RU2463612C1 - Method for determination of rotation rate of submersible asynchronous electric motors - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: 4k four-pole magnets with radially magnetised heteropolar zones are arranged on the shaft of the submersible electric motor on dielectric beads positioned on the both butt-end sides of k non-magnetic intermediate bearing of the rotor and having a diameter equal to that of the rotor core assemblies. Two magnets turned towards each other with their analogous poles are mounted on each bead circumferentially, in a diametrically opposite way. All the magnet pairs are oriented in strictly the same direction. During the rotor rotation a frequency sequences of electromotive force pulses are generated in the three-phase winding while a frequency sequences of current pulses are generated in the phases of the power cable feeding the submersible electric motor. With the help of a land-mounted measurement current transformer one performs transformation of the frequency sequences of phase current pulses and the sinusoidal current consumed by the submersible electric motor from three-phase feed voltage. A frequency sequences of voltage pulses proportional to that of phase current pulses is recovered through filtration of the current transformer output voltage with the help of a band pass filter having flange pass bands z-f_mjn and z-f_max. With the help of a voltage comparator and a frequency divider a new sequence of rectangular pulses is formed from the recovered pulse frequency sequence, the rectangular pulses repetition frequency is decreased z times and is equal to the submersible electric motor rotation frequency where z is the number of the stator magnetic conductor slots, f_min and f_max are the maximum and minimum allowable frequencies of the submersible electric motor rotation in the ESP unit.

EFFECT: simplification of measurement and measurement results transfer to the surface.

10 dwg, 6 tbl

Description

The invention relates to techniques for measuring the parameters of electric machines and can be used in installations of electric centrifugal pumps (ESP), which extract oil from deep wells and use squirrel-cage rotary asynchronous electric motors (SEM) as a drive.

Known methods for indirectly determining the rotational speed of asynchronous motors, in which speed information is obtained from a mathematical model of the motor given in the form of a system of differential equations, using iterative methods, a high order observer, and other calculation methods (Bose V.K. Modern Power Electronics and AC Drivers. - Prentice Hall, 2002; Volkov A.V. Identification of flux linkage of a rotor of a frequency-controlled asynchronous motor // Electrical Engineering. 2002. No. 6. P.40-46). Indirect methods for determining the rotational speed are currently underdeveloped and do not have the necessary accuracy due to the regime and temperature changes in the parameters of a real motor, the non-sinusoidal shape of the stator currents and the influence of a long cable in the case of deep ESPs.

Also known are mechanical, optical, electrical and other methods of direct measurement of the speed of rotation of shafts, mechanisms and electric motors. Devices that implement the mechanical method have low accuracy and low reliability; devices that implement the optical method, with its high measurement accuracy, are very complex and inconvenient to use (UK Patent No. 1396889, CL G1A, 1974). The most modern, simple, convenient and accurate are electrical methods using the phenomenon of electromagnetic induction. A known method (Karpov R.G. Electronics in tests of heat engines. - M .: Mashgiz, 1963. P.103-111), by which a frequency sequence of emf pulses is obtained in a stationary signal winding located on a permanent magnet due to the intersection of a ferromagnetic insert, mounted on a rotating shaft, the fields of a permanent magnet, the resulting sequence is converted into a sequence of pulses with a constant duration and amplitude, and this sequence of pulses is converted further into an analog voltage, the value which is proportional to the speed of rotation. Due to the double conversion of the frequency sequence of EMF pulses, the accuracy of the measurement method is reduced; in addition, additional conversion of the analog output voltage to a digital code is required to coordinate this measurement method with modern monitoring and control systems.

Closest to the claimed method in terms of technical nature and the achieved results is the method (Ageikin D.I. et al. Sensors of control and regulation. - M .: Mechanical Engineering, 1965, S. 466-468; Utyamyshev RI Technique for measuring rotation speeds . M-L., 1961. S.7-8), in accordance with which the magnetic field is excited by a permanent magnet located on a rotating shaft, a frequency sequence of emf pulses is obtained due to the intersection of the fixed magnet by the field of the permanent magnet at each revolution of the shaft of the fixed signal winding , machining Pipeline pulse sequence induced by filling them with a stable high frequency pulses, the number of which per unit time is determined by the rotational speed (AS USSR №449302, G01p 3/54, 05.11.74).

