Loss Calculation And Air-cool Thermal Dissipation Design Of Electric-source Transmitter

At present, more than8%growth rate of GDP leads to over exploitation ofmineral resources, which makes mine crisis is increasingly serious. Hence, theexploration for mineral is gradually skewed towards deep exploration. For the deepmineral resources exploration, Controlled Source Audio-frequency Magneto-Telluricmethod has many advantages, such as signal strength, anti-interference ability, andobtained rapid development and wide application. However, high-power transmittersystem is required in CSAMT method as the artificial field source. Switching powersupply with the advantages of high efficiency, small volume, high power density, isan essential element of high-power transmitter.In the process of circuit design, topology determination means work status ofdevices is also determined. And cooling thermal dissipation design is simplified byusing structure of the bridge circuit series. On the basis of JLEM-II multi-functionelectromagnetic transmitter platform, heat loss in power-electronic devices isanalyzed and calculated in detail, including devices of different voltage levels anddifferent working state, switching transistor and power diode. According to the losscalculation results, reasonable layout for power devices is designed.In high-power switching power supply, the efficiency is usually over90%,while the output power up to20kW, the loss can be more than1kW. Therefore,natural convection heat transfer method is difficult to achieve because of huge cost,so as that cooling thermal dissipation design is essential. Considering wildapplications, forced air cooling design is adopted. Thermal resistance model isconcluded in series or parallel according to the basic law of heat transfer. Accordingto the calculation of convective heat transfer coefficient, based on summarizing theresults of previous research, Nusselt Number expression is simplified to make itmore fit to engineering requirements. With the calculation of wind pressure drop caused by the heat sink, combining with the working curve of the fan, reasonablechoice for fan was made and series or parallel connection was designed. An exampleof cooling thermal dissipation design for the instrument has been expressed as animportant part of the equipment design. And according to former design process, thegeneral process of cooling system design is concluded..In this article, efficiency, waveform, temperature and stability test of theinstrument has been carried on after all the design is completed. The efficiency testof the instrument shows efficiency error of the instrument is less than2%. Waveformtest shows that different working state has a great effect on the transistor switchingcondition, and is directly related to the loss. The temperature test shows that the riseof the heat sink is less than25degrees Celsius, and the junction temperature is lessthan the set value as well. The stability test shows that, loss calculation and thermaldissipation design of the transmitter is a reasonable and effective scheme, and theinstrument can work stably for a long time. All the above test shows that the losscalculation method adopted in this paper is reasonable and effective, and the thermaldissipation scheme meets the design requirements.