Spin start is a function that detects motor rotor speed at start-up and then matches drive output frequency to the detected rotor speed.
Loads that are still spinning can cause higher currents to flow in the drive at start-up and potentially damage the Optidrive.
Spin Start should be used on any application where the motor shaft may be already turning when the drive is enabled.
For example, loads that may still be coasting to stop when the drive is re-enabled (high inertia loads), or fans that free-wheel due to natural air-flow when the drive output is disabled.
Optidrives without Spin-start that are started into spinning loads should instead enable DC brake on Start.