Electronic AC Loads

Programmable electronic AC loads simulate defined electrical consumers by drawing controlled current and power from an AC source or device under test (DUT). Depending on the model, they can reproduce resistive, inductive, capacitive, and nonlinear load characteristics as well as adjustable power factors. This enables stable and reproducible testing of AC power supplies, generators, inverters, UPS systems, and other grid-connected equipment.

The ET System portfolio includes conventional electronic AC loads, which convert the absorbed energy into heat, and regenerative AC loads, which return absorbed energy to the AC mains. Available systems support applications ranging from laboratory and development testing to automated production equipment and high-power test benches.

Typical applications include testing AC power sources, uninterruptible power supplies, generators, onboard chargers, inverters, energy storage systems, and industrial power electronics. The appropriate AC load is selected according to phase configuration, voltage, current, active and apparent power, frequency range, power factor, crest factor, dynamic response, regenerative capability, interfaces, and mechanical integration. For generating controlled AC voltage and grid conditions, explore our programmable AC power supplies and grid simulators.

How to Select an Electronic AC Load

Selecting a suitable electronic AC load starts with the electrical characteristics of the AC source or device under test (DUT). In addition to voltage, current, and power, the required phase configuration, frequency range, power factor, crest factor, load behavior, dynamic performance, regenerative capability, automation interfaces, and mechanical integration should be considered.

• Phase configuration: Determine whether the DUT is single-phase, split-phase, or three-phase. For three-phase testing, check whether each phase can be controlled independently and whether balanced and unbalanced load conditions are supported.
• Voltage and frequency: Define the required RMS voltage, peak voltage, and frequency range. Clarify whether three-phase voltage values are specified phase-to-neutral (L-N) or phase-to-phase (L-L). If DC testing is also required, verify that the load supports AC and DC operation.
• Current and power: Check the required RMS current, peak current, active power in kW, and apparent power in kVA. Maximum voltage, current, and power may not always be available simultaneously, so the complete operating area should be evaluated.
• Load modes: Depending on the application, constant current, constant power, constant resistance, or combined operating modes may be required. Verify which modes are available in AC and DC operation.
• Power factor and reactive power: Define whether resistive, inductive, or capacitive load behavior must be simulated. Check the supported power-factor range and whether both leading and lagging current are required.
• Crest factor and nonlinear loads: Power supplies, UPS systems, and other devices with rectifier inputs can draw highly nonlinear current. Verify the adjustable crest factor, current waveform, peak-current capability, and support for rectifier-type or application-specific load simulation.
• Dynamic performance: For transient testing, check the load slew rate, switching time, minimum event duration, programmable sequences, and transition behavior between different load levels and operating modes.
• Conventional or regenerative operation: Conventional AC loads convert absorbed energy into heat and require sufficient cooling. Regenerative AC loads return energy to the mains and can reduce heat generation and cooling requirements in continuous and high-power testing.
• Bidirectional source and load operation: If the test system must both generate grid conditions and absorb energy from the DUT, a bidirectional AC source and load may be more suitable than separate instruments. This is particularly relevant for inverter, onboard-charger, drive, and energy-storage testing.
• Accuracy and measurement: Check the measurement accuracy and resolution for voltage, current, active power, apparent power, reactive power, power factor, frequency, and energy. Harmonic analysis and sufficiently fast data acquisition may also be required.
• Interfaces and automation: For automated test equipment (ATE), verify remote-control commands, sequence functions, trigger options, data acquisition, software compatibility, and available interfaces such as LAN, CAN, RS232, RS485, USB, SCPI, analog control, and digital I/O.
• Mains connection and regeneration: Check the available mains voltage, phase configuration, input current, connection type, and facility requirements for energy regeneration. High-power systems may require fixed wiring and dedicated electrical protection.
• Mechanical integration and cooling: Consider dimensions, weight, rack installation, airflow, cooling requirements, AC connections, emergency shutdown, interlocks, and protection against accidental contact.
• Parallel operation and scalability: For higher current or power requirements, verify whether the selected series supports parallel or master-slave operation and which operating limits apply to the combined system.

For application-specific test benches, ET System can combine electronic AC loads, AC power supplies, grid simulators, DC equipment, measurement technology, safety components, and control systems through test system integration. For support with selecting a suitable AC load, contact our technical sales team.