Aiming to improve the reliability of a three-level neutral-point-clamped power inverter, an in-situ health monitoring method is proposed by harnessing the inverter operational characteristics and degradation sensitive electrical parameters to address the IGBT wire bonding faults. The zero voltage state provides an inherent redundant feature that allows a power switch diagnosed during its normal operation in a neutral-point-clamped power inverter. The proposed prognostic approach obtains both the wire bonding failure features and junction temperature from the terminals of an IGBT module, which is regarded as non-invasive on-line health monitoring. The system performance can be affected by the designated testing point and testing window. The proposed technique allows unhealthy wire bonding in IGBT modules online monitored during the operation period of the inverter.