Normal electrical environments
Devices survive a mechanical and climatic use environment with bumps, shocks, extreme temperatures and fluctuating air humidity. The products also experience a use period with a changing electrical environment. Power voltages vary, and voltage dropouts can occur from time to time as well as transient, short-term power surges and spikes. This is an expression of the normal electrical environment, which electronic devices are constantly subjected to. Lifetime calculations for electronics refer to the use environment and other relevant parts of a product’s life cycle as a “Mission profile”.
Lifetime calculation, acceleration model
When calculating lifetimes it is important that you always know the severity of the use environment. This allows you to calculate how long the device is subjected to both minor rigors and extreme harshness. If you have also determined the connection between “wear at low severity” and “wear at high severity” as a mathematical formula, then it is possible to calculate a total wear in e.g. a use period of 10 or 25 years with known, varying use environments. This is what makes knowledge about the electrical use environment so interesting.
Logging of voltage data
For many years now, Danish Energy has been carrying out systematic logging of 230V mains voltage. A number of voltage meters are always in place across all areas of Denmark, and they are moved around to different installation sites at monthly or weekly intervals. The meters register both the voltage value and frequency etc., as well as anomalies such as voltage dropouts, voltage spikes and transients. In total, more than 70 years of logging of voltage quality has been carried out in Denmark since 2009. It is possible to use data that is representative of the electrical environment, because the logging is so comprehensive and because it is carried out across the whole of Denmark. In other words, an electrical “Mission Profile” is created.
Time compression test run
It is possible to use data that is representative of the electrical environment, because the loggings are so comprehensive, and because they are carried out across the entire country. If for example a transient of 1 kV occurs once on average each week (604.800 seconds), a test with 1 kV can be carried out on a device, for example with 1 transient every 20 seconds. This is an acceleration factor of 30,240.
25 years of life on the Danish mains voltage with 1 kV transients can thus be carried out in about 7 hours.
Naturally, it must be possible to justify the time compression and its physical impact on a product. With time compression it is essential that components in the power supply are able to cool down between each transient. In the real world, it would take an entire week for varistors, for example, to be able to cool down between each transient. And if the same transients continue constantly and rapidly to heat up, then this gives a misleading picture of the wear on such components.
One of the main objectives of “LED power electronics to last!” is to be able to custom build acceleration models for mains connected LED lighting products based on knowledge of the Danish electrical use environment. The project runs for the rest of 2017.
If you would like to know more about electric mission profiling and the project ´LED power electronics to last´, please contact Senior Technology Specialist Per Thåstrup Jensen
, tel. +45 43 25 13 62.