JP6226794B2 - Squirrel-cage induction motor - Google Patents

Description

  The present invention relates to a structure of a squirrel-cage induction motor.

  The squirrel-cage induction motor includes a rotor in which a conductor is cast in a slot. A rotor is manufactured by aluminum die casting in which aluminum is embedded in a slot (for example, Patent Document 1). However, in recent years, in order to improve the efficiency of an electric motor, the rotor is formed by copper die casting having higher conductivity than aluminum. A squirrel-cage induction motor that has been manufactured is also in practical use.

Japanese Patent Laid-Open No. 2003-9483

  If the conductor in the slot of the rotor is changed, the efficiency of the electric motor may be reduced, or the starting characteristics may be deteriorated.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a technique for improving the efficiency and starting characteristics of a squirrel-cage induction motor.

One embodiment of the present invention is a squirrel-cage induction motor having a rotor made of laminated steel plates and formed with a plurality of slots. A conductor is cast in the slot, a conductor wire having a resistance lower than that of the cast conductor is arranged on the inner periphery of the slot, and a conductor having a resistance higher than that of the cast conductor is arranged on the outer periphery of the slot. Is done. The conductor having a low resistance value is a copper wire, and the copper wire has an insulating coating for a portion in the laminated steel plate of the rotor and does not have an insulating coating for a portion protruding from the end face of the rotor.

  According to this aspect, the efficiency of the squirrel-cage induction motor is improved by using a conductor having a low resistance value, and the starting characteristics of the squirrel-cage induction motor can be improved by the conductor having a high resistance value.

  Note that any combination of the above-described constituent elements, and those obtained by replacing the constituent elements and expressions of the present invention with each other among methods, apparatuses, systems, etc. are also effective as an aspect of the present invention.

  According to the present invention, the efficiency and starting characteristics of a squirrel-cage induction motor can be improved.

It is sectional drawing of a cage induction motor. It is sectional drawing of the rotor and rotating shaft of the cage induction motor which concern on one Embodiment of this invention. FIG. 3 is an enlarged plan view of a part of the rotor of FIG. 2.

  FIG. 1 is a cross-sectional view of a squirrel-cage induction motor 10 cut along a vertical plane including a central axis.

  The stator 34 is formed by laminating a number of thin plate-like (for example, 0.5 mm thick) electromagnetic steel plates that have been punched into the same shape. The stator 34 is fitted to the inner periphery of the frame 30 by shrink fitting, for example. A coil 38 made of copper wire is wound around a plurality of slots formed in the stator 34.

  The rotor 36 is also formed by laminating a number of thin plate-shaped electromagnetic steel plates that have been punched into the same circular shape. In the rotor 36, a circular hole for inserting the rotary shaft 12 is formed in the center, and a plurality of slots 36a having the same shape extending in the radial direction are formed at equal intervals on the outer peripheral side (see FIG. 3). The circular hole of the rotor 36 is fixed to the rotating shaft 12 by an interference fit.

  The frame 30 is made of, for example, aluminum die cast, cast iron, or steel plate, and supports the weight of the rotor and the stator and has a role of radiating heat generated in the rotor and the stator to the outside of the electric motor. In order to improve the heat dissipation performance, a large number of heat radiation fins 40 extending in a direction parallel to the rotation axis are installed on the outer periphery of the frame 30.

  The rotating shaft 12 is rotatably supported by bearings 16 and 17 on both flanges 14 and 15 extending from the frame 30 to the inner diameter side. The flanges 14 and 15 may be formed integrally with the frame 30, or may be fixed to the frame 30 after being formed separately.

  A fan 18 is disposed on the rear end side of the rotary shaft 12. A fan cover 32 is disposed further outside the fan 18.

  In the conventional induction motor, a cast conductor such as aluminum or copper is cast into a slot 36 a formed in the rotor 36 by die casting. Short-circuiting rings 37 that are integrated with the conductors in the slots are formed on both end faces of the rotor 36.

  On the other hand, in the squirrel-cage induction motor according to the embodiment of the present invention, a conductor having a lower resistance value than the cast conductor and a conductor having a higher resistance value than the cast conductor are disposed in the slot 36a.

  FIG. 2 is a cross-sectional view of the rotor 36 and the rotating shaft 12 of the squirrel-cage induction motor according to the embodiment of the present invention, and FIG. 3 is an enlarged plan view of a part of the rotor 36.

  As shown in FIG. 3, a wire 56 or a bar 58 of a conductor (hereinafter also referred to as a low resistance conductor) having a resistance value lower than that of the cast conductor is disposed on the inner peripheral side of the slot 36 a of the rotor 36. In addition, a wire 50 or a bar 51 of a conductor (hereinafter also referred to as a high resistance conductor) having a higher resistance value than the cast conductor is disposed on the outer peripheral side of the slot 36a of the rotor 36.

