Force-heat combined test device

Abstract

The utility model discloses a force and heat combined test device, which comprises a test piece fixing seat and an integral rack, the bottom right side of the integral rack is fixedly connected with the bottom left side of the test piece fixing seat; a test piece to be tested is fixedly arranged at the top of the test piece fixing seat; the test piece is positioned in an inner side cavity of the heater; the heater is located at the top of the test piece fixing seat; the heater is used for applying a thermal load to the test piece on the inner side; the right side of the integral rack is respectively provided with two sets of force loading systems which are distributed up and down; and the two sets of force loading systems are respectively connected with the test piece and are used for applying a force load to the test piece. The mechanical-thermal combined test device disclosed by the utility model is scientific in design, and can provide a relatively real comprehensive environment of air thermal load and aerodynamic load borne by an aircraft in the flight process for simulation of an aircraft steering engine room and an air inlet fairing; and the working performance of the aircraft steering engine room and the air inlet fairing can be better examined in the next step.

Description

Technical Field

[0001] The utility model relates to the technical field of air thermal load and aerodynamic load loading, in particular to a combined force and heat test device. Background Art

[0002] Aircraft technology research requires increasingly extreme conditions due to the constantly changing external environment. This is especially true during high-speed flight, where the aerodynamic thermal environment experienced by the aircraft's servo compartment (specifically, the flight control fins and engines) is even more severe. Currently, a more realistic simulation environment is needed to verify the servo compartment's performance under both thermal and aerodynamic loads, including rudder shaft rotation and rudder swing. Furthermore, the coordination and matching of the structure's static strength, static stiffness, and deformation under these complex conditions should be assessed.

[0003] During the flight of an aircraft, some important components cannot withstand excessively high temperatures. It is necessary to simulate a high-temperature environment outside the air inlet fairing. Under the insulation of the composite materials, the temperature inside the aircraft is not too high, and to verify whether certain specific composite materials can provide a relatively stable low-temperature environment.

[0004] In addition, there is partitioned loading in the hot zone loading, which needs to meet the different temperature stress requirements of the two sections of the servo cabin and the air inlet fairing, which involves the research and analysis of strong thermal coupling and thermal convection dynamics.

[0005] However, the existing test system cannot accurately meet the mechanical and thermal load requirements of the aircraft servo cabin and air inlet fairing at the same time.

[0006] Therefore, there is an urgent need to develop a technology to solve the above technical problems. Utility Model Content

[0007] The purpose of the utility model is to provide a combined force and heat test device to address the technical defects of the prior art.

[0008] To this end, the utility model provides a combined force and heat test device, which includes a test piece fixing seat and an integral stand;

[0009] The bottom right side of the overall test stand is fixedly connected to the bottom left side of the test piece fixing seat;

[0010] The test piece to be tested is fixedly mounted on the top of the test piece fixing seat;

[0011] The test piece is located in the inner cavity of the heater 7;

[0012] The heater is located on top of the test piece holder;

[0013] A heater, used to apply a thermal load to the test piece inside it;

[0014] On the right side of the overall test stand, there are two sets of force loading systems distributed upper and lower respectively;

[0015] Two sets of force loading systems are respectively connected to the test pieces and are used to apply force loads to the test pieces.

[0016] It can be seen from the technical solution provided by the above-mentioned utility model that, compared with the existing technology, the utility model provides a combined force and heat test device, which is scientifically designed and can provide a relatively realistic comprehensive environment of air thermal loads and aerodynamic loads that the aircraft is subjected to during flight for the test piece (specifically, the aircraft servo cabin and the air inlet fairing), which is conducive to better evaluating the working performance of the test piece (specifically, the aircraft servo cabin and the air inlet fairing) in the next step, and has great practical significance.

