winding layers of the metallized film capacitor is 500 to 2000.
In one embodiment, the dimensions of the strain gauges 2 and 3 are 36mm × 41 mm; the dimensions of the strain gauge 4 and the strain gauge 5 were 37mm × 43 mm.
In one embodiment, the metallized film capacitor is a cylindrical wound capacitor.
The invention relates to an interlayer pressure measuring device based on a metallized film capacitor, which creatively designs a single-chip vertical double-grid-area foil type resistance strain gauge and a measuring circuit matched with the single-chip vertical double-grid-area foil type resistance strain gauge, changes external element compensation in the prior art into internal compensation of a measured element, and subtracts extra error resistance variation of two grid areas of the resistance strain gauge which is extremely sensitive to pressure and temperature in the vertical direction, thereby completely offsetting the error caused by the extra error resistance variation in principle, and only keeping the normal resistance variation generated by the strain gauge driven by mandrel deformation, so that the measuring precision is greatly improved (the extra resistance variation caused by the pressure and temperature variation in the process of removing the metallized film cannot be compensated by an external compensation mode, and the error cannot be eliminated). Meanwhile, because the single strain gauge is adopted for internal compensation, an additional capacitor element used for external compensation is omitted, a measuring system is simplified, the number of the strain gauges used for detecting one element is reduced from 2 to 1, and the cost is saved. Therefore, compared with the existing measuring device and method, the invention simplifies the measuring system, reduces the using amount of the strain gauge and improves the measuring precision.
The embodiment of the present invention further provides a specific implementation of the method for measuring interlayer pressure based on a metallized film capacitor, which is applied to the device for measuring interlayer pressure based on a metallized film capacitor, and the method specifically includes the following steps, with reference to fig. 5 and 8:
step 100: the amount of deformation of the mandrel 7 before and after the metallized film is peeled from the metallized film capacitor 1 is measured from the resistances of the strain gauge 2, the strain gauge 3, the strain gauge 4, and the strain gauge 5.
It will be appreciated that since the metallized film capacitor element is formed by winding a metallized film around a mandrel, when the mandrel is wound into a capacitor element, the strain gauge and the mandrel are simultaneously compressed by the stacked layers of metallized film to cause shrinkage deformation, and when the outer film layer is removed, the deformation of the mandrel is restored accordingly. Since each film was uniformly wound around the mandrel, the thickness of the strain gauge was only about 30 μm, and the influence of the size of the strain gauge itself on the test results was negligible, it was considered that the degree of shrinkage was the same at each position of the mandrel. Namely, when the special capacitor element removes the metallized films layer by layer, the diameter of the mandrel is recovered because the stress applied on the mandrel is correspondingly reduced, the circumference of the circular section of the mandrel is recovered in equal proportion, and the metal wires of the strain gauge are driven to recover in equal proportion, so that the resistance value of the strain gauge is correspondingly changed. The deformation recovery amount of the mandrel can be calculated by measuring the change condition of the resistance of the strain gauge through the bridge.
Step 200: the pressure between the metallized films is calculated from the amount of deformation obtained in step 100 and the elastic modulus of the mandrel 7.
It will be appreciated that during the elastic deformation phase of a material, its stress and strain are in a proportional relationship (i.e. obeying hooke's law), the proportionality coefficient of which is known as the modulus of elasticity.
In steps 100 and 200, since the metallized film is under tension during winding, the mandrel is subjected to a corresponding compressive stress after winding, which stress is uniform, and the effect of the common transmission of the stress of all the wound metallized film layers to the mandrel is to cause a certain amount of uniform radial compression deformation to eventually build up on the mandrel. And if a plurality of metallized films are disassembled, the stress exerted on the mandrel by the disassembled metallized films in a superposed manner is released, and the deformation of the mandrel can be correspondingly recovered. According to the pressure transmission characteristic, the stress required for enabling the mandrel to generate the corresponding deformation quantity is equal to the pressure between the innermost layer of the corresponding stripped metalized film and the outermost layer of the unreleased metalized film, and the value is as follows:
P＝Δε×Em
wherein P is the pressure value, Delta epsilon is the deformation recovery quantity of the mandrel, EmIs the mandrel elastic modulus (as a known quantity). Δ ε can be measured using foil resistance strain gauges attached to the mandrel surface and an electrical bridge, the principle of which is shown in FIGS. 9 and 10.
