Programmable DC Electronic Loads: Next-Gen Power Test Solutions

An air-cooled dissipative DC load absorbs DC power and converts 100% of that electrical energy into heat inside the unit using heavy-duty copper heat sinks and internal fan banks. This is cost-effective for lower power levels (<3 kW) or intermittent benchtop use.

A grid-tied regenerative DC load incorporates an internal active front-end (AFE) inverter. Instead of generating waste heat, it converts incoming DC energy back into synchronized, low-distortion AC current fed back directly into the local building grid. This saves immense electrical costs in burn-in rooms and EV pack manufacturing plants while reducing air conditioning infrastructure requirements.

All standard electronic loads require a small minimum operating voltage across their internal power transistors (typically 0.7V to 3.0V) to conduct rated load current. However, a single hydrogen fuel cell cell operates around 0.6V to 0.8V under load, and can drop close to 0V during extreme current stress tests.

Without low-voltage or zero-volt capability (often achieved via internal bias power supplies or specialized FET arrangements), a standard load will drop out of Constant Current mode, making full polarization curve mapping impossible. APS offers low-voltage modified load options designed specifically for fuel cell and energy harvesting characterization.

Consult an Application Engineer regarding Near-Zero Volt models →

When high-power testing demands current levels beyond a single chassis (e.g., needing 1500 Amps at 1000 Volts), multiple DC load units are connected in parallel. In an APS master-slave configuration, a dedicated high-speed analog control bus connects the master chassis to slave chassis units.

The Master unit receives the SCPI programming commands or local front-panel setpoints, measures incoming sense line voltage, and generates high-bandwidth internal reference signals distributed to all Slave units simultaneously. This ensures precise current sharing within <1% tolerance across all paralleled FET blocks and prevents single-chassis over-current trips during steep dynamic step transients.

When pulling high currents (e.g., 500A), even low-resistance copper cables experience voltage drops according to Ohm's Law ($V_{drop} = I \times R_{cable}$). If the electronic load measures voltage only at its own front-panel input terminals, it will report a lower voltage than what is actually delivered by the DUT, severely skewing Constant Voltage (CV), Constant Resistance (CR), and Constant Power (CP) modes.

By connecting dedicated Remote Sense (+S / -S) wiring directly to the output terminals of the DUT, the load's internal high-impedance feedback amplifier measures actual DUT terminal voltage—effectively bypassing lead resistance voltage drops up to several volts.

High-energy testing presents real thermal and electrical hazards. Industrial-grade programmable DC loads must integrate multi-layered hardware and software safety interlocks, including:

• Over-Voltage Protection (OVP): Instantly disconnects or limits load if voltage spikes beyond cell safety limits.
• Over-Current Protection (OCP): Prevents destructive short-circuit drawing during thermal runaway testing.
• Over-Power Protection (OPP): Automatically clamps current to prevent exceeding power stage dissipation ratings.
• Over-Temperature Protection (OTP): Thermal sensors on internal heat sinks trigger safe shutdowns if air intakes are blocked.
• Reverse Polarity Protection: Prevents catastrophic FET damage if battery cables are accidentally connected backward.