[0017] The combined force and heat test device provided by the utility model is a set of devices for conducting combined force and heat tests on aircraft servo cabins and air inlet fairings. It can realize multi-channel force loading and multi-heat zone loading at the same time, solving the problem that the servo cabin and air inlet fairing under existing conditions cannot simulate the comprehensive environment of air thermal loads and aerodynamic loads that the aircraft is subjected to during flight. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the overall structure of a combined force and heat test device provided by the utility model;

[0019] Figure 2 This is a test control flow chart of a combined power and heat test device provided by the utility model;

[0020] Figure 3 This is a structural schematic diagram of a heater provided in a combined power and heat test device provided by the present invention;

[0021] Figure 4 A schematic diagram of the state of a combined force and heat test device provided by the present invention when force loading is performed;

[0022] In the figure, 1 is the test piece fixing seat, 2 is the integral step, 31 is the first horizontal suspension beam, 32 is the second horizontal suspension beam, 4 is the first cylinder, and 5 is the second cylinder;

[0023] 6 is the first cylinder mounting plate, 7 is the heater, 8 is the first adapter rod, 9 is the first connecting rod, and 10 is the first force sensor;

[0024] 60 is the second cylinder mounting plate, 80 is the second adapter rod, 90 is the second connecting rod, 100 is the second force sensor; 200 is the rudder blade;

[0025] 14 is the first quartz lamp, 15 is the second quartz lamp; 161 is the first ceramic base, 162 is the second ceramic base, 163 is the gap; 17 is the copper busbar, and 18 is the base support leg. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0028] In the description of this patent, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," and "set" should be understood in a broad sense. For example, they can refer to fixed connection or set, detachable connection or set, or integral connection or set. Those skilled in the art will understand the specific meanings of the above terms in this patent based on the specific circumstances.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined.

[0030] See also Figures 1 to 4 The utility model provides a combined force and heat test device, which can be used to simulate the comprehensive environment of air thermal load and aerodynamic load that the aircraft servo cabin part in the test piece is subjected to during the flight, and provide air thermal load for the air inlet fairing simulation part in the test piece.

[0031] The utility model provides a combined force and heat test device, comprising a test piece fixing seat 1 and an integral stand 2;

[0032] The bottom right side of the integral stand 2 is fixedly connected to the bottom left side of the test piece fixing seat 1;

[0033] The test piece to be tested is fixedly mounted on the top of the test piece fixing seat 1;

[0034] The test piece is located in the inner cavity of the heater 7;

[0035] The heater 7 is located on the top of the test piece fixing seat 1;

[0036] A heater 7, for applying a heat load to the test piece inside the heater;

[0037] On the right side of the integral platform 2, two sets of force loading systems are respectively provided, one above the other;

[0038] Two sets of force loading systems are respectively connected to the test piece (specifically, they can be two force loading locations required in advance on the test piece) to apply force loads to the test piece.

[0039] In the present invention, in a specific implementation, the test piece is preferably a whole composed of an aircraft steering gear cabin and an air intake fairing, that is, a steering gear cabin and an air intake fairing;

[0040] A test piece is fixedly mounted on an outer surface of an engine model;

[0041] The engine model is fixedly connected to the top of the test piece fixing seat 1 .

[0042] It should be noted that the shape, size, and weight of the engine model are identical to those of the engine actually installed on the aircraft. The engine model's outer surface bosses are connected to the servo nacelle and air intake fairing, serving as test pieces, and the appropriate test components are installed to simulate actual flight conditions.

[0043] In the present invention, in a specific implementation, the test piece fixing seat 1 can be formed by fixing a plurality of castings together, and the castings are connected with M20 screws.

[0044] In the present invention, in a specific implementation, the overall stand 2 can be formed by a plurality of ingots fixedly connected, and the ingots are connected with M20 screws.

