Online and offline isolated current monitoring of parallel switched high-voltage multi-chip IGBT modules

This paper presents the application and the implementation of planar PCB air-coil based current sensors for online current monitoring and offline switching losses characterization of high-voltage, multi-chip IGBT modules. Two types of sensors are presented: a planar PCB Rogowski coil, for measuring alternating currents, and a prototype of a HOKA current sensor, capable of broadband current measurement from DC to 50 MHz without derating. These sensors present superior advantages with respect to the shunt technology since they are more compact, isolated, fighter and integratable. They are advantageous also with respect to conventional magnetic wound current sensors, since the performance characteristics of the planar PCB sensors are more reproducible. The issues related to the measurement of the current sharing of parallel connected modules are analyzed as well as the problems related to the thermal optimization and current sharing within a multi-chip IGBT power module. The advantages of the current measurement in order to perform the monitoring and fault detection of the modules are discussed. In addition, the techniques used to measure the current within a power module are reviewed. Experimental results of current measurements and dynamic performance are included.