How do you test a very high-current and/or high-voltage power source? You measure the voltage, current, and power, but you need to test the source under typical and maximum load conditions. So what do you use for a load, especially if it must dissipate up to tens of kilowatts?
The MEL series of modular electronic loads from PPM Inc. can handle up to 60 kW in one 8-ft rack (see the figure). If you’re testing high-power vehicle batteries and control systems, fuel cells, aircraft power systems, generators and alternators, windmills, solar panels, or battery chargers, the MEL product line is worth a look.
The series solves three basic test load problems facing design and production engineers. First, these computer-controlled products are simple to set up, so users can focus on testing. Second, the MEL units are flexible and expandable, making them less subject to obsolescence. Finally, they let users select only the features they want.
Models are available for voltages up to 600 V and 2000 A. The load units are easily switched and controlled by high-power semiconductors on massive heatsinks with fan cooling. Each MEL unit is factory- or field-expandable from 1 to 5 kW. They also come in master or slave models. Users can stack the load units to increase the power-handling capability. For example, one master and 15 slaves will provide up to 80 kW of load capacity. The loads may be operated in a constant voltage, current, power, or conductance (resistance) mode with values within ±0.2% of full scale.
Measurement and control of the load can be via IEEE 488 (GPIB) or RS-232 interfaces. Measurements offer 14 bits of precision and provide ±0.25% of full-scale accuracy. A 0- to 10-V external dc can be used for control. Frequency response is dc to 10 kHz. Alternate USB 2.0 and Ethernet 10/100 interfaces can be selected. Most systems are PC-controlled, but a separate control module/panel is also available. And, the units are fully compatible with National Instruments’ LabVIEW.
PPM also makes the EL line of lower power electronic loads for benchtop testing up to 300 W. For configuration details and pricing on the MEL units, contact the company.