Measuring both leakage and fault currents in a semi-conductor device
At a glance
To measure the leakage current of a few mA in an SCR when it is turned off. The measurement should survive the current surge of about 60kA when the device is turned on. The same coil to be used for measuring both currents.
Measuring the leakage current requires a sensitive system. The input stages of the sensitive integrator must be designed to withstand the large coil voltage caused by the current surge.
Rocoil engineers produced a solution with two
integrators connected to the same rigid coil. The 'leakage current'
integrator was designed using resistors that had the watt rating to
withstand the coil output at 60kA. During the current surge the
integrator would overload and saturate but recover as soon as the
current was reduced. The 'current surge' integrator was designed to make
accurate measurements at the larger current. This application
illustrates the linearity of a Rogowski coil where the same coil can be
used to measure a very wide range of currents.