The disadvantage of the prototype is the complexity of the implementation in asynchronous SEMs of deep-pumping oil-producing ESPs associated with the design features and operating conditions of the SEM (see Appendix 1), due to which the installation of a frequency sensor of an induction type with a rotating permanent magnet and a fixed multi-turn signal winding on its shaft significantly complicate its design and reduce reliability. In addition, for transmitting a frequency sequence of EMF pulses to a ground control station, a multi-kilometer (1.5 ... 3.7 km) cable line will be required, which, like the power supply cable, must be oil and gas resistant, allow operation in an aggressive environment at ambient temperature 95 -110 ° C and reservoir pressure up to 20 MPa, have armor protection from mechanical damage and a large tensile force. Placing such a cable together with a power cable on a submersible motor in a limited volume of existing oil well pumping wells is, as a rule, practically impossible.

The objective of the present invention is to simplify the implementation of the method in asynchronous PEM of deep oil-producing ESP.

The problem is achieved due to the fact that in the method of determining the rotational speed by which a permanent magnet is installed on the motor shaft and a frequency sequence of emf pulses is obtained, according to the invention, they are placed on the shaft of a submersible induction motor on non-magnetic dielectric washers located on the end sides k of non-magnetic intermediate bearings rotor and having a diameter coinciding with the diameter of its packages of 4k four-pole magnets with radially magnetized bipolar With these zones, two magnets diametrically opposite are mounted on each washer around the circumference, facing each other with the same poles, they orient all pairs of magnets on the washers when the rotor is assembled in exactly one direction, receive frequency sequences of emf pulses in the three-phase stator winding when the rotor rotates, and in the phases of the power cable supplying the SEM, the frequency sequence of current pulses, transform the frequency sequence of phase current pulses and blue the soidal current consumed by the PED from a three-phase supply voltage, a frequency sequence of voltage pulses is allocated that is proportional to the frequency sequence of phase current pulses by filtering the output voltage of the transformer by means of a bandpass filter having boundary transmission frequencies z · _min and z · _max , formed from the selected frequency sequence pulses using a voltage comparator and a frequency divider a new sequence of rectangular voltage pulses, the repetition frequency to toryh lowered in z and time coincides with the frequency of rotation of the rotor of the SEM, where z - number of slots in the stator yoke SEM, ƒ _min and ƒ _max - minimum and maximum allowable speed in the SEM ESP (Appendix 1).

The specified set of operations, which differs from the known one and has not been applied before, allows to obtain a new technical result, which consists in measuring the speed of rotation of the SEM without installing an induction speed sensor on its shaft, the function of which is performed by the structural elements of the SEM, which simplifies the transfer of measurement results to the surface and facilitates their removal by simply connecting a current transformer to the phase of the ground section of the power cable.

The invention is illustrated by the accompanying drawings, in which Fig. 1 shows a block diagram of a method implementation, Fig. 2 is a drawing for explaining the formation of emf pulses in conductors of a stator winding winding of a PED of dimension 117, Fig. 3 shows timing diagrams of the functioning of structural block elements. It contains a non-magnetic dielectric washer 1, a three-phase stator winding PED 2, a power supply cable line 3, a current measuring transformer 4, a resistance 5, a bandpass filter 6, a voltage comparator 7 and a frequency divider 8. Two phases of the stator winding 2 are connected via a cable line 3 to the two phases Ua, Ub of a three-phase sinusoidal voltage source, the third phase of the stator winding 2 is connected to the third phase Uc of the source through a cable line 3 and the primary winding of the current measuring transformer 4. Secondary trans winding formatter 4 is loaded with resistance 5 and connected to the inputs of the bandpass filter 6, its output is connected to the input of the voltage comparator 7, the output of the comparator 7 is connected to the input of the frequency divider 8, and the output of the divider 8 is the output of the circuit, while one of the terminals of the secondary winding of the current transformer 4 is grounded.

Figure 2 shows the non-magnetic package of the stator 9, the conductors of the long winding 10 passing through the grooves of the non-magnetic package of the stator 9, the air gap 11 between the non-magnetic dielectric washer of the rotor 1 and the non-magnetic package of the stator 9, a four-pole magnet 12 with radially magnetized bipolar zones.

