A real time Vce measurement issues for high power IGBT module in converter operation

A real time on-state collector-emitter (V_ce) voltage monitoring is sensitive due to a stray inductance and a parasitic capacitance inside high power IGBT modules. An additional circuit used to monitor the on-state V_ce introduces small current into the module. Though the current is low in comparison to the converter current, the effect on gate driving signals cannot be neglected during worst case switching operations. The worst case situation is occurred during turn-on and turn-off period of the switches at low on-time of the IGBT. Furthermore, during this period, when the common terminal of the measurement circuit is not in contact properly, the consequences of the error will be higher by deteriorating the gate driving signals. This type of error may occur due to the vibration or during implementation of the measurement circuit in the converter. This paper presents the influence of the error into the measurement and shows the measurement of current and voltage transients during the converter operation. The selection of the components for the measurement circuit is also discussed. The effect in gate driving signals with and without the error events are presented. Finally, a real time V_ce measurement of IGBT module in the converter operation is presented.