CN1731656A - High-speed Induction Generator with Multi-phase Rectification/Three-phase Auxiliary Excitation Control - Google Patents

Abstract

The invention relates to a high speed asynchronous motor that controlled with m phase rectification/three-phase auxiliary excitation, where in m=3, 6, 9, 12, 15.... The generator exploits the combination rotor of the real hollow core type rat cage winding of have the ring narrow gam, or takes the full real core rotor of the wreath form ditch, or takes to protect the wreath or colligation to take of fold a slice of type rat cage rotor; The generator embedded inside the stator slot puts two sets of windings, a set of m/3 Y that move the pi/m electricity angle one by one in order connects a method three round a power windings for constitute mutually, be alongside of a capacitor, through commutate to equip exportation; Commutate to equip medium m/3 three commutate the bridge direct current side to have already merge, establish mutually with string to merge a mixture to connect three kinds of method of method; Another three-phase auxiliary excitation winding, circumscribe a double to change to flow device, its power unit direct current side connects electric capacity, don't establish power supply; Should equip the adoption definite direction control technique, follow behind the frequency of the electric voltage of stator winding, mutually, regulate the electric current of the auxiliary excitation winding, maintain to change to flow to equip the power unit direct current side electric capacity electric voltage and m to commutate to output electric voltage for the initial value mutually.

Description

High-speed Induction Generator with Multi-phase Rectification/Three-phase Auxiliary Excitation Control

technical field

The invention relates to a high-speed induction generator with m-phase rectification/three-phase auxiliary excitation control, wherein m=3, 6, 9, 12, 15....

Background technique

In independent systems such as ships, aircraft, vehicles, and oil drilling platforms, the demand for electric energy is increasing, and the volume and weight of the power supply system are also increasing with the increase in capacity. Therefore, the power density of the power generation and power supply system must be increased. and efficiency, reducing its size and weight.

An effective way to increase the power density of the power generation system is to increase the speed of the generator. The commutation spark problem of traditional DC generators limits the increase of speed and capacity; the rated frequency of ordinary synchronous generators is mostly 50Hz, and its speed is up to 3000 rpm. For example, in the synchronous generator (Patent No.: ZL94107628.8) invented by the applicant who supplies power simultaneously with three-phase AC and multi-phase rectification, the rotating speed is limited by the frequency of AC power supply; the brushless AC synchronous power generation with power electronic converter Machine, such as the applicant's patent: although the synchronous generator (patent number: ZL94206766.5) with rotor quadrature shaft stable winding is not limited by frequency, it can increase the speed and increase the power density, but due to its excitation generator and rotating rectifier And other parts, make the structure of the rotor complex, and also limited by the mechanical strength, it is difficult to greatly increase the rotating speed. Induction generators (also called asynchronous generators) have a simple rotor structure, high mechanical strength, and can run at high speeds. The power density is much higher than that of synchronous generators and DC generators of the same capacity. However, when the traditional induction generator is connected in parallel with the large power grid, the excitation adjustment device may not be needed, because its power factor is very low, so the efficiency is also low; the induction generator in the independent system can only use parallel capacitors to realize the excitation when the load changes Adjusting the voltage stabilizing function, the excitation system has a large volume and complex control, and the voltage stabilizing control effect is poor because the capacitor cannot be continuously adjusted. With the development of power electronics technology, power electronics technology can be used to solve the bottleneck problem of induction generator excitation control in independent systems:

(1) A passive LC device is connected in parallel at the output end of the generator, and properly controlled to make it equivalent to a variable capacitor, so as to provide a variable leading reactive current according to the load change, and generate an excitation magnetic potential to compensate the load current The resulting voltage change keeps the output terminal voltage constant, but the volume and weight of the inductance required for the control system are too large, which limits the capacity of the induction generator;

(2) An inverter device connected in parallel at the output end of the generator provides variable reactive power to compensate the excitation power required for load changes, which can stabilize the terminal voltage. However, due to the low power factor of general induction generators, the The large capacity of the inverter device is required, which determines that it is only suitable for induction generators with small and medium power.

