Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1989-08-16
1990-12-25
Ro, Bentsu
Electrical generator or motor structure
Dynamoelectric
Rotary
310112, 310171, 310185, 310254, 318605, H02K 2912
Patent
active
049805940
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an electric motor comprising a rotor, a stator and at least two pole pairs. One particularly preferred application of the electric motor according to the invention is small-size accurate servomotors of high capacity.
At present, feed-back information required by servomotors is generally obtained from at least partially separate transducing means attached to the motors, such as an optical or magnetic coder, a tachogenerator, or resolver. A drawback of these known solutions is that the volume and weight of the motors is high. In addition, the adjusting system is subject to disturbances, which is due to the clearances and flexibility of the coupling.
The object of the present invention is thus to eliminate the drawbacks described above. According to the invention it has been found that a resolver can be integrated into the basic structure of the motor if the number of pole pairs in the motor is at least double as compared with that of the resolver. With this kind of motor, the above-described drawbacks of the prior art are eliminated by providing the motor with an integral resolver in which the primary winding of the resolver is arranged in the rotor of the motor and that the secondary winding of the resolver is wound around the stator of the motor in such a manner that the winding wire extends alternately inside and outside the stator.
As is known, the absolute angle position, velocity, and direction of the rotor can thus be determined on the basis of signals generated in the, secondary winding of the resolver. These signals can be used for further controlling the commutation, velocity, and positioning of the motor.
According to the invention it is possible, if desired, to integrate a synchro or some other transducing means of the type with a rotating transformer in the basic structure of the motor. Amongst these, however, the resolver is the most useful alternative in view of the control of the servomotor, for instance, wherefore it is used in this particular case. As used herein, the term "resolver", however, has to be considered to have a wider meaning in such a way as described above.
A motor effected according to the invention is clearly smaller and lighter than known motors comprising a separate resolver for obtaining feed-back information. Consequently, the present invention is particularly suited for uses in which a small size and lightness are among the basic requirements set for the motor. Such uses include e.g. aeroplanes. In addition, the structure according to the invention eliminates the liability to disturbances caused by the flexibility and clearances. One more major advantage of the present invention is that a motor constructed in accordance there with is cheaper than comparable motor of the prior art.
In the following the invention and its preferred embodiments will be described in more detail with reference to the examples of the attached drawings, wherein
FIG. 1 is a partial longitudinal cross-section of a brushless permanent magnet motor in which the number of pole pairs in the resolver is one,
FIG. 2 is a cross-sectional view of the motor of FIG. 1 in the direction of the line A--A,
FIGS. 3a and 3b illustrate one way of winding the secondary windings of the resolver in the motor shown in FIGS. 1 and 2,
FIGS. 3c and 3d illustrate an alternative way of winding for the way of shown in FIGS. 3a and 3b,
FIG. 4 is a simplified view of the secondary winding of the resolver as a planar view for the demonstration of noise voltage,
FIG. 5 illustrates a noise voltage occurring in the secondary winding of the resolver in the case of a quadripole motor, and
FIG. 6 illustrates a noise voltage occurring in the secondary winding of the resolver in the case of a bipolar motor.
FIGS. 1 and 2 illustrate a hexapolar brushless permanent magnet motor, the rotor and stator of which are indicated with the reference numerals 1 and 2, respectively. The rotor periphery is formed by six magnetic poles N1 to N6, of which the three upper poles N1 to N3 are visible in the sectional view of FI
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Innoke Oy
Ro Bentsu
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