Electric drives conquer our daily lives: Powertools like Cordless screwdrivers, angle grinders, electric bikes and electric cars must function with maximum efficiency over the greatest possible load ranges. Test standards, such as DIN IEC 60034-2-3, define the test requirements for determining the efficiency of such inverter-fed drives. The underlying chopped rectangular voltage and the associated current must lead to a maximum of 0.3% incorrect power statement true to phase and amplitude.
In order to achieve this 0.3% accuracy, the theoretical frequency consideration of a square wave voltage requires the consideration of all frequencies up to the 19th harmonic of the switching frequency of the inverter. At 10-20 kHz switching frequency this is 0-380 kHz signal bandwidth in which the signal fidelity of all components must be better than 0.3%. This requires a measurement technique with 2 to 4 MHz continuous sampling rate without distorting filters. Especially in high-performance automotive electric motors, ever higher battery voltages with currently up to 800 V are used.
With a bandwidth of 380 kHz, a pulsed 800 V signal becomes a real challenge. The high art is to build the high-voltage divider in such a way that its total measurement error over the entire frequency, voltage and temperature ranges is guaranteed to remain less than 0.3% - and that even though the non-linearities of all electronic components are already making a massive impact here. At the same time, the pulsating current of this 800 V pulsating inverter voltage must be measured. A real challenge for the galvanic isolation of the current input. This combination of required bandwidth and accuracy can only be achieved worldwide with the Precision measuring device LTTsmart
No other power meter can meet the signal accuracies required by the standards in terms of voltage AND frequency. It fails either because of the accuracy or because of the bandwidth. The LTTsmart is the only solution you can rely on to support your test bench design. Perspective up included!