Contents of the invention

The object of the present invention is to provide a design method of an m-phase rectification/three-phase auxiliary excitation control high-speed induction generator, wherein m=3, 6, 9, 12, 15.... The rotor and shaft of the generator are integrally forged solid rotors made of high-strength alloy steel, and squirrel cage guide bars are embedded to form a composite rotor. The stator has two sets of windings. The rectification device supplies power to the DC load, and another set of three-phase auxiliary windings is externally connected to a static inverter excitation regulator, which is used to adjust the excitation magnetic potential when the load and speed change, and keep the rectified output voltage unchanged. The two sets of windings are insulated from each other, there is no electrical connection, only magnetic field coupling. The induction generator has the following advantages:

(1) It can be directly matched with the high-speed prime mover to significantly increase the generator speed and reduce its volume and weight;

(2) High power density, good mechanical strength, simple structure and good economy;

(3) With rectifier load, the power factor is high and the electromagnetic compatibility is good, which overcomes the defects of low power factor and low efficiency of ordinary induction generators;

(4) Solve the complex problem of traditional induction generator excitation control, and realize the stable and continuous regulation of generator output voltage.

The main features of the induction generator power supply system described in this application are:

a The generator rotor is forged into a solid structure with integral high-strength alloy steel. The surface of the rotor core is evenly grooved along the circumferential direction, and guide bars are embedded. After welding with the two end plates, a composite rotor is formed. The surface of the rotor core is evenly opened along the axial direction. There is an annular narrow groove to reduce the eddy current loss on the surface of the iron core. The generator rotor has high mechanical strength and is suitable for high-speed operation;

b In the same group of slots of the stator, a set of symmetrical three-phase auxiliary excitation windings and a set of asymmetrical m-phase rectifier windings composed of m/3 symmetrical three-phase windings are embedded, and m/3 three-phase windings connected in star form are in turn Displacement 180°/m electrical angle, where m=3, 6, 9, 12, 15...;

c The phase displacement between the axis of the three-phase auxiliary excitation winding and the axis of the m-phase rectifier winding is α electrical angle, 0≤α≤180°/m, and the three-phase auxiliary excitation winding is also connected in star form;

d According to the different requirements of the coupling strength of the two sets of windings, the m-phase rectifier winding can adopt the same or different winding structure form as the three-phase auxiliary excitation winding, so that the winding short distance and distribution coefficient are consistent or inconsistent;

e Each Y winding of the m-phase rectifier winding is connected in parallel with a three-phase Y-connection or Δ-connection excitation capacitor, and is connected to the input terminal of the corresponding three-phase rectifier bridge;

f According to different DC load voltages and currents, m/3 three-phase rectifier bridges can be output in parallel or in series on the DC side, and when m/6=integer and greater than 1, they can also be output in series-parallel hybrid connection;

When g m/3 three-phase rectifier bridges are connected in parallel or in series-parallel hybrid connection, each two three-phase rectifier bridges can be connected with phase-to-phase balance reactor IPR to improve the AC current waveform and power factor;

h The three-phase auxiliary excitation winding of the generator is externally connected with an excitation regulator. The excitation regulator is composed of an inverter/rectification bidirectional current conversion device. It adopts digital directional control technology and automatically follows the voltage frequency and phase of the stator winding to adjust its auxiliary excitation winding current. It can keep the capacitor voltage on the DC side of the converter unchanged, and maintain the m-phase rectified output voltage constant;

i Only capacitors are used on the DC input side of the converter device without external DC power supply.

The above technology realizes the high power density, high efficiency and excellent power supply quality of the m-phase rectification/three-phase auxiliary excitation control high-speed induction generator.

