Resynchronization or resync is a feature that allows the device to catch a windmilling motor on-the-fly and ramp the motor to the commanded speed when the motor was spinning in the commanded direction.

If speed is greater than FWD_DRV_RESYN_THR such that sufficient BEMF is being produced, then drive directly switches to closed loop drive else motor is ramped using open loop before handing off to closed loop.

When recommended:

• Resync helps significantly when motor has high inertia. High inertia motors take up a lot of time to start and stop. If a motor was already spinning in commanded direction prior to run command, resync can save the time to brake, stop and restart using motor startup methods.
  • Examples: Ceiling fans due to high inertia.
• If external factors like wind is present that rotates the motor in the commanded direction, resync is recommended to be enabled for faster and smoother startup.
  • Example: pedestal fans due to possibility of wind causing rotation.
• Repeated start-stop routine during operation in moderate to high inertia motors.
  • Example: CPAP(continuous positive airway pressure) motors.