Arc discharge suppression method for an aircraft power distribution device

Abstract

The application provides an arc discharge suppression method of an aviation power distribution device, and the method comprises the following steps: establishing a two-dimensional model and a three-dimensional model based on a bus bar structure, and establishing simulation boundary conditions under different temperatures and air pressures; carrying out electric field distribution analysis under different voltages, and determining the highest point of the local field intensity of the bus bar; modifying the chamfer parameter of the bus bar based on the highest point of the local field intensity of the bus bar; and testing the bus bar after the chamfer is modified based on an arc voltage test system. The arc discharge suppression method of the aviation power distribution device can measure the arc discharge characteristics of the current equipment, obtain the process constraint conditions, and propose a feasible improvement method, so that the product reliability is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aviation power distribution insulation, and particularly relates to an aviation power distribution device arc discharge suppression method. BACKGROUND

[0002] The aviation power supply device bears many functions such as power and control in the aircraft, and its working state determines whether the aircraft is safe. Due to the influence of the aircraft on the size and power of the device, the power supply equipment needs to consider the needs of small size and large power in design. At the same time, due to the high flight altitude of the aircraft, it is easy to cause gas breakdown under low air pressure at high altitude, and stable arc discharge is caused due to the high power of the power supply, which poses a great threat to the insulation of the equipment.

[0003] The bus bar is a current-carrying device in the aviation power supply equipment, which is usually made of high-conductivity metal materials such as copper and aluminum. Since the power supply contains multiple voltage components, the current components of different voltage levels are usually output by multiple bus bars. With the increase in the number of bus bars, the insulation distance in the small volume is reduced, and the probability of arc discharge increases.

[0004] Arc discharge is a gas discharge phenomenon with extremely serious harm, which mainly occurs due to the breakdown of gas insulation. The occurrence of persistent arc discharge can cause power supply short circuit, thereby causing local high temperature and causing local ablation of the conductor part. If the discharge occurs on the surface of the PCB insulation, it will cause the formation of carbonized electrical marks on the surface, reduce the surface resistance, form a conductive channel and cause a larger leakage current. The sudden heat and the temporary and violent release of a large amount of gas that accompanies this phenomenon inevitably cause electronic equipment failure.

[0005] Studies have shown that the occurrence of arc discharge is closely related to air pressure, humidity, insulation surface leakage current, and local electric field distortion. The above conditions will cause a significant change in the initial discharge voltage. Due to the particularity of the application scene of the power supply equipment applied to the aircraft, the initial voltage of arc discharge under different working conditions has a large distribution range. The initial voltage under different altitudes, temperatures and humidity environments may change by an order of magnitude. Once local arc discharge occurs, its large power supply capacity is easy to form self-sustaining continuous discharge phenomenon, thereby causing irreversible damage to the circuit board.

[0006] Therefore, in order to ensure the normal operation of the power supply equipment and eliminate the arc discharge hidden danger in the equipment, the arc discharge characteristics of the current equipment need to be measured, the process constraint conditions are obtained, and practical means for improvement are proposed to improve the product reliability. SUMMARY

[0007] Aiming at the above problems, the present application provides an arc discharge suppression method for an aviation power distribution device, the method comprising:

[0008] A two-dimensional model and a three-dimensional model are established based on the bus bar structure, and simulation boundary conditions under different temperatures and pressures are established;

[0009] An electric field distribution analysis under different voltages is carried out to determine the local field strength maximum point of the bus bar;

[0010] Based on the local field strength maximum point of the bus bar, the chamfer parameter of the bus bar is modified;

[0011] The bus bar with the modified chamfer is tested based on an arc voltage test system.

