Abstract: A rotating electric machine for a compressor includes a case, a plurality of teeth, coils and insulating films. The teeth are circumferentially arranged around a predetermined axis forming a center of the teeth. Each tooth has a first end disposed radially at an opposite side thereof from the predetermined axis. The a back yoke has a circular outer periphery, and a cylindrical inner periphery connecting the first ends of the teeth. The outer periphery has a plurality of concave parts opening radially inwardly toward the teeth at positions overlapping with the teeth as viewed radially. A minimum distance measured from an exposure surface of each tooth to the concave part overlapping therewith is smaller than a radial width of the back yoke at a portion where the concave parts are not provided. The exposure surfaces extend radially inwardly of the inner periphery.

Abstract: A rotary compressor includes a compression mechanism, an electric motor and a controller. The compression mechanism includes a piston and a cylinder having two cylinder chambers. The electric motor is configured to change volumes of the cylinder chambers by eccentrically moving the cylinder and the piston relative to each other. The controller is configured to change an output torque of the electric motor in accordance with a variation in a load torque of the compression mechanism in one turn of rotation.

Abstract: It is an object of the present invention to provide techniques for improving efficiency and torque of a motor while achieving thinning of the motor. In a brushless DC motor, a rotor includes a magnetic-field creating magnet and a stator includes an armature winding. The magnetic-field creating magnet and the armature winding are placed to locally face in a radial direction orthogonal to an axial direction. This reduces a thickness of the brushless DC motor which extends in the axial direction. Also, a short-circuit yoke plate for joining and magnetically short-circuiting the north pole and the south pole of a permanent magnet is placed on a negative side in the axial direction with respect to the magnetic-field creating magnet. By provision of the short-circuit yoke plate, a magnetic path on a negative side in the axial direction with respect to the magnetic-field creating magnet can be shortened.

Abstract: A motor has a rotor core with a plurality of first non-magnetic layers and a plurality of second non-magnetic layers. The rotor core has a plurality of magnets. The first and second non-magnetic layers are positioned to cancel n-th order harmonics. Therefore, a specific order, for example 5-th order and 7-th order, harmonics component of a magnetic flux distribution waveform (induction voltage waveform) is reduced and unnecessary radial force and thrust force is prevented from occurrence, while sufficient magnetic flux is maintained.

Abstract: A motor includes a rotor core, permanent magnets and non-magnetic layers. The permanent magnets are embedded in the rotor core with each of the permanent magnets defining a pole of the rotor having a pole center and a peripheral edge section, with the peripheral edge section located in a vicinity between the poles and a vicinity of the rotor surface. The non-magnetic layers are located in a vicinity of the rotor surface at a pole center side position with respect to the peripheral edge section of each of the permanent magnets. The peripheral edge sections and the non-magnetic layers are positioned to cancel 5-th or 7-th order harmonics of an induction voltage. The poles are disposed at every approximately constant interval, varying in a constant angle. The peripheral edge sections and the non-magnetic layers are independent from one another, and the rotor core is interposed between them.

Abstract: A first non-magnetic portion, a second non-magnetic portion, and a third non-magnetic portion are arranged around an axis, from an end toward the center of a permanent magnet burying hole. A fourth non-magnetic portion is further provided between the second non-magnetic portion and the third non-magnetic portion. Angles around the axis are determined as follows with reference to a position between permanent magnet burying holes. The position between the first non-magnetic portion and the second non-magnetic portion is expressed by a first angle. The position between the third non-magnetic portion and the fourth non-magnetic portion is expressed by a second angle, and the second angle is twice the first angle. The end of the third non-magnetic portion located closer to the pole center is expressed by a third angle.