When implementing the method for determining the speed of rotation of the SEM carry out the following actions. Install 4k four-pole magnets 12 with radially magnetized bipolar zones having a magnetizing force sufficient to act through the air gap 11 (millimeter fractions, Table 2, Appendix 1) when the rotor rotates on the stator winding conductors 10 . The magnets are placed in pairs of 12 on the dielectric washers 1 (Fig. 1) around their circumference diametrically opposite so that the magnets of one pair are located relative to each other with the same poles. Dielectric washers are the structural elements of the SEM (Fig.6, Appendix 1), have a diameter equal to the diameter of the rotor packages, and are located on the end faces k of the non-magnetic intermediate rotor bearings.

All pairs of magnets on the washers are oriented when the PED rotor is assembled strictly in one direction to achieve synchronous and in-phase motion of the field of each of the rotating magnets relative to the stator winding conductors 10 passing through the grooves of its non-magnetic packets. Receive in the conductors 10 of the stator winding (for example, phase C windings) the frequency sequence of pulses of bipolar emfs Evr (Fig.3), undergoing inversion through a time interval of 0.5T ₂ , where T ₂ is the period of rotation of the rotor of the SED. The temporal shape of these emfs in a complex way depends on the spatial distribution of the magnetic field, on the angular velocity of rotation ω (Fig. 2) of the PED rotor, on the geometry of the groove, on the relative position of the magnet 12 and the groove, on the size of the magnets, therefore the angular and radial dimensions of the mounted magnetic inserts determined empirically to obtain a induced temporal form, as close as possible to a sinusoidal one, from the induced emfs of Heb. Due to the fact that the increment of flux linkage in the conductors 10 with the synchronous and in-phase approximation of 4k magnetic inserts to the groove and when moving away from it have the same magnitude and opposite in sign values, independent of the angular velocity of rotation of the rotor ω, they obtain the same voltsecond area for positive and negative impulses induced bipolar emf Heb. This important property ensures the conversion of current pulses in the transformer 4 and in the bandpass filter 6 without the methodological error arising in these elements of the structural circuit when the current pulses in the phase of the long winding PEM have a constant component that is not equal to zero, and also when its value changes from due to changes in the amplitude of these pulses.

In phase C of the SEM winding, distributed over the z / 3 grooves of the stator packets, the frequency sequence of the induced emfs is obtained in the form of a series of pulses of Ef.vr (Fig. 3), which undergo inversion through a time interval of 0.5T ₂ and are equal on the basis of the law of electromagnetic induction

where B is the magnetic induction, T; d is the thickness of the dielectric washer, m; ν is the velocity of the magnets, m / s (directions B and ν are mutually perpendicular); n is the number of effective conductors in the groove of the stator magnetic circuit of the PED.

Get in three phases of the stator winding during rotation of the rotor three induced pulse sequences of emf Ef.vr, offset from each other by an angle of 120 ° and creating in phase C of a three-wire power cable frequency sequences of current pulses of Ip.vr (Fig. 3), consisting of z current pulses repeating with the rotor speed of the SEM. The amplitude of z / 3 pulses is approximately 2 times greater than that of 2z / 3 current pulses, because the latter in phase c are formed due to the action of the emf induced in the windings of phases A and B of the stator PED.

Using a measuring current transformer, the 4 frequency sequence of current pulses Iph.vr is transformed together with the phase current consumed by the SEM from a three-phase source Ua, Ub, Uc and two to three orders of magnitude greater than the current pulses of Iph.vr. To do this, include the primary winding of the measuring current transformer 4 in the phase of the ground section of the power cable 3, and the secondary winding is loaded on the resistance 5 and is grounded with one terminal. Get in resistance 5 a sinusoidal voltage proportional to the current consumed by the SEM from a three-phase source Ua, Ub, Uc, and a frequency sequence of voltage pulses proportional to the frequency sequence of current pulses Iph.vr in phase C of cable 3.

The second component of the output voltage of the current transformer 4 is separated from the first sinusoidal component by filtering the output voltage using a band-pass filter 6 with the cut-off frequencies of the passband z · _min and z · _max and the decrease in the amplitude-frequency characteristic beyond the cutoff frequencies of at least 80 dB / dec . A filter of this kind provides reliable separation of frequency pulses (Fig. 8, Appendix 2) of the voltage

(k _i and k _f are the transfer coefficients of the current transformer and filter) with an amplitude of tens of millivolts, firstly, from a sinusoidal voltage superior to two to three orders of magnitude, the frequency of which can be changed using the frequency converter of the control station for deep ESPs ranging from от _min up to ƒ _max , i.e. from 40 Hz to 60 Hz (see Appendix 1) and, secondly, from spurious voltages with frequencies of 5 ... 15 kHz created by the frequency converter.

