CN114006491A

CN114006491A - Design method for unequal-turn winding of five-phase asynchronous motor

Info

Publication number: CN114006491A
Application number: CN202111297308.3A
Authority: CN
Inventors: 夏云彦; 宋勃奇
Original assignee: Harbin University of Science and Technology
Current assignee: Harbin University of Science and Technology
Priority date: 2021-11-04
Filing date: 2021-11-04
Publication date: 2022-02-01

Abstract

本发明公开了一种五相异步电动机不等匝数绕组设计法，所述电机为五相电机，所述方法采用单元电机分析法，简化了分析过程，提高了精确度。本发明从推导绕组系数入手，推导不等匝时的理论匝数比与实际匝数比，进而进行不等匝绕组与样机原绕组气隙磁密波形谐波分解图及启动电流倍数等性能比较，以上均被有效改善。本发明应用范围较广，可用于其它任意多相电机的不等匝绕组设计。The invention discloses a five-phase asynchronous motor winding design method with unequal turns, the motor is a five-phase motor, and the method adopts a unit motor analysis method, which simplifies the analysis process and improves the accuracy. The invention starts from deriving the winding coefficient, deduces the theoretical turns ratio and the actual turns ratio when the turns are unequal, and then compares the performance of the unequal turn winding and the original winding of the prototype with the air gap magnetic density waveform harmonic decomposition diagram and the starting current multiple. , the above have been effectively improved. The invention has a wide application range and can be used for the unequal-turn winding design of other arbitrary multi-phase motors.

Description

Design method for unequal-turn winding of five-phase asynchronous motor

Technical Field

The invention belongs to the field of design and research of windings of five-phase motors, and particularly relates to an unequal turn winding design method of a five-phase motor.

Background

The induction motor has the advantages of simple structure, reliable operation, convenient maintenance and the like. The five-phase motor eliminates harmful subharmonic magnetomotive force of 5, 7 times and the like in the traditional three-phase motor, thereby effectively improving the utilization rate of iron core materials, improving the torque density and the like.

The windings are the main components of the motor, which relies on the electrical potential induced in the windings and the current passing through the windings to generate an electromagnetic torque. In the synthetic magnetomotive force of the motor, higher harmonic magnetic potential generally exists, which has adverse effect on the performance of the asynchronous motor. The application of the unequal-turn winding aims at improving the air gap flux density waveform and reducing the additional loss. Therefore, unequal turn windings have been a problem that motor designers need to address.

Disclosure of Invention

Aiming at the above, a 15kW 1460r/min prototype is taken as an example, and unequal-turn winding design of a five-phase asynchronous motor is carried out. The winding can reduce harmonic frequency, improve air gap flux density waveform, and improve performances such as starting current multiple.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention discloses an unequal turn winding design method of a five-phase asynchronous motor, wherein the motor is a five-phase motor, and the method comprises the following steps:

step 1: simplifying a prototype by adopting a unit machine analysis method, and providing an unequal turn connection mode of one phase end part;

step 2: analyzing the harmonic content of the motor and deducing a winding coefficient formula;

and step 3: according to a winding coefficient formula, finding out a theoretical turn ratio and an actual turn ratio when harmonic waves are less;

and 4, step 4: and carrying out harmonic analysis on the actual turn ratio, and comparing the harmonic content and partial performance of the air gap flux density waveform before and after the improvement of the winding.

In step 1, when the distribution of the number of the slots occupied by the five phases along the circumference of the air gap is periodic and the number of repetitions of the whole circumference is an integer, the number of slots in each period constitutes a unit motor.

Let the number of the unit machine be t, t is the greatest common divisor of z and p, where z is the number of slots and p is the number of pole pairs. Thus, z ═ tz₀，p＝tp₀Wherein z is₀And p₀The number of slots and the number of pole pairs of the unit motor are respectively.

Let the number q of slots per pole per phase be N/D, when D is odd, t be P/D, P₀D; when D is even number, t is 2P/D, P₀＝D/2。

In step 2, for five-phase windings with q as an integer, if the five-phase windings are connected into a 36-degree phase-band winding with spatial distribution, the harmonic content existing in the unit motor is v₀＝1，9，11，19，…

Compared with the prior art, the invention has the following beneficial effects:

1. the unequal turn winding design method provided by the invention starts with the derivation of the winding coefficient, selects the turn ratio and has more accurate result.

2. The invention adopts a unit motor analysis method, thereby simplifying the analysis process.

3. The five-phase unequal-turn winding design method provided by the invention has a wide application range, and can be analogized to unequal-turn winding design of any other multi-phase motor.

Drawings

FIG. 1 is an exploded view of the air gap flux density waveform of a prototype winding;

2-a, 2-b, respectively, are a connection diagram and an equivalent diagram of the winding end with E phases of unequal turns;

FIG. 3 is a harmonic exploded view of the flux density waveform of the air gap of the unequal-turn winding.

Detailed Description

The invention provides a design method of an unequal-turn winding of a five-phase asynchronous motor, which is specifically described below by combining the drawings and an embodiment.

Example (b):

the present invention is a 15kW 1460r/min five-phase asynchronous motor as an example, the original design is a single-layer winding, and an exploded view of air gap flux density harmonic is shown in FIG. 1.

Step 1: the prototype z is 40, p is 2, the number of phases m is 5, q is z/10, p is N/D is 2, i.e. N is 2 and D is 1. Splitting a prototype by adopting a unit machine analysis method, namely t is p/D is 2, z is₀＝＝z/t＝20，p₀＝D＝1。

The five-phase winding is divided into A, B, C, D and E five phases, with the end connections for the E phase shown in FIG. 2-a. Let the large number of coil turns be a. The number of turns of the small coil is b.