Abstract: It is an object of the present invention to provide techniques for improving efficiency and torque of a motor while achieving thinning of the motor. In a brushless DC motor, a rotor includes a magnetic-field creating magnet and a stator includes an armature winding. The magnetic-field creating magnet and the armature winding are placed to locally face in a radial direction orthogonal to an axial direction. This reduces a thickness of the brushless DC motor which extends in the axial direction. Also, a short-circuit yoke plate for joining and magnetically short-circuiting the north pole and the south pole of a permanent magnet is placed on a negative side in the axial direction with respect to the magnetic-field creating magnet. By provision of the short-circuit yoke plate, a magnetic path on a negative side in the axial direction with respect to the magnetic-field creating magnet can be shortened.

Abstract: A motor has a rotor core with a plurality of first non-magnetic layers and a plurality of second non-magnetic layers. The rotor core has a plurality of magnets. The first and second non-magnetic layers are positioned to cancel n-th order harmonics. Therefore, a specific order, for example 5-th order and 7-th order, harmonics component of a magnetic flux distribution waveform (induction voltage waveform) is reduced and unnecessary radial force and thrust force is prevented from occurrence, while sufficient magnetic flux is maintained.

Abstract: For the purpose of preventing demagnetization of a magnet (32) without any cost increase and improving the max torque and the efficiency of an electric motor (20) by suppressing deterioration of magnetic flux density, a permanent magnet-type electric motor (20) comprises a stator (21) and a rotor (25) disposed in the stator (21), in which a plurality of permanent magnets (32), (32) forming a magnetic pole are inserted in magnet insertion portions (31), (31) of a yoke (26) in such manner that the magnets (32), (32) form in line in the circumferential direction thereof, wherein each magnet (32) is divided into a central magnet (33) that is positioned at the central portion in the width direction of the magnet insertion portion (31) and end magnets (34), (34) that are positioned at end portions of the magnet insertion portion (31), and the end magnets (34), (34) have greater coercive forces than the central magnet (33), whereas the central magnet (33) has a greater magnetic flux density than the end magnets (34)

Abstract: For the purpose of preventing demagnetization of a magnet (32) without any cost increase and improving the max torque and the efficiency of an electric motor (20) by suppressing deterioration of magnetic flux density, a permanent magnet-type electric motor (20) comprises a stator (21) and a rotor (25) disposed in the stator (21), in which a plurality of permanent magnets (32), (32) forming a magnetic pole are inserted in magnet insertion portions (31), (31) of a yoke (26) in such manner that the magnets (32), (32) form in line in the circumferential direction thereof, wherein each magnet (32) is divided into a central magnet (33) that is positioned at the central portion in the width direction of the magnet insertion portion (31) and end magnets (34), (34) that are positioned at end portions of the magnet insertion portion (31), and the end magnets (34), (34) have greater coercive forces than the central magnet (33), whereas the central magnet (33) has a greater magnetic flux density than the end magnets (34)

Abstract: Permanent magnet housing spaces 3b and spaces 3c for flux barrier are formed within a rotor 3. A minimum value of a distance from a portion on a boundary face of the permanent magnet housing space in a rotor surface side which portion corresponds to an edge section of a permanent magnet 4 in its width direction to boundary faces of the both spaces in a rotation shaft side of the rotor 3 is determined to be greater than a distance of the permanent magnet housing space 3b in the thickness direction at an edge section of the permanent magnet 4 in its width direction, so that initial performance is maintained by preventing demagnetization of the permanent magnet due to a negative magnetic field from occurring. Thus a decrease in the cost of a brushless DC motor is realized by decreasing the volume of the permanent magnet.

Abstract: In a brushless DC motor system, an RMS value of an input current of a voltage-fed inverter (702) is detected by a current transformer (705) and an RMS value detector circuit (706). A rotation speed of a brushless DC motor (703) is detected based on a cycle of a position signal outputted by a position sensor circuit (704). Then, in response to the RMS value of the input current and the rotation speed, the phase of the inverter output voltage relative to the phase of the motor counter-electromotive voltage is set to a phase at which the motor efficiency comes generally to a peak, and a switching command to the voltage-fed inverter (702) is generated. With this constitution, when the applied voltage waveform is controlled only by the voltage-fed inverter in response to the rotor-position detection signal, the motor attains high-efficiency operation without involving any increase in cost and yet regardless of load conditions.