JPS62268339A - Three-phase synchronous motor - Google Patents

Abstract

PURPOSE:To reduce the occurrence of abnormal torque by removing the influential higher harmonics of high degree in particular of what is contained in the void flux which causes abnormal torque to a three-phase synchronous motor. CONSTITUTION:A three-phase synchronous motor is constituted by relatively skewing the conductor groove of a stator core by an electrics angle of 2pi/n (where n represents the degree of higher harmonics selected as an object for removing the influence) against a rotor pole 3. The rotor pole 3 arranged through an interpolar separating groove 4 skews one cycle of higher harmonics, i.e. by an electric angle of 2pi/n, using n for the higher harmonic degree. Thus, in the part corresponding to the n-th degree higher harmonics of the torque produced to the rotor pole 3, the n-th degree higher harmonic torques are induced, which have the reverse direction and size one another. Consequently, the n-th degree higher harmonic torquew of the void flux acting on the rotor pole is cancelled and no influence gets exercised. The abnormal torque by the n-th degree higher harmonics is therefore produce no longer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a Sanwa Do 3IJl electric motor with a relatively small capacity (for example, an output of 31 W or less) which is designed to smooth torque.

[Conventional technology]

In a three-phase synchronous motor, magnetic flux (hereinafter referred to as "
air gap magnetic flux. ) to various harmonics (5.7th, 11th
, 13, 17, etc.) are included, resulting in magnetic flux fluctuations.

Therefore, under the influence of these harmonics, l-lucrysopulus (torque increases or decreases or fluctuates; hereinafter referred to as "abnormal torque") occurs. In order to avoid this, the conductor grooves (slots) of the stator core are often spaced from the rotor magnetic poles.

Conventionally, the skew is based on the idea that the air gap magnetic flux is smoothed, and the stator is generally pinched by one slot as shown in FIG. In addition, in Figure 3,
1 is a stator core, 2 is a stator slot, 3 is a rotor magnetic pole, and 4 is a separation groove between the skewed magnetic poles.

In this way, the distance between slot 2 and the magnetic pole H? #4
Since the stator and the rotor do not completely match and face each other, and the magnetic flux path between the stator and rotor is always secured, fluctuations in the magnetic flux in the air gap are reduced, and abnormal torque generation is reduced.

On the other hand, it is also being considered to reduce the fluctuation of the air gap magnetic flux itself, and designs are being made to increase the number of slots installed in the stator or to close the openings of the slots. .

[Problem to be solved]

As mentioned above, various measures have been taken to prevent abnormal torque generation. However, none of these methods focus on the harmonics that are the cause of abnormal torque generation and take direct countermeasures, so there is a problem in that torque ripples inevitably remain.

For example, in the conventional skew of the conductor grooves of the stator, relatively high-order high #jA] waves (e.g., 11th order or higher) are generated.
The effects of harmonics can be removed, but harmonics with a large influence (for example, the 5th or 7th order) may be removed by chance, but if they remain without being removed and cause torque ripple. There are many.

In addition, the method of increasing the number of slots in the stator to smooth the torque is possible and effective for large motors, but it is subject to manufacturing constraints for small motors, so It is not possible to increase the number from 1 to too many.

Furthermore, the method of closing the opening of the slot requires a complicated manufacturing process, and is only used in electric motors in a very limited field.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a three-phase synchronous motor with fewer manufacturing restrictions and with less occurrence of abnormal torque.

[Means for solving problems]

In order to achieve the above object, the three-phase synchronous motor of the present invention removes harmonics of a particularly large order among the harmonics contained in the air gap magnetic flux that cause abnormal torque generation. That is, (1) the conductor grooves of the stator core were skewed by 2π/n in electrical angle with respect to the rotor magnetic poles (where n is the order of the harmonic selected as a target for removing the influence).

(2) Next, when the n-th harmonic (for example, the 7th harmonic) is removed by the above-mentioned means, the influence of the r-th harmonic (for example, the 5th harmonic) that was not removed may remain. In such a case, a separate measure for removing the r-order harmonic is required. The countermeasure is to replace the stator core.
(Groove) It was decided to do this by selecting the number.

In other words, the inventors of the present application have devised a method for removing harmonics of a specific order that has a large influence without first increasing the number of slots N provided in the stator core, and have filed a separate patent application (Patent Application No. 61-1884), but this method was also adopted.

The specific means for doing so are as follows.

