You can use electronic loads to test many different devices, including
- AC and DC power sources,
- power converters,
- uninterruptible power supplies (UPSes), and
- electrochemical sources, such as batteries and fuel cells.
Electronic loads, such as the Sorensen SL Series, shown in Figure 1, are much easier to use than a bank of power resistors and a lot more flexible, too. This is especially true when your test needs a variable load. Electronic loads can, for example, simulate the different power states of a mobile device, including the sleep, power conservation and full power modes. To do this with a bank of power resistors, you'd have to design a complicated switching network to switch in and out the necessary resistors.
Electronic loads also provide a more realistic load than a bank of power resistors. Most loads ramp up and down, but when you use a bank of power resistors, the load changes in steps. With an electronic load, you can ramp up and ramp down the load to the unit under test in much the same way that a complex electronic load in the field would.
In addition to testing power supplies, you can use electronic loads test test converters of all types, including DC-DC, AC-DC, and DC-AC converters, you can use electronic loads to measure parameters, such as maximum and minimum current and voltage ratings, load regulation and noise (with appropriate filtering), as well as test overcurrent and overpower protection, in either a laboratory or production environment.
Fully testing a UPS requires an AC source, DC source, DC load and AC load. The DC load is used to test the battery backup and charger within the UPS, while an AC load is utilized to test the AC output of the UPS. When testing the AC output of the UPS, you should supply purely resistive loads and loads that have high crest factor waveforms. High crest factor waveforms simulate the powering of switchmode power supplies, commonly found in computers and printers.
Electronic loads can be used to test battery capacity. This can be done in constant power mode (CP) to provide a consistent drain that does not change as the battery voltage drops. Electronic loads are also used in battery forming operations as part of the charge/discharge cycling.
Battery manufacturers are under constant pressure to develop high power density batteries for both handheld applications and hybrid vehicles. To do that, they need an electronic load that they can tailor to their application. Electronic loads allow them to quickly and easily modify load profiles, which in the end, speed up battery development.
For more information, download the AMETEK Programmable Power app note, DC Electronic Load Selection.