RU2023341C1 - Superconductor electric machine - Google Patents

Abstract

FIELD: electric machine engineering. SUBSTANCE: invention refers to polyphase hysteresis electric motors with use of high-temperature superconductors which are employed in cryogenic systems. Electric motor has stator with blade up core and polyphase, multipole winding, rotor on which outer surface active elements from high-temperature superconducting material fabricated in the form of nonsalient poles over cylindrical surface of rotor are located in the form of continuous hollow cylinder or multilayer structure produced from thin layers of superconducting films and of layers of dielectric or rods of squirrel-cage. EFFECT: enhanced specific torque and power factor. 4 cl, 14 dwg

Description

 The invention relates to hysteretic electric machines using high-temperature superconductors (HTSC GM) and can find application in cryogenic systems (including aerospace).

 Known hysteresis engines with various designs of rotors. The positive qualities common to all structural schemes are the large starting torque and the moment of entry into synchronism, a slight change in current from starting to idling and from idling to rated load, short acceleration time, etc. Their disadvantages include a low power factor, not exceeding 0.3-0.45 (a large magnetizing current, reaching 90-95% of the nominal). In addition, synchronous hysteresis motors develop a low mechanical moment on the shaft.

 Closest to the technical nature of the present invention is a synchronous electric machine containing a stator having a core with a multiphase winding forming magnetic poles, a rotor having a shaft and a housing with active elements rigidly fixed to it. Active elements are made of superconducting diamagnets made in the form of separate cylindrical segments, the number of which is equal to the number of pairs of stator poles.

 The disadvantage of this design is the inability to operate the machine in asynchronous mode while providing a constant torque on the shaft. In addition, the design of the prototype does not allow you to adjust the rotor speed (in engine mode) and to expand the range of the generated frequency (in generator mode) by switching the number of pairs of poles of the stator winding without additional design changes on the rotor. Low values of the coefficient of use of the active volume of high-temperature superconducting (HTSC) material on the rotor due to the presence of jumpers between the segments reduces the developed moment on the shaft of the machine. The relatively high values of the inductive resistances of the prototype determine the low values of the power factor.

 The aim of the invention is the expansion of functionality, as well as increasing the specific mechanical moment and power factor.

 The goal is achieved in that in a superconducting electric machine containing a magnetically conductive stator, made lined, and having grooves distributed along its inner surface, a multiphase multipolar winding located in these grooves and a winding cylindrical rotor mounted on the shaft of the machine with active elements fixed to its surface, made of high-temperature superconducting material, the active elements on the rotor are evenly distributed around its periphery. In addition, the active elements can be made in the form of a continuous hollow cylinder; a multilayer structure consisting of alternating thin layers of high-temperature superconducting films and dielectric layers; rods forming a squirrel cage, and the rotor is made with grooves in which they are placed.

 Thus, the positive effect of this set of distinctive features is that when operating, for example, in motor mode, changing the number of stator poles automatically leads to a change in the number of rotor poles, making it possible to control the rotor speed. In addition, due to the demagnetizing effect of the magnetic field of the rotor on the external magnetic field, the inductive resistance of the motor decreases, which leads to an increase in power factor and specific mechanical moment.

 The invention is illustrated in FIG. 1-14.

A superconducting electric machine (Fig. 1) contains a magnetically conductive stator 1, made lined and having grooves distributed along its inner surface, in which a multiphase multipolar winding 4 is placed, a winding cylindrical rotor 3 mounted on the machine shaft with active elements 2 fixed to its surface, made of a high-temperature superconducting material, for example, YBa ₂ Cu ₃ O ₇ ceramics operating in a cryogenic medium at a temperature of liquid nitrogen (77.8 K). In FIG. 2, 3, 4 show structural variants of active elements from HTSC material, which can be made in the form of a continuous hollow cylinder 5; represent a multilayer structure consisting of thin layers of HTSC films deposited according to a certain technology on fiberglass layers 6; made in the form of rods 7, forming a squirrel cage, placed in the grooves of the rotor 3.

