A scalable life cycle inventory of an automotive power electronic inverter unit—part I: design and composition

Abstract

Purpose A scalable life cycle inventory (LCI) model, which provides mass composition and manufacturing data for a power electronic inverter unit intended for controlling electric vehicle propulsion motors, was developed. The purpose is to fill existing data gaps for life cycle assessment (LCA) of electric vehicles. The model comprises new and easy-to-use data with sufficient level of detail to enable proper component scaling and more in-depth analysis of inverter units. It represents a stand-alone three-phase inverter with insulated gate bipolar transistors (IGBTs), typical in electric vehicles. This article (part I) explains the modeling of the inverter design including the principles for scaling, exemplifies results, and evaluates the models' mass estimations. Methods Data for the design of power electronic inverter units was compiled from material content declarations, textbooks, technology benchmarking literature, experts in industry, and product descriptions. Detailed technical documentation for two electrically and electronically complete inverter units were used as a baseline and were supplemented with data for casings, connectors, and bus bars suitable for automotive applications. Data, theory, and design rules were combined to establish a complete model, which calculates the mass of all subparts from an input of nominal power and DC system voltage. The validity of the mass estimates was evaluated through comparison with data for real automotive inverter units. Results and discussion The results of the LCI model exemplifies how the composition of the inverter unit varies within the model range of 20-200 kW and 250-700 V, from small passenger car applications up to distribution trucks or city buses. The models' mass estimations deviate up to 14% from the specified mass for ten examples of real inverter units. Despite the many challenges of creating a generic model of a vehicle powertrain part, including expected variability in design, all results of the model validation fall within the targeted goal for accuracy. Preamble This is the first article in a series of two presenting a new scalable life cycle inventory (LCI) data model of a power electronic inverter unit for control of electrical machines in vehicles, available to download. In part I, it is described how the LCI model was established, how it is structured, and the type of results it provides, including a validating comparison with real-world inverter units. It also covers design data and the principles for scaling of the main active parts-the power module and the DC link capacitor. Part II presents how new production datasets were compiled from literature and factory data to cover the manufacturing chain of all parts, including the power module fabrication, mounting of printed circuit boards, and the complete assembly. Part II also explains the data collection methods, system boundaries, and how to link the gate-to-gate inventory to the Ecoinvent database in order to establish a complete cradle-to-gate LCI.

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“…It should be noted that a method can occur in more than one subcategory. For example, Caduff et al use power laws based on empirically observed scaling relationships to scale windmills [35] and heating devices [36] which are both mature products, while similar approaches are applied to model the scale up from lab to industrial size [37,38]. Also, often several methods are combined per study.…”

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