The Evolution of BYD’s Electric Motor: A Lean Design Case Study

TL;DR

BYD's 2024 electric motor is 20% lighter and more powerful than its 2019 version by eliminating parts and simplifying assembly at every level.

Key Points

• 1.Housing: Went from 3 castings + 1 large extrusion (requiring welding) to a single integrated casting that combines the motor housing and gearbox housing with built-in water cooling channels.
• 2.Rotor magnets: Switched from a deep 3-magnet-per-pole radial layout to a shallow double-V pattern, reducing expensive neodymium magnet material while increasing power output.
• 3.Stator winding: Replaced stranded wire winding with bar winding, fitting more copper into each slot while using less total copper — higher power density at lower per-part cost once production volume justifies the equipment investment.
• 4.Assembly process: Eliminated a hidden bearing retainer plate requiring blind screws (a cross-threading failure risk) in favor of simple Z-axis drop-in assembly, cutting labor time and eliminating a defect source.
• 5.Inverter: New design uses double-sided copper heat sinks to cool power switches, which also shields electromagnetic interference — eliminating a separate stamped aluminum EMI shield and enabling three tiny onboard current sensor chips to replace large iron-core sensors with bulky wiring harnesses.
• 6.Overall result: The new drive unit weighs 86 kg vs. 103 kg, delivers over 200 hp (vs. ~200 hp before), costs less, and reflects an industry-wide convergence toward this exact motor architecture across Tesla, GM, Ford, and Hyundai.