JP5298957B2 - Permanent magnet motor - Google Patents

Description

  The present invention relates to an improvement in a permanent magnet type electric motor.

Conventionally, in permanent magnet motors, permanent magnets are embedded in the rotor so that the polarities are alternately different from each other in the direction around the axis of the rotation shaft, and the permanent magnets are surrounded by the outer periphery of the rotor. The thing of the structure which arrange | positions a cage-type conductor is known (for example, refer patent document 1).
According to this conventional permanent magnet type electric motor, current flows in the cage conductor in a direction that hinders the change in the magnetic flux generated with the rotation of the rotor. As a result, the eddy current loss of the permanent magnet and the iron loss of the rotor are reduced.

Japanese Patent Publication No.59-23179

However, according to this type of permanent magnet type motor, since the magnetic flux of the high frequency component by the PWM control cannot pass through the rotor, the back electromotive force due to the high frequency component is not generated in the stator coil, and the inductance of the stator coil is increased. As a result, the current flowing in the stator coil continues to increase, the harmonic current generated by PWM control increases, and this should be suppressed in a normal permanent magnet motor without a cage conductor. There is a problem that the high frequency current resulting from the magnetic flux of the high frequency component by PWM control becomes large.
The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a permanent magnet type electric motor capable of ensuring inductance while suppressing magnetic flux fluctuations generated in a rotor.

  According to the present invention, coils having opposite winding directions are provided on the front side and the rear side in the rotation direction of each magnetic pole portion of a rotor in which a permanent magnet is embedded, thereby preventing changes in interlinkage magnetic flux passing through the coils. The coils are connected in series so that currents generated in the directions are opposite to each other.

  According to the present invention, since the coils are provided on the front side and the rear side in the rotational direction of the rotor so that the winding directions are opposite to each other and the coils are connected in series, the interlinkage magnetic flux generated in each coil. As a result, zero is obtained, and by ensuring the inductance when the stator coil faces the magnetic pole part, an increase in harmonic current due to PWM control can be suppressed.

FIG. 1 is a graph showing an example of magnetic flux fluctuations that occur in a normal permanent magnet motor that is not provided with a conventional concentrated winding squirrel-cage conductor that is currently mainstream. FIG. 2 is an external view showing the configuration of the rotor of the permanent magnet type electric motor according to Embodiment 1 of the present invention. FIG. 3 is an explanatory view showing the flow of the D-axis magnetic flux. FIG. 4 is an explanatory diagram showing the flow of the Q-axis magnetic flux. FIG. 5 is a graph showing a comparison of the inductance for each coil type of the magnetic pole part. FIG. 6 is a graph showing a comparison of the amplitude of the PWM harmonic current for each coil type of the magnetic pole portion calculated based on the inductance shown in FIG. FIG. 7 compares the eddy current loss of a permanent magnet in the case of a normal permanent magnet motor in which no coil is arranged in the magnetic pole part, and the eddy current loss in the case where the coil according to the embodiment of the present invention is arranged in the magnetic pole part. It is a graph shown. FIG. 8 is an explanatory view showing the positional relationship of the coils with respect to the plate-like permanent magnet. FIG. 9 is a partially enlarged perspective view of a rotor in which a plate-like permanent magnet is divided into two at the center in the rotational direction and two plate-like divided magnets are arranged in a V shape and embedded in each magnetic pole portion. . FIG. 10 is an explanatory view showing an example of a method for manufacturing a rotor according to the present invention.

FIG. 2 is a perspective view showing an external configuration of the cylindrical rotor 1 of the permanent magnet type electric motor according to the present invention. The rotor 1 is formed by laminating disc-shaped steel plates in the rotation axis direction.
The rotor 1 has a rotor core portion 2 as a core yoke portion at the center thereof, and has a plurality of magnetic pole portions 3 as core back yoke portions in the circumferential direction at the radially outer peripheral portion thereof. The magnetic pole portions 3 are formed at equiangular intervals in the circumferential direction of the rotor 1. Between the magnetic pole parts 3 adjacent to each other, there are gaps 4 that extend long in the direction of the rotation axis, and the boundaries of the magnetic poles of the magnetic pole parts 3 are defined by the gaps 4.

