JP3837954B2 - Connection pattern switching device - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to an apparatus for switching a connection pattern of armature windings of a motor, and more particularly to a connection pattern switching apparatus suitable for improving the versatility of a motor by making it possible to change the characteristics of the motor.
[0002]
[Prior art]
In the conventional motor, the armature windings are connected in a pattern uniquely determined in the design stage, and the connection pattern of the armature windings is a fixed structure. That is, in a three-phase six-pole motor, for example, when coils wound around the poles of each phase are connected in series, after the motor is completed, the coils wound around the poles of each phase are reconnected in parallel. I couldn't.
[0003]
[Problems to be solved by the invention]
By the way, the characteristics of such a motor are determined by the armature current flowing by the armature voltage applied to the motor, the magnetic flux generated between the stator and the rotor, and the like. Among these, the elements that determine the magnetic flux between the stator and the rotor include the gap distance between the stator and the rotor, the shape of the magnet formed on the rotor, and the like, and the armature current is the value of the armature winding of the stator. It depends heavily on reactance. For example, in the torque-rotation speed characteristic which is one of the characteristics of the motor, as the reactance of the armature winding increases, the maximum rotation speed decreases but the maximum torque output increases.
[0004]
However, the conventional motor has a fixed structure in which the gap between the stator and the rotor and the shape of the magnet formed on the rotor are fixed, and the connection pattern of the armature winding is also a fixed structure. It was very difficult to change its properties after completion. For this reason, in order to change the characteristics of the motor, it is necessary to replace it with another motor having different specifications, and there is a thing with poor versatility.
[0005]
Therefore, the present invention has an object to solve such a conventional problem, and provides a connection pattern switching device suitable for improving the versatility of a motor by making it possible to change the characteristics of the motor. The purpose is that.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a connection pattern switching device according to claim 1 according to the present invention includes a plurality of coils wound around each of at least three poles, and a stator in which armature windings are formed by the plurality of coils. And a rotor provided rotatably inside the stator, wherein the first coil, the second coil, and the third coil of the plurality of coils are arranged in parallel in that order. Connecting, between the one ends of the adjacent coils of the three coils, between the other ends of the adjacent coils, between the one end of the first coil and the other end of the second coil, and respectively a switch between said other end of said one end and said third coil of said second coil, Oyo said first coil from the first common contact provided on the outer side of said plurality of coils Wherein forming a third current path connecting the one end of the coil, respectively, a switch provided in said current path connecting the one end of the first common contact and the first coil, the external side of said plurality of coils Forming a current path connecting the other end of the first coil and the second coil from a second common contact provided on the second common contact, and connecting all of the current paths connected to the second common contact A switch is provided, and switching means for switching each switch independently is provided.
[0007]
With such a configuration, when the coil connection pattern between a plurality of poles is switched so that the reactance of the armature winding is increased, the maximum number of revolutions can be obtained when the same armature voltage is applied to the motor before and after switching. However, the maximum torque output increases. Conversely, if the coil connection pattern between multiple poles is switched so that the reactance of the armature winding is reduced, the maximum torque output will decrease but the maximum torque output will be reduced if the same armature voltage is applied to the motor before and after switching. The characteristic that the rotational speed increases is obtained.
[0009]
According to a second aspect of the present invention, there is provided a connection pattern switching device comprising: a plurality of coils wound around at least three poles; a stator having armature windings formed by the plurality of coils ; and an inner side of the stator. a rotor rotatably provided, a device to be applied to motors with in the first coil of the plurality of coils, the second coil and the third coil connected in parallel in this order, the three Among the coils, between one ends of the adjacent coils, between the other ends of the adjacent coils, between the one end of the first coil and the other end of the second coil, and of the second coil each contact each switch is provided, the end of the first from the common contact of the three coils provided on the outer side of the plurality of coils between said other end of said one end and said third coil The current path is formed, to form the current path that connects the other end of each of the plurality of second from a common contact of the three coils provided on the outer side of the coil, the switch to all of said current path And switching means for switching each of the switches independently.
[0010]
With such a configuration, as the reactance of the armature winding is increased, switch the connection pattern of the coil in the machining gap of several, when applied to the same armature voltage to motor after previous switching, the maximum rotation The number is reduced, but the maximum torque output is increased. Conversely, as the reactance of the armature winding is reduced, switch the connection pattern of the coil in the machining gap of several, when applied to the same armature voltage to motor after previous switching, the maximum torque output is reduced The characteristic that the maximum rotational speed increases is obtained.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 are diagrams showing an embodiment of a connection pattern switching device according to the present invention.
