Electricity: motive power systems – Synchronous motor systems – Synchronization systems
Patent
1992-06-24
1998-08-18
Shoop, Jr., William M.
Electricity: motive power systems
Synchronous motor systems
Synchronization systems
318712, 318722, 318778, 318799, 318820, 318832, H02P 414
Patent
active
057962332
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a synchronous motor and, more particularly, to an induction synchronous motor having a plurality of stators.
BACKGROUND OF THE INVENTION
Generally, a synchronous motor requires a starter for having its rotor accelerated up to a rotation speed of a rotating magnetic field produced by stator windings and also a means for effecting direct current magnetic excitation for rotor windings.
An induction synchronous motor is one in which the starter is omitted but an arrangement is made such that the synchronous motor itself is provided with starting torque. Such a motor does not require a starter since rotor windings are short-circuitted for the motor to operate as an induction motor but brushes are required for the direct current magnetic excitation of the rotor windings which is indispensable for the synchronous operation. That is, as the rotating speed of the rotor approaches the synchronous speed, the short-circuitting of the rotor windings is removed so that the direct current flows from an external power supply source through the brushes thereby forming magnetic poles on the rotors. Such magnetic poles are attracted by the rotating magnetic fields produced in the stator windings and this causes the rotor to rotate in the synchronous speed. The brushes require checking and maintenance, which adds to an extra maintenance cost, so that there is a strong desire to develop brushless synchronous motors.
As conventional synchronous motors having brushless structures, those known include a permanent magnet type and a reluctance type motor but such motor is limited to one with only a small capacity since there are problems associated with a demagnetization factor or a low power factor. Also, such a synchronous motor as an inductor-type has a drawback in that the arrangements necessary for magnetic passages are unavoidably complicated thereby increasing the overall motor size. The same problem is true in a motor in which an alternate-current magnetic excitator and a rotary rectifier are used. Further, in a brushless three-phase synchronous motor of a self-excitation type in which a diode is connected to a rotor winding and a harmonic magnetic field is processed by a rectangular wave voltage of an invertor, a drawback is that a magnetomotive force of the rotor is insufficient so that no sufficient output can be obtained. Also known is a brushless three-phase synchronous motor of a self-excitation type. In such a motor, a diode is inserted in one phase of three-phase stator windings whereby a static magnetic field is superimposed over a positive phase component rotating magnetic field and an alternating current voltage due to the static magnetic field is induced in the rotor windings to rotate in the synchronous speed. By having the voltage thus induced rectified through a diode, the rotor winding is DC-excited and a positive phase component of magnetic field acts thereby producing a synchronous torque. However, a drawback in such a motor is that an inductor starting is impossible since the start is by eddy currents and the starting torque is small.
The technical problems to be solved are to provide a synchronous motor in which the starting torque and the synchronous torque are large and which does not require brushes thereby facilitating maintenance of the motor and does not require any such means as a starter thereby facilitating structural simplification of the motor.
SUMMARY OF THE INVENTION
In order to overcome such problems as explained above, the present invention provides an induction synchronous motor comprising: rotary axis with a predetermined space being provided between the first and second rotor cores and a plurality of rotor conductive members provided on each of the first and second rotor cores; second rotor core, respectively; 180.degree. with respect to a first phase difference of 0.degree. in an electric angle between a voltage induced in the rotor conductive member based on a rotating magnetic field produced around the first rotor core su
REFERENCES:
patent: 3280400 (1966-10-01), Roe
patent: 4038588 (1977-07-01), Heyne et al.
patent: 4503377 (1985-03-01), Kitabayashi et al.
patent: 4785213 (1988-11-01), Satake et al.
patent: 4866364 (1989-09-01), Chiarion
patent: 4931715 (1990-06-01), Lee et al.
Onogi Yukio
Satake Toshihiko
Satake Engineering Co. Ltd.
Shoop Jr. William M.
Sircus Brian
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