 As the main constructive option, a machine with a continuous hollow cylindrical active element was selected.

A superconducting electric machine with HTSC active elements operates, for example, in engine mode, as follows. When voltage is applied to the stator winding 4, the rotating magnetic field created by it penetrates the HTSC cylinder and induces a complex system of current zones due to the penetration of Abrikosov filaments into the HTSC element moving synchronously with the external magnetic field of the stator (see Fig. 5). In FIG. 5, the following notation is accepted: ω _c = ω / p is the angular frequency of rotation of the magnetic field; p is the number of pole pairs; ω is the circular frequency of the current in the stator windings; I _c - current density in the stator winding. In FIG. 6 shows the distribution of currents in the stator winding, and FIG. 7 is a scan of the obtained pattern of the distribution of induced currents in the HTSC element shown in FIG. 5. Here n is the number of phases of the stator; I _s is the superconducting component of the density of the induced critical current in the HTSC element; r _s is the interface between the current zones in the HTSC element, x (r, φ) is the distribution function of the critical currents in the HTSC.

 In FIG. 8-10 shows a diagram of the formation of current layers in a HTSC cylindrical element located in a rotating magnetic field, shown in FIG. 11 and 12 for motor and generator modes, respectively.

(0, Вy, 0). На фиг. 10 приведено распределение критического тока I_s в круглом ВТСП образце, находящемся в поперечном магнитном поле В_y=const(B_y< B_p) при появлении нарастающей во времени t компоненты индукции поля В_х=В_х(t). Эти распределения качественно соответствуют начальному этапу формирования токовых слоев в цилиндрическом ВТСП во вращающемся с частотой ω_c внешнем магнитном поле B_x= B_x(t) ≃

B

t. При дальнейшем развитии токовых слоев для стационарного режима вращения поля ω_c=const картина распределения В_s и I_s в ВТСП становится симметричной (см. фиг. 11 и 12). Она характеризуется некоторой глубиной проникновения поля δ в ВТСП и неподвижной стационарной относительно поля В границей раздела r_s= r _s( φ) токовых слоев с различной ориентацией Is. На фиг. 11 распределение В_s и I_s соответствует случаю работы ГМ в режиме двигателя - 1>s=(ω_c-ω_p)/ω_c>0, где ω_p - круговая частота вращения ротора; s - скольжение; ω_c =

- угловая частота вращения магнитного поля в р-полюсной машине; ω- круговая частота тока в обмотках статора; на фиг. 12 - работе ГМ в режиме генератора - s>1. Эпюра распределения тангенциальной составляющей суммарного поля B_Σφ внутри ВТСП элемента при I_c<I_*, где I_с - ток возбуждения (статора); I_* - ток статора, при котором происходит полное проникновение критических токов в керамический ВТСП элемент, описывается кусочно-ломаной функцией и представляет собой волну, движущуюся синхронно с внешним магнитным полем статора ГМ. Токовая зона в ВТСП элемента при I_c< I_* с точностью до членов 0 (δ²) может быть представлена в виде двух областей: реликтовой зоны 1, где напряженность электрического поля E = -∂A $\genfrac{}{}{0ex}{}{\text{°}}{\text{Σ}}$ /∂t и радиальная компонента индукции B_Σr отсутствуют, и активная зона 2, где E = -∂A $\genfrac{}{}{0ex}{}{\text{°}}{\text{Σ}}$ /∂t и B_Σrотличны от нуля (см. фиг. 11-13).In FIG. Figures 8 and 9 show a typical distribution of the magnetic field induction B _r and the critical current I _s in a flat plate and a circular sample of high-temperature superconductors in a single-phase external magnetic field

(0, By, 0). In FIG. Figure 10 shows the distribution of the critical current I _s in a round HTSC sample located in a transverse magnetic field B _y = const (B _y <B _p ) when the field induction component B _x = B _x (t) increases with time t. These distributions qualitatively correspond to the initial stage of the formation of current sheets in a cylindrical HTSC in an external magnetic field B _x = B _x (t) ≃ rotating with a frequency ω _c