In this embodiment, the connection pattern switching device according to the present invention is applied to the case where the connection pattern of the armature winding of the motor 10 is switched in the system in which the motor 10 is driven by the driver 20 as shown in FIG. It is.
[0014]
First, the configuration of a system to which the connection pattern switching device according to the present invention is applied will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of a system to which a connection pattern switching device according to the present invention is applied.
As shown in FIG. 1, the system includes a motor 10 that is a three-phase AC motor, a driver 20 that drives the motor 10, a switcher 30 that switches connection patterns of armature windings 12 a to 12 c of the motor 10, The armature windings 12a to 12c of the motor 10 are star-connected.
[0015]
The driver 20 controls, for example, a load current applied to the motor 10 so that the rotational speed of the motor 10 becomes a speed command value based on a speed command value given from the outside. A detection value from a speed detector (not shown) that detects the speed is input, and the load current value to the motor 10 is feedback-controlled so that the difference between the detection value and the speed command value is eliminated.
[0016]
Next, the configuration of the motor 10 will be described with reference to FIG. FIG. 2 is a cross-sectional view of the motor 10.
As shown in FIG. 2, the motor 10 includes a cylindrical stator 14 and a rotor 15 that is rotatably provided inside the stator 14 via an air gap.
[0017]
The rotor 15 includes an iron core 15a, a plurality of permanent magnets M _{N1 to} M _S6 attached to the outer peripheral surface of the iron core 15a, and a shaft 15b press-fitted into the center of the iron core 15a.
Twelve permanent magnets M _{N1 to} M _S6 having the same configuration are attached to the outer peripheral surface of the iron core 15 a at equal intervals, and the permanent magnets M _{N1 to} M _N6 arranged _alternately are the The other permanent magnets M _{S1 to} M _{S6 that} are mounted with the N pole facing outward in the radial direction and disposed therebetween are mounted with the S pole facing outward in the radial direction of the rotor 15.
[0018]
On the inner peripheral surface of the stator 14, convex poles are alternately formed at equal intervals corresponding to the three phases of the A phase, the B phase, and the C phase. The A phase is composed of six poles A ₁ to A ₆ formed at equal intervals every other two, and similarly, the B phase is right next to the A phase pole in the clockwise direction and every other two. It consists of _six poles B _{1 to} B ₆ formed at intervals, and the C phase consists of _six poles C _{1 to} C ₆ formed on the right side of the B phase pole in the clockwise direction and at equal intervals. It has become. As a result, the poles are arranged on the inner peripheral surface of the stator 14 in the order of A ₁ -B ₁ -C ₁ -to -A ₆ -B ₆ -C ₆ .
[0019]
Armature coils L _{A1 to} L _C6 are wound around the poles A _{1 to} C ₆ , respectively. Coils L _{A1 to} L _A6 constitute an A-phase armature winding 12a among the armature windings, and coils L _{B1 to} L _B6 constitute a B-phase armature winding 12b among the armature windings. The coils L _{C1 to} L _C6 constitute a C-phase armature winding 12c among the armature windings.
Next, the connection configuration of the coils L _{A1 to} L _C6 will be described with reference to FIG. Since each of the armature windings 12a to 12c has the same configuration, only the connection configuration of the armature winding 12a will be described below, and that of the armature windings 12b and 12c will be described. Omitted. FIG. 3 is a connection diagram showing a connection configuration of the armature winding 12a.
[0020]
As shown in FIG. 3, the armature winding 12a is configured by connecting coils L _{A1 to} L _A6 and 16 switches S _{1 to} S ₄₃ . Each of the switches S _{1 to} S ₄₃ is composed of, for example, a relay switch, and can take one of an on state and an off state in accordance with a switching signal from the switch 30. Note that these switches S _{1 to} S ₄₃ are not limited to relay switches, and may be constituted by, for example, power semiconductor switches.
[0021]
The connection configuration will be described. First, in FIG. 3, five switches S _{1 to} S ₅ are connected in series, and separately from this, six switches S _{11 to} S ₁₅ are connected in series. Then, connected to the 3-phase AC power source end of the switch S ₅ (P ₆ points) are not shown (U point), one end of the switch S ₁₁ (P ₁₁ points) other armature winding 12b, the wiring of the 12c It is connected to a point (O point).