Frequency voltage pulses U _{1 are} converted into a sequence of rectangular pulses U ₂ (Fig. 3) using a voltage comparator 7.

Form from a sequence of rectangular voltage pulses U _{2 a} sequence of pulses U ₃ at the output of the circuit (Fig. 1), the repetition rate of which is reduced by a frequency divider 8 by a factor of z and coincides with the rotation frequency of the short-circuited rotor of the SEM.

New in the claimed method is the placement on non-magnetic structural elements of the rotor of the PED - dielectric washers of permanent magnets oriented during the assembly of the PEM in a strictly defined direction. This technical solution, which does not follow a specialist from the prior art, creates a frequency sequence of emf pulses with amplitude (conductors 6, Appendix 2) in the conductors of a three-phase stator winding, allowing the use of a stator winding of the SEM to determine the rotation speed of its squirrel-cage rotor.

The technical advantage of the method in comparison with the prototype and with other known methods implemented in various speed sensors is that the measurement results are transmitted to the control station of the ESP according to the proposed method by the power electric power cable of the SEM without the use of a special measuring multi-kilometer cable, the placement of which together with power cable in a limited space of deep-well wells, as a rule, is almost impossible. The implementation of the method is not associated, unlike the prototype, with a significant complication of the design and a decrease in the reliability of the SEM.

All this confirms the technical and economic efficiency of the method, the implementation of which can be carried out using highly coercive, heat-resistant permanent magnets of samarium-cobalt and nd-iron-boron with a magnetizing force of the order of 6 · 10 ⁴ kA / m, a downhole cable line of the type KPBK and extension cord type KPBP, standard single-phase measuring current transformer, for example ТНШ-0.66-УЗ (ТЗ), a bandpass filter built on RC elements and operational amplifiers (Fig. 10, Appendix 2), analog voltage comparator Integrated circuits such as KR521CA3 and others; and a frequency divider on digital integrated circuits such as KR1533IE7 and others.

The method can find application in a frequency-controlled energy-saving electric drive for direct measurement of the speed of rotation of asynchronous SEMs of deep-pumping ESPs.

Annex 1

Design and characteristics of submersible electric motors

The main type of submersible electric motors for driving electric centrifugal pumps (Bogdanov A.A. Submersible centrifugal pumps for oil production. - M .: Nedra, 1968. P.131 ... 163; Ivanovsky V.N., Beijing S.S., Sabirov A. A. Installations of submersible centrifugal pumps for oil production. - M .: State Unitary Enterprise. Oil and Gas Publishing House, 2002. S.65 ... 86) are vertical-type asynchronous oil-filled with a squirrel-cage rotor made in a cylindrical steel casing. PEMs operate in an aggressive environment of formation fluid at a high ambient temperature (95-110 ° C), reservoir pressure of about 20 MPa and in a limited volume: the outer diameter of the electric motor is determined by the inner diameter of the casing of the oil well and is in the range of 96 ... 138 mm. Power of electric motors reaches 500 kW. Small diameters and large powers make it necessary to increase the length of electric motors. For example, a PED series electric motor with a diameter of 123 mm and a power of 75 kW has a length of 8062 mm. Submersible electric motors are made bipolar (the pitch of the turns of the stator winding sections 180 °) at a speed of 3000 synchronous rpm at a nominal frequency of the stator current of 50 Hz. In addition, they must have high reliability, give maximum useful power in a limited volume and therefore have a number of features.

To reduce losses in the multi-kilometer cable supplying the SEM, to improve the starting conditions and technical characteristics of the SEM, electric motors are performed at increased voltages significantly exceeding the voltage of the power network 380 V. The voltage of the SEM depends on power, diametrical dimensions, a number of other conditions and ranges from 500 to 3000 V This led to the need for special field transformers that increase the output voltage of control stations. In addition, since the suspension length of the electric pump in the well varies widely, the voltage losses in the cable line will fluctuate accordingly. Therefore, in order to ensure operating voltage at the SEM clamps with an acceptable deviation of ± 5% of the nominal value, field transformers are made with multi-stage adjustment (up to 32 steps) of voltage from the high side.

