An apparatus includes a controller. To control current through a motor winding, the controller monitors a magnitude of current supplied through the motor winding. The controller compares the magnitude of current to a threshold value. In response to detecting that the magnitude of current crosses the threshold value, the controller terminates a flow of the current through the motor winding. In one application, termination of the current through the motor winding supports more efficient use of energy to drive the motor winding. For example, via the controller, terminating the current through the motor winding to prevent the current from flowing in a reverse direction through the motor winding.

Electric motors and methods of controlling electric motors are described herein. The electric motors include a mobile component having at least one permanent magnet coupled thereto and a stator spaced apart from the mobile component. The stator includes at least one stator pole having a ferromagnetic core and a coil wrapped around the ferromagnetic core. The ferromagnetic core is naturally attracted to the at least one permanent magnet. The motors also include a magnetic position control system configured to monitor a position of the at least one permanent magnet relative to the stator and controllably deliver an electric pulse to the coil of each stator pole to generate a repulsive magnetic flux on the ferromagnetic core to cancel an attraction force between the ferromagnetic core and the at least one permanent magnet to control movement of the mobile component.

A motor-driving control system includes an actuator configured to generate rotational force by driving received current, a current provider configured to provide current to the actuator while repeatedly turning on and off the current at a preset period and duty, and a controller configured to estimate a rotation position or a rotation speed of the actuator in a section in which the current of the current provider is turned on or off and to control the current provider to follow a speed command based on the estimated rotation position or rotation speed.

A motor-driving control system includes an actuator configured to generate rotational force by driving received current, a current provider configured to provide current to the actuator while repeatedly turning on and off the current at a preset period and duty, and a controller configured to estimate a rotation position or a rotation speed of the actuator in a section in which the current of the current provider is turned on or off and to control the current provider to follow a speed command based on the estimated rotation position or rotation speed.

Selectable current limiting for a power tool. One embodiment provides a method for selectable current limiting for a power tool including determining, using a current sensor, an average current and determining whether the average current exceeds a predetermined current threshold. The method also includes determining a deviation of the average current from the predetermined current threshold and reducing a PWM duty ratio proportional to the deviation of the average current from the predetermined current threshold. The PWM duty ratio corresponds to a PWM signal provided to an inverter bridge.

An apparatus for controlling an AC power supply for an electric motor, said AC power supply being derived from a DC voltage. The apparatus including a comparer configured to provide a comparison of a modulation index of a motor control signal with a reference value. This current data provider is configured to provide current data based on a torque demand signal; a speed signal indicating the speed of rotation of the AC motor; and an indication of the DC voltage modified on the comparison for control of the motor control signal which is based on the motor current data.

An apparatus for controlling an AC power supply for an electric motor, said AC power supply being derived from a DC voltage. The apparatus including a comparer configured to provide a comparison of a modulation index of a motor control signal with a reference value. This current data provider is configured to provide current data based on a torque demand signal; a speed signal indicating the speed of rotation of the AC motor; and an indication of the DC voltage modified on the comparison for control of the motor control signal which is based on the motor current data.

A wastegate actuator includes a direct-current motor, a shaft for opening and closing a wastegate valve of a turbocharger, and a screw mechanism for converting a rotary motion of the direct-current motor into a linear motion of the shaft, and the screw mechanism has a lead angle in accordance with a current of the direct-current motor that is required to hold the shaft at a position.

A wastegate actuator includes a direct-current motor, a shaft for opening and closing a wastegate valve of a turbocharger, and a screw mechanism for converting a rotary motion of the direct-current motor into a linear motion of the shaft, and the screw mechanism has a lead angle in accordance with a current of the direct-current motor that is required to hold the shaft at a position.

A system is provided with a set of removable battery packs and a set of power tools each including a motor, a controller, and a battery receiving portion. For each power tool, the controller is configured to identify a type of battery pack coupled to the battery receiving portion and limit a maximum amount of electric current drawn from the battery pack by the motor based on the identified type of the battery pack. The greater a ratio of an impedance of the motor to an impedance of the battery pack, the less the controller limits the maximum amount of electric current drawn from the battery pack such that for a given battery pack of the set of removable battery packs, the lower the impedance of the motor, the more current the motor draws from the given battery pack.