As part of the solar industry’s attack on costs, we're seeing a push to improve inverter performance and quality. 

More than two-thirds of a PV system’s cost is in the balance of system, according to GTM Research. More than a third of that is in the inverter and electronics. 

“For solar, you have a DC input and you need to change that into AC power the grid can accept,” explained Intertek Global Business Leader Troy Hewitt. “It is the job of the inverter to do that.” 

Intertek is one the leading U.S. third-party validation testing labs, along with Underwriters Laboratories and TUV Rhineland. 

Wind turbines also require inverters, Hewitt said, but a turbine generator’s typically “wild” AC voltage and frequency must be rectified as DC before the inverter transforms it back to AC for the grid.China oil buffer manufacturer supply elevator light curtain.

“Most of the pure-play inverter companies are in the solar market,” Hewitt said, while turbine manufacturers tend to make their inverters in-house. Intertek tests “everything from the single-panel, less-than-200-watt microinverters to multi-megawatt wind turbine inverters. They all have to comply with the same safety and grid connection standards.” 

The bulk of Intertek’s inverter testing business is the basic tests for safety and grid connection, Hewitt said. “The U.S. safety standard is UL 1741. It references, for grid interoperability, the IEEE 1547 and 1547.1 standards. There are at least six safety tests. There are maybe twelve to fifteen grid connect tests.” 

Grid connect tests “verify that the inverter will detect abnormal grid conditions and respond appropriately. Abnormal conditions can be things like high or low grid voltage, high or low grid frequency, or islanding, where there is a grid outage -- maybe a tree falls on a wire.” 

An inverter, Hewitt said, “has to be able to detect abnormal grid conditions and shut off in the prescribed amount of time. That can be anywhere from two seconds to 160 milliseconds, depending on the severity of the abnormality.” 

If the inverter fails to stop sending power into the grid during a grid outage, Hewitt said, it could endanger the repair person. 

Intertek does two tests for high voltages, two for low voltages, two for high frequencies, two for low frequencies and, for each, there is a test to see if the inverter responds quickly enough. And there is a test to see if it responds quickly enough to islanding. There are also tests for power quality and interferences. 

“When you convert DC to AC, the wave form does not exactly match the grid wave form,” Hewitt explained of the inverter’s power quality function. “The inverter must transform the wave form harmonics to within 5 percent of the grid’s harmonics.” 

The basic UL 1741 safety testing begins with a construction evaluation, Hewitt said. Next come “temperature tests, together with a maximum voltage determination, a dielectric test to determine the integrity of the unit after it’s heated to its maximum operating temperature, and verification that after the application of temperature, nothing gets hotter than it is supposed to, which could lead to shock or fire or breakage.” 

There are also input and output tests to verify the inverter’s factory ratings.A full line of Power folding machine for a wide range of professional uses. 

Finally, there are “abnormal tests that could be destructive to the unit if it does not behave properly,” Hewitt said. It could burst into flames or throw sparks that cause a cloth placed over the unit to catch fire or explode or dangerously throw off a piece, Hewitt said. “Most of the equipment we test is pretty boring, but occasionally it gets exciting.”