DE102015103317A1 - induction motor - Google Patents

Abstract

The efficiency of an induction motor is increased. In an induction motor, a groove clearance pitch factor in a stator slot (34a) is equal to or greater than 38% and β is in a range of 0.46 to 0.56, where WS is the width of the stator teeth (34b), σS the pitch of the stator slots (34a) is and β = WS / σS.

Description

The invention relates to the field of induction motors and more particularly to an induction motor with optimized electromagnetic design.

It will be the priority of JP 2014-063102-A , filed on Mar. 26, 2014, which is hereby incorporated by reference in its entirety.

Induction motors are electric motors equipped with a stator which generates a rotating magnetic field and a rotor in which an induced current is generated by the rotating magnetic field and which is rotated by the torque generated together with the rotating magnetic field (such as off JP 2003-9483-A is known).

In order to realize the high efficiency of the induction motors, an optimization of the electromagnetic design is required.

The invention is therefore based on the object to provide a technique for increasing the efficiency of an induction motor.

This object is achieved by an induction motor according to claim 1. Advantageous developments of the invention are specified in the dependent claims.

One aspect of the invention relates to an induction motor in which a groove gap pitch factor in a stator slot is equal to or greater than 38% and β is in a range of 0.46 to 0.56, where W _{s is} the width of the stator teeth , σ _{S is} the pitch of the stator slots and β = W _S / σ _S.

The efficiency of the induction motor can be increased by setting the electromagnetic design parameters of the stator as described above.

In addition, any combinations of the above constituent elements and those obtained by replacing the constituent elements or expressions of the invention with each other between the devices, methods, systems or the like are also effective as the aspects of the invention.

According to the invention, the efficiency of the induction motor can be increased.

Other features and advantages of the invention will become apparent upon reading the following description of preferred embodiments, which refers to the drawings, in which:

1 a cross-sectional view of a squirrel cage induction motor, which is related to an embodiment of the invention;

2 a partial cross-sectional view of a stator and a rotor of the basket-shaped induction motor;

3 Fig. 12 is a graph illustrating the changes of the efficiency of the electric motor when the value of β is changed;

4 Fig. 12 is a graph illustrating the changes of the efficiency of the electric motor when the value of β is changed;

5A . 5B Views illustrating the stator shapes in the cases β = 0.46 and β = 0.56, respectively; and

6 Fig. 12 is a graph illustrating the changes of the efficiency of the electric motor when the value of D _S / W _{S is} changed.

1 is a cross-sectional view when a basket-shaped induction motor 10 which is related to an embodiment of the invention, cut by a vertical plane containing a central axis.

A stator 34 is formed by stacking a large number of sheet-like electromagnetic steel sheets (for example, having a thickness of 0.5 mm) punched in the same shape. The stator 34 is at an inner circumference of a frame 30 adapted, z. B. by shrinkage fit. In several grooves in the stator 34 are formed, are coils 38 made of copper wire.

A rotor 36 is formed by stacking a large number of sheet-like electromagnetic steel sheets punched in the same circular shape. The rotor 36 has a circular hole for insertion of a rotary shaft 12 which is formed in its center, with several grooves 36a of the same shape extending in a radial direction are formed at equal intervals on one side of the outer circumference of the rotor (see FIG 2 ). The rotary shaft 12 is by interference fit in the circular hole of the rotor 36 attached.

The frame 30 is z. B. made of cast aluminum, made of cast iron or made of a steel sheet, carries the weight of the rotor and the stator and plays a role in deriving the heat generated in the rotor, the stator or the like to the exterior of the electric motor. In order to improve the heat dissipation performance, there are a large number of radiation fins 40 . which extend in a direction parallel to the rotating shaft, on the outer circumference of the frame 30 Installed.

The rotary shaft 12 is through the flanges 14 and 15 on both sides, different from the frame 30 extend to one side of an inner diameter, over the bearings 16 respectively. 17 rotatably supported. The flanges 14 and 15 can with the frame 30 be formed in one piece or can be formed separately and on the frame 30 be attached.

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

2 is a partial cross-sectional view when the stator 34 and the rotor 36 the basket-shaped induction motor 10 are cut open by a plane orthogonal to the rotation shaft.

The stator teeth 34b with the same shape extending in the radial direction are at equal intervals in the circumferential direction of the stator 34 formed, wherein the stator slots 34a that has an opening on the side of the rotor 36 have defined between the stator teeth. A copper wire 42 is several times around the stator slots 34 wrapped to form coils. If an alternating current is fed through the coils, a rotating magnetic field will be generated at the stator teeth 34a and the stator yokes generated.

The forms of the stator grooves 34a and the stator teeth 34b have a great influence on the electromagnetic design of the stator. In 2 For example, the width W _{S of} the stator teeth, the distance σ _{S of} the stator slots and the height D _{S of} the stator slots are shown as the parameters that should be considered in the electromagnetic structure of the stator. In addition, when the width of the stator teeth is not constant in the radial direction, the width W _{S of} the stator teeth represents the average value of the width in the radial direction.

The inventor of this application has found that a ratio β of the width of the stator teeth to the distance of the stator slots = W _S / σ _S , a ratio of the height of the stator slots to the width of the stator teeth D _S / W _S , a selection of a slot or Winding gap fill factor (the cross-sectional area of the element wire except for a coating of the copper wire within a groove / the cross-sectional area of the groove) and an average flux density of the stator teeth are important in increasing the efficiency of the induction motor.

Under the above, if the copper wire is wound so as to make the groove gap pitch equal to or larger than 38%, the efficiency of the induction motor can be made particularly high.

