Current measurement using compensated coaxial shunts

The measurement of high levels of current over a wide bandwidth poses many problems to the user of high speed, power semiconductor devices. Requirements for a compact layout and low insertion impedance for the current measuring device often make conventional current transformers and resistive shunts unusable. Other desirable features such as DC current measurement, fast transient response with no overshoot and a high r.m.s. current rating, further restrict the choice of measuring equipment. The current monitor must also show a high degree of noise rejection since measurements typically take place in the presence of large stray fields, some of which may contain significant high frequency components. Finally, the device should be physically small and have the minimum possible insertion impedance. Describes a purpose built current monitor. The work concerns a coaxial current shunt with a new compensation system specifically designed for monitoring the anode and gate current in a GTO thyristor test rig. The shunt was designed to provide accurate current measurements of pulse currents of up to 5000 A with slew rates in excess of 5000 Aμ s^-1 and a rise time of less than 25 ns