A semi-anechoic chamber structure for a rail vehicle and a method for testing passing noise

Abstract

The invention discloses a semi-anechoic chamber structure and a passing noise testing method for a whole rail vehicle, which comprises a semi-anechoic chamber (19) and a load chamber (18); a motor (1), a synchronous box (2) and a gearbox (3) are installed in the load chamber, and the output shaft of the motor is connected to the synchronous box and the gearbox in sequence; a transmission system and a load area are arranged in the semi-anechoic chamber, a universal joint shaft (4), a torque meter (5), and a track (17) formed by a plurality of wheel hub pairs (6) suspended and linked in sequence are installed in the transmission system and load area, and the output end of the universal joint shaft is connected to the rotating shaft of the wheel hub pair via the torque meter; the load chamber is arranged adjacent to the transmission system and the load area, and the output shaft of the gearbox is connected to the input end of the universal joint shaft via a through-wall shaft (E). The invention can be used to carry out indoor equipment and vehicle acoustic performance testing research under different load conditions of rail vehicles.

Description

Technical Field

[0001] The present invention relates to a rail vehicle noise test study, in particular to a rail vehicle full vehicle semi-anechoic chamber structure and a pass-by noise test method. Background Art

[0002] Anechoic chambers primarily provide a free sound field for acoustic measurements. Hemi-anechoic chambers provide a semi-free sound field for acoustic measurements. Except for the ground, sound waves can propagate in an infinite space without any reflective surfaces.

[0003] With the development of today's society, passengers' expectations for rail vehicle noise levels are becoming increasingly stringent, leading to even stricter noise level requirements for second-generation urban rail vehicles. Therefore, vehicle acoustic performance research is essential during the vehicle design process. This involves accurately determining the vehicle's body sound insulation and sealing performance, as well as the acoustic performance of the air conditioning and ventilation system, axle drive system, and traction system. This allows for prediction of vehicle noise indicators and provides effective data support. A semi-anechoic chamber is an essential tool for accurately determining acoustic performance indicators.

[0004] Traditional methods for testing rail vehicle pass-by noise require on-track testing, which occupies track resources and strains dynamic shunting lines. Furthermore, pass-by noise testing places stringent technical requirements on the track. Only a few testing institutions worldwide meet these noise testing requirements, and few in China do. Pass-by noise also requires that rolling stock be measured while exerting two-thirds of its tractive force. This tractive force requires the braking force of a companion vehicle, which inevitably generates wheel friction noise, thus affecting the accuracy of the pass-by noise test.

[0005] Currently, noise levels of active vehicle equipment are measured and evaluated on individual sub-components under no-load conditions. This deviates from the noise performance of the equipment in actual operation, significantly impacting the accuracy of overall vehicle noise predictions. Furthermore, during the vehicle design phase, noise performance is only assigned to individual components, with no requirements for the active device system. Dynamic coupling between active vehicle components can lead to variations in system noise performance, further increasing the inaccuracy of overall vehicle noise predictions.

[0006] The rail transit vehicle industry has many semi-anechoic chambers, but there are basically no semi-anechoic chambers with transmission systems. Therefore, it is impossible to conduct research on vehicle dynamics and vehicle acoustic performance under load conditions and estimate vehicle noise indicators in the laboratory. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to address the shortcomings of the current poor prediction accuracy of vehicle noise indicators and the inability to truly simulate vehicle wheel-rail noise to carry out vehicle sound leakage and sound insulation performance testing and research. The present invention provides a rail vehicle semi-anechoic chamber structure and pass-by noise testing method that can truly simulate vehicle wheel-rail noise indoors, carry out sound leakage and sound insulation performance testing and research of the whole vehicle under load conditions, and improve the accuracy of vehicle noise indicator prediction.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A semi-anechoic chamber structure for a whole railway vehicle comprises a semi-anechoic chamber and a load chamber for providing the semi-anechoic chamber with power and load required by a test locomotive; a motor, a synchronous box and a gearbox are installed in the load chamber, the output shaft of the motor is connected to the input end of the synchronous box, and the output end of the synchronous box is connected to the input end of the gearbox; a transmission system and a load area are provided in the semi-anechoic chamber, a universal joint shaft, a torque meter, and a track formed by a plurality of wheel hub pairs suspended and linked in sequence are installed in the transmission system and load area, the output end of the universal joint shaft is connected to the rotating shaft of a group of wheel hub pairs of the track via the torque meter; the load chamber is arranged adjacent to the transmission system and load area, and the output shaft of the gearbox is connected to the input end of the universal joint shaft via a through-wall shaft.

