| IGBT chips and electrode are connected by pressure contact instead of bond wires in press pack IGBT,eliminating the bond wire off and the degradation of the solder layer.This structural design allows the double side cooling on the collector side and the emitter side.Thermal resistance of press pack IGBT is greatly reduced compared with that of IGBT modules,improving the reliability of the device.Another advantage of press pack IGBT is the short circuit failure mode(SCFM).To prevent shut down of the system due to a failed module,redundant modules are included in the system to share the voltage and the failed device is still able to carry the load current.This makes press pack IGBT has significant advantages in flexible high voltage direct current systems.The clamp fixture is designed for the press pack IGBT at the voltage level of 3300V.The design of the clamp fixture involves the selection of insulating material,the design of force spreader,the selection of contact surface machining precision and the selection of disc spring.A new design of force spreader with toroidal dispersion pressure is proposed.The design is verified by simulation.Simulation results show that compared with the traditional force spreader,this new design makes the pressure distribution on the collector electrode plane more uniform and reduces the size and weight of the force spreader.The pressure distribution on the collector electrode plane of the device is measured by Fuji prescale film.The measurement result shows that the clamp fixture can evenly disperse the pressure to the collector electrode plane.Then,the testing platform of press pack IGBT is designed.The double pulse method is applied in the platform.The DC bus capacitance and load inductance calculation,capacitor charging circuit design,voltage and current measurement instruments selection,and control circuit design are completed.The switching waveform of press pack IGBT is realized by the testing platform.The testing voltage reaches 1800V and the testing current reaches 1500A.The switching characteristics test under different voltage and current level is achieved.The influence of parasitic inductance on the switching waveform is analyzed.The parasitic inductance of IGBT's testing platform affects the switching parameters and the switching losses of IGBT.Therefore,it is important to extract the parasitic inductance of the testing platform to accurately obtain the switching parameters of IGBT.The traditional parasitic inductance extraction methods ignore the influence of the parasitic resistance and bring error to the parasitic inductance extraction.In order to improve the accuracy of parasitic inductance extraction,a method of parasitic inductance extraction of IGBT testing platform based on turn on process is proposed.By analyzing the process of current rise time,a parasitic inductance calculation model taking parasitic resistance into account is established.The simulation results show that the calculation error of this method is lower than that of the conventional method.The parasitic inductance of the testing platform is extracted by this method,which provides the basis for accurate calculation of IGBT switching parameters. |
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