The object of the present invention is achieved in the following manner: the m-phase rectification/three-phase auxiliary excitation control high-speed induction generator of the present invention, wherein m=3, 6, 9, 12, 15.... The rotor core and shaft are integrally forged from high-strength alloy steel. The surface of the rotor is uniformly processed with Z ₂ grooves along the circumferential direction, and guide bars are embedded inside. The two ends of the core are covered with copper plates with the same cross-section as the rotor core. The trapezoidal guide bars and the ends After the copper plate is welded, the squirrel-cage rotor winding is formed, which together with the conductive and magnetically conductive integral alloy steel rotor constitutes a composite rotor. The surface of the rotor core is evenly opened with annular narrow grooves along the axial direction to reduce the eddy current loss of the rotor. The rotor of the induction generator has high mechanical strength and can meet the requirements of high-speed operation, thereby significantly improving the power density of the generator. The rotor can also be a solid rotor with an annular narrow groove or a laminated squirrel-cage rotor reinforced with binding straps or high-strength material retaining rings; when the generator speed is not very high, the rotor can be directly laminated with ordinary silicon steel sheets. Laminated core and squirrel cage winding structure.

Two sets of stator windings insulated from each other are embedded in the stator slot of the generator, and a set of m-phase power windings is connected by m/3 Y mutual shift π/m electrical angle connection, and m/3 Y connection or Δ connection After the m-phase self-exciting capacitors composed of three-phase capacitors of the method are connected in parallel, the m-phase rectifier device composed of m/3 three-phase rectifier bridges supplies power to the DC load. m/3 three-phase rectifier bridges can be output in parallel or in series on the DC side, and when m/6=2, 3, 4..., they can also be output in series-parallel hybrid connection to obtain different rectification outputs Voltage, and various connection methods have 2m sub-pulse rectified output waveforms. When m/3 three-phase rectifier bridges are connected in parallel or series-parallel hybrid connection, the DC side of every two parallel-connected three-phase rectifier bridges can be directly connected in parallel, and a balance reactor IPR can also be connected to improve the AC current. Waveform, improve power factor. The other set is a three-phase auxiliary excitation control winding, which has the same number of pole pairs as the m-phase rectifier winding, and is externally connected to a three-phase static excitation regulator. The excitation regulator is composed of an inverter/rectifier bidirectional converter device. It adopts digital directional control technology to automatically follow the frequency and phase of the stator winding voltage to adjust its auxiliary excitation winding current, which can keep the capacitor voltage on the DC side of the converter unchanged and maintain m Phase rectification output voltage is constant.

When the prime mover drives the rotor of the induction generator to reach the rated speed for no-load operation, the residual magnetism of the rotor generates a residual magnetic potential in the m-phase power winding, and the potential acts on the m-phase self-excited capacitor to generate a leading potential of 90° electrical angle. The current flows through the m-phase winding to generate the armature reaction magnetic potential in the same direction as the residual magnetism, thereby enhancing the air gap magnetic field and further increasing the potential of the m-phase winding until a stable voltage is established. When the m-phase winding rectifies and outputs DC power, the winding current demagnetization armature reaction, commutation reactance voltage drop and internal impedance voltage drop will cause the rectified output voltage to drop. The excitation regulator adopts m-phase rectification output voltage feedback, and uses digital directional control technology to adjust the auxiliary excitation winding current output by the converter, so as to stabilize the m-phase rectification output voltage. The generator is similar to the general induction generator, and operates in the generator state, and the rotor speed n=(1-s)n ₁ (s<0) is higher than the synchronous speed n ₁ =60f ₁ /p. When the rotational speed fluctuates, the excitation system can automatically track and change the current size and frequency of the three-phase auxiliary excitation winding, and keep the m-phase rectified output voltage of the generator unchanged.