The number of slots N in the stator core is determined by N - number of poles l x number of phases m x number of grooves for each pole and each phase q, but the value of the number of grooves q for each pole and each phase should be selected as an integer number. do.

In addition, the order of harmonics that have a large influence and that you especially want to remove is r
Then, the stator winding pitch S is 5-(rt)/r
(for short section winding) or s=r/(r+t) (
(In the case of long section windings) However, t: Choose an odd number.

The number N of slots is determined so that the above relationship is satisfied and three-phase balanced winding is possible.

[Effect]

When the above-described means of the present invention is adopted, the effects of two harmonics of the air gap magnetic flux, which are particularly problematic, are eliminated.

In other words, if the conductor grooves of the stator core are skewed by 2π/n in electrical angle with respect to the rotor magnetic poles, the torque ripple generated in the rotor magnetic poles by the n-th harmonic of the air gap magnetic flux will be as described below (Fig. 1 and (see related explanation), and the influence of the n-th harmonic on the torque disappears.

Furthermore, if the number of stator slots is determined according to the design method described above, the same effect as increasing the number of grooves q for each pole and each phase can be obtained without increasing the total number of slots that much, and the winding pinch can be reduced. By selecting a predetermined value, a harmonic current of a specific (order r) will not flow in the secondary circuit (for details, see Japanese Patent Application No. 1884/1984).

Therefore, if measures are taken against the n-th harmonic (e.g., the 7th harmonic) due to the skew of the rotor magnetic poles with respect to the stator conductor grooves, and the r-th harmonic (e.g., the 5th harmonic) on the stator side, it is possible to prevent abnormal torque generation. Two harmonics that have a large influence can be removed at the same time.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Note that this example shows an example of the scope of the claims.

FIG. 1 is a detailed explanatory diagram of the present invention, showing the relationship between the waveform of the air gap magnetic flux and the skew of the stator conductor grooves with respect to the rotor magnetic poles. In order to simplify the drawing and explanation, a case is shown in which the influence of the seventh harmonic included in the air gap magnetic flux is removed,
The explanation will be based on the case where the electric motor has two poles.

In FIG. 1, 5 is the fundamental waveform of the air gap magnetic flux, and 6 is the seventh harmonic waveform. L indicates the stator magnetic pole spacing, and W indicates the rotor core width (length in the rotation axis direction). The half cycle width of the fundamental waveform 5 is spaced apart from the magnetic poles, which is π (mechanical angle minus electrical angle) in the case of a two-pole motor. As shown in the figure, the rotor magnetic poles 3 arranged through the separation grooves 4 correspond to one cycle of the harmonic, assuming that the harmonic order is n (in this example, it is the seventh harmonic, so n-7). In other words, the electrical angle is 2π/
Skew by n.

In this way, the part corresponding to the n-th harmonic in the torque generated at the rotor magnetic poles will be the n-th harmonic torque (ripple) at the position ■, and at the position ■, respectively, as shown by the dotted lines. are induced, and they have mutually opposite directions and magnitudes. Therefore, the nth harmonic torque of the air gap magnetic flux acting on the rotor magnetic poles is canceled out and has no effect. That is, in a synchronous motor equipped with a rotor made in this manner, abnormal torque due to n-th harmonics will not occur.

Although this embodiment has been described with reference to the case where the harmonic order n=7, the present invention is not limited to this, and harmonic orders with a large influence are selected to be removed. For example, the values of 5.7, 11, 13, 17
．． A desired harmonic can be selected from harmonics of orders such as .

Furthermore, the present invention can be similarly applied regardless of the number of poles of the motor, such as 2-pole, 4-pole, 6-pole, etc.

Although the above-mentioned skew of the stator conductor grooves with respect to the rotor magnetic poles greatly reduces the occurrence of abnormal torque, abnormal torque due to harmonics of unerased orders may remain and become a problem. In such a case, countermeasures may be taken on the stator side as well, and specific measures will be explained below with reference to FIG.

FIG. 2 is an explanatory diagram of one embodiment of the stator, and for the purpose of simplifying the drawing and explanation, it shows the case where the influence of the fifth harmonic included in the air gap magnetic flux is removed, and it is also used in a small synchronous motor. This figure shows a design in which the number N of slots in the stator core is as small as possible to be practical.

That is, the number of poles l-2, the number of phases m-3, the number of grooves for each pole button q
= 2.5 (inconsistent number), number of slots N-2X3X2
．． This is the case when 5=15. The stator winding pitch was short-pitch winding, and t=1.

