Reliability testing is a critical component of inverter product development and production. What good is an inverter rich in features and performance if it can’t maintain near perfect uptime?
This article will serve as an introduction to the world of string inverter reliability and answer:
What are inverter manufacturers doing to increase the reliability of their products?
Which reliability metrics are the most important?
Inverter testing is an exhaustive process. Prior to assembly each component should be individually inspected for quality. In addition to a visual and physical inspection, certain components (capacitors, resistors, integrated circuits) may be x-rayed to confirm that no manufacturing defects are hidden within. For a truly reliable inverter, however, quality begins at the design table.
The first step inverter manufacturers should undertake is the minimization of parts prone to failure. This routinely includes fans and LCD screens. Over time the motors in fans burn out and LCD screen routinely fail after years exposed to the elements.
Once a robust design is in place and inverters begin rolling off the production line, quality control testing should be done to ensure reliability and performance and to simulate real-life exposure. Testing facilities are home to a spectrum of environmental chambers intended to simulate thermal cycling, humidity, UV exposure, freezing temperatures, exposure to marine conditions and extreme vibration.
Top rated manufacturers will also subject their products to Highly Accelerated Life Testing (HALT). HALT testing is designed to simulate an accelerated lifetime of potential stresses inverters might face. This test illuminates weak points in an inverter that may not exhibit symptoms until after several years of operation. By exposing these weak points in the factory they can be proactively addressed and minimized.
Inverters should also be subjected to a burn-in test prior to leaving the manufacturing facility. Similar to other environmental tests, this test occurs in an environment simulation chamber at a pre-set temperature and humidity. Inverters are then connected to a power source and run for several hours to ensure no defects are present in the materials or assembly. Manufacturers such as Huawei burn-test every inverter that rolls off their line, guaranteeing a reliable product always arrives at the job site.
When evaluating an inverter manufacturer, failure or replacement rate is the most common metric for measuring the reliability of inverters. Look for a figure well under 1% per year in this category. In almost every situation, string inverters minimize downtime because if a single unit fails the system as a whole will continue to operate (assuming multiple inverters makeup the system)