Optimization of Laminated Stack Solutions for Electric Motors in Electrified Vehicles

The electrification of vehicles marks the introduction of new products to the automotive market and a continued effort to optimize their performance. The electric motor is an important component with which a further optimization of efficiency, power density and cost can be achieved. Additional benefits can be realized in the laminated core. This paper presents an innovative method to produce laminated stacks by a chain of processes different from conventional ways. The process chain presents a sequence of precision blanking, buffering, heat treatment and gluing. The effect of these processes is compared with existing solutions that typically contain some individual features but usually not the combination that enhances the overall effect.

The heat treatment decreases residual stresses from previous process steps and reduces power losses in the laminated core. Depending on the design, benefits around 20% are found. The bonding of lamellae by gluing maintains their flatness and prevents short circuits between lamellae by other processes like interlocking or welding. This reduces the occurrence and impact of eddy currents and the associated power losses. Lower power losses increase power density of the stack and electric motor. The presented manufacturing process also supports this by an improved stacking factor. The improved efficiency reduces thermal stress on critical electric drive components and leads to higher (continuous) power at the system level. Alternatively it can help to reduce the volume and weight of the motor, auxiliary systems and battery, leading to a more cost effective solution.