Abstract: An electrical motor comprises a stator 1 and a rotor 2, the stator 1 having poles 3 facing circumferential surfaces of the rotor 2 so that the stator 1 forms a magnetic circuit with the rotor 2. The stator 1 further has stator windings 5 grouped into two or more phase windings A, B, which phase windings are separately energisable to induce stator magnetic fields which interact with magnetic fields associated with the rotor 2. A voltage across a stator phase winding is detected by voltage detecting means.

Abstract: An electrical machine comprises a rotor without windings, a stator having an armature winding 24, 25 and a field winding 10 for generating a magnetomotive force in a direction extending transversely of the magnetomotive force generated by the armature winding. An electronic circuit 40 is provided for controlling the current in the armature winding 24, 25 such that periods in which a magnetomotive force in one direction is associated with a first current pulse alternate with periods in which a magnetomotive force in the opposite direction is associated with a second current pulse. A position sensor is provided for monitoring the rotational position of the rotor and for supplying output signals at a rate dependent on the speed of rotation of the rotor. Furthermore a control system supplies control signals to the circuit 40 to control the current in the armature winding 24, 25 in response to the output signals.

Abstract: An electrical machine comprises a rotor without windings, a stator having an armature winding 24, 25 and a field winding 10 for generating a magnetomotive force in a direction extending transversely of the magnetomotive force generated by the armature winding. An electronic circuit 40 is provided for controlling the current in the armature winding 24, 25 such that periods in which a magnetomotive force in one direction is associated with a first current pulse alternate with periods in which a magnetomotive force in the opposite direction is associated with a second current pulse. A position sensor is provided for monitoring the rotational position of the rotor and for supplying output signals dependent on the speed of rotation of the rotor. Furthermore a control system 32 supplies control signals to the circuit 40 to control the current in the armature winding 24, 25.

Abstract: An electrical machine comprises a rotor without windings, a stator having an armature winding (24,25) and a field winding (10) for generating a magnetomotive force in a direction extending transversely of the magnetomotive force generated by the armature winding. An electric circuit (40) is provided for controlling the current in the armature winding (24, 25) such that periods in which a magnetomotive force in one direction is associated with a first current pulse alternate with periods in which a magnetomotive force in the opposite direction is associated with a second current pulse. A position sensor is provided for monitoring the rotational position of the rotor and for supplying output signals dependent on the speed of rotation of the moor.

Abstract: An electrical machine comprises a rotor without windings, a stator having an armature winding 24, 25 and a field winding 10 for generating a magnetomotive force in a direction extending transversely of the magnetomotive force generated by the armature winding. An electronic circuit 40 is provided for controlling the current in the armature winding 24, 25 such that periods in which a magnetomotive force in one direction is associated with a first current pulse alternate with periods in which a magnetomotive force in the opposite direction is associated with a second current pulse. A position sensor is provided for monitoring the rotational position of the rotor and for supplying output signals at a rate dependent on the speed of rotation of the rotor. Furthermore a control system supplies control signals to the circuit 40 to control the current in the armature winding 24, 25 in response to the output signals.

Abstract: An electrical motor comprises a stator 1 and a rotor 2, the stator 1 having poles 3 facing circumferential surfaces of the rotor 2 so that the stator 1 forms a magnetic circuit with the rotor 2. The stator 1 further has stator windings 5 grouped into two or more phase windings A, B, which phase windings are separately energisable to induce stator magnetic fields which interact with magnetic fields associated with the rotor 2. A voltage across a stator phase winding is detected by voltage detecting means.

Abstract: A two-phase switched reluctance motor comprises a rotor without windings, a stator having windings, and an electronic control circuit for controlling the current in the windings to effect rotation of the rotor. The control circuit includes a capacitance bridge defining a floating point to which one end of each of the windings is coupled to form a resonance circuit. Switching transistors are connected to the windings and are switched in synchronism with rotation of the rotor so as to produce current pulses which are limited by the build-up of voltage at the floating point of the capacitance bridge. This ensures that the current in the windings returns naturally to zero at the end of each excitation pulse, thus providing more efficient power operation and reducing the acoustic noise of the machine.

Abstract: An electrical machine comprises a four-pole stator 2 provided with a field winding 10 and an armature winding 11, each of the windings 10, 11 being split into two coils 22, 23 or 24, 25 closely coupled and wound so that diametrically opposite portions of both coils are disposed within diametrically opposite stator slots. A two-pole rotor (not shown) without windings is rotatable within the stator 2, and a circuit is provided for energising the armature coils 24 and 25 when direct current is supplied to terminals 26 and 27 of the circuit. Switches 28 and 29 in series with the coils 24 and 25 are switched alternately to effect alternate energisation of the coils 24 and 25 so as to generate, as a result of the opposite winding of the coils, magnetomotive forces in opposite directions.

Abstract: A switched reluctance electrical machine system including a switched reluctance machine, a rechargeable DC energy store and principle voltage terminals connectable to an external power source. The switched reluctance machine comprises a rotor, a stator and windings wherein the windings include at least two closely-coupled coils and a power converter for controlling current flow in the windings. The power converter has first and second circuits. The first circuit contains one of the closely-coupled coils and the principle voltage terminals while the second circuit contains the other of the closely-coupled coils and the energy store. A first switching arrangement is connected in series with the coils in the first circuit and a second switching arrangement is connected in series with the coils in the second circuit.

Abstract: A method of driving an electric motor having at least one coil winding comprising using a switching operation when the current in the winding is to be switched from a first state to a second state. The switching operation has at least first and second switching steps, the interval between which is approximately equal to half the period of a dominant frequency of vibration of the motor (or to an integral multiple of the period plus a half). This reduces vibrations causing acoustic noise, enabling the motor to be operated more quietly. One or more intermediate steps may be included in the switching operation.

Abstract: An apparatus for programmed audio annotation comprises a user's computer system having a display and a modem associated therewith, and a host computer system having an audio synthesizer unit and a memory unit associated therewith. The modem of the user's system and the audio synthesizer unit of the host system are coupled telephonically. An application program is executed on the user's computer system. The application program generates a sequence of screens for display to the user. Associated with each such screen is a digital word that is provided as part of a command to the modem. In response to such command, the modem transmits a dual tone multiple frequency (DTMF) signal which is received by the audio synthesizer unit of the host computer system. The memory unit of the host computer system contains digitized audio data corresponding to audio messages associated with each of the display screens of the application program.

Abstract: An occasional chair is provided with two Z-shaped sides, two cross-members, and a seat comprising a rim and a mesh. The mesh allows for ventilation and the Z-shaped sides make the chair flexible. A plurality of these chairs can be stacked for easy storage.