Description of drawings

Figure 1 is the schematic diagram of m-phase rectification/three-phase excitation high-speed induction generator

Figure 2 is a schematic diagram of a twelve-phase rectification/three-phase auxiliary excitation high-speed induction generator

Figure 3.a is the parallel connection method of four three-phase rectifier bridges and balanced reactors

Figure 3.b is a series-parallel hybrid connection of four three-phase rectifier bridges and balanced reactors

Figure 3.c is the series connection of four three-phase rectifier bridges

Figure 4 is the schematic diagram of the main circuit of the cascaded three-level bidirectional pulse width modulation auxiliary excitation device

Figure 5 is a schematic diagram of the control strategy of the auxiliary excitation device

Figure 6.a is a side sectional view of the rotor core

Figure 6.b is an axial cross-sectional view of the rotor core

Figure 7 is an expanded view of the stator twelve-phase winding

Figure 8 is an expanded view of the stator auxiliary excitation control winding

In the figure, Y ₁ , Y ₂ ,...Y _m/3 are m/3 three-phase symmetrical windings that are sequentially displaced by π/m electrical angle in the m-phase power winding, and 1 is the three-phase auxiliary excitation control winding of Y connection , 2 is the composite rotor equivalent winding, 3 is the main circuit of the three-phase auxiliary excitation regulator, C is the m-phase self-excitation capacitor, C ₁ is the DC side capacitor of the main circuit of the three-phase excitation converter, BG ₁ , BG ₂ , BG _3. BG ₄ is a three-phase rectifier, 4 is a balanced reactor group circuit, 5, 6, 7, 8, 9, and 10 are cascaded bidirectional pulse width modulation converter main circuit power units, 11 is a rotating shaft, and 12 is a The rotor core, the rotating shaft and the rotor core are integrally forged, 13 is the rotor guide bar, 14 is the axial annular groove on the surface of the rotor, and 15 is the rotor end ring.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing.

Figure 2 is a schematic diagram of the twelve-phase rectification/three-phase auxiliary excitation high-speed induction generator system, the motor works in the generator state, the speed n=(1-s)n ₁ >n ₁ =60f ₁ /p, the slip s <0, n ₁ is synchronous speed. Among the twelve-phase power windings, the three-phase windings of Y ₁ , Y ₂ , Y ₃ , and Y ₄ are mutually shifted by an electrical angle of 15°, and each three-phase winding is connected in parallel with a three-phase Y-connection or △-connection self-exciting capacitor C , connected to the three-phase uncontrollable or controllable rectifier bridge. The DC side of the four three-phase rectifier bridges BG ₁ , BG ₂ , BG ₃ , and BG ₄ in the twelve-phase rectifier device can be directly connected in parallel, that is, in Fig. 2 and Fig. It can also be connected in parallel as shown in Figure 2 and Figure 3.a, every two three-phase rectifier bridges are connected in parallel after an IPR to change the commutation process of the rectifier component current and improve the twelve-phase AC current. Waveform, improve the power factor of the induction generator. The connection method of the balance reactor IPR is best to connect the two rectifier bridges Y ₁ and Y ₃ with one IPR, and the two rectifier bridges Y ₂ and Y ₄ to connect one IPR with an electrical angle of 30°. The four three-phase rectifier bridges can be connected in series and parallel through balanced reactors, as shown in Figure 3.b; it is also possible to directly connect two three-phase rectified bridges in parallel on the DC side without the balanced reactor. Compared with the parallel connection method, the output voltage of the series-parallel connection method is doubled, and the output current is reduced to one-half of the latter. The series connection of four three-phase rectifier bridges is shown in Figure 3.c, the rectified output voltage is four times that of Figure 3.a, and the output current is one quarter of that in Figure 3.a.

