Development of new pole-changing winding for lifting and transport mechanisms

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Introduction
In many industries and warehouses, hoisting machines such as cranes, conveyors, and telphers are used to transfer and transport goods.Taking into account their widespread prevalence and the large value of the installed power, as well as the complexity of the operation mode, particular importance is attached to the problems of saving electricity and resources by improving the electric drive.In this area, special attention is paid, in particular, to the creation of new energy-and resource-saving electric drives, which make it possible to facilitate the start-up process and ensure the exact stop of highly inertial hoisting-transport mechanisms [1].
In this direction, in particular, one of the priority tasks is the development of two-speed pole-switching motors that meet the requirements of an electric drive of hoisting-transport mechanisms.Along with this, an urgent task is the development of two-speed motors of new pole-changing windings (PCHW) schemes with improved electromagnetic properties and simple manufacturing technology.
A review of literary sources showed that most of the existing methods for constructing PCHW circuits do not allow building windings that are close in technological and electromagnetic properties to conventional windings used in serial single-speed machines [2].
The research aims to develop and study pole-changing windings for two-speed motors of hoisting-transport mechanisms

Materials and Methods
To build the PCHW, Professor H.G. Karimov proposed the method of "Discretely-given spatial functions" [10], which was improved in the works of M.K.Bobojanov, D.A. Rismukhamedov and F.N. Tuychiev for constructing the PCHW for both large and close pole ratios [11].According to this method, to simplify constructing a PCHW circuit, the concept of the current distribution of the winding is introduced, which is represented as a discrete, specified spatial function (DSSF).
As an example, consider the process of obtaining a PCHW circuit for a pole ratio of 1/5 with the number of slots Z = 30.A normal m-zone winding with the number of poles p 2 =5 was taken as the initial winding, and a normal 2m-zone winding with p 1 =1 was taken as a "typical" one.This winding has a «star-double star» switching scheme [15].
Here, for 2p 1 =2, the number of slots per pole and phase is q 1 =5; for the number of pairs of poles 2p 2 =10, the number of slots per pole and phase is q 2 =2.Then, the current distribution corresponding to the lower layers of the two windings is examined together to build the PCHW circuit.Table 1 shows the combination of the DSSF of the lower layers of the two windings.
Table 1.Combination of the lower layers of the DSSF of 2 and 10-pole windings.Table 2 shows the synthesis process of the polar coil 2p=2, where the third line contains the layer of the synthesized winding, that is, the DSSF of the PCHW belonging to the lower pole p 1 =1.This is achieved by modulating the DSSF of the original winding using the DSSF of a typical winding.The meaning of the «approximation» is to determine in each slot the sign of the state of the DSSF conductor of the synthesized winding, depending on the state of the DSSF conductor of a typical winding in this slot and based on the relative position of the vectors of phase currents in a three-phase system [9].
For example, if the position of the DSSF conductor in the original winding is equal to «b» (3-slot), and for a typical DSSF in the same phase as «a», which is known from the location of the three-phase system, currents that are close to «a» «-b», not «b» (direction of instantaneous currents corresponds), therefore, the synthesis winding is written «-b» for DSSF; if the DSSF of the original winding is «c» (6-slot), the DSSF of the typical winding is «-c», then «-c» is written in the DSSF of the synthetic winding.Table 3. Combining the bottom layers of two windings.Thus, the procedure for constructing the polar part of the 2p1 pole-changing winding consists in sequentially viewing the current states in each phase and recording the synthesized DPPF winding based on the above rules.
By modulation, we obtain a coil with a zone of 2m for 2p1=2 pairs of poles so that the number of coils on the branches is equal to the number of coils sitting side by side -3 and 4, 13 and 14, 23 and 24 must have different signs.After that, these two layers are combined into the DSSF.Table 3 shows the combination of the DSSF of the lower layers of the two windings.4 shows the distribution of the coils of the PCHW along the branches of the «star-double star» chain.