From the above description, the interlayer pressure measuring method based on the metallized film capacitor applied to the interlayer pressure measuring device based on the metallized film capacitor of the invention creatively designs the single-chip vertical double-gate area foil type resistance strain gauge and the matched measuring circuit, changes the external element compensation in the prior art into the internal compensation of the element to be measured, the resistance strain gauge has the advantages that the extra error resistance variation of the two grid regions of the resistance strain gauge which is extremely sensitive to the pressure and the temperature in the vertical direction is subtracted, the error caused by the extra error resistance variation is completely offset in principle, and only the normal resistance variation generated by the strain gauge driven by the deformation of the mandrel is reserved, so the measurement precision is greatly improved (the extra resistance variation caused by the pressure and the temperature variation in the process of removing the metallized film cannot be compensated by an external compensation mode, and the error cannot be eliminated). Meanwhile, because the single strain gauge is adopted for internal compensation, an additional capacitor element used for external compensation is omitted, a measuring system is simplified, the number of the strain gauges used for detecting one element is reduced from 2 to 1, and the cost is saved. Therefore, the invention simplifies the measuring system, reduces the using amount of the strain gauge and improves the measuring precision.
In one embodiment, referring to fig. 11, step 100 specifically includes the following steps:
step 101: the amount of change in resistance of the strain gauge 2 and the amount of change in resistance of the strain gauge 3 before and after peeling the metallized film from the metallized film capacitor were measured by the wheatstone bridge principle from the initial resistances of the strain gauges 2 and 3 and the resistances of the strain gauges 4 and 5, respectively.
It will be appreciated that a foil-type electrical resistance strain gauge is a strain sensor that reflects changes in the shape of an object to which the substrate is attached by changes in electrical resistance caused by the deformation characteristics of the wire under stress. When the metal wire is deformed under the action of external force, the total resistance of the metal wire is correspondingly changed due to the corresponding change of the cross section area and the resistivity, and the relationship between the resistance change and the deformation is as follows:
Δr/r＝Kε
wherein, Δ r is the resistance variation, r is the initial resistance value, ε is the deformation, and K is the sensitivity coefficient of the strain gauge.
Step 102: the difference in the amounts of resistance change of the strain gauges 2 and 3 due to the deformation of the mandrel was calculated from the amounts of resistance change of the strain gauges 2 and 3 before and after the metallized film was peeled from the metallized film capacitor.
Specifically, the "difference between the resistance variations of the strain gauges 2 and 3 caused by the deformation of the mandrel" in step 102 refers to a difference between the resistance variation of the strain gauge 2 caused by the deformation of the mandrel and the resistance variation of the strain gauge 3 caused by the deformation of the mandrel, and it can be understood that the resistance variations of the strain gauge 2 in step 102 include: the resistance variation of the strain gauge 2 caused by the deformation of the mandrel, the resistance variation caused by the stress of the strain gauge 2 and the resistance variation of the strain gauge 2 caused by the temperature change; the amount of resistance change of the strain gauge 3 includes: the amount of change in resistance of the strain gauge 3 due to deformation of the mandrel, the amount of change in resistance due to stress on the strain gauge 3, and the amount of change in resistance of the strain gauge 3 due to temperature change.
The strain gauge should not be subjected to forces perpendicular to its surface when making measurements. Because the acting force perpendicular to the surface of the strain gauge can cause the metal wire to generate additional deformation, the sectional area, the length and the resistivity of the metal wire can correspondingly change under the action of compression, and further the total resistance change of the metal wire does not completely reflect the deformation change of the sensitive direction x, but is doped with the undesirable additional deformation change under the influence of the acting force in the perpendicular direction, which is shown in fig. 4.
Step 103: the deformation amount of the mandrel is calculated from the difference between the resistance variation amounts of the strain gauges 2 and 3 caused by the deformation of the mandrel.
In one embodiment, the method for measuring interlayer pressure based on the metallized film capacitor further comprises: and (3) zeroing the output of the static program control strain gauge to obtain the initial deformation quantity of the strain gauge 2 and the strain gauge 3.