  Each magnetic pole portion 3 has a buried hole, and a plate-like permanent magnet 5 is buried in each buried hole. The plate-like permanent magnets 5 are arranged such that the magnetic poles N or S of magnets adjacent to each other in the rotational direction have opposite polarities with respect to the stator (not shown).

  The magnetic pole portion 3 is provided with coils 6 and 7 whose winding directions are opposite to each other on the front side and the rear side in the rotational direction of the rotor 1. As shown in FIG. 2, the coils 6 and 7 are connected in series so that the currents i based on the electromotive force generated in the direction preventing the change of the linkage flux Φ passing through the coils 6 and 7 are opposite to each other. The crossing point Q of the coil 6 and the coil 7 is symmetrical with respect to the magnetic flux penetrating the coil 6 and the coil 7, and is located at the center position in the rotation direction of the rotor 1 and in the rotation axis direction center of the rotor 1. Located in position.

  With respect to the rotor 1, the interlinkage magnetic flux generated by the stator coil is a D magnetic flux when the stator magnetic pole part is directly opposed to the magnetic pole part 3 of the rotor 1, and the stator magnetic pole is placed in the gap 4 between the magnetic poles of the rotor 1. As shown in FIG. 3, the D-axis magnetic flux Φ from the stator coil penetrates the magnetic pole part 3 from the front, and the Q-axis magnetic flux Φ from the stator coil is As shown in FIG. 4, the magnetic flux flows from the gap portion 4 through the rotor core portion 2 toward the adjacent gap portion 4 and the magnetic flux passing through the outer peripheral surface portion 3 a of the magnetic pole portion 3. There is almost no interlinkage.

  Since the winding directions of the coils 6 and 7 are opposite in the rotation direction front side and the rotation direction rear side of the rotor 1, respectively, as shown in FIG. 3, the direction in which the current i1 flows and the direction in which the current i2 flows Are opposite to each other in the direction in which the magnetic flux changes, and the interlinkage magnetic flux Φ passing through the coils 6 and 7 is equivalent to “0”. Therefore, the magnetic flux from the stator coil is not suppressed by the coils 6 and 7 but goes to the adjacent magnetic pole portion 3 through the rotor core portion 2, so that a D-axis inductance is ensured.

  On the other hand, as shown in FIG. 4, the Q-axis magnetic flux Φ mainly passes through the outer peripheral surface portion 3 a and passes from one of the adjacent gap portions 4 between the magnetic pole portions 3 toward the other gap portion 4. Q-axis inductance is also ensured. Since the magnetic flux Φ ′ from some stator coils penetrates the coils 6 and 7, the magnetic flux from the stator coils is suppressed accordingly.

FIG. 5 is a graph showing an example of the inductance for each coil type of the magnetic pole part 3. In FIG. 5, (a) shows a D-axis inductance L _D and a Q-axis inductance L _{Q in} the case of a normal concentrated winding permanent magnet type electric motor in which no coil is arranged in the magnetic pole part 3, and (b) shows The D-axis inductance L _D and the Q-axis inductance L _{Q in} the case of the permanent magnet type motor in which the coils 6 and 7 according to the embodiment of the present invention are arranged in the magnetic pole part 3 are shown. A D-axis inductance L _D and a Q-axis inductance L _{Q in} the case of a permanent magnet type motor in which a coil of a loop is arranged are shown. An axis inductance L _D and a Q axis inductance L _Q are shown. As apparent from FIG. 5, the D-axis inductance L _D and the Q-axis inductance L _{Q in} the case of the permanent magnet type motor with the cage-type conductor arranged are very small as shown in FIG. On the other hand, the D-axis inductance L _D and the Q-axis inductance L _{Q in} the case of the permanent magnet type motor in which the coils 6 and 7 according to the embodiment of the present invention are arranged in the magnetic pole portion 3 are as shown in FIG. In addition, an inductance equivalent to the D-axis inductance L _D and the Q-axis inductance L _{Q in} the case of a normal permanent magnet type motor in which no coil is arranged in the magnetic pole portion 3 shown in FIG. Further, the D-axis inductance L _{D in} the case of the permanent magnet type motor in which the coils 6 and 7 according to the embodiment of the present invention are arranged in the magnetic pole part 3 is a single loop coil in the magnetic pole part 3 shown in FIG. D-axis inductance L _D compared with D-axis inductance L _D in the case of permanent magnet type electric motor arranged it is much improved. In FIG. 5, (mH) represents a unit of inductance.

