Motor current sensing in electric power tools
AssigneeDefond Manufacturing Limited
InventorRaymond Wai Hang Chu
Life of this patent
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Abstract
A device for sensing motor current for over-current protection in an electric power tool. The tool includes an electric motor supplied with electrical power via a live cable and incorporates over-current protection including a tripping circuit with a current sensor associated with the live cable. The device includes a toroid of the sensor and two cable segments connected in parallel to a section of the live cable such that the motor current will be distributed among the cable segments and live cable section in respective proportions. The toroid extends around one cable segment for sensing the respective proportion of the motor current.
Claims14
In an electrical power tool comprising an electrical motor supplied with electrical power via a live cable, over-current protection including a tripping circuit comprising:
- a current sensor associated with the live cable,
- a device for sensing the motor current for over-current protection, which comprises a part of the current sensor and
- at least one cable segment having opposite ends connected in parallel to a section of the live cable across two junctions such that the motor current will be distributed between the cable segment and the section of the live cable in respective proportions, wherein the sensor part extends around one of the cable segment and the section of the live cable for sensing the respective proportion of the motor current.
In an electrical power tool comprising an electrical motor supplied with electrical power via a live cable, over-current protection including a tripping circuit comprising a current sensor associated with the live cable, a method of sensing the motor current for over-current protection, comprising:
- providing at least one cable segment having opposite ends,
- connecting the cable segment at opposite ends in parallel to a section of the live cable across two junctions such that the motor current will be distributed between the cable segment and the section of the live cable in respective proportions, and
- arranging a part of the sensor to extend around one of the cable segment and the section of the live cable for sensing the respective proportion of the motor current.
Dependencies are inferred from the claim text.