To control the regime of oil production, energy-saving frequency regulation of the speed of rotation of the SEM is applied, which is carried out using frequency converters installed at the control stations of the operation of the ESP. The range of regulation of the speed of rotation of the SEM is regulated by manufacturers, as well as TU-3381-026-21945400-97, which allows continuous operation of the SEM in the ESP from a minimum speed of f _min ≥40 Hz to a maximum f _max ≤60 Hz. In this case, the maximum frequency is limited, as a rule, by the power of the electric pump, and the minimum - by the possibility of disruption of the supply of formation fluid from the depth of the well to the surface.

The main technical data of submersible electric motors in operation at the fields are given in table 1. Technical data of submersible electric motors of Russian production are given in table 3. The design of the electric motor of the PED series is shown in Fig. 4, where the following notation is adopted: 1 - shaft; 2 - flat cable; 3 - plug connector; 4 - output ends of the stator winding; 5 - stator winding; 6 - stator housing; 7 - an intermediate bearing; 8 - non-magnetic package of the stator; 9 - active stator packet; 10 - engine rotor; 11 - an oil filter; 12 - hole inside the shaft for oil circulation; 13 - check valve for filling the engine with oil; 14 - sump; 15 - turbine for oil circulation; 16 - supporting heel.

The main structural elements of the electric motor are the stator and rotor. The stator of the PED consists of active packets 9, assembled from separate sheets of annealed electrical steel E12 or E13 and from non-magnetic packets 8, stamped from brass or non-magnetic stainless steel. Non-magnetic bags serve as bearings for the rotor bearings.

The length of the active package is determined by the distance between the bearings 7 on the rotor shaft (based on the calculation of the shaft for deflection) and ranges from 300 ... 450 mm. The length of non-magnetic packages corresponds to the width of the intermediate rotor bearings and varies between 32 ... 45 mm. Active and non-magnetic stator packets, alternating between each other, are tightly seated in the stator housing 6 and are fixed on both sides at the ends by locking rings. When assembling the stator, a number of special operations are performed, including the orientation of the stator sheets, the pressing of the sets of sheets in a strictly oriented state into the stator housing. The number of active packages depends on the power of the engine, which can be made with three packages, fifteen or more.

In the grooves of the stator, a three-phase winding was laid out in a tight way from a special round wire with polyimide-fluoroplastic film insulation, for example, PPI-U, PEU-200, PFD wires manufactured in Russia and the CIS. Winding phases are connected to a star. The main data of the stator windings of submersible electric motors of the PEM series are given in table 2.

Inside the stator is placed the rotor 10 (figure 4) with a core. The latter is a set of individual packages having each independent squirrel-cage winding. Rotor packages are bursted from stamped sheets with grooves made of electrical steel of grades E12, 2212 or 2215. The length of each package depends on the distance between

intermediate radial bearings of the rotor, which in turn is determined by the calculation of the deflection of the shaft. The number of packages depends on the power of the electric motor. Figure 5 shows the package of the rotor of the electric motor PED17-119. The winding of each package consists of copper rods installed in its grooves and copper short-circuit rings connecting the rods at their ends. The rotor packages are mounted on the shaft on the key and are separated by intermediate radial plain bearings. The rotor shaft is hollow to ensure oil circulation, made of high strength steel.

The rotor of the electric motor of the type PED assembly is presented in Fig.6, where the following notation is accepted: 1 - splined end of the shaft; 2 - heels; 3 - hole in the shaft for oil circulation; 4 - turbine for pumping oil; 5 - rotor package; 6 - intermediate radial plain bearing; 7 - nut for mounting rotor packages on the shaft; 8 - hole for supplying oil to a radial bearing; 9 - the key of the rotor. The main data of the rotor windings of submersible motors are shown in table 4.

