Structure Design And Study On Energy Feedback Of Flameproof Integrative Variable-Frequency Motor

Flameproof integrated inverter motor is the power system of thin coal seam planningand mining equipment that integrated inverter and motor into a sealed explosion-proofchamber. It was not easy to transfer heat in closed environment, therefore motor’s coolingsystem need to be optimized. The traditional two quadrant inverter drives motor whendecelerating or braking, motor state transform to generator state. The feedback energy ofDC bus consume on the breaking resistor. It not only leads to waste of energy and also risetemperature in the flameproof cavity that will affect the life of electronic devices with theinverter. From the optimizing structure and further saving energy point of view, paper willresearch four quadrant flameproof integrated inverter motor with energy feedback.Firstly, optimize the cooling system design of flameproof integrated variablefrequency motor. Via calculating the volume of the device and work loss of dynamicbraking and energy regenerative braking at the same level, it can be realized that energyfeedback main circuit occupied the flameproof cavity volume and energy loss is muchsmaller than dynamic braking by contrast. Calculated loss as the load, analyzed heatdissipating path of the inverter motor and created finite element temperature field ofcalculation model of inverter’s main circuit. Paper proceed three cooling model with aspecific method of assembling, created a simulation model in Ephysics software at sametime, calculated the temperature field correspond to the three cooling mode and analyzedof the advantages and disadvantages of the three methods of cooling.Secondly, expand the study of dual-PWM inverter with energy feedback. Through theanalysis working principle of the energy feedback and topology of three-phase activeinverter, the mathematical model under the static coordinate and synchronous rotatingcoordinate system is to be established. Feed-forward decoupling control strategy is used tobe achieved active and reactive current decoupling under synchronous rotating coordinatesystem. Energy feedback system controlled strategy is dual closed loop direct currentcontrolled method, space voltage vector modulation is applied on switch status of power electronic devices. Meanwhile, paper identifies PI double closed-loop structure parametersand provides power electronic devices of current circulation process when applied spacevoltage vector. Finally, paper completes energy feedback system hardware and softwaredesign based on putted forward study theory.Lastly,75kW/1140V energy feedback inverter unit is used to simulate in the Matlabsoftware and a small power energy feedback experiment platform was build to verifycontrol strategy. The waveform results shows that the proposed energy feedback unit has ahigher power factor, more stable bus voltage, better dynamic and steady-state performance.