[0010] The present invention incorporates a track consisting of drivable hubs within a semi-anechoic chamber, and a power system (load chamber) is arranged outside the chamber. Power from the load chamber is transmitted to the drivable hubs via through-the-wall shafts. The power system provides 200kW-1600kW per axle and a speed range of 80km / h-400km / h. This load capacity covers the different axle power requirements of urban rail transit vehicles, heavy-duty electric locomotives, and power-intensive EMUs. The speeds meet the requirements of urban rail transit vehicles to high-speed EMUs, enabling the present invention to conduct acoustic performance testing of equipment and vehicles under varying load conditions on rail vehicles.

[0011] In general, the semi-anechoic chamber structure of a railway vehicle of the present invention solves the following problems:

[0012] (1) Improve the accuracy of vehicle noise index prediction

[0013] Currently, noise levels of active vehicle equipment are measured and evaluated on individual sub-components under no-load conditions. This deviates from the noise performance of the equipment in actual operation, significantly impacting the accuracy of overall vehicle noise predictions. Furthermore, during the vehicle design phase, noise indicators are only assigned to individual components, with no requirements for the active device system. Dynamic coupling between active vehicle components can lead to variations in system noise performance, further increasing the inaccuracy of overall vehicle noise predictions.

[0014] The present invention sequentially connects a load chamber motor, a synchronous box, a gearbox, a universal joint, a torque meter, and a track formed by multiple wheel hub pairs suspended and linked in sequence. This allows the track in the semi-anechoic chamber to simulate an actual line track to provide a load for the test locomotive. The test locomotive is then forced to idle to a set speed. A 2 / 3Fmax traction force is then applied via the test locomotive's inverter. Simultaneously, the motor speed in the load chamber is monitored to adjust and control the motor speed, ensuring that the load provided by the motor reaches 2 / 3Fmax traction load and torque and maintains a dynamic equilibrium state. On this basis, the test locomotive is operated on the track and exerts a 2 / 3Fmax traction load, thereby achieving a pass-by noise test under simulated load conditions. Because this pass-by noise test is conducted while the active equipment components onboard the test locomotive are in operation, the accuracy of vehicle noise prediction can be improved.

[0015] (2) Conduct vehicle sound leakage and sound insulation performance testing and research by realistically simulating vehicle wheel-rail noise

[0016] Traditional methods for testing and researching vehicle sealing require the use of track resources and impact vehicle operations and OEM production. The present invention utilizes a semi-anechoic chamber with a transmission system. This chamber utilizes the interaction between the track, formed by multiple wheel hub pairs suspended and linked in sequence, and the wheels of the locomotive under test to generate noise, effectively simulating vehicle wheel-rail noise. This allows for testing and research of vehicle sound leakage and sound insulation performance.

[0017] (3) Vehicle radiated noise testing and estimation

[0018] Vehicle radiated noise testing places high demands on the test environment and track conditions, which are often difficult to achieve in real-world conditions. The present invention's semi-anechoic chamber with a transmission system provides a free sound field that meets these requirements through the use of sound insulation measures within the chamber. This allows for not only noise testing and evaluation of a stationary vehicle, but also for testing and studying vehicle acceleration noise, braking deceleration noise, and constant-speed passing noise while maintaining a towed load.

[0019] (4) Accurately evaluate the acoustic performance of the vehicle under load conditions

[0020] Most traditional semi-anechoic chambers only provide an acoustic environment. The automotive industry has incorporated road simulators into acoustic laboratories to analyze road noise spectrum under dynamic vehicle conditions. However, in the rail transit industry, rail vehicle noise research is currently limited to static and no-load conditions, which differs from actual vehicle noise assessment conditions and can lead to deviations between final test results and design. To address this issue, the rail vehicle power system is introduced into a semi-anechoic chamber. This provides a load to the vehicle under acoustically free conditions, enabling its onboard equipment to meet actual operating power requirements and accurately assessing the vehicle's acoustic performance under operating conditions.

