Research And Design Of The Fast Power Cycling Aging Test Bench For IGBT Modules

As a part with the highest failure rate in power converters, the reliability issue of IGBT modules is one of the key factors of restricting the power converters widely used. As the typical design life of IGBT modules is usually above 20 years, an accelerated aging test is needed to complete and validate the researches. By an accelerated aging test, it only takes a short of time to determine IGBT failure mechanism, and find the characteristic parameters which can reflect the IGBT aging states. These aging parameters can be used for the IGBT reliability researches including condition monitor, fault diagnosis and life prediction.The principle of fast power cycling aging test is making the IGBT junction temperature fluctuate in the large range. However, the different control strategies will lead to huge difference between the failure mechanism and failure period. Furthermore, Due to the differences of IGBT device, it can only obtain accurate and general test conclusion from the analysis of a large number of IGBT devices’ aging data In order to meet the requirement of conducting aging test for multiple IGBT modules at the same time, this paper puts forward an aging scheme by adding a parallel controlled switch for each IGBT module. This scheme can not only apply to several control strategies, such as the constant ΔTj strategy, the constant ΔTc strategy, the fixed heating time ton and heat dissipation time toff strategy. In this paper, every testing scheme of aging control strategy is discussed detailedly. Following, the designed hardware parts of aging test bench is introduced from three aspects, including electrical connection, the chip and case temperature measurement, the cooling water system. The main circuit can age four IGBT modules at the same time, the electrical connection parts and cooling-water system are separated by a steel plate which can avoid electrical failure by water leakage. All working stations share a water pump by installing a two-position three way magnetic valve, this can effectively reduce test bench’s volume.To design an appropriate protection system, the possible electrical failure and water circulation system faults is detailed analysed in this paper. Based on the functional requirements and design principles of monitoring system in the test bench, a two level monitoring system consists of PLC and Win CC interface is also designed. With easy extensibility of PLC and friendly interface of Win CC, the test bench is easy to expand aging position and reflect the current state of each component real time.The experimental prototype is validated with the constant junction temperature swing ΔTj and the constant case temperature swing ΔTc power cycling tests, and the control precision is satisfactory. At present, the designed aging test bench is performing aging tests for four IGBT modules at the same time. The condition of the designed bench is good for a long running time.