One of the barriers to the adoption of hybrid and pure electric vehicles is the cost of the traction motor. The Department of Energy has set the following very aggressive technical and economic performance goals for electric vehicle traction motors: $4.7/kW, 1.6 kW/kg, and 5.7 kW/l (Source: https://www1.eere.energy.gov/vehiclesandfuels/pdfs/program/eett_roadmap_june2013.pdf.) In particular, the cost per kilowatt target will be very difficult to meet, since current estimates of electric vehicle traction motor costs are greater than $10/kW using mature electric machine designs and production technologies.
There are many technological approaches to reduce the traction electric motor cost while maintaining high power density. One promising approach uses segmented laminations to reduce the amount of scrap generated during the lamination stamping process. Currently, approximately 40 percent of the incoming electrical steel is scrapped in non-segmented designs. Segmentation of the laminations, ideally both stator and rotor, potentially allows for stamping die layouts which minimize the scrap. Historically, segmented laminations have not been used for electric vehicle traction motors because of concerns of losses at high speeds due to higher order space harmonics. Recently, new low space harmonic fractional slot concentrated winding layouts have been developed which may accommodate segmented laminations in electric vehicle traction motors. Very little public information, however, is available about the impact of segmentation on structural, electromagnetic, and thermal properties of the machine and their associated manufacturing issues which are critical for adoption by automotive Original Equipment Manufacturers (OEMs).
The goal of this engineering and business oriented IPRO project is to develop low-scrap segmented lamination technology, for both stators and rotors, with minimum impact or ideally enhancement of the power conversion properties of the electric vehicle traction motors. The team will investigate the impact of reduced scrap segmented lamination designs including structural and electromagnetic behavior to determine the potential tradeoff between power conversion properties and cost reduction. The team will also investigate and design prototype scale manufacturing jigs and test fixtures to determine technical feasibility and viability of the low scrap segmented motor technology for widespread adoption by the automotive industry. Basic costing and economic studies will also be carried out to assess market demand.
The electromagnetic, structural, and thermal design of the electrical machine becomes much more complicated when using segmented laminations. A multidisciplinary team of students is needed to tackle the multi-physics nature of the problem and also assess the likelihood of market adoption. Initial design work will be carried out using finite element analysis and CAD. The team will work with Tempel Steel to specify the fabrication of test coupons and segmented designs that it will laser cut. Tempel Steel is a leading manufacturer of motor and transformer laminations in Chicago. The fabricated parts will be tested to determine their basic strength and electromagnetic properties. The team will also be involved in the design of test fixtures and prototyping basic manufacturing jigs.