[0022]
The switch S ₂ of the switch S ₁ coil L _A1 is connected by connecting and the P ₁₁ points opposite terminals (P ₁ point), the midpoint of the switch S _1, S ₂ and (P ₂ points) switches S _11, the coil L _A2 by connecting a midpoint of S ₁₂ (P ₁₂ points) is connected, a midpoint of the midpoint of the switch S _2, S ₃ and (P ₃ points) switches S _12, S ₁₃ (P ₁₃ The coil L _A3 is connected.
[0023]
The coil L _A4 is connected by connecting midpoint of the switch S _3, S ₄ and (P ₄ points) and the midpoint of the switch S _13, S ₁₄ (P ₁₄ points) among the switches S _4, S ₅ the point (P ₅ points) and the coil L _A5 are connected by connecting the middle point of the switch S _14, S _{15 (15} points P), opposite terminal (P ₁₆ points) the switch S ₁₄ switches S ₁₅ And P ₆ are connected to the coil L _A6 .
[0024]
On the other hand, the switch S ₂₁ is connected by connecting _one point and the P ₁₂ point P, switch S ₂₂ is connected by connecting the _two points and the P ₁₃ point P, by connecting the _three points and the P ₁₄ point P switch S ₂₃ is connected. Further, the switch S ₂₄ is connected by connecting the _four points and the P ₁₅ point P, switch S ₂₅ is connected by connecting the _five points and P ₁₆ points P.
The switch S ₃₁ is connected by connecting the _two points and the point U P, switch S ₃₂ is connected by connecting the _three points and the U point P, switch S ₃₃ is by connecting the _four points and the point U P It is connected. Further, the connection switch S ₄₁ is entered into the P ₁₃ points and the point O, the switch S ₄₂ is connected by connecting a _14-point P and the point O, the switch S ₄₅ connects a _15-point P and the point O It is connected.
[0025]
Next, the configuration of the switch 30 will be described with reference to FIG. FIG. 4 is a diagram illustrating a connection switching pattern of the switch 30.
As shown in FIG. 4, the switching device 30 has four switching patterns, and outputs a switching signal to each of the switches S _{1 to} S ₄₃ based on the designated switching pattern, whereby the armature winding The switches S _{1 to} S ₄₃ are turned on / off so that the reactance of 12a is variable.
[0026]
The first switching pattern is a pattern in which the coils L _{A1 to} L _A6 are connected in series so that the reactance of the armature winding 12a is maximized, and the switch 30 is designated as the first pattern. Each of the switches S _{1 to} S ₅ , the switches S _{11 to} S ₁₅ , the switches S _{31 to} S ₃₃ , and the switches S _{41 to} S ₄₃ are turned off and the switches S _{21 to} S ₂₅ are turned on. A switching signal is output to the switches S _{1 to} S ₄₃ .
[0027]
In the second switching pattern, the coils L _{A1 to} L _A3 are connected in series and the coils L _{A4 to} L _A6 are connected in series so that the reactance of the armature winding 12a is the second largest. a pattern for connecting in parallel, switching device 30, when the second pattern is designated, and switches S ₁ to S _5, the switch S ₁₁ to S _15, switches S _23, switches S _31, S _33, A switch signal is sent to each of the switches S _{1 to} S ₄₃ so that the switches S ₄₁ and S ₄₃ are turned off and the switches S ₂₁ , S ₂₂ , S ₂₄ , S ₂₅ , the switch S ₃₂ , and the switch S ₄₂ are turned on. Is output.
[0028]
In the third switching pattern, the coils L _A1 and L _A2 are connected in series, the coils L _A3 and L _A4 are connected in series, and the coils L _A5 and L _A6 are set so that the reactance of the armature winding 12a is the third largest. A pattern in which these are connected in series and further connected in parallel. When the third pattern is designated, the switch 30 is configured to switch S _{1 to} S ₅ , switch S _{11 to} S ₁₅ , switch S ₂₂ , S ₂₄ , switch S ₃₂ , and switch S ₄₂ are turned off, and switches S ₂₁ , S ₂₃ , S ₂₅ , switches S ₃₁ , S ₃₃ , and switches S ₄₁ , S ₄₃ are turned on. A switching signal is output to each of the switches S _{1 to} S ₄₃ .