In one embodiment, the number of layers to be peeled each time in the process of peeling the metallized film from the metallized film capacitor is 10 to 100.
From the above description, the interlayer pressure measuring method based on the metallized film capacitor applied to the interlayer pressure measuring device based on the metallized film capacitor of the invention creatively designs the single-chip vertical double-gate area foil type resistance strain gauge and the matched measuring circuit, changes the external element compensation in the prior art into the internal compensation of the element to be measured, the resistance strain gauge has the advantages that the extra error resistance variation of the two grid regions of the resistance strain gauge which is extremely sensitive to the pressure and the temperature in the vertical direction is subtracted, the error caused by the extra error resistance variation is completely offset in principle, and only the normal resistance variation generated by the strain gauge driven by the deformation of the mandrel is reserved, so the measurement precision is greatly improved (the extra resistance variation caused by the pressure and the temperature variation in the process of removing the metallized film cannot be compensated by an external compensation mode, and the error cannot be eliminated). Meanwhile, because the single strain gauge is adopted for internal compensation, an additional capacitor element used for external compensation is omitted, a measuring system is simplified, the number of the strain gauges used for detecting one element is reduced from 2 to 1, and the cost is saved. Therefore, the invention simplifies the measuring system, reduces the using amount of the strain gauge and improves the measuring precision.
To further illustrate the present solution, the present invention provides a specific application example of the interlayer pressure measurement method based on the metallized film capacitor, which is applied to the interlayer pressure measurement device based on the metallized film capacitor, by taking the foil type strain gauge as an example, and the specific application example specifically includes the following contents, see fig. 5 and fig. 12.
S0: and (3) zeroing the output of the static program control strain gauge to obtain the initial deformation quantity of the strain gauge 2 and the strain gauge 3.
S1: the amount of resistance change of the strain gauge 2 and the amount of resistance change of the strain gauge 3 before and after peeling the metallized film from the metallized film capacitor were measured.
Referring to fig. 7, the initial resistances R of the bridge resistors R1 and R2 corresponding to the wire grid region of the strain gage 2 and the wire grid region of the strain gage 3 are equal, and R3 and R4 are the internal resistances of the strain gauge bridge and have equal values.
Because the resistance change rate of the resistance strain gauge is very small, according to the Wheatstone bridge principle, the following principle is provided:
ΔU∝(R1-R2)/R＝(ΔR1-ΔR2)/R
wherein R is the initial resistance of a single gate of the strain gauge, Δ U is the voltage variation under stress, and Δ R1 and Δ R2 are the gate resistance variations of strain gauges 2 and 3, respectively, and they have:
ΔR1＝rT1+rP1+r1
ΔR2＝rT2+rP2+r2
s2: the difference between the amounts of change in resistance of the strain gauge 2 and the strain gauge 3 due to deformation of the mandrel was calculated.
In S1, rT1And rT2Are respectively a gate region resistor R1And R2The additional resistance change value generated under the action of the force perpendicular to the direction of the strain gauge,because the specifications of the two grid regions are consistent and the pressures are also uniform, r isT1＝rT2。rP1And rP2The extra resistance change values of the two grid regions caused by temperature change are respectively, and the heating and heat dissipation balance is consistent because the specifications of the two grid regions are consistent and the environments are consistent, so rP1＝rP2。r1And r2The resistance strain variation (actually expected to be measured) generated by the gate region of the strain gauge along with the diameter variation of the mandrel of the capacitor element is respectively, because the variation trend of the mandrel diameter is opposite to the axial expansion trend, and the resistance strain variation is characterized by comprising the following components in percentage by weight according to the mechanical characteristics of materials:
according to the mechanical properties of materials
r2＝-ρr1
Where ρ is the poisson's ratio of the mandrel material. Therefore, there are:
ΔU∝(R1-R2)/R＝(ΔR1-ΔR2)/R
＝[(rT1+rP1+r1)-(rT2+rP2+r2)]/R
＝(1+ρ)r1/R
based on the principle of foil type resistance strain gauge
r1/R∝Kε
Wherein K is the sensitivity coefficient of the strain gauge, and epsilon is the strain capacity of the strain gauge.
S3: the amount of deformation of the mandrel 7 is calculated.
