An important characteristic of standby generators is their voltage and frequency response to sudden changes in load. CANDURA’s PQPro™ is a three phase power quality analyzer that can easily capture high resolution data during load changes. Set for continuous waveform storage RMS voltage, current, frequency and power are stored five times per second (200 millisecond resolution) as well as every cycle of voltage and current waveforms with a resolution of 256 samples per cycle. CANDURA’s software, PV II™, quickly presents the data in graphical form for a convenient visual representation of the test results. Following are graphical results for a three phase stand alone generator test using a 100A load bank.


Figure 1: Voltage and Current response to load steps

Figure 2: Voltage and Frequency response to load steps

Figure 3: Voltage and Power response to load steps
Figure 4: Voltage and Current waveforms at start of first load step

The preceding graphs show a complete picture of the generator response to a load test. For a 100A load step the voltage droop was 17% and the frequency droop was 13%. The generator restored voltage and frequency within 3 seconds.