Rogowski transducers for high bandwidth high current measurement

The 300A Rogowski current waveform transducer was tested using a simple IGBT switch with an inductive load. A 5m Omega co-axial shunt was connected in series with the IGBT for comparison. The initial current at turn-on is due to snubber discharge; thereafter the inductor current ramps up until the IGBT is turned off. The current waveforms closely correspond even with a turn-off slope in excess of 500A/ mu s. Tests with a 1500A Rogowski transducer have reproduced current transients in excess of 2000A/ mu s. For use for the measurement of high frequency power, or power associated with semiconductor switching transients, a small time delay of 90ns should be introduced into the voltage measurement signal before multiplying this by current to obtain the instantaneous power. It is concluded that the Rogowski coil with appropriate integrator design can provide current waveform measurement to a very high bandwidth in excess of 1MHz, and forms a very attractive easy-to-use measuring instrument.