Figure 6 shows a fragment of the assembly drawing of an electric motor of type ED32-117, which shows the structural elements of the rotor located in the bore of the intermediate non-magnetic package of the stator PED. There is a radial friction pair: the bearing and the bearing sleeve with a radial hole, which should coincide with the radial hole 8 (Fig.6) on the rotor shaft. Coincidence adjustment is achieved through flat steel shims of 0.5 mm thickness, worn on the shaft on both sides of the bearing bush. Together with adjusting washers, two washers made of fiberglass STEF1 with a thickness of 2 mm are used, which play the role of a friction pair with the end of the adjusting washers. For these glass-fiber laminate washers, according to the claimed method of determining the rotation speed, two four-pole highly coercive and heat-resistant permanent magnets with radially magnetized bipolar zones with opposing poles between adjacent magnets having each sufficient force (more than 6 × 10 ⁴ kA / m) to act through the air gap on the conductors of the stator windings of the PED, while the magnets They are oriented on all washers when assembling the rotor strictly in a certain direction in order to obtain synchronous and common-mode action from the field of all pairs of rotating magnets on the conductors of individual sections of the stator winding of the PED.

Appendix 2

Modeling a structural diagram of the implementation of the method for determining the speed of rotation of submersible induction motors

Circuit modeling (Fig. 7) of the circuit (Fig. 1) was carried out by means of the Electronics Workbench 5.12 program for the PEDN32-117-1000 submersible motor included in the installation kit of the UETSNM5-50-1700 together with a centrifugal pump 2ETsN5-50-1800, cable type KPBK3h16 and a field transformer TMPN-100 / 1170-73KHL1, for which, taking into account the voltage loss in the cable line, a tap on the HV side with a line voltage of 1170 V is recommended for this installation (from materials on a single complete set of ESPs with 2007 additions).

As a measuring current transformer 4, most suitable for PED32-117-1000, a transformer of the TNSh-0.66-UZ (T3) brand with a rated primary current of 30 A and a load resistance of 5 equal to 1 Ohm was selected. The main data on PEDN32-117-1000 (TU-3381-026-21945400-97) are given in Table 6.

The SEM phases are indicated in Fig. 7 by stat blocks and are presented in the form of a multi-circuit equivalent circuit (Fig. 9b), the parameters of which are given in Table 5 (A.Yu. Kovalev. Modeling of submersible asynchronous electric motors as part of the installation of electric centrifugal pumps: diss. And tech. Omsk, 2010). Cab blocks are modeled in the diagram of Fig. 7 of the phase of the borehole cable in the form of a classic U-shaped equivalent circuit (Fig. 9a), the parameters of which are determined for a cable of the KPBK type with a cross section of 16 mm ² and a length of 2000 m according to well-known formulas (E.M. Risthein. Power supply of industrial plants: Textbook for universities. - M.: Energoatomizdat, 1991. - 424 p.).

для кабеля КПБП сечением 16 мм², вычисленное на основании данных (Погружные центробежные насосы для добычи нефти, Богданов А.А. Изд-во Недра, 1968 г. - 272с.), составляет 2,6; ω=314 рад/с - угловая скорость вращения ротора ПЭД. Результаты расчета параметров R_л, L_л, C_л представлены в таблице 5 (см. фиг.10).where l is the cable length, m; F is the cross section, m ² ; λ is the specific conductivity at 20 ° C, adopted for copper, taking into account the twist on the twist and fretting equal to 51.2 MSm / m; α is the temperature coefficient of resistance equal to 0.004 deg ^-1 for copper; t _k is the temperature of the cable core corresponding to the temperature of the formation fluid in the well and taken equal to 90 ° C; D _cf - the geometric mean distance between the phase conductors of the cable; r _equiv - reduced (taking into account the cross-sectional shape and surface effect) the radius of the phase conductor. Attitude

for the KPBP cable with a cross section of 16 mm ² , calculated on the basis of data (Submersible centrifugal pumps for oil production, Bogdanov A.A. Nedra Publishing House, 1968 - 272 s.), is 2.6; ω = 314 rad / s is the angular velocity of rotation of the rotor of the SEM. The calculation results of the parameters R _l , L _l , C _{l are} presented in table 5 (see figure 10).

. Источники U_a.вч, U_b.вч, U_c.вч моделируют наличие в питающем напряжении высших гармонических составляющих за счет действия в станции управления УЭЦН преобразователя частоты с синусоидальной ШИМ на несущей частоте 5 кГц.Measuring current transformer 4 is modeled by a current-voltage converter TA with a transfer resistance of 0.2 Ohms. The three-phase supply voltage supplied from the step-up transformer to the cable conductors is modeled by the phase voltages U _a , U _b , U _{c of a} frequency of 50 Hz (Fig. 7), determined through the known linear voltage U _l = 1170 V by dividing it by

. Sources U _a.hf , U _b.hf , U _c.hf simulate the presence of higher harmonic components in the supply voltage due to the action of a frequency converter with a sinusoidal PWM at a carrier frequency of 5 kHz in the ESP control station.