When the speed of the induction generator reaches the working speed, the induced potential of the twelve-phase winding generated by the residual magnetism of the rotor acts on the capacitor C to generate a current with an electrical angle of 90° ahead of the potential. The magnetomagnetic potential forms self-excitation and establishes no-load voltage. In addition to the function of establishing the voltage, the capacitor C can also change the current commutation process of the rectifier element, improve the waveform of the twelve-phase alternating current, and improve the power factor and efficiency. The three-phase auxiliary excitation control winding is connected to the three-phase AC side of a bidirectional converter, and the DC side of the converter device is connected in parallel to a chargeable and discharging energy storage element capacitor C ₁ with a certain capacity, and no DC power supply is provided. The converter adopts 12-phase rectified voltage signal feedback, uses DSP technology to realize the directional control of the stator Y winding voltage, automatically tracks the voltage frequency and phase of the auxiliary excitation winding of the stator, keeps the voltage of the DC side capacitor _C1 of the converter device unchanged, and at the same time The current required by the Y winding output keeps the output voltage of the twelve-phase rectification basically unchanged, and can also adjust the output power of the twelve-phase rectification of the generator in the multi-machine parallel power supply system. The principle circuit of the converter device for excitation is different from the general converter device. Theoretically, the AC output is pure reactive current. Considering the influence of power device loss and excitation winding loss, the converter device is in the rectification working state in a timely manner to provide the necessary active power. power to maintain the capacitor _C1 voltage basically unchanged.

In the embodiment of the present application, the auxiliary excitation device adopts a cascaded bidirectional pulse width modulation PWM converter circuit. Attached Figure 4 is the schematic diagram of the main circuit of the auxiliary excitation device. This method reduces the withstand voltage level of a single power device, realizes multi-level output equivalent to a higher switching frequency with a lower switching frequency, and reduces the auxiliary excitation current of the generator. Harmonic components, reducing harmonic losses.

Based on the established m-phase rectification/three-phase auxiliary excitation control high-speed induction generator dynamic model, the present application proposes the excitation device control strategy shown in Fig. 5 . Its control strategy is described as follows: take the stator auxiliary excitation winding voltage orientation as the core, collect the three-phase winding voltage U _sabc , and generate fundamental wave unit sine and cosine signals through DSP operation, so as to maintain the excitation current frequency and twelve-phase rectifier winding voltage The frequencies are the same; the twelve-phase rectification output voltage feedback signal u _dc is compared with the reference voltage u ^* _dc , and then the PI regulator A is calculated to obtain the reactive current command amplitude; the DC side capacitor voltage feedback signal of each power unit is used After u _cl is compared with the reference voltage u ^* _cl , and then calculated by PI regulator B, the active current command amplitude of capacitor charge and discharge is obtained; the active current and reactive current command amplitudes are multiplied by the unit sine and cosine signals respectively, and then The three-phase current reference signal i ^* _sabc is then superimposed and synthesized and calculated by the regulator C, and compared with the output current signal i _sabc of the converter device, the instantaneous signal of active current and reactive current command output by the PWM main circuit is controlled. Among them, the active current is used to charge and discharge the capacitor u _cl on the DC side of the power unit, compensate the capacitor voltage fluctuation caused by the loss of the main circuit and harmonics, asymmetry, etc., and keep u _cl constant; the reactive current signal controls the additional excitation output by the converter device The amplitude of the winding current compensates the change of the output voltage caused by the change of the speed or the change of the load current, and keeps the output voltage constant. The above control strategy has no direct dependence on the parameters of the multi-winding induction generator, and can maintain the rectified output voltage of the induction generator under the condition of changing speed and load; it can also adjust the output voltage of the generator, or when multiple machines are connected in parallel In the power supply system, the output power of a single induction generator is adjusted.

Figure 6.a is an axial cross-sectional view of the core, and Figure 6.b is a side cross-sectional view of the rotor core. The rotor shaft and iron core are integrally forged with high-strength alloy steel. There are ₂ slots evenly opened in the circumferential direction of the rotor. The copper guide bars with the same shape as the slots are embedded in the slots. No additional slot wedges are required. Ring welded to form a squirrel cage winding, forming a composite rotor with a magnetically conductive and conductive solid rotor. There are annular narrow grooves equally spaced along the axial direction on the surface of the rotor core to reduce the eddy current loss in the core on the surface of the rotor; the depth and width of the annular groove are based on the rotor The penetration depth of the main subharmonic current on the surface is determined.

