Utility capacitor-switching transients (CSTs) are responsible for numerous nuisance tripping of PWM adjustable speed drives (ASDs) and result in costly down times. During a CST event, the dc link voltage of the ASD can momentarily rise to greater than 1.3 p.u. resulting in nuisance tripping. In this paper, a new approach to mitigate nuisance tripping of PWM ASDs is discussed. In this approach, the soft-charge resistor available in most ASDs, is momentarily introduced in the series path of the

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... wer flow to effectively damping the CST. Further, damping effect is electronically adjusted. The proposed approach demonstrates a method that can be incorporated within an ASD to electronically damp the oscillatory transient generated during a CST event. The advantages of the proposed approach are i) electronic damping for CST event is achieved by low cost modifications to ASD hardware; ii) it adapts to several utility resonance conditions. The required additional hardware for ASDs to be immune to CSTs, can be viewed as an add-on option. This paper discusses the analysis, simulation and experimental performance on a 480 V, 16 kVA commercial ASD equipment. Index Terms-Adjustable speed drives, capacitor switching transients, electronic damping, power quality.