[0012] Preferably, before the bus bar with the modified chamfer is tested based on the arc voltage test system, the method further comprises:

[0013] The bus bar is coated with a first layer of bisphenol F epoxy resin material, and the coating thickness is set to 100 μm;

[0014] After coating, vacuum degassing is performed on the epoxy resin in a liquid state, the degassing pressure is set to 1 kPa, and the degassing time is set to 20 min;

[0015] After degassing, the sample is placed in an 80°C constant temperature oven for 2 h;

[0016] After taking out the sample, the epoxy resin surface is cleaned with alcohol and sprayed with a three-proofing paint, the spraying thickness is set to 100 μm, and the sample is placed in a constant temperature oven for 5 h.

[0017] Preferably, the arc voltage test system comprises:

[0018] An experimental box for placing a test sample;

[0019] A high-speed camera arranged in the experimental box, the high-speed camera being used for photographing a breakdown path of visible light;

[0020] A high-frequency current transformer connected with the test sample, the high-frequency current transformer being used for detecting a discharge current;

[0021] An oscilloscope connected with the high-frequency current transformer.

[0022] Preferably, the arc voltage test system further comprises:

[0023] A display connected with the high-speed camera, the display being used for displaying the photographed breakdown path of visible light;

[0024] When the breakdown path of visible light appears in the high-speed camera and the high-frequency current signal appears in the oscilloscope, the voltage value is recorded.

[0025] Preferably, the arc voltage test system further comprises:

[0026] A low-power power supply connected to the sample.

[0027] Preferably, the low-power power supply comprises an aviation power supply of 400 Hz.

[0028] Preferably, the sample comprises:

[0029] A PCB board arranged in the test box.

[0030] A bus bar arranged on the surface of the PCB board.

[0031] Preferably, the bus bar comprises:

[0032] A first bus bar arranged on the surface of the PCB board.

[0033] A second bus bar arranged on the surface of the PCB board; wherein the first bus bar and the second bus bar are arranged at equal intervals.

[0034] Preferably, the test box comprises a pressure regulating box, a temperature regulating box and a humidity regulating box.

[0035] Preferably, the arc voltage test system tests the modified bus bar, comprising:

[0036] The first bus bar and the second bus bar are arranged at equal intervals on the surface of the PCB board and placed in the test box.

[0037] The high-speed camera is turned on and the high-frequency current transformer is connected.

[0038] The test box is adjusted to reach the set air pressure value, temperature value or humidity value.

[0039] The step-by-step gradient voltage rising mode is adopted, and the voltage rising speed is set to 50V / 30s.

[0040] When the breakdown path of visible light appears in the high-speed camera and the high-frequency current signal appears in the oscilloscope, it is considered that the arc voltage is reached and the voltage value is recorded.

[0041] The present application has the following beneficial effects:

[0042] The present application measures the arc discharge characteristics of the current equipment, obtains the process constraint conditions and proposes practical and feasible improvement methods to improve the product reliability. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 A schematic diagram of an arc ignition voltage test system provided for an embodiment of the present application is shown in FIG. 1.

[0044] Figure 2 A schematic diagram of an arc ignition voltage test sample provided for an embodiment of the present application is shown in FIG. 2. DETAILED DESCRIPTION

[0045] The present application relates to a method for researching arc discharge suppression of an aviation power distribution device, and provides a relatively complete research scheme for improving the insulation performance of a busbar.

[0046] First, a small power supply is used to replace a large power supply to determine the arc ignition voltage, and an arc ignition voltage test platform is established to implement various power supply tests and introduce an operating overvoltage to verify the arc suppression performance. Based on a small power supply, an arc ignition voltage test platform is built to implement different air pressures and temperature and humidity, a high-speed camera is selected to access the experimental unit, and a high-frequency current transformer (HFCT) is selected to synchronously develop discharge current detection.

[0047] Based on finite element electric field calculation, electric field strength analysis and busbar chamfer design are carried out under two-dimensional and three-dimensional models to realize busbar electric field parameter optimization. Finally, an electric field improvement scheme based on multi-layer insulation material coating is proposed, in which high insulation performance insulation materials are used to coat the busbar inside, and three-proofing paint required by PCB is selected for secondary coating outside, so as to improve the insulation performance, improve the stability and safety of the aviation power distribution device, and ensure the safety of the aircraft flight.