Result and Discussion
The resulting winding is symmetrical concerning the power source on the side of both poles.The vectors of the electromotive forces of the branches of the same name of each phase are mutually symmetric to each other; that is, they are equal in amplitude and shifted at an angle of 2π/3 el.rad. in phase.
One of the main indicators of the developed PCHW is the winding ratio.The winding coefficient can be calculated separately for each harmonic using the generalized method [16] and the matrix method [7].The geometric sum of electromotive forces where, Е is the amplitude of the electromotive force, conventionally assumed to be equal to one; i is coil number;γ is spatial angle between grooves; γ = 360p/Z, Z is the number of slots in the stator; y is winding step; ν is harmonic number.
If N is the number of coils connected in series, the amplitude of the resulting electromotive force is determined as follows: .
where, N is number of coils in a phase or branches.
Considering the above, the winding v is harmonic distortion . .

res win
The winding coefficient for 2p 1 and 2p 2 is k win1 =0.633 and k win2 =0.866, respectively, with a winding step y = 15 (see tables 5 and 6).The coefficient of differential dissipation for any electrical machine does not depend on the geometric dimensions of the stator and rotor packages.The differential scattering coefficient is determined using the Gerges diagram (figure 3) as follows [17]: where, R g is radius of gyration, R 1 is fundamental harmonic radius.
If the value of σ 0 is small, the lower the composition of the higher harmonics and the better the winding parameters.
The radius of gyration and the radius of the fundamental harmonic in the formula (4) are determined as follows.
where, J p is polar moment of inertia, k win is winding coefficient of the fundamental harmonic.
When the winding is lengthened by one more slot, that is, at a step of y = 16, the harmonic composition of the magnetizing forces and the winding coefficients of the same orders have the same values at a step of y=14, the differential scattering coefficient also has the same value.
At step y=15, in addition to the first harmonic, the 5th, 7th, 11th, 13th and 17th harmonic are present, their amplitude as a percentage of the total harmonic is ν5=12.76%,ν7=9.09%,ν11=5.78%,ν13=4.89%,ν17=3.74%respectively, taking into account the winding coefficients, their influence is reduced ν5=14.42%,ν7=5.19%,ν11=3.33%,ν13=2.77%,ν17=2.12%.The differential scattering coefficient is σ0=9.7%.As can be seen from the above analysis of the PCHW for a ratio of 1:5 with the basic scheme «Y/YY» in 30 stator slots from the side of 2p=2 poles with a step of y=15, the content of higher harmonic is minimal (even harmonics do not take place) and accordingly, the value of the differential scattering coefficient is the smallest.
Since both speeds are equivalent in these two-speed motors, the electromagnetic properties of the PCHW on both sides must be optimal.Therefore, we choose to step y=15 as the optimal step.

Conclusion 4
1. Based on studying the operating modes of electric drives of hoisting-and-transport mechanisms operated at industrial enterprises and analyzing the literature in this area, the need to improve the motors on the drive of these mechanisms is substantiated.As a result, the need to develop two-speed asynchronous motors for a large speed ratio with one winding with improved electromagnetic properties and simple manufacturing technology was identified.
2. Using the DPPF method, a new PCHW with a pole ratio of 1:5 was developed based on the «Y/YY» scheme with the number of stator slots equal to 30, with improved electromagnetic properties and simple manufacturing technology.
4. Analysis of the electromagnetic properties of the developed PCHW showed that, in comparison with a close analog, the coefficient of differential scattering of the PPO from the side p=1 decreases from 1.7% to 1.3%, and from the side p=5, it decreases from 15.9% to 9.7%, and also in the picture of magnetomotive forces, the presence of higher harmonic forces from the side of the first speed decreases to 6%, and from the side of the second speed to 20%.

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а а b b с с а а b b с с р 2 =5 b c c a a b b c c a a b b c c р 1 =1

Table 4 .Fig. 1 .
Fig. 1.Basic diagram of a pole-changing windingUsing the phase combination table, following the obtained DSSF, you can get the numbers of the coils distributed along the branches and build a schematic diagram of the connection of the PCHW.The «star-double star» scheme can be divided into the following branches: for the first phase A-D, D-0; for the second phase B-E, E-0; for the third phase C-F, F-0.Table4shows the distribution of the coils of the PCHW along the branches of the «star-double star» chain.Figure1shows a schematic electrical diagram of the proposed three-phase poleswitchable winding, consisting of six parts: coils numbered 1, 2, 7, 8, 13, connected in series according to sections A-D; coils with numbers 14, 19, 20, 25, 26, connected in series according to sections D-0; coils numbered 21, 22, 27, 28, 3, connected in series according to sections B-E; coils with numbers 4, 9, 10, 15, 16, connected in series according to sections E-0; coils with numbers 11, 12, 17, 18, 23, connected in series according to sections C-F; coils with numbers 24, 29, 30, 5, 6, connected in series according to sections F-0.The pictures of the magnetomotive forces of the obtained PCHW are presented in figure2.

Fig. 2 .
Fig. 2. Pictures of the magnetomotive force of the obtained PCHW.