Abstract: A motor with reduced radial forces includes a first motor part made up of 2P permanent magnet poles surrounding a second motor part formed by a magnetic yoke having a number T of pole teeth and with an air gap between the first and second motor parts. The first and second motor parts are moveable relative to one another. Exciter coils are mounted on the pole teeth and the pole teeth are separated by pole gaps. For a motor with a number 2P magnet poles and a number T of pole teeth which do not have a common submultiple greater than 1, each of the pole teeth have a centrally located auxiliary slot facing the air gap thereby to reduce undesirable radial forces.

Abstract: An electrical actuator for a throttle device has a stator and a rotor, the rotor being coupled to the throttle device and comprising a permanent main magnet. The stator includes in axially extending slots therein auxiliary permanent magnets which interact with the rotor magnet to exert a magnetostatic torque (T.sub.MS) on the rotor which tends to rotate it to a pre-set rest position. The stator also has an energizing coil which when actuated results in an electromagnetic torque (T.sub.EM) on the rotor which is opposed to the magnetostatic torque and causes the rotor to pivot through a limited angle of rotation. The thickness and width of the auxiliary permanent magnets are selected so that the cross-sectional area thereof provides a maximum value of the magnetostatic torque (T.sub.MS) per unit volume thereof, thus minimizing the necessary volume and weight of the auxiliary permanent magnets.

Abstract: An improved spindle motor, particularly for a hard-disc drive, having a stator in the form of a cylindrical coil carried by a mounting plate and a permanent magnet rotor carried on a rotatable hub. At its outer circumference the rotor generates a field perpendicular to the axis of rotation. A bell-shaped portion of the hub surrounds the coil. The hub is supported on the motor shaft by axial and radial hydrodynamic bearings. A soft-iron sleeve-shaped yoke externally surrounds the coil configuration. This permits the coil to be free of soft-magnetic parts, thereby reducing its inductance and improving the dynamic drive characteristics of the motor. The coil is preferably formed by curved foil windings, so there are no winding slots. This avoids the production of detent torques.

Abstract: A magnetic drive arrangement comprising a plurality of magnetically cooperating parts which are moveable relative to one another, one of the parts being connected to a drive shaft and one of the parts being stationary, the fields produced by the permanent magnets being modulated by soft-magnetic flux-carrying parts which include at least one toothed iron yoke, wherein structures are provided on both sides of the iron yoke to generate magnetic fields by means of permanent magnets at the sides facing the iron yoke, with the magnetic fields alternatively exhibiting north poles and south poles along the circumference.

Abstract: A throttle valve in a gas conduit (3), such as for example an intake of an internal-combustion engine, is pivotable from an idling position into operating positions by means of a valve shaft (5), the valve shaft (5) carrying an actuator body formed by a magnetised rotor body (9) which, via an air gap (10), cooperates with pole shoes (15) of a stationary excitation section (11), which is electrically energisable by a pick-up, which pole shoes surround said rotor body externally, the excitation section (11) comprising a U-shaped stator whose limbs (12a, 12b) form the pole shoes (15), which cooperate with the permanent-magnet rotor body (9) at the air gap, in such a manner that the rotor body (9) is subjected to magnetic torques which tend to pull said rotor body into a well-defined rest position, in order to thereby return the throttle valve (4) in a direction opposite to the opening direction into a well-defined rest position in the non-energised condition.

Abstract: An electric motor with permanent-magnet excitation, particularly an internal-rotor or external-rotor motor, having motor parts which are movable relative to one another. One motor part forms a multi-pole excitation field in an air gap by means of permanent magnets and the other motor part comprises a coil configuration situated in the air gap. The coil configuration is free of soft-magnetic material. The permanent-magnetically excited motor part includes a cylindrical yoke having substantially radial slots which are uniformly spaced about the circumference and in which the permanent magnets are mounted. The permanent magnets are magnetized in a circumferential direction with directions of magnetization which change from magnet to magnet.

Abstract: The invention relates to an electric motor with permanent-magnet excitation, particularly inside-rotor and outside-rotor motors, comprising motor sections (10, 20) which are movable relative to one another, of which the first motor section (10) forms a multi-pole excitation field in an air gap (1) by means of permanent magnets (11) and of which the second motor section (20) is a soft-iron yoke (21) having pole teeth (22) which project towards the air gap (1) and which carry excitation coils (23).

Abstract: A brushless d.c. motor having a number of permanent magnetic pole pairs and a number of salient poles wherein the ratio between the number of permanent magnetic pole pairs and the number of salient poles is greater than unity but less than 2:1 and the ratio between the widths of the salient poles and the widths of the permanent magnetic pole pairs is greater than 0.2 but not greater than 1.2.

Abstract: A counter (24) increments several times during the duty cycle of a microprocessor (10), and a comparator (30) connected to both outputs a High signal when the microprocessor output exceeds the counter output and outputs a Low signal when the counter output is at least the microprocessor output. The microprocessor output is proportional to desired motor speed for an elevator door drive motor according to a velocity profile stored in a ROM (18). Thereby, the High:Low ratio of the comparator output is a pulse width modulation signal, which is amplified (34) for the motor (12), at a much higher frequency than the microprocessor duty cycle.