In addition, if a current flowing through the coils is controlled so that the average flux density of the stator teeth becomes equal to or larger than 1.7 T, the efficiency of the induction motor can be made particularly high.

In the following, the determination of the ratio β and the range of D _S / W _{S will be} described.

3 Fig. 12 is a graph showing the changes of the efficiency of the electric motor when the value of β is changed in an induction motor whose capacity is 0.75 kW. The horizontal axis of the drawing represents the voltage, while the vertical axis represents the efficiency.

In induction motors, it is generally important to make high the peak efficiency in a given voltage range in the above graph. It can be seen that, if the efficiency of a voltage range A, the in 3 is illustrated by an arrow, and a change is made from β = 0.43 to β = 0.46, the peak efficiency increases greatly. In addition, it can be seen that if a change from β = 0.56 to β = 0.59 is made, the peak efficiency drops to a great extent.

From this observation, it can be seen that if β is caused to fall within a range of 0.46 to 0.56 in this induction motor whose capacitance is 0.75 kW, the efficiency of the induction motor becomes high.

4 FIG. 12 is a graph illustrating changes in the efficiency of the electric motor when the value of β is changed in an induction motor whose capacity is 2.2 kW. The horizontal axis of the drawing represents the voltage, while the vertical axis represents the efficiency.

It can be seen that, if the efficiency of a voltage range A, the in 4 is illustrated by an arrow, and a change is made from β = 0.43 to β = 0.46, the peak efficiency increases greatly. In addition, it can be seen that if a change from β = 0.56 to β = 0.59 is made, the peak efficiency drops to a great extent.

From this observation, it can be seen that if β is caused to fall in a range of 0.46 to 0.56 in this induction motor whose capacity is 2.2 kW, the efficiency of the induction motor becomes high.

Moreover, from the 3 and 4 It can be seen that the value of β, which realizes high efficiency, does not depend on the capacity of the induction motors.

5A and 5B are views illustrating the stator shapes in the cases β = 0.46 and β = 0.56, respectively.

As in 5A As can be seen, at β = 0.46, the width of the stator teeth becomes narrow compared to the stator slots. If β is made smaller than 0.46, there is a possibility that the mechanical strength of the root portions of the stator teeth may be insufficient, the teeth may be broken or the noise caused by the magnetostriction may increase.

How out 5B As can be seen, at β = 0.56, the width of the stator slots becomes narrow compared to the stator teeth. If β is made larger than 0.56, the cross-sectional area of the grooves becomes small. Therefore, the cross-sectional area of the coil also becomes small, whereby the efficiency of the induction motor decreases.

6 Fig. 12 is a graph illustrating the changes of the efficiency of the electric motor when the value of D _S / W _S in an induction motor whose capacity is 0.75 kW is changed. The horizontal axis of the drawing represents the voltage, while the vertical axis represents the efficiency.

It can be seen that, if the efficiency of a voltage range B in 6 is illustrated by an arrow, and a change is made from D _S / W _S = 2.5 to D _S / W _S = 3.0, the peak efficiency increases greatly. In addition, it can be seen that if a change is made from D _S / W _S = 5.5 to D _S / W _S = 6.0, the peak efficiency drops to a great extent.

From this observation, it can be seen that if D _S / W _{S is} caused to fall in a range of 3.0 to 5.5 in this induction motor, the efficiency of the induction motor becomes high, and it is more preferable if effected in that D _S / W _S falls within a range of 4.0 to 5.0.

As described above, in this embodiment, a guide with respect to the electromagnetic structure of the stator for realizing a high efficiency of the induction motor is explained. That is, the high efficiency of the induction motor can be realized by designing the shape of the stator so that the ratio β of the width of the stator teeth to the distance of the stator slots falls within a range of 0.46 to 0.56 and so that the ratio D _S / W _{S of} the height of the stator slots to the width of the stator teeth falls within a range of 3.0 to 5.5.

In the high efficiency induction motor according to this embodiment, the layer thickness of the stacked steel sheets of the stator becomes smaller as compared with the induction motors with the related art constructions having almost the same level of efficiency. Therefore, the induction motor can be made compact. Accordingly, the manufacturing costs by reducing the materials, such. As the copper wire, the electromagnetic sheets and the aluminum conductors are reduced.

Above, an embodiment of the invention has been described. Of course, for the person skilled in the art, the embodiment is merely illustrative, and various modified examples are possible through the combination of the respective constituent elements, and such modified examples are within the scope of the invention.

Moreover, although the basket-type induction motor has been described in the embodiment, the invention can similarly be applied to any induction motors having a structure in which the coils are wound around the stator and the rotating magnetic field is generated, regardless of the structure of the rotor.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 2014-063102-A [0002]
• JP 2003-9483-A [0003]

Claims (4)

Induction motor ( 1 ), in which a slot fill factor in a stator slot ( 34a ) is equal to or greater than 38%, where β is in a range of 0.46 to 0.56, where W _{S is} the width of the stator teeth ( 36b ), σ _{S is} the distance of the stator slots ( 34a ) and β = W _S / σ _S. Induction motor ( 1 ) according to claim 1, wherein D _S / W _{S is} in a range from 3.0 to 5.5, where D _{S is} the height of the stator slots ( 34a ). Induction motor ( 1 ) according to claim 1 or 2, wherein β is not dependent on engine capacity. Induction motor ( 1 ) according to one of claims 1 to 3, wherein the average flux density of the stator teeth ( 36b ) is equal to or greater than 1.7T.

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