Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1986-09-02
1987-10-13
Skudy, R.
Electrical generator or motor structure
Dynamoelectric
Rotary
310156, H02K 2100
Patent
active
047000970
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a synchronous machine, more particularly to the shape of field poles of a synchronous machine.
2. Background Art
The schematic sectional diagram of a synchronous machine having armature windings and slots accommodating the windings in a stator thereof and having field poles and magnets in a rotor thereof, is shown in FIG. 1. The stator 21 has slots 22 for accommodating the windings (not shown). Although the slots 22 are provided around the entire periphery of the stator 21, only a portion of them are shown in FIG. 1, the rest are omitted The rotor 11 comprises field poles 12 and magnets 13. The magnets 13 are made, for example, of ferrite or the like. The field poles 12 are punched from a thin plate. The thin plates are piled and fixed by fastening with a bolt (not shown) through a hole 14. When alternating current is supplied to the armature windings of the stator 21, the rotor 11 rotates
In the above-mentioned synchronous machine, hitherto, the length of the portion of the field pole 12 facing to the slots 22 along the circumferential direction is determined by the shape of the magnet 13 and the shape of the end portion 15 of the field pole 12, which is limited by thin plate punching, and the length dimension did not take into consideration the pitch of the slots 22. In the synchronous machine produced as mentioned above torque ripple occurs at no load rotation, that is, slot ripple caused by the slots. Slot ripple occurring at no load rotation has a harmful effect due to a lack of uniformity of the velocity when the synchronous machine is operated at a light load as a servomotor. It is already known that the above-mentioned slot ripple can be reduced without considering the relationship between the slot pitch and the length of the field pole 12 along the circumferential direction, if the distribution of the magnetic flux density in an air gap between the stator 21 and the rotor 11, is sinusoidal. However, realization of this state is very difficult, and in particular, it prevents miniaturization of the synchronous machine. Accordingly, it became necessary to determine the optimum relationship between the slot pitch and the length of the field pole 12 along the circumferential direction, to reduce the slot ripple at no load rotation in the synchronous machine.
The present invention was made in consideration of the above-mentioned necessity.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a synchronous machine capable of reducing the slot ripple and decreasing the lack of uniformity of the velocity at light load operation as a servomotor, by determining the length of the field pole along the circumferential direction to an integer multiple of l
of the slot pitch, where the number of the slots per pole per phase .beta. is expressed by an irreducible fraction m
.
According to the present invention, there is provided a synchronous machine comprising a stator having armature windings matching a .phi. phase power source and S number slots accommodating the armature windings; a rotor having a number of field poles identical with the P number of poles of the rotor and magnets for exciting the field poles; wherein where the number of the slots per pole per phase S/P.phi. is expressed by the irreducible fraction m
, i.e. S/P.phi.=m
, where m and n are integral numbers representing the numerator and denominator, respectively of S/P.phi. reduced to an irreducible fraction, the length of the portion of the field pole facing to the slots of the stator along the circumferential direction is selected out of the integer multiple value of l
of the slot pitch length in the stator
BRIEF EXPLANATION OF DRAWINGS
FIG. 1 is a schematic sectional diagram of a synchronous machine for explaining the backgroud art regarding the present invention;
FIG. 2 is a schematic sectional diagram of a synchronous machine according to an embodiment of the present invention;
FIG. 3 is an enlarged and expanded diagram of the relationship be
REFERENCES:
patent: 3210584 (1965-10-01), Jorgensen
patent: 3230434 (1966-01-01), Bauerlein
patent: 3334254 (1967-08-01), Kober
patent: 3654503 (1972-04-01), Whitney
patent: 3671780 (1972-06-01), Knudson
patent: 3671789 (1972-06-01), Menzies
patent: 4327302 (1982-04-01), Hershberger
patent: 4385250 (1983-05-01), Welburn
patent: 4475051 (1984-10-01), Chai
patent: 4486678 (1984-12-01), Olson
patent: 4543506 (1985-09-01), Kawada et al.
Amemiya Yoichi
Iwamatsu Noboru
Kawada Shigeki
Sogabe Masatoyo
Fanuc Ltd.
Skudy R.
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