Brushless Motor Drive Overcurrent Limiting Dynamics

The patent applies dynamics by making the duty factor limit value changeable over time rather than fixed. The control device dynamically adjusts the limit value based on the duration of overcurrent detection, initially setting it to a small value and gradually increasing it toward a predetermined target value. This dynamic adjustment prevents instantaneous and large changes in duty factor, thereby reducing rotating sound and motor noise while still protecting the motor from overheating.

The patent changes the parameter of duty factor limit value from a static predetermined ratio to a time-varying parameter. The control device modifies the limit value based on elapsed time during overcurrent conditions, transitioning it from a small initial value to a larger target value. This parameter change strategy allows the system to balance motor protection with noise reduction by controlling the rate of duty factor adjustment.

The patent applies dynamics by implementing a time-dependent duty factor limit value that continuously evolves during overcurrent conditions. Instead of switching between fixed small and large duty factor modes, the control device gradually increases the limit value from a small initial value toward a predetermined target value based on elapsed time. This creates a smooth, monotonic transition that prevents repeated switching and the associated mechanical impacts and noise.

The patent uses feedback by continuously monitoring the overcurrent condition and adjusting the duty factor limit value accordingly. The control device detects overcurrent status and uses elapsed time as feedback to determine the appropriate limit value, ensuring the duty factor adjustment progresses smoothly from small to large values rather than oscillating between modes, thereby reducing mechanical impacts and noise.