Abstract: A vacuum generating apparatus for a vacuum cleaner is provided, in which an axial type coreless brushless direct-current (DC) motor is implemented in the form of a rotor-impeller integration structure. The vacuum generating apparatus includes an axial type brushless DC motor in which disc-shaped upper and lower rotors are symmetrically disposed facing the upper and lower portions of a disc-shaped stator at either end of a rotating shaft rotatably supported in the inner circumferential portion of the stator, upper and lower impellers integrally fixed in the upper and lower rotors, respectively, and upper and lower housings whose outer circumferential portions are combined with the outer circumferential portions of the respective disc-shaped stator such that air sucked via sucking inlets formed at the center of the housings is guided to a discharging outlet together with the stator. A single rotor structure can also be adopted.

Abstract: A stator assembly operated in a 2-phase drive manner including first and second stator coils wound in a star shape with a plurality of projections and a plurality of grooves, and arranged with a predetermined phase difference; and an annular supporting body into which the first and second stator coils are inserted for supporting the coils, insulating them from each other. Each stator coil includes four projections and four grooves, and there is a phase difference .theta. between the first and second stator coils, the difference determined by the following equation: .theta.=360/2P.+-.360/P, wherein P denotes the number of a rotor's magnetic poles.

Abstract: A two-phase brushless direct-current (BLDC) motor having a single Hall effect device. The BLDC motor includes a stator comprised of 2n coils grouping as first and second phase coils at a uniform interval, and a rotor which N-pole and S-pole magnets of the same number as that of the stator coils are alternately disposed, the 2n magnets forming n pairs, each pair of magnets are disposed at a uniform interval, wherein a distant ratio from the center of one N-pole magnet to the centers of the S-pole magnets adjacent the N-pole magnet is established into 1:1.4. Since 2n auxiliary magnets are disposed annularly on the rotor with the same length as each other corresponding to the N-pole and S-pole magnets, a single Hall effect device detects the magnetic pole by magnetic flux of the rotating auxiliary magnets and generates the rotating position signal of the rotor, so that a switching controller can activate the first and second phase coils alternately.

Abstract: A double rotor-type brushless direct-current motor includes first and second annular-shaped rotors each having a plurality of north and south-polar magnets which are alternately disposed at a predetermined distance; a rotating shaft connected to a central portion of the rotors thorough a bushing; upper and lower cases receiving and rotatably supporting opposite ends of the rotating shaft; an annular-shaped stator having a plurality of stator coils supported by a molding filler to apply electromagnetic force to the first and second rotors in an opposite direction to each other, the stator being mounted between the first and second rotors at a predetermined clearance; and a control printed circuit board for applying a driving current with respect to the stator, the control printed circuit board being mounted one of the upper and lower cases; wherein the upper and lower cases, the control printed circuit board, the first and second rotors have a plurality of ventilating holes for circulating air from the outer s

Abstract: A dielectric ceramic composition for microwave applications consists essentially of the compound having a formula B'B.sub.2 "O.sub.6, wherein B' is at least one metal selected from the group of Mg, Ca, Co, Mn,Ni and Zn, and wherein B" is one of Nb or Ta, and additionally includes at least one compound selected from the group of CuO, V.sub.2 O.sub.5, La.sub.2 O.sub.3, Sb.sub.2 O.sub.5, WO.sub.3, MnCO.sub.3, MgO, SrCO.sub.3, ZNO, and Bi.sub.2 O.sub.3 as an additive, wherein the amount of the additive is 0.05% to 2.0% by weight of the total weight of the composition.