IGBT water-cooled radiator used in electric vehicle motor controller is compact in structure, and the activity of cooling water in the channel is complex, which makes it difficult to determine the appropriate activity state model for the thermal simulation of water-cooled radiator. For the IGBT module, which is the primary heat source of the new type of water-cooled motor controller, the corresponding cooling system is planned according to the practical work situation, and the heat dissipation is analyzed according to Fluent software, and the concrete distribution of temperature field and water flow field is obtained. The analysis results show that the heat dissipation structure planning is reasonable, and the abundant allowance of temperature rise is ensured under the condition of meeting the practical requirements. The test results of three fixed-point thermistor measurement points show that they are in good agreement with the simulation results, which further verifies the rationality of the cooling system. With the increasing prominence of environmental protection and environmental problems, clean, energy-saving and efficient electric vehicles are becoming more and more popular at home and abroad. With regard to the development of electric vehicles, the environment and conditions of the whole vehicle have made many stringent requests for the heat dissipation planning of motor controllers. For example, electric vehicles frequently start directly on slopes, requiring the motor controllers to have strong overload tolerance and stable performance; the control and lightweight design planning of electric vehicles themselves should be carried out.
The structure of motor controller is very compact. The maximum water temperature of IGBT water-cooled radiator used in motor controller during the day can reach about 65 C, which requires that IGBT water-cooled radiator has strong heat dissipation performance. Considering that the high temperature will shorten the life of the equipment and reduce the reliability, it is necessary to develop a reasonable heat dissipation system to make it run in a reliable temperature range. In current engineering applications, heat dissipation analysis mostly relies on empirical design, lacking of corresponding numerical simulation or experimental verification. Wang Cheng and Zhou Hanyi have tested that the thickness of copper foil on the circuit board is the most important factor affecting the heat dissipation of the motor controller, but there is no corresponding numerical simulation. Xuliang and Tao Wenfil simulated the three-dimensional laminar flow and heat transfer of a water-cooled radiator with a square cross-section cross-row spoiler column, but did not touch the turbulence model and experimental verification. The water-cooling channel of centralized water-cooled motor is distributed in the motor housing.
According to the flow direction of the coolant, it can be divided into two types: circumferential type and axial type. The circumferential waterway distributes spirally along the circumferential direction of the casing, and the cooling water moves in the circumferential direction along the spiral direction of the ribs. It is characterized by smooth waterway and small process loss. Axial waterway is composed of parallel fins placed in the axial direction of the motor. Water flows into the waterway and moves around the motor along the axial direction of the fins. It is characterized by simple structure, and it is not easy to have a large temperature gradient at both ends of the motor. This paper takes the construction of an electric vehicle motor controller as an example. It consists of a case, an outer cover, IGBT components, a water-cooled radiator, a supporting capacitor, a control board component, a drive board component, a composite bus bar, a copper bar and a wiring seat. Six 2MBI 1400VXB-120P-50 IGBT elements are installed on the water-cooled radiator, which are connected by a composite bus and control circuit to form an inverting circuit. IGBT components heat loss accounts for the majority of motor controller loss, and the heat of IGBT components is dissipated by water-cooled radiator. Therefore, IGBT components and water-cooled radiator are the main points of thermal analysis plan of motor controller, and also the research direction of this article. IGBT components need to be driven and controlled when they are used, and the system is complex. IGBT components can not operate for a long time under extreme conditions.
The loss characteristics of IGBT components are closely related to the chip temperature, which causes great test errors simply because of the change of temperature. Because the chip of IGBT components is encapsulated by insulating materials, it is necessary to remove the insulating materials before the temperature of the internal chip can be measured, which can easily cause mechanical damage to the IGBT components. The cost of IGBT components is high. Many factors indicate that IGBT element should not be used as test heat source directly, but should be replaced by imitation heat source when the water-cooled radiator is tested more precisely.
In this paper, the simulated heat source body is 250 mm x 90 mm x 35 mm aluminium block. The bottom of the aluminium block is milling a slot with a cross section of 4 mm x 4 mm. After drilling 12 round holes with a diameter of 14 mm on the aluminium block, the device has 12 uniform heating tubes.
This article uses PRO/E software to model. Due to the complexity of the actual model, thermostatic element in order to reduce the amount of accounting and improve the speed of accounting, it is necessary to simplify the model reasonably, that is, to ignore some details which have little influence on the simulation system, such as threaded holes and chamfers. When establishing the cooling water model, the grooves of the cooling water near the cooling column are cut out by the cutting instructions operated by the components. Since the model is axisymmetric, half of it can be analyzed. Only by using ICEM-CFD software can the model be divided into different grids. The maximum grid size is set to 0.
0lm, and the maximum grid size of heat sink column is set to 0.001m. The tetrahedral grid division method is selected. The total number of meshes and nodes is 813 317 and 124 532 respectively.
IGBT module and current module are combined actively. It is found that the grid quality is good and there is no negative grid, which meets the next accounting request. Oscillating modes are the inherent characteristics of elastic structures.
The actual oscillating response characteristics of structures under various effects of vibration sources can be known by modal analysis. Therefore, modal analysis is the main method of constructing dynamic programming and equipment fault diagnosis. Six device holes on water-cooled radiators are restrained to carry out restrained modal analysis. Rate scale is 10 Hz to 500 Hz, so the modal order and corresponding frequency value are plotted by obtaining the oscillation frequency results of each stage within 500 Hz. The short circuit of the three-phase line at the output end of the motor controller of electric vehicle results in overcurrent. When the impact load of the electric vehicle occurs or when the electric vehicle climbs the hill and the driving motor is blocked, the two phases of the driving motor are connected for a long time, and the phase line inductance is full, resulting in overcurrent. The over-current fault is caused by the lack of phase in the power supply side of the motor controller, the disconnection of the output side and the internal fault of the motor. Due to the influence of electromagnetic interference, the leakage current of the drive motor becomes larger, and the shaft current and voltage occur, which results in the over-current of the motor controller. The control circuit of the motor controller is subject to electromagnetic interference, which results in the fault of the control signal and the over-current when the speed response signal is lost or abnormal. Incorrect parameter setting of motor controller and faulty hardware circuit can also lead to overcurrent. In a short time, too large change of IGBT current value will also lead to over-current; for example, instantaneous power failure, current spikes, resulting in over-current; motor controller reset and start again, resulting in over-current. Overcurrent of motor controller is mainly caused by short acceleration and deceleration time, sudden change of load, too low or too high voltage, phase break, short circuit, leakage current, electromagnetic interference and failure of internal components of motor controller. Over-current protection of motor controllers for electric vehicles is very important.
From the beginning of the design of motor controllers to the final product, all design, development, procurement, processing and debugging need to be analyzed, and troubleshooting problems need to be considered systematically. According to Fluent fluid analysis software, the three-dimensional temperature field and flow field of IGBT module of a new motor controller for pure electric vehicle are simulated. The temperature distribution and flow field distribution of IGBT module cooling system of the controller are visually shown, which is conducive to the thermal analysis and structure improvement of the controller. Through simulation and experiment, it is verified that the heat dissipation structure of the controller has excellent heat dissipation effect and meets the goal of stable operation of the controller. Han Xinjiang (1977.11-), male, Han, Shanghai, undergraduate, research direction: new energy vehicle drive system research.