Ehsan Abdi Jalebi - Engineering Department, University of Cambridge, Cambridge, CB۲ ۱PZ, UK.
Paul Roberts - Engineering Department, University of Cambridge, Cambridge, CB۲ ۱PZ, UK.
Richard McMahon - Engineering Department, University of Cambridge, Cambridge, CB۲ ۱PZ, UK.

Rotor bar current measurement is a valuable step in verifying the theory of electrical machines design and control. However, because the rotor is moving, the approach is difficult to implement. This paper presents the design and evalution of an approach to real-time rotor bar current measurement using the Rogowski coil as a current transducer. Rogowski coils have become an increasingly popular method of measuring current within power electronics equipment due to their advantages of low insertion loss and reduced size compared to an equivalent current transformer. The design of the associated integrating amplifier is discussed in detail, including the advantage, tradeoffs and limitation of the approach. Bluetooth wireless technology is employed to transmit data between the moving rotor and the computer which logs the data. Experimental results from a system for measuring the rotor bar current in a Brushless Doubly Fed Machine (BDFM) are presented.

Rotor bar current measurement, Rogowski coil, Bluetooth wireless technology