[0029]
The fourth switching pattern is a pattern in which the coils L _{A1 to} L _A6 are connected in parallel so that the reactance of the armature winding 12a is minimized, and the switch 30 is designated as the fourth pattern. The switches S _{21 to} S ₂₅ , the switches S _{31 to} S ₃₃ , and the switches S _{41 to} S ₄₃ are turned off, and the switches S _{1 to} S ₅ and the switches S _{11 to} S ₁₅ are turned on. A switching signal is output to each of the switches S _{1 to} S ₄₃ .
[0030]
The description of the armature windings 12b and 12c is omitted, but the switch 30 switches the connection pattern of the armature windings 12a and changes the connection pattern of the armature windings 12b and 12c to the armature windings. The connection pattern is switched to the same as 12a.
Next, the operation of the above embodiment will be described with reference to FIGS. FIG. 5 is a diagram showing a connection state of the armature winding 12 a, and FIG. 6 is a graph showing the torque-rotational speed characteristics of the motor 10.
[0031]
First, when the first switching pattern is designated for the switch 30, the switch 30 outputs a switch signal to each of the switches S _{1 to} S ₄₃ in the armature winding 12 a, thereby switching the switch S _1. ˜S ₅ , switches S _{11 to} S ₁₅ , switches S _{31 to} S ₃₃ , and switches S _{41 to} S ₄₃ are turned off, and switches S _{21 to} S ₂₅ are turned on. As shown in a), the coils L _{A1 to} L _A6 are connected in series. Therefore, the reactance of the armature winding 12a is “6L” when the reactance of each of the coils L _{A1 to} L _A6 is L, which is the maximum value among the four switching patterns.
[0032]
Similarly, in the armature winding 12b, the coils L _{B1 to} L _B6 are connected in series, and in the armature winding 12c, the coils L _{C1 to} L _C6 are connected in series.
In this state, when a predetermined armature voltage is applied to the motor 10, the rotor 15 rotates and, as shown by the solid line in FIG. 6, the maximum rotational speed is the minimum N ₁ of the four switching patterns. As for the maximum torque output, a torque-rotational speed characteristic having the maximum T ₁ among the four switching patterns is obtained.
[0033]
Normally, the torque output of the motor 10 is determined by the magnetic flux generated between the rotor 15 and the stator 14 and the current flowing through the armature windings 12a to 12c. The current flowing through the armature windings 12a to 12c is a value obtained by dividing the applied armature voltage by the winding resistance of the coils L _{A1 to} L _C6 in accordance with Ohm's law because the back electromotive force is small at low rotation. However, when the rotational speed increases, the counter electromotive force, which is a reaction induced voltage, is generated by the magnetic flux of the rotor 15 in a direction that cancels the armature voltage, so that the current flowing through the armature windings 12a to 12c decreases. Thereby, the rotation speed of the motor 10 can take a value in a range where the back electromotive force does not exceed the armature voltage.
[0034]
Therefore, when the reactance of the armature windings 12a to 12c is increased, the amount of increase in the counter electromotive force with respect to the increase in the number of rotations is increased, so that the maximum number of rotations is decreased. Since the magnetic flux generated between the two increases, the maximum torque output increases. This means the torque-rotational speed characteristic of the motor 10 when switched by the first switching pattern.
[0035]
Next, when the second switching pattern is designated for the switch 30, the switch 30 outputs a switch signal to each of the switches S _{1 to} S ₄₃ in the armature winding 12 a, so that the switch S ₁ to S _5, the switch S ₁₁ to S _15, switches S _23, switches S _31, S _33, and the switch S _41, S ₄₃ are turned off, switches _{S 21, S 22, S 24} , S 25 Since the switch S ₃₂ and the switch S ₄₂ are turned on, the coils L _{A1 to} L _A3 are connected in series and the coils L _{A4 to} L _A6 are connected in series as shown in FIG. Furthermore, these are connected in parallel. Therefore, the reactance of the armature winding 12a is “1.5L”, where L is the reactance of each of the coils L _{A1 to} L _A6 , and is the second largest value among the four switching patterns.