And S2, comprising: from Δ U ∈ (1+ ρ) K ∈, the mandrel deformation amount ∈ can be obtained, and the influence of temperature and vertical pressure on the measurement error is eliminated.
S4: and calculating the interlayer pressure of the metallized film.
Calculating the interlayer pressure of the metallized film according to the deformation quantity of the mandrel and the elastic modulus of the mandrel, specifically: stripping the metallized film of the capacitor element layer by layer, and after n layers are stripped, if the strain difference of the mandrel is delta epsilon compared with the initial complete state, the sum of the pressures exerted by the stripped metallized film on the outermost layer of the residual metallized film is
ΔP＝ΔεE
Wherein, Delta P is pressure variation, Delta epsilon is mandrel deformation recovery quantity, EmIs the mandrel elastic modulus (as a known quantity). The step Δ P is the value of the interlayer pressure between the innermost layer of the stripped metallized film and the outermost layer of the remaining metallized film in the state that the metallized film of the device is not stripped completely. When a section of metallized film is stripped, the number of stripped layers and the difference value of the mandrel strain are recorded, and then a relation curve between the pressure intensity between every two layers of metallized films and the number of the metallized films can be obtained after calculation, as shown in fig. 13.
From the above description, the interlayer pressure measuring method based on the metallized film capacitor applied to the interlayer pressure measuring device based on the metallized film capacitor of the invention creatively designs the single-chip vertical double-gate area foil type resistance strain gauge and the matched measuring circuit, changes the external element compensation in the prior art into the internal compensation of the element to be measured, the resistance strain gauge has the advantages that the extra error resistance variation of the two grid regions of the resistance strain gauge which is extremely sensitive to the pressure and the temperature in the vertical direction is subtracted, the error caused by the extra error resistance variation is completely offset in principle, and only the normal resistance variation generated by the strain gauge driven by the deformation of the mandrel is reserved, so the measurement precision is greatly improved (the extra resistance variation caused by the pressure and the temperature variation in the process of removing the metallized film cannot be compensated by an external compensation mode, and the error cannot be eliminated). Meanwhile, because the single strain gauge is adopted for internal compensation, an additional capacitor element used for external compensation is omitted, a measuring system is simplified, the number of the strain gauges used for detecting one element is reduced from 2 to 1, and the cost is saved. Therefore, compared with the existing measuring device and method, the invention simplifies the measuring system, reduces the using amount of the strain gauge and improves the measuring precision.
The foregoing description has been directed to specific embodiments of this disclosure. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims may be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing may also be possible or may be advantageous.
Although the present application provides method steps as described in an embodiment or flowchart, additional or fewer steps may be included based on conventional or non-inventive efforts. The order of steps recited in the embodiments is merely one manner of performing the steps in a multitude of orders and does not represent the only order of execution. When an actual apparatus or client product executes, it may execute sequentially or in parallel (e.g., in the context of parallel processors or multi-threaded processing) according to the embodiments or methods shown in the figures.
Although embodiments of the present description provide method steps as described in embodiments or flowcharts, more or fewer steps may be included based on conventional or non-inventive means. The order of steps recited in the embodiments is merely one manner of performing the steps in a multitude of orders and does not represent the only order of execution. When an actual apparatus or end product executes, it may execute sequentially or in parallel (e.g., parallel processors or multi-threaded environments, or even distributed data processing environments) according to the method shown in the embodiment or the figures. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, the presence of additional identical or equivalent elements in a process, method, article, or apparatus that comprises the recited elements is not excluded.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment. In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of an embodiment of the specification. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
The above description is only an example of the embodiments of the present disclosure, and is not intended to limit the embodiments of the present disclosure. Various modifications and variations to the embodiments described herein will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present specification should be included in the scope of the claims of the embodiments of the present specification.
