BYD had four patents detailing variable-flux permanent-magnet synchronous motor technology, published by the China National Intellectual Property Administration (CNIPA) recently, following their filing in May 2024. The filings, CN121055622A, CN121055630A, CN121055623A, and CN121055631A, describe mechanisms for adjusting rotor magnetic flux to improve efficiency across a range of operating speeds. These patents build on BYD’s prior work in variable flux motor technology and represent a technical evolution of the concept.
A Variable Flux Permanent Magnet Synchronous Motor (VF‑PMSM) is a type of motor in which the internal rotor magnetic flux can be adjusted according to operational conditions. Conventional permanent magnet synchronous motors have a fixed rotor flux, which provides strong torque at low speeds but reduces efficiency at higher speeds due to counter-electromotive forces. A VF‑PMSM dynamically regulates flux to maintain efficiency across low- and high-speed operation, enabling more consistent torque output and reduced energy loss.
Flux adjustment is achieved through movable or controllable components within the rotor or magnetic circuit. At low speeds, magnetic flux is maximised to deliver strong torque. At higher speeds, flux is reduced to minimise opposing forces and maintain efficiency without excessive energy consumption. This approach can improve overall energy efficiency, extend high-speed range, and optimise torque performance without increasing battery capacity.
The 2025 BYD patents provide practical implementations of VF‑PMSM technology. CN121055622A describes a magnetic-flux-adjustment component integrated with an electric motor and drive system. CN121055630A describes a magnetic regulation component movable relative to the rotor to expand high-efficiency operating regions. CN121055623A introduces an axial adjustment assembly that modifies rotor magnetic flux along its axis. CN121055631A presents a configuration in which the radial area of a magnetic conductive part can be adjusted, allowing fine-tuning of internal flux. All technical descriptions correspond to CNIPA abstracts, ensuring verifiable accuracy regarding magnetic flux regulation mechanisms and rotor designs.
In addition to these three VF‑PMSM patents, BYD filed and published other 2025 patents related to electric motor structures and drive systems. These filings include rotor and stator hardware designs, magnetic flux management components, and other motor-related innovations. The public patent record indicates that BYD’s research and development in motors and powertrain systems is ongoing. However, no additional public reports confirm commercial deployment or experimental results specifically for VF‑PMSM technology.
For electric vehicles and other new energy vehicles (NEVs), VF‑PMSM technology can improve efficiency across a range of driving conditions. By adjusting rotor magnetic flux, these motors reduce energy loss at high speeds, extend driving range, and maintain consistent torque at low speeds. This allows more predictable energy consumption during long trips, reduces thermal stress on motor components, and optimises battery usage for both fully electric and hybrid powertrains.
Together, the patents illustrate BYD’s ongoing development of high-efficiency motors capable of variable-flux control, addressing a limitation of fixed-flux permanent-magnet motors.
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