Abstract: An electric tool including a motor configured to be driven by a PWM control of a semiconductor switching element by using a power supply, a power transmission mechanism configured to transmit a rotation of the motor to an end tool, and a controller configured to control a rotation of the motor by a duty ratio of a PWM signal, wherein the controller is configured to set the duty ratio to a reference duty ratio less than 100% when a voltage of the power supply applied to the electric tool is within a predetermined range including a rated voltage of the electric tool, and wherein the controller is configured to drive the motor by setting the duty ratio to be higher than the reference duty ratio when the voltage of the power supply applied to the electric tool is lower than the predetermined range.

Abstract: The invention relates to an electric device (1) comprising an alternating current electric motor (3) and a control inverter (5) for controlling the phase or phases of the motor (3). The motor (3) comprises, on at least one winding of at least one phase (PA, PB, PC), a point (Ma, Mb, Mc) for measuring a voltage relative to a predefined potential (M), the measurement point (Ma, Mb, Mc) being chosen so that it divides the winding into a first (Za1; Zb1; Zc1) and a second (Za2; Zb2; Zc2) portion such that the electromotive forces (ea1, ea2) induced in the two portions are phase-shifted relative to one another and means (11A; 11B; 11C) for measuring the voltage between the measurement point and the predefined potential. The invention also relates to an associated method for measuring electromotive forces.

Abstract: The present invention relates to a power-wrench comprising an electrical converter-fed motor having a permanent-magnetized rotor and a stator provided with winding, the motor winding (1) comprising at least two winding parts, which independently of each other are connected and disconnected by a switch-over device (4). According to the invention, a first winding part (2) may be arranged to control the magnetic field of the motor so that the motor, having the first winding part (2) connected, is adapted for the threading-down phase of the nut driving and operates with low torque and high number of revolutions adapted to said phase, as well as that a second winding part (3) may be arranged to control the magnetic field of the motor so that the motor, having the second winding part (3) connected, is adapted for the final-threading phase of the nut driving and operates with high torque and low number of revolutions adapted to said phase.

Abstract: An apparatus and method of powering a light source are provided. The apparatus includes a motor, a voltage stabilizing circuit, and a light source. The motor includes a field assembly and an armature assembly. The field assembly includes an intermediate tap on a field winding that forms a variable field winding power source. The stabilizing circuit connects to the intermediate tap and includes a voltage regulator having an output that is connected to a light source to be stabilized.

Abstract: An alternating current induction motor having a multitapped RUN winding and including a controller which automatically determines an instant tap selection in response to changes in applied a.c. electric power voltage level appearing immediately at the motor terminals. A measure of instant level of the motor terminal voltage is utilized to automatically reselect the RUN winding tap selection in order to maintain a near constant level of magnetic excitation in the stator field irrespective of immediate changes or variations in the available motor terminal voltage. Electric lawn mowers, power tool motors and other heavily loaded motors which may normally be operated at the end of various lengths of especially long and lossy extension cords or the like may advantageously utilize my control technique to maintain operation with an about normal and constant level of power, independent from usual performance degrading voltage drop losses commonly encountered in the extension cord.

Abstract: A switch device is mounted between the power supply and a multi-tap series field winding in a series or compound motor. The switch is responsive to changes in rotational speed or load current in order to change the effective excitation turn ratio of the series winding.

Abstract: A wiper apparatus using a three brush, permanent magnet motor in which a zener diode has a cathode connected to the low speed brush and an anode connected to the high speed brush. The zener breakdown voltage of the zener diode is chosen so that it reverse conducts during at least some portion of each wipe cycle during operation with the high speed brush on a wet window to limit peak wiper speeds and reduce strain on the wiper mechanism. Variations including a transistor, relay or additional zener diode controlled by the zener diode and connected in parallel therewith provide for reduced current and therefore power dissipation in the zener diode at the expense of somewhat limited speed limiting.