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US 11,894,723 B2Granted
Electric tool
AssigneePanasonic Intellectual Property Management Co., Ltd.
InventorsFumiiki Yoneda, Kenji Hanamura, Masayuki Nakahara
Life of this patent
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Abstract
An electric tool includes an AC motor (an electric motor) and a control unit. The AC motor includes a permanent magnet and a coil. The control unit is configured to perform control on operation of the AC motor. The control performed by the control unit includes field weakening control. In the field weakening control, the control unit causes a flux-weakening current to flow through the coil. The flux-weakening current is a current that generates, in the coil, a magnetic flux that weakens a magnetic flux of the permanent magnet.
Claims6
An electric tool, comprising:
- an electric motor including a permanent magnet and a coil;
- and
- a control unit configured to perform control on operation of the electric motor,
- the control performed by the control unit including field weakening control by which the control unit causes a flux-weakening current to flow through the coil, the flux-weakening current being a current that generates, in the coil, a magnetic flux that weakens a magnetic flux of the permanent magnet
- the control unit having a function of changing a magnitude of the flux-weakening current in the field weakening control,
- the control unit being configured to, when a predetermined increase condition is satisfied, perform gradual-increase control of increasing an absolute value of the flux-weakening current over time in the field weakening control,
- the control unit being configured to, when a predetermined decrease condition is satisfied, perform gradual-decrease control of decreasing the absolute value of the flux-weakening current over time in the field weakening control, the predetermined decrease condition being different from the predetermined increase condition, a rate of change of the flux-weakening current in the gradual-decrease control being less than a rate of change of the flux-weakening current in the gradual-increase control.
4 more elements
Dependencies are inferred from the claim text.