  After the wire rods or rods of the low resistance conductor and the high resistance conductor are disposed in the slot 36a, the molten cast conductor 52 is cast into a gap formed in the slot by a die casting machine. By doing so, the movement of the low resistance conductor and the high resistance conductor in the slot is prevented.

  Although FIG. 3 shows a state in which the low resistance conductor, the cast conductor and the high resistance conductor are accommodated only in some slots, actually, these conductors are similarly arranged in all slots. Either the low resistance conductor wire 56 or the bar 58 may be disposed in all slots, or the low resistance conductor wire 56 may be disposed in some slots, and the low resistance conductor rod 58 may be disposed in the remaining slots. It may be arranged.

  As shown in FIG. 2, the low resistance conductor wire 56 (or bar 58) and the high resistance conductor wire 50 (or bar 51) disposed in the slot are slightly longer than the axial length of the rotor 36. It may be cut in advance and inserted into each slot. The molten cast conductor can be introduced into the slot using a conventional die-cast machine after the wire or bar is inserted. By doing so, an increase in the manufacturing cost of the rotor can be suppressed.

  When the cast conductor is aluminum, the low resistance conductor is, for example, copper, and the high resistance conductor is, for example, high resistance aluminum, magnesium, or zinc.

  As described above, when a conductor having a higher resistance value than the cast conductor is disposed on the outer peripheral side of the slot, the resistance on the outer peripheral side of the slot where current concentrates at the start of the squirrel-cage induction motor increases. Can improve the starting characteristics. However, the efficiency of the squirrel-cage induction motor decreases due to the increase in resistance.

  In the present embodiment, a conductor wire or bar having a lower resistance than the cast conductor is disposed on the inner peripheral side of the slot. As a result, the current flowing in the slot increases, so that a decrease in the efficiency of the squirrel-cage induction motor due to the arrangement of the high resistance conductor can be suppressed.

  The size of the wire or rod of the high resistance conductor arranged on the outer peripheral side of the slot is a trade-off between the improvement of the starting current and the reduction in the efficiency of the electric motor.

  When copper is selected as the low resistance conductor, a commercially available copper wire may be used as the wire 56. The advantage of using a commercially available copper wire is that it can be obtained at a low price and is also used as a stator coil. Abundant, relatively soft and easy to insert into the slot.

  Of the copper wire, the portion in the laminated steel sheet of the rotor after being inserted into the slot is preferably used with an insulation coating such as enamel. Thereby, since the state where the copper wires are insulated is maintained, a stray current having a component parallel to the magnetic field generated in the rotor is less likely to flow, so that loss can be suppressed.

  In addition, it is preferable to remove the insulating coating in advance so that a current flows in a portion of the copper wire that protrudes from the end face of the rotor after being inserted into the slot, regardless of the direction in which the copper wire extends.

  In the embodiment, when the cast conductor is aluminum, a copper wire or rod having a lower resistance value than aluminum on the inner circumferential side of the slot, and a high resistance aluminum wire or rod having a higher resistance value than aluminum on the outer circumferential side of the slot Said to arrange. The present invention can be applied even when the cast conductor is other than aluminum. For example, in the case of copper die casting, a wire or bar made of a material having a resistance value lower than that of copper may be arranged on the inner circumferential side of the slot, and a wire or bar made of a material having a higher resistance value than copper may be arranged on the outer circumference side of the slot. .

  The rotor of the squirrel-cage induction motor of the present invention is not limited to manufacturing using an existing aluminum die casting machine, and the rotor may be manufactured using a newly designed die casting machine. Further, the method of casting the conductor is not limited to die casting, and may be casting, for example.

  The embodiment of the present invention has been described above. It is to be understood by those skilled in the art that these embodiments are exemplifications, and that various modifications can be made to combinations of the respective components, and such modifications are within the scope of the present invention.

  10 induction motor, 34 stator, 36 rotor, 36a slot, 50 high resistance conductor wire, 51 high resistance conductor rod, 52 cast conductor, 56 low resistance conductor wire, 58 low resistance conductor rod.

Claims (2)

A squirrel-cage induction motor having a rotor composed of laminated steel plates and formed with a plurality of slots,
A conductor is cast into the slot,
In the inner circumferential side, lower conductors of resistance than cast conductors are arranged,
On the outer periphery side of the slot, a conductor having a higher resistance value than the cast conductor is disposed ,
The low resistance conductor is a copper wire,
The squirrel-cage induction motor according to claim 1, wherein the copper wire has an insulating coating for a portion in the laminated steel plate of the rotor and does not have an insulating coating for a portion protruding from the end face of the rotor . The squirrel-cage induction motor according to claim 1, wherein the conductor having a high resistance value is a wire or a bar.

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