[0036]
Similarly, in the armature winding 12b, the coils L _{B1 to} L _B3 are connected in series, the coils L _{B4 to} L _B6 are connected in series, and these are further connected in parallel to form the armature winding 12c. The coils L _{C1 to} L _C3 are connected in series, the coils L _{C4 to} L _C6 are connected in series, and these are further connected in parallel.
In this state, when the same predetermined armature voltage as described above is applied to the motor 10, the rotor 15 rotates, and the maximum rotational speed is the second smallest among the four switching patterns as shown by the dotted line in FIG. N ₂ , and the maximum torque output has a torque-rotational speed characteristic in which T ₂ is the second largest among the four switching patterns.
[0037]
Next, when the third switching pattern is designated for the switch 30, the switch 30 outputs a switch signal to each of the switches S _{1 to} S ₄₃ in the armature winding 12 a, so that the switch S _{1 to} S ₅ , switches S _{11 to} S ₁₅ , switches S ₂₂ and S ₂₄ , switch S ₃₂ , and switch S ₄₂ are turned off, and switches S ₂₁ , S ₂₃ , S ₂₅ , switches S ₃₁ , S ₃₃ and switches S ₄₁ and S ₄₃ are turned on, so that coils L _A1 and L _A2 are connected in series, coils L _A3 and L _A4 are connected in series, and coil L _A5 is turned on as shown in FIG. , L _A6 are connected in series, and these are connected in parallel. Therefore, the reactance of the armature winding 12a is “0.667L” when the reactance of each of the coils L _{A1 to} L _A6 is L, which is the third largest value among the four switching patterns.
[0038]
Similarly, in the armature winding 12b, the coils L _B1 and L _B2 are connected in series, the coils L _B3 and L _B4 are connected in series, and the coils L _B5 and L _B6 are connected in series. In the armature winding 12c, the coils L _C1 and L _C2 are connected in series, the coils L _C3 and L _C4 are connected in series, and the coils L _C5 and L _C6 are connected in series. Connected to
[0039]
In this state, when the same predetermined armature voltage as described above is applied to the motor 10, the rotor 15 rotates, and the maximum number of rotations is the second of the four switching patterns as shown by the one-dot chain line in FIG. 6. A torque-rotational speed characteristic is obtained in which N _{3 is} large and the maximum torque output is T _{3 which} is the second smallest among the four switching patterns.
Next, when the fourth switching pattern is designated for the switch 30, the switch 30 outputs a switch signal to each of the switches S _{1 to} S ₄₃ in the armature winding 12 a, and the switch S ₂₁ to S _25, the switch S ₃₁ to S _33, and the switch S ₄₁ to S ₄₃ is turned off, the switch S ₁ to S _5, and the switch S ₁₁ to S ₁₅ is turned on, FIG. As shown in FIG. 5 (d), the coils L _{A1 to} L _A6 are connected in parallel. Therefore, the reactance of the armature winding 12a is “0.167L” when the reactance of each of the coils L _{A1 to} L _A6 is L, which is the minimum value among the four switching patterns.
[0040]
Similarly, in the armature winding 12b, the coils L _{B1 to} L _B6 are connected in parallel, and in the armature winding 12c, the coils L _{C1 to} L _C6 are connected in parallel.
In this state, when the same predetermined armature voltage as described above is applied to the motor 10, the rotor 15 rotates and, as shown by the two-dot chain line in FIG. N ₄ , and the maximum torque output has a torque-rotational speed characteristic that is the minimum T _{4 of the four} switching patterns.
[0041]
The necessity for switching as described above lies in limiting the current of the driver. For example, a driver capable of flowing an infinite current may flow a large current with the connection pattern shown in FIG. 5D, but in reality, only a finite value can flow, so the switching method of the present invention is effective.
In this way, in the present embodiment, the switch 30 is provided, and the switch 30 has the coils L _A1 to ₆ in the _six poles A _{1 to} A ₆ so that the reactance of the armature winding 12a is variable. The connection pattern of L _A6 can be switched, and the connection patterns of the coils L _{B1 to} L _{B6 in} the _six poles B _{1 to} B ₆ can be switched so that the reactance of the armature winding 12b can be changed. The connection patterns of the coils L _{C1 to} L _{C6 in} the _six poles C _{1 to} C ₆ can be switched so that the reactance of the winding 12c is variable.
