- Inverters for PV systems, battery storage, and electromobility must endure harsh environmental factors such as weather, dirt, high voltages, and long operating times.
Despite these challenges, high-quality inverters typically last 20 to 25 years. However, the specific construction methods, materials, and designs that ensure this lifespan remain unclear, especially for newer applications like PV and electromobility.
To address this, inverters are often over-engineered with safety margins, using materials and processes that offer durability without a detailed understanding of aging and failure mechanisms. This results in higher costs.
In response, Fraunhofer IMWS, the University of Stuttgart’s Institute for Machine Elements, and German companies SMA, Electronicon Kondensatoren, and Merz Schaltgeräte have developed a methodology to improve service life and reliability predictions for inverters and their key components.
“Our results enable precise design in the development of new inverters and faster tests in quality control,” said Sandy Klengel, a project manager at Fraunhofer IMWS. “This allows manufacturing costs to be reduced, as we have a much deeper understanding of the behavior of the components.”
Fraunhofer IMWS studied fault and aging processes in film capacitors and electromechanical switching devices, such as DC circuit breakers and relay assemblies.
Researchers created defects and triggered degradation mechanisms in lab conditions using specially developed test setups. They factored in material interactions, varying electrical loads, and environmental influences like seasonal temperature changes, humidity, and corrosive agents like salt spray.
They then assessed which phenomena were relevant for real-world use by comparing lab results with field-aged components that remained defect-free.
The findings revealed issues such as cracks in ceramic layers affecting insulation, oxide layer formation, demetallization, polymer degradation, thermal damage, and solder deterioration. Researchers also noted crystalline deposits, local melting, contamination, and housing component failures.
The team compiled these findings into a catalog summarizing failure types, characteristics, and causes. They also used numerical simulations to better understand failure physics, such as local current density and heat loss in switches.
“With the results, manufacturers can now reduce material requirements and testing effort and thus lower device costs – without compromising the reliability and service life of the inverters,” said Klengel.
Author: Ralph Diermann
This article was originally published in pv magazine and is republished with permission.
