(DSD)

ACeDrive consortium plans more efficient EV powertrain

Led by GKN, the ACeDrive consortium is developing a lighter and more efficient volume EV powertrain suitable for production by 2023.

It’s called ACeDrive, which may sound innocuous for an auto-industry project, but the consortium that formed it has announced that it seeks to develop the world’s lightest and most efficient volume electric vehicle (EV) powertrain. Involving two major suppliers, a research university and the UK government-backed Advanced Propulsion Centre (APC), the aggressive targets for the ACeDrive (Advanced Cooling and control of high speed e-Drive) include a 25% reduction in cost, a 25% reduction in packaging size and a 20% reduction in weight combined to deliver a 10% increase in efficiency.

The project’s powertrain includes a downsized electric motor, optimized transmission and high frequency inverter within a single unit with shared cooling via fewer interfaces. Its final design phase has begun following simulation and analysis, prototyping rigs and vehicle testing is scheduled for next year and production is slated for 2023. To get some detail on ACeDrive, Automotive Engineering spoke with GKN Automotive and Drive System Design (DSD).

Gordon Day, general manager GKN automotive innovation centre

Automotive Engineering: What is GKN Automotive’s role within the project?
Gordon Day: GKN Automotive conceived ACeDrive and has the lead role within the project consortium. GKN Automotive is responsible for the complete design and development and also owns the related intellectual property.

AE: Who set the aggressive project targets?
GD: The targets have been set by GKN Automotive and are intentionally tough and aimed to stretch the team at our UK innovation centre and fellow consortium partners. With ACeDrive we aim to bring certain APC roadmap technology steps to reality, but a decade earlier than envisioned.

AE: What is likely to be the biggest challenge?
GD: We expect some of the toughest challenges from implementing efficiency improvements as well as delivering advanced cooling and thermal management technologies to the market at a competitive cost.

AE: Will the powertrain be based on proven components?
GD: This is an entirely new design and approach undertaken by our advanced engineering team at the innovation centre working alongside our consortium partners. Within the project we are taking ACeDrive from an experimental and research level to full system vehicle concept demonstration.

AE: Will you be using advanced materials?
GD: We have exacting design targets for ACeDrive and reduced cost is a primary element. To manage system cost accordingly we don’t intend to make use of highly advanced materials.

AE: Will you be using a single- or multi-speed transmission for ACeDrive? What criteria guided your decision?
GD: Choice of single- or multi-speed transmission is generally driven by the application specification. ACeDrive targets performance appropriate for a premium battery electric vehicle (BEV). We have set stretch targets for the e-motor speed and torque characteristics to meet the needed vehicle performance with a single-speed transmission.

AE: Is ACeDrive an interim powertrain, and what’s its anticipated its lifespan? Will volume be sufficient for convincing economies of scale?
GD: ACeDrive is still at an early stage of development, however first application in 2023 is still realistic. We’ve targeted a modular e-drive as would be appropriate for a premium BEV and have purposely aimed to avoid OEM specific requirements that may be overly compromising at this stage in development. In fact, the ACeDrive project delivers technology building blocks which can be scaled and applied to other GKN Automotive eDrive platforms. With that considered, elements of ACeDrive may reach the market sooner.

AE: What is your long-term view of volume electrified powertrains (fuel cells, etc.), and when can we expect the lighter, cheaper batteries?
GD: At the innovation centre and as part of GKN Automotive ePowertrain globally, we are fully focused on the electric drive system which is all downstream of the energy storage. ACeDrive could equally accompany a fuel-cell installation, BEV or hybrid platform. For ACeDrive we have chosen an 800V configuration. This is for performance reasons, as well as to be fully compatible with the latest high-speed charging systems coming to market via companies like Ionity.

The launch of high-speed 800V charging providing 350kW of charging power, providing over 200 miles (320km) of range within 10 minutes, alongside continued reductions in the price of batteries, should really change the game to push much wider adoption of battery EVs. It’s a fascinating industry upheaval towards electrification. In all cases, electric drivelines are required and we are excited to bring ACeDrive through its development and to meet this growing need.

