Development of Humidity-Temperature-Cycle (HTC) Tests on Module Basis

Humidity temperature cycle (HTC) tests aim to provoke condensation and are thus considered to show other failures and to be more realistic than standardized tests like the H3TRB. One HTC test used in the field of photovoltaic (PV) application is the damp heat test mentioned in the IEC 62093 (6.9) standard. The described test procedure is designed for whole converter units but not suitable for simple test vehicles on (sub-) module basis without adaption. However, tests with smaller modules can be favorable, e.g., if designs, materials, or packaging techniques are tested. Main aim of this work is to adapt the damp heat test according to the IEC 62093 (6.9) to get from converter level to module level. The standard requires not only to apply a voltage but also defines a certain percentage of applied power. There are several short phases during one cycle when power and voltage are applied. During these phases, operation leads to power loss and the generation of waste heat. Within this work, simulation of humidity diffusion and distribution inside a module with and without power loss of the semi-conductor devices was performed. The results showed an influence of the power loss and the following waste heat. Therefore, power loss is also taken into account for the adapted test on module basis. The use of a DC-DC converter should be avoided in the developed setup for testing on (sub-)module level, but testing should also be in a relevant range. Therefore, the waste heat has to be created differently. The approach is to alternate conduction losses and application of high voltage during the phases of high power of the IEC 62093 (6.9). The target waste temperature is calculated from field profiles for a typical summer day provided by Fraunhofer ISE. Suitable heating times are experimentally elaborated.