U.S. Philips Corporation

Henricus M Van Hout

Johannes P Bahlmann

Johannes T Van De Veerdonk

Johannes H Janssen

Jan Janson

Catharinus T Galema

Robertus I Van Steen

A device which detects the angle of rotation of a rotor with respect to a stator of a brushless multi-phase d.c. motor. The rotor comprises a permanent magnet and the stator comprises a plurality of electrical windings. Electric drive signals are applied to the windings in order to drive the rotor. The device includes a drive circuit for applying pulse-shaped electric test signals to the windings while the rotor does not rotate. A measurement circuit detects flyback pulses generated by the motor in response to the test signals. A processing unit processes the durations of the detected flyback pulses in combination in order to determine the angle of rotation. On the basis of the angle of rotation thus determined, the motor can be started such that the rotor is set into rotation in a predetermined direction of rotation.

Device for the detection of an angle of rotation of a brushless multi-phase d.c. motor

A motor drive circuit for driving an electromotor having a permanent magnet rotor and a stator comprising one or more stator windings. When the supply voltage of the motor drive circuit fails, an emergency signal is generated by a signal generator. This emergency control signal activates an auxiliary power supply circuit for extracting electric energy from the motor and supplying the extracted energy to an auxiliary circuit. The auxiliary power supply circuit comprises a rectifier circuit formed by the fly back diodes bridging the switches of an electronic commutation circuit. The drive circuit comprises short-circuit switches bridging the stator windings. In response to the emergency control signal a short-circuit apparatus causes the stator windings to be temporarily intermittently short-circuited. As a result, a capacitor is charged. The energy stored in the capacitor is used for temporarily energizing the auxiliary circuit once the power supply to the drive circuit has failed. If the drive circuit is used with a hard disc drive, the energy supplied by the auxiliary power supply circuit can be used for moving the magnetic head to an idle position.

Motor drive circuit with emergency auxiliary power supply energized by

An electrical multipole machine comprises a first machine section (1), a second machine section (3) and a machine shaft (5), about which one machine section is rotatable relative to the other machine section. The first machine section comprises an annular permanent-magnet body (11) having a plurality of adjacent pole pairs (N; S). The second machine section comprises a lamination assembly (25) having teeth (27-35) and coils (37-45). The teeth comprise tooth surfaces (47-55) which are geometrically spaced from one another by slots (57-65) and from the magnet body by an air gap (67). Near the air gap the slots extend in a tangential direction over at least 80 electrical degrees and at the most 90 electrical degrees, or over at least 130 electrical degrees and at the most 150 electrical degrees. The ratio between the number of poles and the number of teeth is either 4:3 or 2:3.

Three-phase electrical machine with reduced cogging torque

A brushless DC motor is self-starting using only one magneto-sensitive element because the motor is of a two-phase type and is provided with a detection device which detects towards which of the two phases the rotor is mainly directed. A presetting circuit compares the detected rotor position with the state of an energizing circuit in order to set this circuit so that the energizing circuit energizes the stator phases for said specific rotor position in such a way that starting of the motor is guaranteed, although initially with an undefined direction of rotation. By presetting the commutating direction of the energizing circuit the rotor subsequently locks onto the field and rotates in the correct direction if it has started in the incorrect direction.

Self-starting brushless D.C. motor

A multi-phase brushless d.c. motor comprises a permanent-magnet rotor (1) and a stator (2) with stator coils (16, . . . , 21) arranged between three power lines (A, B, C). For the purpose of commutation the motor is provided with switching devices (22A, 22B, 22C) for the cyclic disconnection and connection of the power-supply lines (A, B, C) of the motor to a d.c. power source (25). Each switching device (22) comprises a section (42) which is controlled by the rotor-magnet field for deriving the disconnection instants and a section (43) for deriving the connection instants from a voltage change which is produced on the power-supply line connected to the switching device as a result of another power-supply line being disconnected.

Brushless d.c. motor and switching device for use in such a d.c. motor

An electromagnetic drive unit comprises a stator (2) and an armature (4) which is pivotable about a pivotal axis (5) and which cooperates with the stator via an air gap. In order to minimize the volume and to obtain a maximum efficiency, the armature is arranged coaxially around the stator, the stator comprising at least two polepieces (6A) which are interconnected by a stator member (6B) carrying a coil (8). The armature comprises a plurality of radially magnetized poles (28A, 28B) which correspond in number to at least the number of polepieces, which poles are tangentially juxtaposed with alternately opposite polarities.

Growing community of inventors

Eindhoven, Netherlands

Henricus M Van Hout