[0048] Among them, based on the optimization of the electric field parameters of the busbar, the electric field strength at the edge of the busbar is reduced, and the possibility of gas breakdown is reduced. Finite element electric field calculation is carried out to analyze the electric field strength under two-dimensional and three-dimensional models and optimize the chamfer of the busbar.

[0049] In the embodiment of the present application, a low-power power supply is used to replace a high-power device, an arc ignition voltage test platform is established to implement various power supply tests, and an operating overvoltage is introduced to verify the arc suppression performance.

[0050] In the embodiment of the present application, a 400Hz aviation power supply is used as a test power supply, and a high-frequency alternating current transformer is made of high-frequency magnetic conductive material to realize the manufacturing of a 400Hz high-voltage alternating current power supply.

[0051] In the embodiment of the present application, a nickel-zinc ferrite is used as the magnetic core of the winding, and a high-frequency transformer with a transformation ratio of 1:100 is wound as an alternating current high-voltage power supply for testing. The voltage range can be Vrms=0-10kV.

[0052] In the embodiments of the present application, a high-speed camera is selected to access the test unit, and a high-frequency current transformer (HFCT) is selected as a trigger to synchronously carry out discharge current detection.

[0053] Based on the arc voltage improvement and the three-proofing requirements of the low-voltage part, the present application proposes an electric field improvement scheme based on multi-layer insulation material coating, in which a high-insulation material is used to coat the bus bar internally, and a three-proofing paint required by a PCB is selected to perform secondary coating externally, so as to improve the insulation performance.

[0054] In order to describe the arc resistance improvement effect of the hardware and the insulation coating, the method determines the improvement effect parameter method, the hardware improvement coefficient Kha is a ratio between the maximum field strength F0 before the chamfer improvement and the maximum field strength F1 after the chamfer improvement, and the value is greater than 1; the low-pressure improvement coefficient Kp is Kp = Up / Up0; the high-temperature improvement coefficient KT is KT = UT / UT0; and the high-humidity improvement coefficient KH is KH = UH / UH0.

[0055] In other embodiments of the present application, the specific content is as follows:

[0056] 1. The bus bar electric field parameter optimization based on hardware effectively suppresses the electric field distortion phenomenon caused by the bus bar corner;

[0057] 2. A small-power alternating current, direct current and overvoltage power supply is used to build an arc voltage test platform capable of realizing different air pressures, temperatures and humidities;

[0058] 3. The arc voltage improvement and verification method based on multi-layer insulation material coating proposes an electric field improvement scheme based on multi-layer insulation material coating, in which a high-insulation material is used to coat the bus bar internally, and a three-proofing paint required by a PCB is selected to perform secondary coating externally, so as to improve the insulation performance;

[0059] 4. Based on the arc resistance improvement effect of the hardware and the insulation coating, the low-pressure, temperature and humidity coefficients are determined to provide reasonable specifications for insulation coating design.

[0060] In other embodiments of the present application, the present application adopts the following technical solutions:

[0061] 7.1 Bus bar electric field parameter optimization based on hardware

[0062] In the initiation mechanism of the arc, the gas insulation breakdown will occur before the arc, and the gas insulation breakdown is closely related to the distribution of the local electric field. The conventional busbar device is processed by cutting in the factory, and usually has relatively sharp corners, which can easily cause local electric field distortion. When the strength of the distorted electric field exceeds the air breakdown field strength at the gas pressure, the gas breakdown will be triggered, and the conductive path will be formed in the insulation area after the gas breakdown, thereby further triggering the stable burning arc under the action of the high-power power supply. Therefore, the electric field strength at the corner of the busbar can be reduced based on the optimization of the busbar electric field parameters to reduce the possibility of gas breakdown. To achieve this purpose, the present application uses finite element electric field calculation to carry out electric field strength analysis and busbar chamfer optimization under two-dimensional and three-dimensional models. The specific implementation method is as follows:

[0063] 1. Establish two-dimensional and three-dimensional models according to the existing busbar structure.

