Mitsubishi Denki Kabushiki Kaisha

Tomohiro Kikuchi

Shinichi Yamaguchi

Takashi Miyazaki

Haruyuki Kometani

Masatsugu Nakano

Moriyuki Hazeyama

Hideaki Arita

Takashi Yoshioka

Yukari Toide

Katsumi Hayami

Akihiro Daikoku

Takashi Tamura

Akhiro Daikoku

Chiyo Fujino

In a combination of, for example, a rotor having eight magnetic poles and a stator having twelve slots and pulsating components of permeance, which generate a sinusoidal cogging torque having maxima of the same number as the number of poles of the rotor, pressurizing parts arranged in predetermined positions, applying a force at an outer periphery of the stator and directed inwardly cancels the pulsating components of the cogging torque.

Method of manufacturing permanent-magnet synchronous motor

A permanent magnet motorincludes a rotor in which permanent magnetsare fixed. In the rotorthe outer peripheral shape of rotor magnetic-pole portionsis formed so that, in the circumferentially central portion, the distance from the center of the rotor iron coreis longest, and, at the inter-polar space, the distance from the center of the rotor iron core is shortest, and so that the outermost surface of the rotor magnetic-pole portionsforms an arc, and given that sheath thickness tc formed by the outer-side surface of each permanent magnetand the outermost surface of each rotor magnetic-pole portionis practically constant, and letting the thickness of the permanent magnets be the magnet thickness tm, then the relation tc/tm&#x2266;0.25 is satisfied.

Permanent magnet motor

In a combination of, for example, a rotor having eight magnetic poles and a stator having twelve slots and pulsating components of permeance, which generate a sinusoidal cogging torque having maxima of the same number as the number of poles of the rotor, pressurizing parts arranged in predetermined positions applying a force at an outer periphery of the stator directed inwardly to cancel the pulsating components of the cogging torque.

Permanent-magnet synchronous motor

A rotary electric machine includes a frame; a stator whose stator-slot number Ns is 12; a rotor whose rotor-pole number Np is 8, the rotor being disposed inside the stator. The frame has a frame thickness T(&#x3b8;) at mechanical angle &#x3b8;, with respect to a reference line that connects the inner circumferential center of the frame with an arbitrary point, other than the center, around the center that is circularly expanded in a Fourier series. The difference between the stator-slot number Ns and the rotor-pole number Np is k (=|Ns&#x2212;Np|). Stress-relieving spaces and are located in portions of the frame in an arrangement that does not have 90-degree mechanical angle rotational symmetry, in such a way that the sum P of inclusion ratios for the k-th component Tand the Np-th component T, which are the Fourier series expansion coefficients for the frame thickness T(&#x3b8;) expressed by equation (2) is less than 12%. According to this configuration, mechanical strength of the frame and its producibility are maintained, and cogging torque caused by magnetic-circuit distortion in an iron core generated due to the frame shape is also reduced.

Rotary electric machine

A permanent magnet electric motorcomprises a rotorprovided with two stages of permanent magnets in the axial direction on an outer circumferential face of a rotor iron core, and having a shaft shifted by a stage skew angle &#x3b8;r in electrical angle to decrease a first frequency component of cogging torque in the circumferential direction of the rotor iron core between two stages of the permanent magnets, a stator iron coreof cylindrical shape provided with the stator winding for producing a rotating magnetic field causing the rotorto be rotated, and a statordividing the stator iron coreinto plural blocks in the axial direction, and shifted by a stage skew angle &#x3b8;s in electrical angle to decrease a second frequency component of the cogging torque in the circumferential direction of the stator iron core

Permanent magnet electric motor with reduced cogging torque

A permanent-magnet rotating machine includes a rotor having a rotor core carrying on a curved outer surface multiple permanent magnets arranged in two rows along an axial direction. The permanent magnets in one row are skewed from those in the other row in a circumferential direction by a row-to-row skew angle (electrical angle) &#x3b8;e. A stator having a tubular stator core in which the rotor disposed, includes stator coils for producing a rotating magnetic field for rotating the rotor. A lower limit of the row-to-row skew angle &#x3b8;e larger than 30 degrees (electrical angle). A ratio, of cogging torque occurring in the absence of skew to cogging torque occurring when the permanent magnets are skewed, at a row-to-row skew angle of 30 degrees is calculated based on the cogging torque ratio, the row-to-row skew angle &#x3b8;e, and B-H curve properties of the stator core. An upper limit of the row-to-row skew angle &#x3b8;e is not larger than the maximum value at which the cogging torque ratio does not exceed the calculated cogging torque ratio at 30 degrees.

Permanent-magnet rotating machine

A permanent-magnet rotating machine includes a rotor having a rotor core carrying on a curved outer surface multiple permanent magnets arranged in two rows along an axial direction. The permanent magnets in one row are skewed from those in the other row in a circumferential direction by a row-to-row skew angle (electrical angle) &#x3b8;e. A stator having a tubular stator core in which the rotor disposed includes stator coils for producing a rotating magnetic field for rotating the rotor. A lower limit of the row-to-row skew angle &#x3b8;e larger than 30 degrees (electrical angle). A ratio of cogging torque occurring in the absence of skew to cogging torque occurring when the permanent magnets are skewed, at a row-to-row skew angle of 30 degrees is calculated based on the cogging torque ratio, the row-to-row skew angle &#x3b8;e, and B-H curve properties of the stator core. An upper limit of the row-to-row skew angle &#x3b8;e is not larger than the maximum value at which the cogging torque ratio does not exceed the calculated cogging torque ratio at 30 degrees.

A permanent magnet rotating machine includes a rotor with a permanent magnet having circumferential magnetic poles with a skew at boundaries between magnetic poles of the permanent magnet, and a stator having a stator iron core in an almost cylindrical shape and convex poles protruding inwardly, the rotor being disposed within the stator. A skew angle of the skew is smaller than a theoretical angle &#x3b8;(electrical angle) and larger than one-half the theoretical angle &#x3b8;, wherein the theoretical angle &#x3b8;is defined as,&#x3b8;=180&#xd7;(number of magnetic poles in the rotor)/smallest integer of which both the number of magnetic poles in the rotor and the number of magnetic poles in the stator are factors) [deg.].

Growing community of inventors

Tokyo, Japan

Tomohiro Kikuchi