Claims (10)
1. An interlayer pressure measuring device based on a metallized film capacitor, comprising: the device comprises a metallized film capacitor, a first strain gauge, a second strain gauge, a third strain gauge, a fourth strain gauge, a static program-controlled strain gauge and a processor; wherein:
the first strain gauge and the second strain gauge are mutually connected and are arranged on a mandrel of the metallized film capacitor; the sensitive direction of the first strain gauge is perpendicular to that of the second strain gauge, and the sensitive direction of the first strain gauge is parallel to the axial direction of the mandrel;
the third strain gauge and the fourth strain gauge are arranged in the static program control strain gauge;
one end of the first strain gauge is connected with one end of the second strain gauge, one end of the third strain gauge is connected with one end of the fourth strain gauge, the other end of the first strain gauge is connected with the other end of the fourth strain gauge, and the other end of the second strain gauge is connected with the other end of the third strain gauge; two ends of a power supply in the static program-controlled strain gauge are respectively connected between the first strain gauge and the fourth strain gauge and between the second strain gauge and the third strain gauge;
the first strain gauge and the second strain gauge are the same strain gauges, and the third strain gauge and the fourth strain gauge are the same strain gauges;
and the processor is connected with the static program-controlled strain gauge and is used for calculating the interlayer pressure of the metallized film according to the deformation quantity of the mandrel and the elastic modulus of the mandrel, which are measured by the static program-controlled strain gauge.
2. An interlayer pressure measuring apparatus according to claim 1, wherein the number of layers of the metallized film wound of the metallized film capacitor is 500 to 2000.
3. Interlayer pressure measuring apparatus according to claim 1, comprising:
the sizes of the first strain gauge and the second strain gauge are 36mm multiplied by 41 mm;
the dimensions of the third strain gauge and the fourth strain gauge are 37mm × 43 mm.
4. An interlayer pressure measuring apparatus according to claim 1, wherein the metallized film capacitor is a cylindrical wound capacitor.
5. An interlayer pressure measuring method based on a metallized film capacitor, which is applied to the interlayer pressure measuring device based on the metallized film capacitor of any one of claims 1 to 4, and is characterized by comprising the following steps:
respectively measuring deformation quantities of the mandrel before and after the metallized film is stripped from the metallized film capacitor according to the resistances of the first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge;
and calculating the pressure intensity between the metallized films according to the deformation quantity and the elastic modulus of the mandrel.
6. An interlayer pressure measuring method according to claim 5, wherein said measuring the deformation amount of said mandrel before and after peeling the metallized film from the metallized film capacitor based on the resistances of said first strain gauge, second strain gauge, third strain gauge and fourth strain gauge, respectively, comprises:
respectively measuring the resistance variation of the first strain gauge and the resistance variation of the second strain gauge before and after the metallized film is stripped from the metallized film capacitor by utilizing the Wheatstone bridge principle according to the initial resistance of the first strain gauge and the second strain gauge and the resistance of the third strain gauge and the fourth strain gauge;
calculating the difference of the resistance variation of the first strain gauge and the second strain gauge caused by the deformation of the mandrel according to the resistance variation of the first strain gauge and the second strain gauge before and after the metallized film is stripped from the metallized film capacitor;
and calculating the deformation amount of the mandrel according to the difference between the resistance variation amounts of the first strain gauge and the second strain gauge generated by the deformation of the mandrel.
7. The interlayer pressure measurement method of claim 6, wherein the first strain gage resistance change amount comprises: the resistance variation of the first strain gauge generated by the deformation of the mandrel, the resistance variation generated by the stress of the first strain gauge and the resistance variation of the first strain gauge generated by the temperature change.
8. The interlayer pressure measurement method of claim 6, wherein the second strain gage resistance change amount comprises: the resistance variation of the second strain gauge generated by the deformation of the mandrel, the resistance variation generated by the stress of the second strain gauge and the resistance variation of the second strain gauge generated by the temperature change.
9. The interlayer pressure measurement method of claim 6, further comprising: and zeroing the output of the static program control strain gauge to obtain the initial deformation quantity of the first strain gauge and the second strain gauge.
10. The interlayer pressure measurement method of claim 5, further comprising: and in the process of stripping the metallized film from the metallized film capacitor, the number of stripping layers is 10 to 100.
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| CN1201347C (en) * | 2000-08-30 | 2005-05-11 | 阿尔卑斯电气株式会社 | Film capacitor for temperature compensation |
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| CN108267076A (en) * | 2016-12-30 | 2018-07-10 | 中国空气动力研究与发展中心超高速空气动力研究所 | A kind of self-temperature compensating gage |
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