System evaluations have shown that the efficiency of systems is sometimes over-estimated because the efficiency for small loads and for complex loads is often less than that for a resistive load. The practice of over-sizing inverters to ensure the ability to handle surges and load growth results in the inverter being run at low loads much of the time. Resistive load sweep. Reactive load sweep. The power factor is changed after each sweep and the test is repeated for pf values of .3 to 1.
Resistive load sweep with fixed nonlinear parallel load.
This test places a fixed nonlinear load in parallel with the resistive sweep load. The THD of the load current is a function of the nonlinear load current profile and other parallel loads. Complex Load Sweep. The intent is to plot efficiency for a case that is expected to have relatively low efficiency. These curves will bound most of the loads found in practice.