A method for starting a sensorless single-phase electric motor. The electric motor includes a permanent magnetic motor rotor, an electromagnetic motor stator having a stator coil, a power electronics which energizes the stator coil, a current sensor which measures a current flowing in the stator coil, and a control electronics which controls the power electronics. The control electronics is connected with the current sensor. The method includes energizing the stator coil with an alternating drive voltage, monitoring a drive current which is generated in the stator coil by the alternating drive voltage, and commutating the alternating drive voltage whenever the drive current reaches a predefined positive current threshold value or a predefined negative current threshold value.

One example is a system for controlling a motor during startup. The system includes measurement logic, pattern detection logic, and mode logic. The measurement logic monitors a back-electromotive force (BEMF) signal representing a BEMF of an electric motor and the pattern detection logic monitors this signal to detect instances of the monitored BEMF signal exhibiting a predetermined pattern. The mode logic enables control of the electric motor according to a plurality of modes of control. In some examples, the mode logic initially employs a first mode of control and switches from the first mode of control to a second mode of control in response to the pattern detection logic detecting that a BEMF signal exhibits the predetermined pattern over a plurality of commutation states.

One example is a system for controlling a motor during startup. The system includes measurement logic, pattern detection logic, and mode logic. The measurement logic monitors a back-electromotive force (BEMF) signal representing a BEMF of an electric motor and the pattern detection logic monitors this signal to detect instances of the monitored BEMF signal exhibiting a predetermined pattern. The mode logic enables control of the electric motor according to a plurality of modes of control. In some examples, the mode logic initially employs a first mode of control and switches from the first mode of control to a second mode of control in response to the pattern detection logic detecting that a BEMF signal exhibits the predetermined pattern over a plurality of commutation states.

A power tool is provided including a housing, a brushless motor disposed within the housing, a power switch circuit that supplies power from a power source to the brushless motor, and a controller configured to apply a drive signal to the power switch circuit to control the supply of power to the brushless motor. The controller is configured to receive at least one signal associated with a phase current of the motor, detect an angular position of the rotor based on the phase current of the motor within a variable speed range of zero to at least 15,000 rotations-per-minute (RPM), and control the drive signal based on the detected angular position of the rotor to electronically commutate the motor within a power output of zero to at least 1500 watts.

A method for starting a permanent magnet synchronous electric motor comprising a rotor and a stator comprising coils connected respectively to a plurality of phases and a conversion circuit connecting the plurality of phases to a power supply source in order to control the rotation of the rotor of the synchronous motor, the conversion circuit comprising a converter supplying power to a DC-AC converter comprising a plurality of controllable transistors for controlling the rotation of the rotor according to a plurality of successive control phases, the method comprising: ∘ a step of controlling the transistors of the DC-AC converter according to a control table associating each control phase with a configuration of the transistors so as to determine an acceleration ramp of the rotor of the motor, ∘ a step of determining an electrical angle A based on a predetermined acceleration ACC, and ∘ a step of determining a control phase change signal Q if the electrical angle A is greater than a predetermined threshold angle A.sub.seuil.

A power tool is provided including a housing, a brushless motor disposed within the housing, a power switch circuit that supplies power from a power source to the brushless motor, and a controller configured to receive at least one signal associated with a phase current of the motor, detect an angular position of the rotor based on the phase current of the motor, and apply a drive signal to the power switch circuit to control a commutation of the motor based on the detected angular position of the rotor. The controller detects an initial sector within which the rotor is located at start-up, apply the drive signal so as to rotate the motor to a parking angle associated with the detected initial sector, and control a commutation sequence to drive the motor beginning at the parking angle.

A motor controller includes a temperature sensor configured to detect a temperature of a motor. An intermittent operation circuit allows the motor to intermittently operate at a rotation speed up to a phase before the motor reaches a rated rotation speed when it is detected that the motor temperature is at a low temperature range. The intermittent operation circuit includes a position fixing circuit configured to allow a constant electric current to flow through stator coils and to fix the motor in a stopped state. The intermittent operation circuit further includes a forced commutation circuit that allows the motor to rotate at a rotation speed up to the start-up rotation. The position fixing circuit allows the constant electric current to have a greater value as the temperature detected by the temperature sensor is lower, and allows the position fixing circuit and the forced commutation circuit to operate alternately.

A rotor (1) for an electric machine (2) has a rotor body including multiple poles. The rotor (1) further has at least one sensor element (3) for detecting at least one condition variable of the rotor (1), and a signal processing unit (4) connected to the at least one sensor element (3). The signal processing unit (4) is configured to generate measured data from the condition variable of the rotor (1) and to transmit the measured data to a control device (5). Additionally, the rotor (1) has at least one induction coil (7), where each of the at least one induction coil (7) includes at least one electrical conductor (8). The at least one induction coil (7) is arranged at the rotor (1) and is configured to generate electrical energy from a magnetic field that is temporally changing during operation of the electric machine (2).

A rotor (1) for an electric machine (2) has a rotor body including multiple poles. The rotor (1) further has at least one sensor element (3) for detecting at least one condition variable of the rotor (1), and a signal processing unit (4) connected to the at least one sensor element (3). The signal processing unit (4) is configured to generate measured data from the condition variable of the rotor (1) and to transmit the measured data to a control device (5). Additionally, the rotor (1) has at least one induction coil (7), where each of the at least one induction coil (7) includes at least one electrical conductor (8). The at least one induction coil (7) is arranged at the rotor (1) and is configured to generate electrical energy from a magnetic field that is temporally changing during operation of the electric machine (2).

A rotor (1) for an electric machine (2) includes a rotor body with multiple poles. Multiple flux barriers (6.1, 6.2, 6.3, 6.4) are formed in the interior of the rotor body. The rotor (1) further includes at least one sensor element (3) configured for detecting at least one condition variable of the rotor (1), a signal processing unit (4) connected to the at least one sensor element (3) and configured for generating measured data from the detected condition variable of the rotor (1) and transmitting the measured data to a control device (5), and at least one induction coil (7) that includes at least one electrical conductor (8), is arranged in at least one flux barrier (6.1) of the rotor (1), and is configured for generating electrical energy from a leakage magnetic field in this flux barrier (6.1).