[0021] Preferably, a first sound insulation board is laid on the periphery of the area between the transmission system and the load, and the first sound insulation board is supported by first supporting columns to meet the background noise requirement of the semi-anechoic chamber.

[0022] Similarly, a shaft support foundation is provided at the bottom of the area between the transmission system and the load to reduce the transmission of rotational vibration noise.

[0023] Preferably, the semi-anechoic chamber adopts a room-in-room structure, and sound-absorbing wedges are laid on the inner wall and roof of the inner room to meet the cutoff frequency of 50 Hz and the background noise index requirements.

[0024] To meet the load-bearing requirements of the semi-anechoic chamber floor and meet subsequent maintenance requirements, the inner chamber of the semi-anechoic chamber utilizes an independent foundation. This independent foundation comprises a concrete base floor, a second support column supporting the base floor, and a first vibration damper positioned between the base floor and the second support column. The use of the second support column facilitates subsequent maintenance of the independent foundation. Furthermore, the first vibration damper provides maximum isolation from external vibration energy, with a natural frequency below 3Hz.

[0025] Preferably, a through-wall hole is provided on the foundation wall of the inner room of the semi-anechoic chamber, a second vibration absorber is installed at the bottom of the foundation wall, and both ends of the through-wall hole are sealed with second sound insulation boards to prevent the rotational vibration and noise of the load room and the through-wall shaft from being transmitted into the semi-anechoic chamber, thereby ensuring the background noise requirements of the semi-anechoic chamber.

[0026] Preferably, the track is a variable gauge track, which can achieve an adjustable track gauge of 900mm to 1676mm, meeting the requirements of railway vehicle noise performance testing for meter gauge 1000mm, standard gauge 1435mm, and wide gauge 1520mm.

[0027] Based on the same inventive concept, the present invention also provides a method for performing pass-by noise testing using the semi-anechoic chamber structure of a railway vehicle, which comprises:

[0028] a. The motor in the load chamber generates a rotating speed, which is synchronized by a synchronizer box to increase the shaft power. The speed is then transmitted to the gearbox for speed change. After that, the speed is transmitted to a set of wheel hubs on the track in the semi-anechoic chamber through a through-wall shaft, a universal joint shaft, and a torque meter, causing the wheelset of the test locomotive to idle.

[0029] b. The motor and transmission system in the load chamber rotate to make the locomotive idle to the set speed. When the set speed is stable, the locomotive applies 2 / 3Fmax traction force through the converter. At the same time, the speed of the motor in the load chamber is adjusted and controlled by monitoring the speed of the motor in the load chamber. The load provided by the motor reaches 2 / 3Fmax traction load and torque, and the locomotive is kept in a dynamic equilibrium state.

[0030] c. Use the track formed by the sequential transmission of the wheel hub pairs in the semi-anechoic chamber to simulate the actual line track, so that the test locomotive runs on the track and exerts 2 / 3Fmax traction load to achieve the passing noise test under simulated load conditions.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The semi-anechoic chamber of the present invention provides a semi-free sound field environment for acoustic testing. It can be used to carry out the whole vehicle under load conditions, the whole vehicle sound and vibration transmission path testing and analysis, the vehicle interior noise and external radiated noise testing and research, the acoustic performance testing and research of vehicle active equipment and subsystems, and the whole vehicle sound leakage testing and research by simulating wheel-rail noise.

[0033] 2. The semi-anechoic chamber of the present invention reduces interference from test conditions and environment, improves test accuracy, and saves track line resources.

[0034] 3. The present invention effectively avoids the shortcomings of sound field reconstruction technology and improves the acoustic test environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 Schematic diagram of the semi-anechoic chamber structure of a rail vehicle according to the present invention.

[0037] Figure 2 A top view of the semi-anechoic chamber.

[0038] Figure 3 for Figure 1 Schematic diagram of the local enlarged structure at the through-wall axis.