[0064] 2. Establish simulation boundary conditions at different temperatures and gas pressures.

[0065] 3. Carry out electric field distribution analysis under different voltages to determine the highest point of local field strength.

[0066] 4. Modify the chamfer parameters of the busbar and redevelop the simulation to analyze the electric field optimization effect.

[0067] The simulation theoretical basis is as follows:

[0068] 1) Material parameters

[0069] The electric field distribution after applying voltage is affected by the air and the dielectric constant and conductivity of the PCB along the surface. The specific insulation parameters of the simulation material are shown in Table 1.

[0070] Table 1

[0071] Name Conductivity (S / m) Dielectric constant Conductive strip 5.998 x 10 7 ]] 1 Air 1.8 x 10 -4 ]]> 1 PCB board 1.28 x 10 -11 ]] 3.8

[0072] 2) Simulation principle

[0073] According to the above table, the simulation material parameters are set. In electromagnetic analysis problems, the Maxwell equation group is the most important equation group of electromagnetic dynamics. The Maxwell equation group is composed of several basic equations such as the classical Coulomb law, the Biot-Savart law and the Faraday electromagnetic induction law. The Maxwell equation group is solved by solving the Maxwell equation group, which is also the basis for COMSOL finite element software to solve the superconducting coil by finite element method. The integral form of Maxwell equation is as follows:

[0074]

[0075]

[0076]

[0077]

[0078] The differential form of Maxwell's equations from which the above equations are derived is:

[0079]

[0080]

[0081]

[0082]

[0083] Meanwhile, according to the alternating electric field distribution, it is known that the dielectric constant affects the alternating electric field distribution, and the conductivity affects the direct current electric field distribution.

[0084] 7.2 Arcing voltage test platform based on low-power power supply

[0085] The application adopts low-power alternating current, direct current and overvoltage power supply to build an arcing voltage test platform that can realize different air pressures and temperature and humidity.

[0086] In a feasible implementation manner, a 400Hz aviation power supply is adopted as a test power supply, a high-frequency alternating current transformer is made by cooperating with a high-frequency magnetic material, and the manufacturing of the 400Hz high-voltage alternating current power supply is realized. Compared with a traditional power frequency transformer, the power supply has lower voltage loss. Since the traditional power frequency transformer adopts silicon steel sheet as a magnetic material, it has a large magnetic resistance at a frequency of 400Hz and above, and cannot effectively realize the transformation function. Therefore, the application adopts a nickel-zinc ferrite as a magnetic core of a winding, and a high-frequency transformer with a transformation ratio of 1:100 is wound, which is used as an alternating current high-voltage power supply for testing. The voltage range can be Vrms=0-10kV.

[0087] In a feasible implementation manner, a direct current power supply with a voltage range of 0-30kV and a current of 2mA is adopted as a test direct current power supply.

[0088] In a feasible implementation manner, an operating overvoltage pulse voltage source is adopted as a test overvoltage power supply, and the parameters are as follows: voltage 0-20kV, and repetition frequency 1Hz-1kHz.

[0089] In order to realize the observation of the arcing voltage, a high-speed camera is selected to access the experimental unit, and a high-frequency current transformer (HFCT) is selected to synchronously detect the discharge current, and the structure is as shown in Figure 1 The busbar sample is made at equal intervals, and is fixed on the surface of the PCB, and the structure is as shown in Figure 2 ​

[0090] In one possible implementation, the testing step includes:

[0091] 1. Connect the bus bar to the high-voltage conductor and the ground wire, and place the sample in the test box;

[0092] 2. Turn on the high-speed camera and connect the HFCT;

[0093] 3. Adjust the test box to reach the set air pressure value or temperature and humidity value;

[0094] 4. Use a step-by-step gradient voltage boosting method, and set the voltage boosting speed to 50V / 30s;

[0095] 5. When the high-speed camera shows a visible breakdown path of light and the oscilloscope shows a clear high-frequency current signal, it is considered that the striking voltage has been reached, and the voltage value is recorded.

