Abstract: A circuit includes a first half bridge including a first controllable semiconductor switch and a first diode. The first controllable semiconductor switch is coupled between a first constant supply potential and a center tap of the first half bridge. The first diode is coupled between the center tap and a constant reference potential. A second half bridge includes a second diode and a second controllable semiconductor switch. The second diode is coupled between a second constant potential higher than the first potential and a center tap of the second half bridge. The second controllable semiconductor switch is coupled between the center tap and the constant reference potential. Driver circuitry controls the conducting state of the first and the second semiconductor switch thus controlling the current flow through a field connectable between the center taps.

Abstract: The invention relates to an electrical drive having a motor with a rotor and a stationary stator, which has a coil arrangement, and having a motor controller for controlling the motor, with the motor controller being configured to pass current through the coil arrangement in order to produce an excitation field, with the coil arrangement having a plurality of coil winding sections, and with each coil winding section having a plurality of coil sections, wherein the polarity of at least one coil section of the plurality of coil sections of each coil winding section can be selectively reversed with respect to the other coil sections of the coil winding section. The drive is particularly suitable for use for an electrical tool.

Abstract: A hard disk drive having a plurality of disks mounted on the rotor of a current limited, electronically commutated dc motor. Windings on the stator of the motor are divided into serially connected run and start sections and first and seconds drive circuits are provided to operate the motor by alternatively enabling the first drive circuit to pass currents serially through the two sections of the winding and enabling the second drive circuit to pass currents through only the run sections of the windings. During spin up of the disk drive to operating speed, the first drive circuit is enabled and the second drive circuit is disabled to drive the disks to the speed at which the back emf limits on the acceleration of the motor using both sections of the windings reduces the acceleration to the maximum acceleration achievable at the current limit using the run sections alone. Spin up is then completed by enabling the second drive circuit and disabling the first drive circuit.

Abstract: Method and apparatus for controlling the output frequency of an alternator by maintaining a relatively constant speed of rotation of the alternator rotor are disclosed. The rotor includes an annular stator and a rotor rotatably mounted within. In one embodiment the stator winding is comprised of a plurality of discrete polyphase windings positioned within discrete annular segments of the stator. When the actual rotor speed is below the desired speed, selected stator units are de-energized to decrease the strength of the stator magnetic field, thereby permitting the rotor speed to increase. When the actual rotor speed is greater than the desired speed, selected stator units are energized to increase the strength of the stator magnetic field, thereby exerting a braking force on the rotor to slow it down. In another embodiment each phase of the polyphase stator winding includes a plurality of inductor coils.

Abstract: An electric work vehicle with a battery powered traction motor and pump motor is provided with an auxiliary power supply for a load circuit requiring voltage lower than that of the battery. The pump motor is provided with an auxiliary brush at a location between a pair of motor brushes and the auxiliary load circuit is connected between the auxiliary brush and one of the motor brushes. The auxiliary brush is positioned relative to the motor brush so that it supplies the voltage required by the auxiliary load circuit.

Abstract: The invention provides an electrical machine having an inductor and an armature at least one of which has at least two independent winding assemblies. The switching into and out of circuit of each winding assembly is controlled by a processor which receives monitoring parameters of the machine and desired value parameters, thereby controlling in real time the operating characteristics of the machine. The machine may be a wind-driven generator.