[0039] Description of reference numerals:

[0040] 1—motor; 2—synchronizing box; 3—gearbox; 4—universal joint; 5—torque meter; 6—wheel hub pair; 7—first sound insulation board; 8—first support column; 9—shaft support foundation; 10—exterior wall; 11—interior wall; 12—foundation ground; 13—first vibration absorber; 14—second support column; 15—arc top; 16—sound-absorbing wedge; 17—track; 18—load chamber; 19—semi-anechoic chamber; 20—test locomotive; E—through-wall shaft; E1—foundation wall; E2—second vibration absorber; E3—second sound insulation board; E4—through-wall hole. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with specific preferred embodiments, but the scope of protection of the present invention is not limited thereby.

[0042] For the convenience of description, the relative position relationship of each component, such as up, down, left, right, etc., is described according to the layout direction of the drawings in the specification, and does not limit the structure of this patent.

[0043] like Figure 1 - Figure 3 As shown, an embodiment of the semi-anechoic chamber structure of a railway vehicle according to the present invention includes a load chamber 18 and a semi-anechoic chamber 19 .

[0044] Load chamber 18 provides the power and load required by test locomotive 20 for semi-anechoic chamber 19. Motor 1, synchrotron 2, and gearbox 3 are housed within load chamber 18. The output shaft of motor 1 is connected to the input of synchrotron 2, which in turn is connected to the input of gearbox 3.

[0045] Within semi-anechoic chamber 19, a drivetrain and load compartment is located. This compartment houses a universal joint 4, a torque meter 5, and a track 17 composed of multiple suspended and linked wheel hub pairs 6. The universal joint 4 connects to the rotating shaft of one wheel hub pair 6 of track 17 via the torque meter 5. Track 17 is a variable-gauge track, adjustable to 1000mm, 1435mm, and 1520mm, to facilitate the entry of rail transit vehicles of varying gauges into semi-anechoic chamber 19. During testing, a locomotive 20 under test runs on track 17.

[0046] The noise floor within semi-anechoic chamber 19 is required to be no more than 30dB. The rotation of the transmission system within semi-anechoic chamber 19 generates vibration noise. To meet this noise floor requirement, a first sound insulation panel 7 is installed around the perimeter of the area between the transmission system and the load. The first sound insulation panel 7 is supported by first support columns 8. A shaft support foundation 9 is also installed in the transmission system area to reduce the transmission of rotational vibration noise.

[0047] The semi-anechoic chamber 19 features a room-within-a-room structure. The outer wall 10 of the outer chamber is 300 mm thick, while the inner wall 11 of the inner chamber is 240 mm thick. The inner chamber's roof is a domed roof 15. Sound-absorbing wedges 16 are installed on the inner walls and roof to meet the 50 Hz cutoff frequency and background noise requirements.

[0048] Because the floor of the semi-anechoic chamber 19 has load-bearing specifications and subsequent maintenance requirements, the inner room of the semi-anechoic chamber 19 adopts an independent foundation. The independent foundation includes a foundation ground 12 cast in concrete, a second support column 14 for supporting the foundation ground 12, and a first vibration damper 13 disposed between the foundation ground 12 and the second support column 14. The use of the second support column 14 here facilitates the subsequent maintenance of the independent foundation. At the same time, the first vibration damper 13 can isolate the transmission of external vibration energy to the greatest extent possible, and its natural frequency is less than 3Hz.

[0049] The load chamber 18 is located adjacent to the transmission system and load compartment of the semi-anechoic chamber 19. A through-hole E4 is provided in the foundation wall E1 of the semi-anechoic chamber 19. A through-hole E4 houses a through-hole E. One end of the through-hole E4 connects to the output of the gearbox 3 in the load chamber 18 and the other end connects to the input of the universal joint 4 in the semi-anechoic chamber 19. This introduces the power transmission system into the semi-anechoic chamber 19 and provides varying loads to the rail transit vehicle 20, simulating the vehicle noise radiation state under actual operating conditions of the test locomotive 20. Vehicle radiated noise testing is conducted within the full-vehicle anechoic chamber. A second vibration damper E2 is installed at the bottom of the inner foundation wall E1 of the semi-anechoic chamber 19. Both ends of the through-hole E4 are sealed with second soundproofing panels E3 to prevent rotational vibration and noise from the load chamber 18 and the through-hole E from transmitting into the semi-anechoic chamber 19, thereby ensuring the semi-anechoic chamber 19 meets the required noise floor.