B

t. With the further development of current sheets for the stationary regime of rotation of the field ω _c = const, the distribution pattern of B _s and I _s in the HTSC becomes symmetric (see Figs. 11 and 12). It is characterized by a certain depth of penetration of the field δ into the HTSC and motionless stationary relative to the field At the interface r _s = r _s (φ) of the current sheets with different orientations Is. In FIG. 11 the distribution of B _s and I _s corresponds to the case of the GM working in the engine mode - 1> s = (ω _c -ω _p ) / ω _c > 0, where ω _p is the circular rotational speed of the rotor; s is the slip; ω _c =

- the angular frequency of rotation of the magnetic field in the p-pole machine; ω is the circular frequency of the current in the stator windings; in FIG. 12 - operation of the GM in generator mode - s> 1. Diagram of the distribution of the tangential component of the total field B _Σφ inside the HTSC element at I _c <I _* , where I _c is the excitation current (stator); I _* is the stator current at which critical currents penetrate completely into the ceramic HTSC element, is described by a piecewise-broken function and is a wave moving synchronously with the external magnetic field of the GM stator. The current zone in the HTSC element with I _c <I _* , up to terms 0 (δ ² ), can be represented in the form of two regions: relict zone 1, where the electric field strength E = -∂A $\genfrac{}{}{0ex}{}{\text{°}}{\text{Σ}}$ / ∂t and the radial component of the induction B _{Σr are} absent, and the active zone 2, where E = -∂A $\genfrac{}{}{0ex}{}{\text{°}}{\text{Σ}}$ / ∂t and B _Σr are nonzero (see Figs. 11-13).

In the core 2, the interaction of the currents I _s in the HTSC element with the radial induction component B _Σr leads to the appearance of a tangential force f _φ , which creates a moment acting on the rotor.

 From FIG. 11 and 12 it follows that the reaction of the magnetic field along the longitudinal axis of the HTSC of the active element to the external magnetic field of the stator will be demagnetizing. Therefore, the inductive resistances in the proposed engine will be suppressed, the angle φ will decrease and the power factor will increase.

The authors have developed a general theory of work processes and methods for calculating the characteristics of HTSC hysteresis machines of various structural designs. Based on the obtained analytical relations, the specific values of the losses q and the mechanical moments m of the proposed machine were calculated. In FIG. Figure 14 shows the results obtained, as well as their comparison with similar parameters of other types of electric motors: asynchronous (HELL) with a squirrel-cage rotor and hysteresis with a magnetically hard rotor (DG with MTR). It can be seen that for promising HTSC materials with I _s = 1-50 A / mm ² HTSC GM have the same characteristics with HELL and with HD MTR. At I _s ≥100 A / mm ^{2, the} specific parameters of the HTSC GM are higher than the specific parameters of modern samples of these types of machines.

 The present invention can be used as a hysteresis motor or asynchronous hysteresis alternator. One of the possible applications of HTSC DG is to use it as a submersible engine for operation in a cryogenic environment for pumping liquefied natural gases, as well as cryogenic fuel components on board an aircraft.

Claims (4)

 1. A superconducting electric machine, comprising a stator with a charged core, in the slots of which a multiphase multipolar winding, a winding cylindrical rotor with active elements located on its outer surface from high-temperature superconducting material, characterized in that the active elements are made in the form of a non-polar surface on a non-polar surface rotor.  2. The machine according to claim 1, characterized in that the active elements of the rotor are made in the form of a continuous hollow cylinder.  3. The machine according to claim 1, characterized in that the active elements of the rotor are made in the form of alternating thin layers of high-temperature superconducting films and dielectric layers.  4. The machine according to claim 1, characterized in that the active elements of the rotor are made in the form of rods forming a short-circuited cell placed in the grooves of the rotor.

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