[0045] In the present invention, in a specific implementation, two force loading systems specifically include a first force loading system and a second force loading system;

[0046] A first force loading system, comprising a first cylinder 4;

[0047] One end of the first cylinder 4 is hinged (i.e., rotatably connected) to one end of the first transfer rod 8;

[0048] The other end of the first transfer rod 8 is hinged to the protrusion on the first cylinder mounting plate 6;

[0049] The first cylinder mounting plate 6 is fixedly arranged on the upper end of the integral platform 2;

[0050] The other end of the first cylinder 4 is hinged to the first connecting rod 9 fixed to one end of the first force sensor 10;

[0051] The other end of the first force sensor 10 is connected to one end of the test piece through a first long pull rod 11;

[0052] A second force loading system, comprising a second cylinder 5;

[0053] One end of the second cylinder 5 is hinged (i.e., rotatably connected) to one end of the second transfer rod 80;

[0054] The other end of the second transfer rod 80 is hinged to the protrusion on the second cylinder mounting plate 60;

[0055] The second cylinder mounting plate 60 is fixedly arranged at the lower end of the integral platform 2;

[0056] The other end of the second cylinder 5 is hinged to the second connecting rod 90 fixed to one end of the second force sensor 100;

[0057] The other end of the second force sensor 100 is connected to the other end of the test piece through a second long pull rod 110 .

[0058] It should be noted that for the test piece (such as the aircraft servo compartment and the air intake fairing), a through hole is provided at its end, and the first long pull rod 11 and the second long pull rod 110 are provided with an internal threaded hole at one end facing the test piece. The first long pull rod 11 and the second long pull rod 110 are fixedly connected to the test piece by a first bolt and a second bolt respectively, wherein the first bolt passes through the through hole on the test piece and is threadedly fixedly connected to the internal threaded hole at the end of the first long pull rod 11, and the second bolt passes through the through hole on the test piece and is threadedly fixedly connected to the internal threaded hole at the end of the second long pull rod 110.

[0059] In a specific implementation, the central axis of the first cylinder 4 and the central axis of the second cylinder 5 are perpendicular to each other.

[0060] Furthermore, the angle between the central axis of the first cylinder 4 and the horizontal plane is 45°;

[0061] The angle between the central axis of the second cylinder 5 and the horizontal plane is 45°;

[0062] The distribution height of the first cylinder 4 is gradually reduced from left to right, that is, it is arranged obliquely downward;

[0063] The distribution height of the second cylinder 5 gradually increases from left to right, that is, it is arranged obliquely upward.

[0064] In specific implementation, a first transverse suspension beam 31 is fixedly provided above the first cylinder mounting plate 6;

[0065] The first transverse suspension beam 31 is connected to the cylinder body of the first cylinder 4 via a pull rope (specifically, it can be a sleeve connection);

[0066] Directly above the second cylinder mounting plate 60, a second transverse suspension beam 32 is fixedly provided;

[0067] The second transverse suspension beam 32 is connected to the cylinder body of the second cylinder 5 via a pull rope (specifically, it can be a sleeve connection).

[0068] In terms of specific implementation, the test pieces are the steering gear compartment and the air intake fairing;

[0069] The axial directions of the first cylinder and the second cylinder are perpendicular to the adjacent rudder blades 200 in the steering gear compartment and the air inlet fairing.

[0070] It should be noted that, for the present invention, the overall test stand 2 is required to be at an appropriate height. Specifically, by adjusting the installation position of the cylinder mounting plate, it is ensured that the axial directions of the first cylinder and the second cylinder are perpendicular to the rudder blades in the steering gear compartment and the air inlet fairing serving as the test piece, and the two cylinders are suspended by a crossbeam, and the loading position is consistent with the required area.

[0071] It should be noted that the rudder blade 200 is a part of the test piece composed of the servo cabin and the air inlet fairing, and is an original component of the test piece. The overall shape of the rudder blade 200 is L-shaped. The rudder blade 200 is connected to the rudder shaft, and the rudder shaft is fixed in the servo cabin. The rudder shaft serves as the load-bearing object and assessment object of the test. The entire test environment simulates the comprehensive environment of air thermal load and aerodynamic load during the flight process.

[0072] It should also be noted that due to the flight angle and the test requirements derived from the simulation of flight data, during the test, the axes of the first cylinder and the second cylinder are required to be perpendicular to the rudder blades. This direction is the main content of the assessment and is related to the flight state, making the assessment effect more realistic and conducive to further simulating the stress conditions of multi-angle flight.