[0050] During operation, the present invention generates a rotational speed in the motor 1 within the load compartment 18. This speed is then transmitted to the gearbox 3 for speed change after multi-axis synchronization and shaft power increase via the synchronizer 2. The shifted power is then transmitted via the through-wall shaft E, the universal joint 4, and the torque meter 5 to the wheel hub pair 6 on the track 17, delivering rotational kinetic energy to the locomotive 20 under test. Typically, the locomotive 20 under test has an axle speed of 80 km / h to 400 km / h, shaft power of 200 kW to 1600 kW, and motor power of 2000 kW.

[0051] Load chamber 18 rotates track 17 through motor 1 and the transmission system until test locomotive 20 idles to the set speed. Then, test locomotive 20 controls the inverter to achieve 2 / 3Fmax traction. Load chamber 18 employs speed control logic. When motor 1 and the transmission system rotate in load chamber 18 and the test locomotive 20 idles to the set speed and stabilizes, test locomotive 20 applies 2 / 3Fmax traction through the inverter. Simultaneously, the speed of motor 1 in load chamber 18 is monitored and adjusted to control its speed. This speed is then fed back to the motor of test locomotive 20 via the synchronizer and gearbox, ensuring that the locomotive achieves 2 / 3Fmax traction and maintains dynamic equilibrium.

[0052] The ISO3095 standard stipulates that for high-power electric locomotives (single-axle power P ≥ 1200kW), the locomotive must exert at least 2 / 3 of its maximum tractive force to measure pass-by noise. For example, for a locomotive 20 under test with a single-axle power of less than 2000kW, achieving 2 / 3 of its maximum tractive force requires the load equipment to also achieve a traction load of 2 / 3 of its maximum tractive force. Specifically, the load motor 1 must exert a traction load and torque of 2 / 3 of its maximum tractive force, which is then transmitted to the wheel hub pair 6 of track 17 via the synchronizer 2 and gearbox 3. The wheel hub pair 6 of track 17 simulates actual track on a railway line. This allows the locomotive 20 under test to operate on track 17, formed by the sequential arrangement and linkage of the wheel hub pairs 6, while exerting a traction load of 2 / 3 of its maximum tractive force, thus achieving pass-by noise testing under simulated load conditions.

[0053] Locomotive pass-by noise testing requires an open environment free of reflective objects and obstacles, and the track roughness and attenuation of the locomotive test line must meet the ISO 3095 standard limits. Currently, only five lines worldwide meet these standards, all located in Europe. China lacks either a test line that meets the track roughness and attenuation requirements or a test environment that fully meets the noise testing conditions. Furthermore, pass-by noise testing requires a companion locomotive to enable the test locomotive 20 to achieve 2 / 3 of its Fmax traction load. To prevent the noise generated by the companion locomotive from affecting the test locomotive 20, a noise-neutral trailer is placed between the companion locomotive and the test locomotive 20. Currently, only the China Academy of Railway Sciences has a companion locomotive in China. Therefore, it is difficult to test the noise of rail vehicles. In order to solve this bottleneck problem, the present invention redesigns the semi-anechoic chamber structure to meet the noise test environment requirements; by introducing the load into the semi-anechoic chamber and exerting the load, the problem of the accompanying test vehicle is solved; in addition, the wheel hub pair 6 is rotated and controlled to meet the standard limit of track roughness; the motor 1 in the load chamber 18 exerts 2 / 3Fmax traction power, and then transmits the traction load and torque through the synchronous box and the gearbox, thereby realizing the simulation of different speed conditions of the test locomotive 20 with a traction load of 2 / 3Fmax.

[0054] For drive systems with a single-axle power of more than 2000kW, a synchronizer box 2 is required to synchronize the speeds of the two motors 1 so that their power is greater than 2000kW, and output 2 / 3Fmax load and torque through the gearbox 3, so that the drive system (motor + gearbox) of the test locomotive 20 can exert 2 / 3 Fmax traction, thereby conducting noise testing of the drive system under a 2 / 3 Fmax load in a free sound field environment.