Step 2: such a winding is considered to be formed of a single layer winding of two equal elements, one 4 slots per pole per phase, b conductors per slot, and the other 2 slots per pole per phase, c being a-b conductors per slot, as shown in fig. 2-b.

These are two symmetrical and q is an integer number of five-phase windings, and in the case of the unit motor shown in fig. 2, the winding magnetic potential contains v only₀1, 9, 11, 19, …, etc. oddHarmonic, the harmonic order of which is v' 1, 9, 11, 19, … for the entire motor

And step 3: when the in-slot current is considered to be concentrated at the very center of the slot, i.e., the slot coefficient is 1, the winding coefficient for the v' harmonic is derived as follows:

since the groove pitch angle of the unit motor is 18 DEG at this time, the motor unit is driven to rotate by the motor unit

(wherein a is the groove pitch angle) gives:

wherein v' is 1, 9, 11, 19, …

For the 9 th harmonic and the 11 th harmonic, cos v' 18 ° -0.951, and as can be seen from equation (1), if the 9 th harmonic and the 11 th harmonic are simultaneously eliminated, the requirement should be satisfied

a/b＝1+2cos(-18°)＝2.902 (2)

Therefore, the conclusion is that: as long as the number of turns of the large coil is 2.902 times that of the small coil, the 9 th harmonic and the 11 th harmonic can be eliminated simultaneously, so that the theoretical turn ratio a/b is 2.902.

In practice, a and b must be integers, so that the a/b value can only be made close to 2.902, and Table 1 shows several practical a to b ratios that can be used.

TABLE 1

And 4, step 4: as can be seen from table 1. For the listed a/b values, both the 9 th and 11 th harmonics are greatly attenuated, most ideally 29/10, with a winding factor of four zeros after the decimal point, effectively completely eliminating the 9 th and 11 th harmonics.

Due to z₀As 20, the cyclicity of the winding coefficients indicates: the winding coefficients for v ' 9 and 11 are the same for v ' 31 and 29, respectively, so that the harmonics such as v ' 9, 11, 29, 31, … are cancelledAnd (4) removing.

In summary, it can be concluded that for the five-phase winding with q equal to 2, two coils with reasonable turns can be adopted: except for the v' 19, 21, 39, 41, …, etc., tooth harmonics, all of the remaining harmonics are cancelled.

Fig. 3 is an exploded view of an air gap flux density waveform of an unequal-turn winding at a/b of 29/10, and it can be seen that the air gap flux density waveform can be better modified by the unequal-turn winding design method provided by the invention.

Table 2 shows the comparison between the unequal-turn winding and the original winding, and it can be seen that the unequal-turn winding provided by the present invention can improve the efficiency by 1.07%, reduce the starting current multiple from 5.79 to 5.42, reduce the slip ratio from 0.0267 to 0.016, increase the starting torque multiple from 1.558 to 1.923, and reduce the stray loss by 49.13%.

TABLE 2

Item	Original design winding	Winding with unequal turns	Per unit value
				Efficiency (%)	90.42	91.49	91.00
Slip ratio	0.0267	0.016
				Starting current (times)	5.42	5.79	5.50
Starting torque (times)	1.558	1.923	1.8
				Stray loss (W)	150.0	76.3

Claims

1. an asynchronous motor unequal turn winding design method, is characterized in that, described motor is a five-phase asynchronous motor, and described method may further comprise the steps:

Step 1: Use the unit machine analysis method to simplify the prototype, and give the unequal-turn connection method of one phase end;

Step 2: Analyze the harmonic content of the motor and derive the winding coefficient formula;

Step 3: According to the winding coefficient formula, find the theoretical turns ratio and the actual turns ratio when the harmonics are less;

Step 4: Perform harmonic analysis on the actual turns ratio, and compare the harmonic content of the air gap flux density waveform before and after the winding improvement and some performances.

2 . A method for designing unequal-turn windings for a five-phase asynchronous motor according to claim 1 , wherein in step 1, a unit motor analysis method is adopted, which can simplify the analysis process. 3 .

3. a kind of unequal-turn winding design method based on five-phase asynchronous motor according to claim 1, is characterized in that, in step 1, when five-phase occupied slot numbers along the air gap circumference distribution situation is periodic , and the number of repetitions of the entire circumference is an integer, the number of slots in each cycle constitutes a unit machine. Let the phase of the unit machine be t, where t is the greatest common divisor of z and p, where z is the number of slots and p is the number of pole pairs. Therefore, z=tz ₀ , p=tp ₀ , where z ₀ and p ₀ are the number of slots and pole pairs of the unit motor, respectively. Let the number of slots per pole per phase q=N/D, when D is an odd number, t=P/D, p ₀ =D; when D is an even number, t=2P/D, p ₀ =D/2.

4. a kind of five-phase asynchronous motor unequal-turn winding design method according to claim 1, is characterized in that, in step 2, for the five-phase winding whose q is an integer, if it is connected into a spatial distribution of 36 ⁰ phases With windings, the harmonic content in the unit motor is v ₀ =1, 9, 11, 19, . . .

5. a kind of five-phase asynchronous motor unequal-turn winding design method according to claim 1, is characterized in that, for the five-phase winding with the number of slots per pole per phase q=2, because the unit motor at this moment is The slot pitch angle is 18°, from

(where α is the slot pitch angle):

In the formula, v'=1, 9, 11, 19, . . .