Research On Temperature Rise And Explosion-proof Structure Design Of Variable Frequency Driving Integrated Motor In Industrial Vehicle

In order to achieve simpler structure,smaller size and lighter weight of an industrial vehicle and meeting the requirements of being used under the explosive condition,this thesis presents a comprehensive research on the application of mechatronics technology in the variable frequency drive(VFD)system of an industrial vehicle.By optimizing the design of the cooling system and explosion-proof structure of the integrated VFD system,the temperature rise can be effectively controlled,and the safety level can be further enhanced.The integrated VFD system generally suffers from ventilation deficiency caused by the compact mechanical structure.In addition,huge harmonic content is also found in the integrated VFD system according to the frequency spectrum analysis on the waveform of the pulse width modulation(PWM).In this paper,the power loss of the motor and frequency converter is calculated based on the Joule's law and empirical formulas,while the heat distribution for the motor and frequency converter with the forced air-cooling solution is studied based on the finite element analysis.In order to achieve better cooling performance of the integrated VFD system,a water-cooling technical solution is proposed and studied with the assistance of the COMSOL temperature field simulation.The flameproof structure of the system is redesigned for explosive condition based on the standards of International Electrotechnical Commission(IEC)and further verified by the equivalent model.Finally,the proposed method is experimentally validated by the explosion-proof water-cooling VFD integrated prototype and a significant improvement of the thermal control can be achieved under different operating conditions.The simulated results show that comparing with the conventional air-cooling scheme,the temperature of the motor in the proposed water-cooling system decreased from 67.81 K to 39.65 K with 41.53% reduction and the temperature of IGBT module also decreased by 77.01%(from 43.67 K to 10.04K).Moreover,the experimental result of the temperature in motor stator winding is 1.36 K less than the simulated results.Concretely,both the thermal design requirements and the standard specifications of the explosion-proof structure are satisfied,and thus the proposed method facilitates the engineering application of the VFD integrated machine.