[0055] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make many possible changes and modifications to the technical solution of the present invention using the technical content disclosed above, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiment in accordance with the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A semi-anechoic chamber structure for rail vehicle passing noise testing, comprising a semi-anechoic chamber (19), characterized in that: The semi-anechoic chamber also includes a load chamber (18) for providing the power supply and load required by the test locomotive (20). The load chamber provides a power of 200kW to 1600kW per axle, a speed range of 80km / h to 400km / h, and a load that covers the different axle power requirements of urban rail transit vehicles, heavy-load electric locomotives, and power-centralized EMU power vehicles. The speed meets the requirements of urban rail transit vehicles to high-speed EMUs. A motor (1), a synchronous box (2) and a gearbox (3) are installed in the load chamber, the output shaft of the motor is connected to the input end of the synchronous box, and the output end of the synchronous box is connected to the input end of the gearbox; The semi-anechoic chamber adopts a room-in-room structure, including an outer room and an inner room located within the outer room. The inner room adopts an independent foundation, and the independent foundation includes a foundation ground (12) cast with concrete, a second support column (14) for supporting the foundation ground, and a first vibration damper (13) arranged between the foundation ground and the second support column. A through-wall hole (E4) is provided on the foundation wall adjacent to the load chamber, a through-wall shaft (E) is installed in the through-wall hole, and a second vibration damper (E2) is installed at the bottom of the foundation wall. A transmission system area and a load room area are provided in the inner room, a first sound insulation board (7) is laid between the transmission system area and the load room area, a universal joint shaft (4), a torque meter (5), and a track (17) formed by a plurality of wheel hub pairs (6) suspended and linked in sequence are installed in the transmission system area, the output end of the universal joint shaft is connected to the rotating shaft of a set of wheel hub pairs of the track through the torque meter, the test locomotive is installed in the load room area, the test locomotive is connected to the track, and the track is a variable gauge track with an adjustable gauge range of 900 mm to 1676 mm; The load chamber is arranged adjacent to the transmission system area, one end of the through-wall shaft is connected to the output shaft of the gearbox in the load chamber, and the other end is connected to the input end of the universal joint shaft in the semi-anechoic chamber, and both ends of the through-wall hole are sealed with a second sound insulation board (E3); The noise generated by the interaction between the track formed by multiple wheel hub pairs suspended and linked in sequence in a semi-anechoic chamber and the wheels of the test locomotive is used to realistically simulate vehicle wheel-rail noise, and to carry out vehicle sound leakage and sound insulation performance testing and research.

2. The semi-anechoic chamber structure for rail vehicle pass-by noise testing according to claim 1 is characterized in that: A shaft support base (9) is provided at the bottom of the transmission system area, and a first sound insulation board (7) is supported and installed on the shaft support base (9) via a first support column (8).

3. The semi-anechoic chamber structure for rail vehicle pass-by noise testing according to claim 1, characterized in that: Sound-absorbing wedges (16) are laid on the inner walls and roof of the semi-anechoic room.

4. A method for testing pass-by noise using the semi-anechoic chamber structure for testing pass-by noise of a railway vehicle according to any one of claims 1 to 3, characterized in that include: a. The motor in the load chamber generates a rotating speed, which is synchronized with multiple axes by a synchronizer box and amplified by shaft power. The speed is then transmitted to the gearbox for speed change. The speed is then transmitted to a set of wheel hubs on the track in the semi-anechoic chamber via a through-wall shaft, a universal joint shaft, and a torque meter. The track simulates the actual track to provide load for the locomotive under test, and the wheels of the locomotive under test are made to idle. b. When the locomotive under test idles to the set speed and stabilizes at the set speed, the locomotive under test applies 2 / 3 Fmax traction force through the converter. At the same time, the speed of the motor in the load compartment is adjusted and controlled by monitoring the speed of the motor in the load compartment. The load provided by the motor reaches 2 / 3 Fmax traction load and torque, and the locomotive is kept in a dynamic equilibrium state. c. The locomotive under test runs on the track and exerts 2 / 3 of the Fmax traction load to achieve the passing noise test under simulated load conditions.

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