To properly test photovoltaic inverters, you need an AC power source that can supply the voltage levels, distortions, dips, and interrupts that inverters experience while operating off utility line power.  They must also receive power from the inverter being tested. Four-quadrant linear supplies, such as AMETEK’s RS/MX Series, use two of the quadrants to source power and the remaining two to sink power. In regenerative mode, the RS/MX Series not only sinks power, but actually returns this power to the grid. This saves on both energy costs and on cooling-system costs.