  FIG. 6 shows a comparison of the amplitude of the PWM harmonic current (ripple current) for each coil type of the magnetic pole portion 3 calculated based on the inductance shown in FIG. In FIG. 6, the maximum amplitude of the PWM harmonic current when the DC voltage Vdc = 300 V is applied to the stator coil and the frequency fc = 10 KHz is set separately for the D-axis magnetic flux and the Q-axis magnetic flux. Has been.

  In FIG. 6, (a) shows the amplitude of the PWM harmonic current in the case of a normal concentrated winding permanent magnet motor in which no coil is arranged in the magnetic pole part 3, and (b) shows the magnetic pole part 3 in the embodiment of the present invention. The amplitude of the PWM harmonic current in the case of the permanent magnet type motor in which the coils 6 and 7 are arranged, and (c) is the PWM harmonic current in the case of the permanent magnet type motor in which a single loop coil is arranged in the magnetic pole part 3. Amplitude, (d) shows the amplitude of the PWM harmonic current in the case of a permanent magnet type motor in which a squirrel-cage conductor is arranged in the magnetic pole part 3.

  As is apparent from FIG. 6, the amplitude of the PWM harmonic current when the coils 6 and 7 according to the embodiment of the present invention are arranged in the magnetic pole part 3 is shown in FIG. 6B for the D-axis magnetic flux. As described above, the amplitude of the PWM harmonic current when a single-loop coil is arranged in the magnetic pole part 3 shown in FIG. 6C, and the case where a cage conductor is arranged in the magnetic pole part 3 shown in FIG. The amplitude of the PWM harmonic current is reduced by about 70%, and the increase of the PWM harmonic current is suppressed. The amplitude of the PWM harmonic current in the case where the coils 6 and 7 according to the embodiment of the present invention are arranged in the magnetic pole part 3 is the same as that of the normal concentrated winding in which no coil is arranged in the magnetic pole part 3 shown in FIG. This is almost the same as the amplitude of the PWM harmonic current in the case of a permanent magnet motor.

FIG. 7 shows the eddy current loss of a permanent magnet in the case of an ordinary permanent magnet motor in which no coil is arranged in the magnetic pole part 3, and the eddy when the coils 6 and 7 according to the embodiment of the present invention are arranged in the magnetic pole part 3. The current loss is shown in comparison.
In FIG. 7, the horizontal axis is the current advance angle β (deg), the vertical axis is the eddy current loss (W), and the symbol (a) is the permanent in the case of a normal electric motor in which no coil is arranged in the magnetic pole part 3. An eddy current loss curve of the magnet is shown, and symbol (b) shows an eddy current loss curve when the coils 6 and 7 according to the embodiment of the present invention are arranged in the magnetic pole part 3. This eddy current loss curve is a value obtained when measurement was performed under the conditions where the rotor rotation speed was 4000 (rpm) and the rated current was 283 Arms.

  As is apparent from FIG. 7, the eddy current loss of the permanent magnet when the coils 6 and 7 according to the embodiment of the present invention are arranged in the magnetic pole portion 3 is as shown in FIG. In contrast to the eddy current loss of the permanent magnet in the case of the ordinary concentrated winding permanent magnet motor in which the coil is not disposed in the magnetic pole portion 3 shown in (a) of FIG. A reduction effect of about 22% is obtained.

