Overview
New energy vehicle motor technology is a major trend, creating urgent demand for automated assembly lines.
Permanent magnet synchronous motors are the primary drive motor type for new energy vehicles. The most widely used variant is the permanent magnet synchronous motor, which offers high power density, low energy consumption, compact size, and light weight. A permanent magnet synchronous motor comprises a stator assembly, rotor assembly, housing, end covers, and other auxiliary standard parts. The stator assembly includes the stator core, copper windings, lead wires, and insulation materials and is typically fixed to the motor housing. The rotor assembly includes the rotor core, permanent magnets, shaft, bearings, and other components; it connects to the output shaft and drives the vehicle through gears.
Advantages of Flat-wire Motors
Compared with traditional round-wire motors, flat-wire motors in permanent magnet machines show clear performance advantages:
- Smaller volume and higher power.
- Reduced copper losses and improved efficiency.
- Better thermal performance.
- Lower mechanical and electromagnetic noise.
Comparison of slot fill rate between round wire and flat wire
Manufacturing Complexity and Automation
Flat-wire stator manufacturing is complex and highly dependent on automated equipment. The stator assembly is the core of flat-wire motor design and presents significant production challenges with strong customization. Once a stator design is finalized, any change to the conductor profile or dimensions typically requires costly custom tooling, and compatibility is low. The complete flat-wire stator manufacturing flow includes: insert paper, coil forming, pre-insertion, full insertion, flaring, lead twisting, trimming, welding, coating and varnishing, and copper terminal welding. These many and complex steps make automation dependency higher than for round-wire motors, especially for coil forming and welding where precision requirements are strict and process difficulty is high. Overseas companies have developed deep expertise and an early equipment advantage in this area.
Three Main Assembly Process Stages
Rotors and final assembly lines are relatively simpler, while stator assembly involves multiple complex operations such as non-destructive bending of flat wire, insertion, lead twisting, laser welding, and varnish dipping. There is not yet a single standardized assembly process for flat-wire stators; manufacturers are still exploring process solutions. A few equipment suppliers with delivery experience for flat-wire stator assembly lines outside China include Comau, BorgWarner, and Fisomat. Drawing on prior experience in transmission manufacturing for internal combustion vehicles, a number of firms have developed stator-line assembly processes and technical capability for end-to-end solutions covering stator, rotor, and final assembly lines. Currently, only a few companies in China, such as Haosen Co. and Kelai Electromechanical, have the capacity to undertake flat-wire stator assembly lines.
For the critical stator processes—coil forming, wire insertion, lead twisting, and welding—the required precision and automation level are high. Equipment that has been developed to support these processes includes coil forming machines, automatic insertion machines, twisting machines, and welding machines, with corresponding average production cycle times of 4/360/50/3 s respectively, enabling highly automated stator line operation.
Rotor Production Line
The rotor production line process sequence is: insert magnets into the core, core injection molding, heat curing, rotor stacking, dynamic balancing, magnetization, surface magnetic inspection, rotor pressing, and laser marking. The entire line is complex and demands high automation. Key rotor processes include magnet insertion into the core, core injection molding, rotor stacking, and magnetization. Several firms have developed mature flat-wire motor rotor production lines and final assembly lines.