[0073] In a specific implementation, the outer dimensions of the first cylinder and the second cylinder are 430 mm in length × 430 mm in width × 750 mm in height;

[0074] The first force sensor 10 and the second force sensor 100 are two 5t force sensors, which are designed with a long pull rod and several connecting rods and adapter rods to ensure the degree of freedom when the force is loaded during the test.

[0075] For specific implementation, see Figure 2 As shown, the force loading control system can further employ PID control (Proportional Integral Differential Control). The industrial computer outputs a signal to a pressure regulating valve. The pressure regulating valve, connected to an external gas source, receives the signal and adjusts the gas pressure entering the first and second cylinders. Two pressure sensors connected to the two cylinders then feed the force load back to the industrial computer, achieving closed-loop control. PID control technology is well-known and mature in the art and will not be elaborated upon here.

[0076] In this utility model, the specific implementation is as follows Figure 3 As shown, a plurality of first quartz lamps 14 and a plurality of second quartz lamps 15 are respectively provided at the left and right ends of the top of the heater 7 .

[0077] In a specific implementation, a plurality of first quartz lamps 14 and a plurality of second quartz lamps 15 are fixed on the top of the heater 7 (for example, by an existing clamp).

[0078] In a specific implementation, the heater 7 includes two first ceramic bases 161 spaced apart from each other in the front and back;

[0079] The first ceramic base 161 is vertically distributed;

[0080] The tops of the two first ceramic bases 161 are fixedly connected to the front and rear ends of the horizontally distributed second ceramic base 162 through support rods 160 respectively;

[0081] There are transversely distributed gaps 163 between the front and rear ends of the second ceramic base 162 and the tops of the two first ceramic bases 161;

[0082] The second ceramic base 162 is provided with an opening directly below each first quartz lamp 14 and each second quartz lamp 15 , respectively, and the opening is used to allow the short-wave infrared radiation generated by the quartz lamp to pass through.

[0083] In a specific implementation, a plurality of second quartz lamps 15 are further provided at the right end of the opposite side of the two first ceramic bases 161;

[0084] The first ceramic base 161 is provided with a through hole running longitudinally through the first ceramic base 161 at a position corresponding to each second quartz lamp 15 , and the through hole is used to allow the short-wave infrared radiation generated by the quartz lamp to pass through.

[0085] In a specific implementation, the left and right ends of the bottom of the two first ceramic bases 161 are respectively connected to a vertically distributed base leg 18;

[0086] The base legs 18 are located on the top of the test piece fixing seat 1 .

[0087] It should be noted that the ceramic base has a good heat-insulating effect, which can prevent the heat of the surrounding environment of the heated test piece from escaping to the outside through the location of the ceramic base.

[0088] In a specific implementation, the power supply ends of the first quartz lamp 14 and the second quartz lamp 15 are respectively connected to an external power supply (eg, an existing DC cabinet capable of providing DC power) through a copper busbar 17 .

[0089] It should be noted that the two gaps 163 are used to expose the two ends of the test piece, specifically, to expose the two ends of the L-shaped rudder blade 200 in the steering gear compartment and the air inlet fairing as the test piece, such as Figure 4 shown.

[0090] Figure 4 A schematic diagram of the state of a combined force and heat test device provided by the present invention when force loading is performed; Figure 4 In the figure, a simplified structural diagram of a simulated rudder blade 200 is shown. The rudder blade 200 is a part of a test piece consisting of a servo cabin and an air inlet fairing. The rudder blade 200 is connected to the rudder shaft, and the rudder shaft is fixed in the servo cabin (the rudder shaft, servo cabin and air inlet fairing are omitted in the figure).

[0091] It should be noted that the heater 7, which serves as a heat loading system, adopts a quartz lamp heating method to simulate the aerodynamic heat of the test piece in flight. The quartz lamp heater generates short-wave infrared radiation after being powered on, and further blackens the test piece (i.e., applies a heat-absorbing layer to promote heat absorption) for radiant heating.

