Power Factor for Solar Grid Tie inverters

[BillK-AZ]

Most inverters for photovoltaic (solar) grid tie use specify the power factor as 1 or sometimes .99.

Has anyone in the Forum measured the power factor of currently available inverters?

Some recent installs are exhibiting power factors in the range of 0.93 to 0.95 lagging, but the manufacturer's datasheet and the label on the inverter show power factor of 1. I want to give the manufacturer a chance to respond before identifying. This has been confirmed with two utilities and multiple instruments. The problem seems so rare that there is little data on the subject.

Any input would be helpful.

 

[skeshesh]

Not an expert but interested.

At what point in the system was the PF measured and by whom?

 

[BillK-AZ]

These systems are connected directly to the utility transformer at 480V/3-Ph without loads. The inverter ac output was measured with a Fluke/Reliable Power Quality Meter Model number with 40-amp clamp-on current probes and direct connections to the 480 volt inverter output circuits. Measurements were confirmed using Fluke 289 DMMs for direct voltage measurements and with clamp-on amp probes for current measurements. The voltage, current, VARS and power factor measurements were further confirmed by Shark 100 Energy meters on each system.