Simon Shepherd, DSD head of electrified powertrain

AE: What are DSD’s responsibilities within ACeDrive?
SS: DSD is responsible for development of the internal tools and techniques to support the project, utilizing its simulation-led approach in several areas: validation of the whole e-drive system architecture, consisting of inverter, motor and gearbox, including optimization; analysis and design of the e-drive system’s NVH and efficiency performance; and providing support to GKN and University of Nottingham with regard to gearbox and e-motor design.

Development of the project’s high-speed motor will also be carried out at the leading-edge test facilities of DSD. The company will further develop its test capability to meet the automotive industry’s evolving requirement for higher speed electric motor testing, with intense focus on increased motor efficiency and NVH characteristics at speeds up to and beyond 20,000rpm. University of Nottingham is responsible for the fundamental design of the electric motor, and of the system modules for the power electronics and advanced cooling concepts.

AE: The program development time looks fairly rapid; how is this schedule supported?
SS: DSD has a portfolio of tools designed to reduce development time, such as its Electrified Powertrain Optimization Process (ePOP), which aids the on-time delivery of ambitious technology-led programs. ePOP evaluates the complex array of powertrain considerations, such as cost, mass, performance and energy consumption, to generate an application-specific optimum. This helps to get early stage designs right first time, results in less reliance on latter-stage fine-tuning, and significantly reduces development time.

AE: What are the consortium’s toughest challenges?
SS: The advantage of developing a brand-new electrified powertrain is the ability to start with a blank canvas, but the main challenges relate to advancing technology on all fronts. Aligning the development of each element so that it is possible to bring each strand together into a single, integrated unit will pose the greatest challenge. For example, developing the cooling methods and heat management for both motor and electronic components, which themselves are pushing the boundaries on what has been done before, requires careful balance of trade-offs.

AE: How do you expect to achieve a 25% reduction in cost?
SS: Firstly, significant benefits will be realized by focusing on power-density, effectively achieving the target power with less active material. For example, development and utilization of a high-speed, high power-density motor reduces motor size and so provides the potential for a significant reduction in active materials. Further levels of cost reduction can be achieved by viewing it at a system level. High levels of integration remove interfaces and connector parts, which makes the drive unit cheaper and lighter. Finally, utilization of more efficient silicon carbide MOSFETs (transistors) in the inverter can lead to system level savings in battery capacity reduction and downsizing of passive components, such as the DC capacitors.

AE: The consortium announcement refered to progressing through concept selection. What are the main development stages?
SS: Concept selection refers to the first phase of project management, which considered a wide range of topology options in the inverter, motor and gearbox to ensure clarity and precision of progression by initially identifying the most promising avenues for further study such as utilization of the ePOP tool. These have been analyzed, refined and reviewed in more detail across a range of criteria – mass, efficiency, manufacturability – to where we are now, where concepts are selected and detailed design proceeds. It is the most efficient way of ensuring knowledge-sharing and that each organization is working to its strengths.

AE: Is the powertrain all new or does it use established technology?
SS: The project harnesses established manufacturing and powertrain technology principles, refined wherever possible for optimal use in combination. The project specifically focuses on looking at step changes in the inverter, cooling methods and impacts on the rest of the system. This directly affects the motor, resulting in industry leading power density. The thermal implications of this then require innovative heat management techniques. The gearbox utilizes established manufacturing methods, but uses cutting edge analytical tools and processes to ensure high speed requirements are managed.

AE: What were the considerations on choosing a single speed transmission?
SS: All options were considered, but a single-speed transmission was deemed to provide the optimal blend of cost, efficiency and performance for this particular application. The power of tools, such as ePOP, is that application-specific optimal solutions can be determined. Whilst DSD are seeing clear justification for multi-speed in some applications, the ACeDrive project goals are best achieved with single speed.

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