General-purpose induction motor adaptable for a plurality of types of AC power supply

#This invention relates to an induction motor and, in particular, to an improvement of a three-phase induction motor combined with a deceleration mechanism to be used as a gear motor.

#Existing induction motors used as a gear motor are classified into a single-phase induction motor and a three-phase induction motor. As the single-phase induction motor, a capacitor motor is known. In either event, a deceleration mechanism is directly coupled to an output shaft of the single-phase or the three-phase induction motor when it is used as the gear motor.

#Generally, the single-phase induction motor is larger in volume and produces greater noise and vibration than the three-phase induction motor. In spite of the above-mentioned disadvantages, the single-phase induction motor is inevitably used in a place, such as an ordinary house, where three-phase AC is unavailable but single-phase AC alone can be used. It is therefore desired to suppress the noise and the vibration of the induction motor even in the place where the single-phase AC alone is available.

#FIG. 1 is a sectional view showing an internal structure of a gear motor;

#FIG. 2 shows, partially in section, a general-purpose induction motor according to an embodiment of this invention;

#FIG. 3 shows a circuit structure of a conversion module illustrated in FIG. 2 and a circuit board connected thereto; and

#Now, description will be made of an embodiment of this invention with reference to the drawing.

#Referring to FIG. 1, description will at first be made of a gear motor as a combination of a three-phase induction motor 10 and a deceleration mechanism 20. Specifically, the deceleration mechanism 20 is directly coupled to an output shaft (rotation shaft) 11 of the three-phase induction motor 10. A cooling fan 17 is attached to the rotation shaft. The structure of each of the three-phase induction motor 10 and the deceleration mechanism 20 is well known and the detailed description thereof is omitted herein. A general-purpose induction motor according to this invention is suitable for use as the above-mentioned gear motor.

#Referring to FIGS. 2 through 4, description will be made of a general-purpose induction motor according to a preferred embodiment of this invention. In FIG. 2, the general-purpose induction motor according to the embodiment of this invention comprises the three-phase induction motor 10 having an outer casing 12, and a conversion module 30 mounted on the outer casing 12. The conversion module 30 has a function of converting single-phase AC into three-phase AC. On an upper part of the outer casing 12 of the three-phase induction motor 10, a terminal box 13 is mounted. The terminal box 13 contains various kinds of terminals (not shown) for connection with an AC power supply when the three-phase induction motor 10 is installed at a location where it is used. The terminal box 13 has a cover which can be opened and closed. The conversion module 30 is contained in the terminal box 13. In FIG. 2, the deceleration mechanism (20 in FIG. 1) is not illustrated.