[0096] 7.3 Arcing voltage performance improvement and verification method based on multi-layer insulation coating

[0097] To effectively suppress the arc, the traditional method usually uses single-layer insulation coating. Based on the improvement of arcing voltage and the three-proof requirements of the low-voltage part, the present application proposes an electric field improvement scheme based on multi-layer insulation coating. The bus bar is coated with an insulation material with high insulation performance inside, and a three-proof paint required by the PCB is used for secondary coating outside, so as to improve the insulation performance.

[0098] To achieve the above performance improvement, the present application determines the following coating scheme as an example:

[0099] (1) First, the bus bar is coated with a first layer of bisphenol F epoxy resin material, and the coating thickness is set to 100μm;

[0100] (2) After coating, vacuum degassing is required in the liquid state of the epoxy resin, the degassing pressure is set to 1kPa, and the degassing time is set to 20min;

[0101] (3) After degassing, the sample is placed in an 80℃ constant temperature box for 2h.

[0102] (4) After taking out the sample, clean the surface of the epoxy resin with alcohol and spray three-proof paint, the spraying thickness is set to 100μm, and it is placed in a constant temperature box for 5h.

[0103] This scheme is not limited to one kind of insulation material, and any insulation material suitable for high-voltage application can be coated with two layers by this scheme.

[0104] To fully verify the improvement of arc resistance after coating, the following scheme is used for verification:

[0105] (1) To verify the arc resistance performance of the aircraft in high altitude, first conduct the arc voltage test under 1kPa pressure, and record the arc voltage Up, while selecting the arc voltage Up0 of the bare busbar under the same interval as the reference value of the improvement effect;

[0106] (2) To verify the arc resistance performance of the aircraft in high temperature, conduct the arc voltage test under high temperature, select the temperature as the highest temperature of the equipment operation 115℃, and record the arc voltage UT, while selecting the arc voltage UT0 of the bare busbar under the same interval and temperature as the reference value of the improvement effect;

[0107] (3) To verify the arc resistance performance of the aircraft in high humidity, select the relative humidity of 95%RH, and record the arc voltage UH, while selecting the arc voltage UH0 of the bare busbar under the same interval and humidity as the reference value of the improvement effect;

[0108] 7.4 Parameter determination method of improvement effect

[0109] In order to describe the arc resistance performance improvement effect of the above hardware and insulation coating, the following parameters are determined by the method:

[0110] (1) Hardware improvement coefficient Kha: its value is the ratio between the highest field strength F0 before chamfering and the highest field strength F1 after chamfering, and its value is greater than 1;

[0111] (2) Low pressure improvement coefficient Kp:

[0112] K p =U p / U p0 ;

[0113] (3) High temperature improvement coefficient KT:

[0114] K T =U T / U T0 ;

[0115] (4) High humidity improvement coefficient KH:

[0116] K H =U H / U H0

[0117] It should be noted that the present application ensures the normal operation of the power supply equipment, eliminates the arc discharge hidden danger in the equipment, measures the arc discharge characteristics of the current equipment, obtains the process constraint conditions and proposes practical improvement means, and improves the product reliability.