That is, according to the embodiment of the present invention, the coils 6 and 7 are provided on the front side and the rear side in the rotational direction of the rotor so that the directions of the windings are opposite to each other. The coils 6 and 7 are connected in series so that the current generated in one of the coils 6 (7) flows in the opposite direction to the current generated in the other coil 7 (6) based on the change in the linkage flux. Therefore, magnetic flux fluctuations in the opposite phase can be suppressed, and accordingly, eddy current loss generated in the plate-like permanent magnet 5 and iron loss of the rotor 1 can be reduced.
In other words, in a normal permanent magnet type electric motor that is not provided with a current mainstream concentrated winding squirrel-cage conductor, as shown in FIG. In this case, magnetic flux fluctuations in opposite phases occur. Therefore, if coils are arranged at the front part and the rear part in the rotational direction of the rotor and the coils are connected in series so that the direction of the current flowing through the coils is opposite, the magnetic flux Currents in directions that prevent fluctuations flow in the opposite directions, respectively, and magnetic flux fluctuations in the opposite phase can be suppressed, and loss of eddy currents generated in the permanent magnets and the rotor can be reduced.
Further, since the currents flowing in the coil arranged on the front side in the rotation direction and the coil arranged on the rear side in the rotation direction are opposite to each other, the interlinkage magnetic flux generated in each coil becomes zero as a result. The D-axis inductance when facing the part is ensured, and an increase in harmonic current due to PWM control can be suppressed.

  Further, since the outer peripheral surface of the magnetic pole portion 3 is provided radially outward from the coils 6 and 7, the Q-axis inductance can be ensured, and by securing this Q-axis inductance, the coil is placed in front of each coil of the concentrated winding stator. The PWM harmonic current in the case where the gap 4 which is the intermediate position (Q axis) between the magnetic pole portion 3 and the magnetic pole portion 3 adjacent to the one magnetic pole portion 3 faces each other can also be suppressed.

(Example 2)
FIG. 8 is an explanatory diagram showing an arrangement positional relationship of the coils 6 and 7 with respect to the plate-like permanent magnet 5. FIG. 8A shows the coils 6 and 7 disposed outside the magnetic pole face on the radially outer side of the plate-like permanent magnet 5 and adjacent to or near the plate-like permanent magnet 5. The coils 6 and 7 may be a single turn or a plurality of turns. FIG. 8B shows the coils 6 and 7 arranged on the inner side of the magnetic pole surface on the inner side in the radial direction of the plate-like permanent magnet 5 and adjacent to or near the plate-like permanent magnet 5. In FIG. 8C, the plate-shaped permanent magnet 5 is divided into two at the center in the rotation direction, and is composed of a plate-shaped divided magnet 5a and a plate-shaped divided magnet 5b. A coil 6 is wound around the outer peripheral surface of the plate-shaped divided magnet 5a. Turn to integrate the plate-like divided magnet 5a and the coil 6 and wind the coil 7 around the peripheral surface of the plate-like divided magnet 5b to integrate the plate-like divided magnet 5b and the coil 7 and embed them in the magnetic pole part 3. It is set as the structure to do.
If the coils 6 and 7 are wound around the outer peripheral surface of the plate-shaped permanent magnet to achieve integration, the coils 6 and 7 and the plate-shaped permanent magnet can be combined in a compact manner, and space efficiency can be ensured. .

The terminals 6a and 7a of the coils 6 and 7 are connected in series so that the currents i1 and i2 based on the electromotive force generated in the direction that prevents the change of the interlinkage magnetic flux passing through the coils 6 and 7 are opposite to each other. ing. The connection positions of the terminals 6a and 7a are the center position in the rotation direction and the end portion on one side in the rotation axis direction for each magnetic pole portion 3. Since the connecting portion is provided at the center in the rotational direction for each magnetic pole portion 3 and at the end on one side in the rotational axis direction, the coils 6 and 7 can be arranged symmetrically, and the flux linkage is disturbed. Can be substantially avoided. Moreover, since the connection part or intersection of terminal 6a, 7a is provided in the axial end part side of the rotating shaft of the rotor 1, a connection part or intersection is the obstruction at the time of embedding the plate-shaped permanent magnet 5 to an embedding hole. However, the space efficiency can be improved.
In addition, when employ | adopting the structure of the plate-shaped division | segmentation magnets 5a and 5b, in order to ensure intensity | strength, you may provide the bridge | bridging part of the rotor core part 2 between plate-like division | segmentation magnets.

