There is a well-recognised need for robust simulation tools to support the design and evaluation of future More-Electric Engine and Aircraft (MEE/MEA) design concepts. Design options for these systems are increasingly complex, and normally include multiple power electronics converter topologies and machine drive units. In order to identify the most promising set of system configurations, a large number of technology variants need to be rapidly evaluated.This paper will describe a method of MEE/MEA system design with the use of a newly developed transient modeling, simulation and testing tool aimed at accelerating the identification process of optimal components, testing novel technologies and finding key solutions at an early development stage. The developed tool is a Matlab/Simulink library consisting of functional sub-system units, which can be rapidly integrated to build complex system architecture models.This paper will demonstrate this functionality by applying the tool to assess the suitability of various designs of active power converter circuitry for use with an example MEE/MEA network. Three aspects of the converters’ performance will be considered in order to assess this suitability: efficiency, power quality and fault tolerance. The example case studies will demonstrate the adequacy of the selected variant designs as well as the system level impacts of design decisions.This will enable system designers to rapidly identify variant configurations of electrical components at early design stage that satisfy MEE/MEA system requirements.