[0042]
For this reason, even after the motor 10 is completed, the characteristics can be changed by switching the connection pattern with the switch 30. Therefore, the same motor 10 can be used when the usage is different or when the usage is different even in the same usage, and the versatility of the motor 10 can be improved as compared with the conventional case.
In the present embodiment, the connection patterns of the coils L _{A1 to} L _A6 are switched, and the elements that affect the output of the motor 10 such as the magnets M _{N1 to} M _S6 and the iron core 15a are not changed. Therefore, the output of the motor 10 does not increase or decrease by switching, and only the characteristics of the motor 10 are changed.
[0043]
In the above embodiment, the connection pattern switching device according to the present invention is applied to a three-phase AC motor. However, the present invention is not limited to this, and can be applied to a single-phase or four-phase or more motor.
In the above embodiment, the connection pattern switching device according to the present invention is applied to a motor having 6 poles per phase. However, the present invention is not limited to this. It can also be applied to a motor having the same.
[0044]
In the above embodiment, four switching patterns are provided. However, the present invention is not limited to this. For example, the switches S _{2 to} S ₅ , the switches S _{12 to} S ₁₅ , and the switches S _{21 to} S ₂₄ are turned off. By turning on the switch S ₁ , the switch S ₁₁ , the switch S ₂₅ , the switches S _{31 to} S ₃₃ , and the switches S _{41 to} S ₄₃ , the coils L _A1 and L _A2 are connected in series. And a plurality of switching patterns may be provided, such as adding a fifth switching pattern for connecting the coils L _{A3 to} L _A6 in parallel.
[0045]
In the above embodiment, the switch 30 corresponds to the switching means described in claims 1 and 2 .
[0046]
【The invention's effect】
As described above, according to the connection pattern switching device according to claim 1 or 2 of the present invention, the characteristics can be changed by switching the connection pattern even after the motor is completed. The same motor can be used when the usage is different or when the usage is different even in the same usage, and the versatility of the motor can be improved as compared with the conventional case.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a system to which a connection pattern switching device according to the present invention is applied.
2 is a cross-sectional view of a motor 10. FIG.
FIG. 3 is a connection diagram showing a connection configuration of armature windings 12a.
FIG. 4 is a diagram showing a connection switching pattern of the switch 30;
FIG. 5 is a diagram showing a connection state of an armature winding 12a.
6 is a graph showing torque-rotational speed characteristics of a motor 10. FIG.
[Explanation of symbols]
10 motor 12a~12c armature winding 14 stator 15 rotor 15a iron core 15b shaft 20 drivers 30 switching unit A ₁ -C ₆ pole L _A1 ~L _C6 coil S ₁ to S ₄₃ switch

Claims (2)

The present invention is applied to a motor including a plurality of coils wound around each of at least three poles, a stator in which armature windings are formed by the plurality of coils , and a rotor rotatably provided inside the stator. A device,
Among the plurality of coils , the first coil, the second coil, and the third coil are connected in parallel in that order, and between the one ends of the adjacent coils of the three coils, between the other ends of the adjacent coils. A switch between the one end of the first coil and the other end of the second coil, and between the one end of the second coil and the other end of the third coil ,
A current path is formed to connect the one end of each of the first coil and the third coil from a first common contact provided on the outside of the plurality of coils, and the first common contact and the first the switch provided in the current path connecting the one end of the coil,
A current path is formed to connect the other end of each of the first coil and the second coil from a second common contact provided on the outer side of the plurality of coils, and connected to the second common contact. A switch is provided for all of the current paths
A connection pattern switching device comprising switching means for switching each of the switches independently. The present invention is applied to a motor including a plurality of coils wound around each of at least three poles, a stator in which armature windings are formed by the plurality of coils , and a rotor rotatably provided inside the stator. A device,
Among the plurality of coils , the first coil, the second coil, and the third coil are connected in parallel in that order, and between the one ends of the adjacent coils of the three coils, between the other ends of the adjacent coils. A switch between the one end of the first coil and the other end of the second coil, and between the one end of the second coil and the other end of the third coil ,
Wherein the plurality of the first common contact provided on the outer side of the coil of the three said one end of the coil to form a current path that connects each second common provided on the outer side of said plurality of coils Forming a current path for connecting the other ends of the three coils from the contact points, and providing a switch in all of the current paths,
A connection pattern switching device comprising switching means for switching each of the switches independently.

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