Claims

1. A method for suppressing arc discharge in an aircraft power distribution system, characterized in that, The method includes: Two-dimensional and three-dimensional models were established based on the busbar structure, and simulation boundary conditions were established under different temperatures and pressures. Conduct electric field distribution analysis under different voltages to determine the local maximum electric field point of the busbar; Based on the local maximum field strength point of the busbar, modify the chamfer parameters of the busbar; Testing of the modified chamfered busbar using an arc initiation voltage testing system; The arc initiation voltage testing system includes: a low-power power supply connected to the sample; the low-power power supply includes a 400 Hz aviation power supply; Before testing the modified chamfered busbar using the arc-starting voltage testing system, the following steps are also included: The busbar was coated with a first layer of bisphenol F epoxy resin material, with a coating thickness of 100 μm. After coating, vacuum degassing is required in the liquid state of epoxy resin. The degassing pressure is set to 1 kPa and the degassing time is set to 20 min. After degassing, the sample was placed in an 80℃ constant temperature oven for 2 hours to cure. After removing the sample, clean the epoxy resin surface with alcohol and apply conformal coating with a thickness of 100 μm. Then, allow it to cure at room temperature for 5 hours. The method further includes: to fully verify the improvement in arc resistance after coating, verification is carried out according to the following scheme: (1) To verify the aircraft's anti-arc performance at high altitude, an arc initiation voltage test was first conducted at an air pressure of 1 kPa, and the arc initiation voltage U was recorded. p Simultaneously, the arc initiation voltage U of the exposed busbars with the same spacing was selected. p0 As a reference value for improving the effect; (2) To verify the aircraft's arc resistance performance at high temperatures, an arc initiation voltage test was conducted at high temperatures. The selected temperature was 115°C, the highest operating temperature of the equipment, and the arc initiation voltage U was recorded. T Simultaneously, the arc initiation voltage U of the exposed busbars with the same spacing and temperature was selected. T0 As a reference value for improving the effect; (3) Verify the aircraft's anti-arc performance in high humidity. Select a relative humidity of 95%RH and record the arc initiation voltage U. H Simultaneously, the arc initiation voltage U of the exposed busbar under the same spacing and humidity was selected. H0 As a reference value for improving the effect; Method for determining the improvement parameters: To describe the improvement in arc resistance performance after the above hardware and insulation coating, this method determines the following parameters: (1) Hardware improvement factor Kha: Its value is the ratio between the highest field strength F0 before chamfering improvement and the highest field strength F1 after improvement, and its value is greater than 1; (2) Low pressure lift coefficient K p :K p =U p / U p0 ; (3) High temperature rise coefficient K T :K T =U T / U T0 ; (4) High humidity enhancement coefficient K H :K H =U H / U H0 .

2. The method according to claim 1, characterized in that, The arc initiation voltage testing system also includes: The test chamber is used to hold the test samples; A high-speed camera is installed inside the experimental chamber; the high-speed camera is used to capture the breakdown path of visible light. A high-frequency current transformer is connected to the sample, and the high-frequency current transformer is used to detect the discharge current. An oscilloscope is connected to the high-frequency current transformer.

3. The method according to claim 2, characterized in that, The arc initiation voltage testing system also includes: A display, connected to the high-speed camera, is used to display the breakdown path of the captured visible light. Specifically, when a visible light breakdown path appears in the high-speed camera and a high-frequency current signal appears on the oscilloscope, the voltage value is recorded.

4. The method according to claim 3, characterized in that, The sample includes: The PCB board is installed inside the experimental chamber; Busbars are disposed on the surface of the PCB board.

5. The method according to claim 4, characterized in that, The busbar includes: The first busbar is disposed on the surface of the PCB board; The second busbar is disposed on the surface of the PCB board; wherein the first busbar and the second busbar are disposed at equal intervals.

6. The method according to claim 5, characterized in that, The experimental chamber includes a pressure regulating chamber, a temperature regulating chamber, and a humidity regulating chamber.

7. The method according to claim 6, characterized in that, The arc-starting voltage testing system is used to test the modified chamfered busbar, including: The first and second busbars are placed at equal intervals on the surface of the PCB board and then placed inside the experimental chamber. Turn on the high-speed camera and connect the high-frequency current transformer; Adjust the experimental chamber to reach the set air pressure, temperature, or humidity values; A step-by-step voltage boost method is adopted, with the boost rate set to 50V / 30s; When a visible light breakdown path appears in the high-speed camera and a significant high-frequency current signal appears on the oscilloscope, it is considered that the arc initiation voltage has been reached and the voltage value is recorded.

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