[0092] Specifically, the first quartz lamp 14 and the second quartz lamp 15 can be used to heat the steering gear compartment and the air intake fairing of the test piece, respectively, applying different thermal loads. In other words, a first temperature zone for heating the steering gear compartment and a second temperature zone for heating the air intake fairing can be formed within the heater 7.

[0093] Furthermore, a partition plate is installed between the plurality of first quartz lamps 14 and the plurality of second quartz lamps 15 to reduce heat convection between different temperature zones.

[0094] For specific implementation, see Figure 2As shown, a temperature control system can be further constructed for the heater. This temperature control system employs PID control, which uses a temperature sensor (located inside the test piece) to control the real-time temperature value and target value, and feedback adjustment to control the output signal to the power supply (e.g., a DC power cabinet) of the quartz lamp, thereby regulating the heating temperature and achieving closed-loop control. PID control technology is well-known and well-established in the art and will not be elaborated on here.

[0095] In the present invention, in specific implementation, it also includes a cooling system;

[0096] Cooling system, including fans;

[0097] The fan is used to dissipate heat from the test piece after the test is completed.

[0098] It should be noted that, for the present invention, the cooling system adopts a method of front-to-back ventilation with a fan connected to the air duct for cooling. The air duct is connected to the rear end outlet of the test piece by M6 screws. The test piece is coated with a heat-releasing coating, and it is necessary to prevent the insulation layer from overheating and smoking. After being placed in the loading fixture, other parts that are not subject to heat load testing are wrapped with insulation felt.

[0099] In the present utility model, the specific implementation also includes a data acquisition system;

[0100] A data acquisition system, including a thermocouple (e.g., a K-type thermocouple);

[0101] The thermocouple is glued to the inside of the test piece;

[0102] The temperature data output terminal of the thermocouple is connected to the data acquisition terminal of the temperature inspection instrument;

[0103] The temperature patrol meter is used to receive and store temperature data sent by the thermocouple and display it in real time.

[0104] It should be noted that, in the present invention, a thermocouple is pasted inside the test piece, and temperature monitoring is performed by using a temperature patrol meter to collect real-time data of the thermocouple.

[0105] In terms of specific implementation, the data acquisition system also includes strain gauges;

[0106] Strain gauges are attached to predetermined locations on the test piece (e.g., important locations with high loads);

[0107] It should be noted that strain gauges are used to monitor the strain and stress of test pieces under combined mechanical and thermal tests.

[0108] In specific implementation, when the test piece is a whole composed of an aircraft servo cabin and an air inlet fairing, the data acquisition system also includes a displacement sensor;

[0109] The displacement sensor is installed at the position of the air rudder shaft and the rudder blade of the aircraft's rudder cabin.

[0110] Displacement sensor is used to monitor the displacement of the test piece under the combined mechanical and thermal test.

[0111] It should be noted that displacement sensors are respectively arranged at the rudder shaft and the rudder blade of the test piece. The connection base of the displacement sensors is independent of the test piece fixing base 1 to eliminate the displacement interference caused by the test piece fixing base 1.

[0112] It should be noted that the strain and displacement data are collected by connecting to existing data acquisition equipment.

[0113] In the present invention, the entire force loading system is thermally insulated. All cables and equipment within a 2-meter radius of the test area that may be directly exposed to the quartz lamp are wrapped with fireproof felt or shielded by fireproof felt.

[0114] It should be noted that in this utility model, two force-loading systems can be used to apply force to the test piece, while a thermal-loading system can be used to apply thermal load to the test piece. Then, by using corresponding monitoring components installed on the test piece and combining them with existing test analysis methods, the strain, displacement, temperature, and other data on the test piece are analyzed, thereby analyzing the corresponding performance of the test piece.