(Example 3)
FIG. 9 shows that the plate-like permanent magnet 5 is divided into two at the center in the rotational direction, and is composed of a plate-like divided magnet 5a and a plate-like divided magnet 5b, and the plate-like divided magnet 5a and the plate-like divided magnet 5b are V-shaped. It is arranged to be embedded in each magnetic pole part 3. The coils 6 and 7 are coils 6 and 7 disposed outside the radially inner magnetic pole surface and adjacent to or in the vicinity of the plate-like divided magnets 5a and 5b.
In this embodiment, the coil 6 and the coil 7 are arranged outside the radially inner magnetic pole surface and adjacent to or in the vicinity of the divided magnets 5a and 5b. Is arranged on the inner side of the magnetic pole surface on the inner side in the radial direction and adjacent to or in the vicinity of the divided magnets 5a and 5b, and the coil 6 is wound around the peripheral surface of the plate-shaped divided magnet 5a to form the plate-shaped divided magnet 5a. And the coil 6 may be integrated, and the coil 7 may be wound around the peripheral surface of the plate-shaped divided magnet 5b so that the plate-shaped divided magnet 5b and the coil 7 are integrated and embedded in the magnetic pole portion 3. it can.

Example 4
FIG. 10 is an explanatory view showing an example of a method for assembling a coil to the plate-like permanent magnet 5 according to the embodiment of the present invention. FIG. 10 shows a method of assembling the coils to the plate-like divided magnets 5a and 5b.
First, the plate-shaped divided magnet 5a (5b) and the air-core coil 6a ′ (7a ′) are prepared as shown in FIG. Then, the plate-shaped divided magnet 5a (5b) is surrounded by the air-core coil 6a '(7a') as shown in (b) so that the plate-shaped divided magnet 5a (5b) is surrounded by the air-core coil. 6a '(7a').
Next, the plate-like split magnet 5a (5b) and the air-core coil 6a ′ (7a ′) are exposed to the terminal 6a ″ (7a ″) of the air-core coil 6a ′ (7a ′) (c). The resin-sealed plate-shaped divided magnet 9 is formed by sealing with the resin 8 as shown in FIG. Two of these resin-encapsulated plate-like divided magnets 9 are prepared, and the resin-encapsulated plate-like divided magnet 9 is made to have a magnetic pole portion so that the same magnetic pole faces radially outward or inward as shown in FIG. The terminals 6a "and 7a" are connected so that the currents i1 and i2 based on the interlinkage magnetic flux flow in opposite directions.

  According to this embodiment, since the permanent magnet and the coil are resin-sealed and integrated, the insulation, strength, and assembly of the rotor 1 are improved. In addition, since the resin-sealed plate-shaped divided magnet 9 is installed in the embedded hole formed in each magnetic pole portion 3, it becomes easy to ensure dimensional accuracy, and the resin-sealed plate-shaped divided magnet 9 in the rotor 1. It is also easy to prevent rattling.

DESCRIPTION OF SYMBOLS 1 ... Rotor 2 ... Rotor core part 3 ... Magnetic pole part 4 ... Air gap part 5 ... Plate-shaped permanent magnet 6, 7 ... Coil

Claims (5)

In a permanent magnet type electric motor having a rotor in which a permanent magnet is embedded in a magnetic pole portion formed in a rotation direction,
Each magnetic pole portion of the rotor is provided with coils whose winding directions are opposite to each other on the front side in the rotation direction and the rear side in the rotation direction of the rotor, and the coils are generated in one coil based on the change of the interlinkage magnetic flux. The permanent magnet type motor is characterized in that the current is connected in series so as to flow in the opposite direction to the current generated in the other coil based on the change of the linkage flux.   2. The permanent magnet motor according to claim 1, wherein an outer peripheral surface of the magnetic pole portion is present radially outward from each of the coils.   The permanent magnet type electric motor according to claim 1, wherein an intersection portion or a connection portion of each coil is located on the rotor shaft end side.   The permanent magnet embedded in the magnetic pole portion is composed of a plate-shaped divided magnetic pole on the front side in the rotation direction and a rear side in the rotation direction, and surrounds each plate-shaped divided magnetic pole on the outer peripheral surface of the plate-shaped divided magnetic pole. The permanent magnet type electric motor according to claim 1, wherein each of the coils is wound.   The permanent magnet motor according to claim 4, wherein the divided magnet around which each coil is wound is sealed with resin.

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