With the benefit fierce competition in the steel industry market in recent years, double cold reduction products have been developed towards strength improvement and thickness reduction. The traditional cold-rolling lubrication process with a fixed flow rate and concentration cannot solve the problems which cover uncontrollable shape of strip product and the excessive consumption of lubricating oil. Moreover,based on the analysis of the traditional direct application lubrication system of double cold reduction, a set of design scheme suitable for the emulsion pipeline direct mixing lubrication system of double cold reduction unit is proposed.The design complete the selection of key components which include the static mixer and atomization nozzle selection, pump and oil pump design selection, pipeline design selection, flow type selection, pressure gauge selection, electronic control cabinet design selection and other aspects. Equipment of the emulsion pipeline direct mixing lubrication system of double cold reduction has been developed. Comparing with characteristics of the traditional direct aplication lubrication system, the emulsion pipeline direct mixing lubrication system was better applied to the production practice of a 1220 double cold reduction mill. The consumption of ton of steel was reduced by 9.6%. The rolling energy consumption and oil consumption comprehensive costs decreased by 10.7%, and the strip steel section thickness difference was reduced by 19.3%. In addition, the plate shape quality defect rate decreased by 25.6 %, otherwise creating a large economic benefit for the unit and promoting the application value.
SiC MOSFET/Si IGBT (SiC/Si) hybrid switch usually selects the gate control pattern that SiC MOSFET turns on earlier and turns off later than Si IGBT, with the aim of making the hybrid switch show excellent switching characteristics of SiC MOSFET and reduce switching loss. However, when SiC MOSFET turns off, the fast slew rate of drain source voltage causes the current spike in Si IGBT due to the effects of parasitic capacitance charging and carrier recombination, which will produce additional turn-off loss, thus affecting the overall efficiency and temperature rise of the converter. Based on the double pulse test circuit of SiC/Si hybrid switch, the mathematical model of the turn-off transient process is established. The effects of the remnant carrier recombination degree of Si IGBT, the turn-off speed of SiC MOSFET and the working conditions on the turn-off current spike of hybrid switch are evaluated. Although adjusting these parameters can reduce the turn-off current spike somewhat, additional losses will be introduced. Therefore, a new method to suppress the turn-off current spike is proposed to balance the power loss and current stress.INDEX TERMS SiC MOSFET/Si IGBT, hybrid switch, current spike, suppression method
In conventional parameters design, the driving circuit is usually simplified as an RLC second-order circuit, and the switching characteristics are optimized by selecting parameters, but the influence of switching characteristics on the driving circuit is not considered. In this paper, the insight mechanism for the gate-source voltage changed by overshoot and ringing caused by the high switching speed of SiC MOSFET is highlighted, and we propose an optimized design method to obtain optimal parameters of the SiC MOSFET driving circuit with consideration of parasitic parameters. Based on the double-pulse circuit, we evaluated the influence of main parameters on the gate-source voltage, including driving voltage, driving resistance, gate parasitic inductance, and stray inductance of the power circuit. A SiC-based boost PFC is constructed and tested. The test results show that the switching loss can be reduced by 7.282 W by using the proposed parameter optimization method, and the over-voltage stress of SiC MOSFET is avoided.
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