Current measurement of motor drives and inverters – Influence of shielded and not-shielded motor cable

Inhalt:
For increasing the efficiency of electric drive trains, measurement and testing plays a key role. The requirements to the measurement system concerning hardware (high accuracy, high bandwidth, high sampling rate, isolated high-voltage inputs, etc.) as well as to the software (power calculation for variable frequencies, for DC and AC 1-, 2-, 3- up to 7-phase systems, multiple power calculations, FFT, etc.) are really high. A very important part of the measurement chain for such applications is the current measurement. There are different technologies for measuring the current. The first aim of this article is to determine the difference between an iron-core current clamp, a rogowsky coil, a hall-compensated AC/DC current clamp and a zero-flux current transducer at a measurement of an inverter. The second focus of this article is the analysis of measuring the current between a frequency inverter and a motor of an electric car with and without shielded motor cable.