Electrical machine with reduced audible noise

Details Electrical machine with reduced audible noise Electrical machine with reduced audible noise

1998-12-28

2001-03-27

Tamai, Karl (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C322S089000, C310S051000, C310S184000

Reexamination Certificate

active

06208057

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electrical machines and more particularly to noise reduction designs for electrical machines.
2. Description of the Related Art
In the design of electrical machines, reducing audible noise generated by operation of the machine can be important. One field in which noise reduction is particularly important is in the design of alternators for motor vehicles.
An important operating point at which it is very important for an alternator operate quietly is at engine idle. There, because the vehicle is otherwise relatively quiet due to low engine speed and the lack of wind and road noise, alternator noise can be particularly annoying to the occupants of the vehicle.
The audible noise produced by operation of an automotive claw pole alternator is partly electromagnetic in origin. In particular, a third-harmonic field can produce significant noise. In a common 12-pole alternator, this third harmonic field is a 36-pole field. The third harmonic field is due to the interaction of the magnetomotive force produced by the stator currents with the permanence of the air gap between the rotor and the stator.
Electrical machine designs which can reduce the audible noise generated by electromagnetic fields in the machine will provide significant advantages over the prior art. Particularly in the automotive environment, the advantage will be in the form of increased customer satisfaction.
SUMMARY OF THE INVENTION
The present invention provides an electrical machine comprising a rotor and a stator disposed in opposition to the rotor. The stator further comprises one or more multiple-phase electrical power windings coupled to receive or provide electrical power, and an auxiliary electrical winding. The rotor has “n” magnetic poles, and the auxiliary electrical winding is an “m•n”-pole winding, where “m” and “n” are integers.
The present invention further provides a method for controlling an electrical machine having a rotor and a stator, the stator further having one or more multiple-phase power windings and an auxiliary winding. The method comprises electrically closing the auxiliary winding under some operating conditions and electrically opening the auxiliary winding under other operating conditions. The operating conditions governing the opening and closing of the auxiliary winding can include rotational speed of the rotor of the electrical machine.
Electrical machines and control thereof according to the present invention can reduce the audible noise generated by the machine. In doing so, the present invention provides advantages over the prior art.


REFERENCES:
patent: 4110642 (1978-08-01), Thiele
patent: 4201930 (1980-05-01), Inagaki et al.
patent: 4263526 (1981-04-01), Taguchi et al.
patent: 5122705 (1992-06-01), Kusase et al.
patent: 5172020 (1992-12-01), Hibino et al.
patent: 5256926 (1993-10-01), Hagenlocher et al.
patent: 5691590 (1997-11-01), Kawai et al.
patent: 5708316 (1998-01-01), Ishida
patent: 55-122466 (1980-09-01), None
patent: 62-023348 (1987-01-01), None

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