In Figure 2, (al is a developed view of the stator slots, Figure (b) is a magnetic flux distribution showing the fundamental wave and the 5th harmonic to be removed, and +c+ is fixed?! - This figure shows the relationship between slot positions and pitches in the winding. In the figure, 7 is the fundamental wave, and 8 is the fifth harmonic.

In this example, the harmonic order to be removed is r = 5, and the stator winding pitch is 5 - (r - 1) / r = 415 =
It becomes 0.8. In other words, the slot per pole is 15/2
= 7.5, whereas the winding has 7.5 slots
O, 8= Make it come to 6 slots. By doing this, as shown in the figure, the winding comes exactly at the fourth node of the fifth harmonic, and the fifth harmonic is no longer induced.

Next, we will investigate whether three-phase balanced winding is possible when winding is performed every 6 slots with the total number of slots N-15.

The following equation determines whether or not a three-phase balanced winding is possible.

N is the value obtained by dividing the number of slots N by the greatest common divisor of the number of slots N and the number of pole pairs P. If the number of phases is m, then N87m-integer..., if -, two-layer winding is possible, No/
2 m-integer...In this case, single-layer winding or two-layer winding is possible. If both are integer numbers, a Sanwahei i-button winding can be created, and a S+:r/Sol- number cannot be adopted. 1 In this example, N=-15 and P=1, so N,=
15, and the number of phases m=3, so No/m=15/3
= 5, an integer is obtained, and it can be seen that three-phase balanced winding is possible.

In other words, this example is a feasible design example.

If the stator is designed as described above, the influence of the r-order harmonic (the fifth harmonic in this embodiment) is removed.

Therefore, if the skew of the conductor grooves of the fixed Y-iron core with respect to the rotor magnetic poles, the number N of stator slots, and the winding pitch are determined by the means of the present invention, the effects of the n-th and r-th harmonics can be simultaneously eliminated. be able to.

In addition, when applying harmonic countermeasures to both the rotor and stator in this case, high-order harmonics (e.g., the 7th harmonic) are taken care of on the rotor side, and low-order harmonics (e.g., the 5th harmonic) are taken on the stator side. If harmonics) are removed, the skew angle can be small, making it easier to manufacture the rotor, which is advantageous.

〔effect〕

As described above, according to the present invention, harmonics of orders that have a large influence on abnormal torque generation can be selected and directly eliminated, so a three-phase synchronous motor with less torque ripple can be manufactured. Therefore, it is possible to fold down a small drive source for a servo mechanism that requires particularly smooth torque.

[Brief explanation of drawings]

1 and 2 are detailed explanatory views of the present invention. Second
In the figure, (al is a developed view of the stator slot, fb
l indicates the magnetic flux distribution, and TC) indicates the position of the stator winding. FIG. 3 is an explanatory diagram of the conventional skew of rotor magnetic poles. l... Stator core, 2... Slot, 3... Rotor magnetic pole, 4... Separation groove between magnetic poles. Z Matahi'jinden

Claims (1)

[Scope of Claims] 1. Eliminate the influence of harmonics of orders that cause abnormal torque generation among multiple harmonics contained in the magnetic flux generated in the air gap between the stator core and the rotor magnetic poles. It is a three-phase synchronous motor with countermeasures, and the conductor grooves of the stator core are relative to the rotor magnetic poles in electrical angle of 2π/n (where n is the harmonics selected to remove the influence). A three-phase synchronous motor characterized by a skew (order of). 2. Measures have been taken to remove the influence of the harmonics of the order that are the cause of abnormal torque generation among the multiple harmonics contained in the magnetic flux generated in the air gap between the stator core and the rotor magnetic poles. In a phase synchronous motor, the conductor grooves of the stator core are skewed by 2π/n in electrical angle relative to the rotor magnetic poles (where n is the order of the harmonic selected as a target for removing the influence), and , The number N of slots (grooves) in the stator core is determined by N = number of poles l x number of phases m x number of grooves per pole and each phase q, where the value of the number of grooves q per pole and each phase is an integer number, and The stator winding pitch s satisfies the relationship s=(r-t)/r or s=r/(r+t) where t is an odd number (however, the order of the harmonic selected as a target for removing the influence). Moreover, a three-phase synchronous motor is selected to enable three-phase balanced winding. 3. A three-phase synchronous motor in which t=1 in claim 2.