[0115] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A combined force and heat test device, characterized in that: It comprises a test piece fixing seat (1) and an integral stand (2); The bottom right side of the integral stand (2) is fixedly connected to the bottom left side of the test piece fixing seat (1); A test piece to be tested is fixedly arranged on the top of the test piece fixing seat (1); The test piece is located in the inner cavity of the heater (7); The heater (7) is located on the top of the test piece fixing seat (1); A heater (7) for applying a heat load to the test piece inside the heater; On the right side of the overall platform (2), two sets of force loading systems are respectively provided, which are distributed up and down; Two sets of force loading systems are respectively connected to the test pieces and are used to apply force loads to the test pieces.

2. The combined power and heat test device according to claim 1, characterized in that: Two force loading systems, specifically including a first force loading system and a second force loading system; A first force loading system includes a first cylinder (4); One end of the first cylinder (4) is hinged to one end of the first transfer rod (8); The other end of the first transfer rod (8) is hinged to a protrusion on the first cylinder mounting plate (6); The first cylinder mounting plate (6) is fixedly arranged on the upper end of the integral platform (2); The other end of the first cylinder (4) is hinged to a first connecting rod (9) fixed to one end of a first force sensor (10); The other end of the first force sensor (10) is connected to one end of the test piece through a first long pull rod (11); A second force loading system, comprising a second cylinder (5); One end of the second cylinder (5) is hinged to one end of the second transfer rod (80); The other end of the second transfer rod (80) is hinged to a protrusion on the second cylinder mounting plate (60); The second cylinder mounting plate (60) is fixedly arranged at the lower end of the integral platform (2); The other end of the second cylinder (5) is hinged to a second connecting rod (90) fixed to one end of the second force sensor (100); The other end of the second force sensor (100) is connected to the other end of the test piece via a second long pull rod (110).

3. The combined power and heat test device according to claim 2, characterized in that: The central axis of the first cylinder (4) and the central axis of the second cylinder (5) are perpendicular to each other.

4. The combined power and heat test device according to claim 2, characterized in that: The angle between the central axis of the first cylinder (4) and the horizontal plane is 45°; The angle between the central axis of the second cylinder (5) and the horizontal plane is 45°; The distribution height of the first cylinder (4) gradually decreases from left to right; The distribution height of the second cylinder (5) gradually increases from left to right.

5. The combined power and heat test device according to claim 2, characterized in that: A first transverse suspension beam (31) is fixedly arranged directly above the first cylinder mounting plate (6); The first horizontal suspension beam (31) is connected to the cylinder body of the first cylinder (4) via a pull rope; A second transverse suspension beam (32) is fixedly arranged directly above the second cylinder mounting plate (60); The second transverse suspension beam (32) is connected to the cylinder body of the second cylinder (5) via a pull rope.

6. The combined power and heat test device according to any one of claims 1 to 5, characterized in that: A plurality of first quartz lamps (14) and a plurality of second quartz lamps (15) are respectively provided at the left and right ends of the top of the heater (7).

7. The combined power and heat test device according to claim 6, characterized in that: The heater (7) includes two first ceramic bases (161) spaced apart from each other. The first ceramic base (161) is distributed vertically; The tops of the two first ceramic bases (161) are fixedly connected to the front and rear ends of the horizontally distributed second ceramic base (162) through support rods (160) respectively; There are laterally distributed gaps (163) between the front and rear ends of the second ceramic base (162) and the tops of the two first ceramic bases (161); The second ceramic base (162) is respectively provided with an opening directly below each first quartz lamp (14) and each second quartz lamp (15).

8. The combined power and heat test device according to claim 7, characterized in that: A plurality of second quartz lamps (15) are further provided at the right ends of the opposite sides of the two first ceramic bases (161); The first ceramic base (161) is provided with a through hole running longitudinally through each second quartz lamp (15) at a position corresponding to each second quartz lamp (15).

9. The combined power and heat test device according to claim 7, characterized in that: The left and right ends of the bottoms of the two first ceramic bases (161) are respectively connected to a vertically distributed base support foot (18); The base legs (18) are located on top of the test piece fixing seat (1).

10. The combined power and heat test device according to claim 7, characterized in that: The power supply ends of the first quartz lamp (14) and the second quartz lamp (15) are respectively connected to an external power supply through a copper busbar (17).

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