Design and test of a PCB Rogowski coil for very high dI/dt detection

This study proposes the bespoke design of a printed-circuit-board (PCB) integrated Rogowski coil to detect very high dI/dt´s in an IGBT non-destructive tester. During reverse bias safe operating area (RBSOA) tests of an IGBT, failures of the transistor or of the freewheeling diode can lead to excessive dI/dt in the circuit. If properly detected, this information can be used to successfully implement non-destructive testing strategies, enabling the energy to be diverted from the device under test (DUT) to a protective switch. Hence, the design of the dI/dt sensing element (i.e., the Rogowski coil, in this case) is a fundamental aspect of the overall system design. Here, the PCB Rogowski coil is designed to detect only high dI/dt neglecting normal operating conditions. Initially the PCB Rogowski is designed according to the anticipated dI/dt values during failure and the required output response. The Rogowski circuit is then modeled and transient analysis was performed to aid the design of the damping output resistance. Finally, the experimental test results are presented.