Snap-on Inc.

Christoffer S Fox

Jason Genz

Michael T Rajzer

Daniel Nitzsche

The present invention relates to a method of commutation control of a brushless DC (BLDC) motor. The method uses a controller to control the BLDC motor using a modified six-step commutation. The method adds six intermediate steps that overlap the six-step commutation. Each of the six steps overlap with preceding and following steps, resulting in six additional intermediate steps in which all three phases are active. By doubling the number of steps, current and torque will vary less over time compared with current solutions without increasing the size or changing the design of the motor.

Controlling brushless motor commutation

Overcurrent protection of an electrically powered, motorized device, such as a power tool, wherein the tool includes a tool housing, an output assembly, a trigger, an electrical safety device, a motor, an indicator, a controller, and a power source. The electrical safety device, for example a fuse, is disposed in series with a power connection from the power source to the controller. The controller measures current passing through the electrical safety device in time intervals when the trigger is actuated. The controller determines accumulated thermal energy passing through the electrical safety device, and compares the accumulated thermal energy to a threshold. If the accumulated thermal energy exceeds the threshold, the controller ceases or discontinues to allow power to be provided to the motor from the power source, thereby shutting off the motor. The controller may also activate the indicator to indicate a fault to the user.

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Kenosha, WI, United States of America

Christoffer S Fox