The emfs induced in the conductors of the stator windings by the field of rotating permanent magnets are represented in the schematic model of Fig. 7 by sources E _a.bp , E _b.bp , E _c.bp , which are determined by the formula (1)

for typical values B = 1.6 T; l = 2 mm; n = 4 and the speed of the magnets

where R is the radius of the rotor PED. Sources E _a.vp , E _b.vp , E _c.vp form a sinusoidal voltage (adopted taking into account the capabilities of the Electronics Workbench program) with a frequency f _bp equal to

where f ₂ is the rotational speed of the rotor PEDN32-117-1000

s is the slip of the rotor (see table 5); f is the nominal frequency of three-phase sources U _a , U _b , U _c .

The keys, kl, k2, k3, controlled by the commut block, switch sources E _a.vp , E _b.vp , E _c.vp , - E _a.vp , - E _b.vp , - E _c.vp at time intervals T _2/6 (where T ₂ - rotor rotational period SEM) in a sequence that follows the sequence of passage of the moving magnets past the conductors belonging to the beginnings (a, b, c) and the ends (x, y, z,) of the phase windings are in z / 3 grooves of the stator magnetic circuit.

The band-pass filter (filter) is made in the form of a series connection of four stages, each implemented according to the scheme in Fig. 10, which contains an RC - high-pass filter (C ₁ , R ₁ , C ₂ , R ₂ ), RC - a low-pass filter (C ₃ , R ₃ , C ₄ , R ₄ ), docking operational amplifiers DA ₁ , DA ₂ . The selection of resistances R ₆ , R ₈ regulates the quality factor of the cascades, which is advisable to set the minimum for the input and maximum for the output cascades. The choice of capacitors C ₁ ... C ₄ establishes small detunings between stages in cutoff frequencies of their amplitude-frequency characteristics. As can be seen from the waveform of the voltage U ₁ (Fig. 8), proportional to the current I _f.vr ( _Eq. 2), the bandpass filter 5 provides effective suppression of currents from the supply voltage of 50 Hz and from its higher harmonic component of the frequency of 5 kHz. The output voltage of the filter confidently reproduces the measuring signal — the frequency sequence of current pulses I _f.vr (FIG. 3) _{—in the} form of voltage U ₁ and allows using a voltage comparator 6 and frequency divider 7 a sequence of rectangular pulses U ₃ at the output of the circuit of FIG. 1 following with the rotational speed of the squirrel-cage rotor SEM.

Claims (1)

A method for determining the rotation speed by which a permanent magnet is mounted on the electric motor shaft and a frequency sequence of emf pulses is obtained, characterized in that, in order to simplify the implementation of submersible pumping oil-producing electric pumping units (ESPs) in submersible asynchronous electric motors (ESPs), they are placed on the shaft PEM on non-magnetic dielectric washers located on the end faces of k non-magnetic intermediate bearings of the rotor and having a diameter matching the diameter of its bag , 4k four-pole magnets with radially magnetized bipolar zones, install two magnets diametrically opposite to each other on the washer, opposite the same poles facing each other, orient all pairs of magnets on the washers in exactly the same direction, receive frequency sequences of pulses in the three-phase stator winding when the rotor rotates and, in the phases of the power cable supplying the SEM, the frequency sequences of current pulses are transformed by a ground current transformer of current The sequence of pulses of the phase current, and a sinusoidal current consumption by SEM from three-phase power supply, separated frequency sequence of voltage pulses proportional to the frequency of the phase current pulses, filtering the current transformer output voltage by means of a bandpass filter having cut-off frequencies z transmittance · f _min and z · f _max , form a new sequence directly from the selected frequency sequence of pulses using a voltage comparator and a frequency divider coal voltage pulses, the repetition rate of which is reduced by a factor of z and coincides with the rotation frequency of the short-circuited PEM rotor, where z is the number of slots in the stator magnetic circuit of the PEM, f _min and f _max are the minimum and maximum allowable frequencies of rotation of the PED in the ESP.

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