Accompanying drawing 7 is the expansion diagram of the twelve-phase winding of the stator. The four Y-windings correspond to a space where the mutual electric shift angle is 15°. The rectified voltage of 24 pulses is output through the twelve-phase rectifier bridge, and its pulsation coefficient can reach within 1%. Attached drawing 8 is an expanded view of the stator auxiliary excitation control winding. The auxiliary excitation winding and the twelve-phase rectifier winding are embedded in the same group of stator slots. The twelve-phase winding can be placed in the lower part of the slot, and the excitation winding can be placed in the upper part of the slot. Can be placed in reverse. The rectifier winding of the induction generator adopts a 4Y mutual shift 15° winding, and the minimum harmonic of the armature fundamental current magnetic field is 24±1 order, so the harmonic loss on the rotor surface of the induction generator is greatly reduced.

The description of this embodiment is mainly aimed at the twelve-phase rectification/three-phase auxiliary excitation high-speed induction generator, but since m=3, 6, 9, 12, 15...etc. m-phase rectification/three-phase auxiliary excitation induction generator The principle is basically the same as the twelve-phase rectification/three-phase auxiliary excitation high-speed induction generator, so m=3, 6, 9, 12, 15...etc. m-phase rectification/three-phase auxiliary excitation induction generator is protected by the present invention within range.

Claims (7)

1 A high-speed induction generator with m-phase rectification/three-phase auxiliary excitation control, wherein m=3, 6, 9, 12, 15..., characterized by: a. The rotor core and shaft are integrally forged with high-strength alloy steel. The rotor surface is evenly processed with grooves for embedding guide bars along the circumferential direction. The guide bars and the end metal plates are welded to form a squirrel cage winding. The rotor surface is equidistant along the axial direction. The annular narrow groove is processed to reduce the eddy current loss on the surface of the rotor core, and the squirrel cage winding and the solid rotor form a high-strength composite rotor; b. In the same group of slots of the stator, two sets of stator windings with the same number of magnetic pole pairs and mutual insulation are embedded. One set is composed of m/3 symmetrical three-phase Y-connected windings that shift mutually by π/m electrical angles. Symmetrical m-phase winding, the other is a Y-connected three-phase auxiliary excitation control winding; c. Each Y-connected three-phase winding in the m-phase winding is connected in parallel with a three-phase Y-connected or Δ-connected capacitor for establishing no-load voltage, and supplies power to the DC load through the m-phase uncontrollable rectifier; d. The three-phase auxiliary excitation winding is externally connected with a three-phase power electronic converter device working in two modes of inverter/rectification. The converter device adopts digital control according to the excitation control strategy established on the basis of the dynamic model of the induction generator Technology, automatically track the frequency and phase of the stator auxiliary excitation control winding voltage, adjust the current of the winding, and maintain the m-phase rectified output voltage unchanged. 2. The high-speed induction generator of m-phase rectification/three-phase auxiliary excitation control as claimed in claim 1, characterized in that: The auxiliary excitation device is powered by a three-phase rectification/inversion bidirectional converter device, and the DC side of the converter device is connected in parallel with a capacitor that can be charged and discharged, and no DC power supply is provided; it is formulated on the basis of the dynamic model of this type of multi-winding induction generator The excitation control strategy adopts digital directional control technology, automatically follows the frequency and phase of the stator winding voltage, adjusts the current of the auxiliary excitation winding, keeps the voltage of the DC side of the converter device connected to the capacitor unchanged, and maintains the stability of the m-phase rectified output voltage Change, or adjust the rectified output voltage in a multi-machine parallel power supply system to change the output power of a single generator. 3. The m-phase rectification/three-phase auxiliary excitation control high-speed induction generator as claimed in claim 1 or 2 is characterized in that: in the m-phase uncontrollable rectification device, according to different load voltages and currents, m/3 three-phase The DC side of the phase rectifier bridge can be connected in parallel or in series, and when m/6 is an integer and greater than or equal to 2, a hybrid connection of series and parallel can also be used. 4. The m-phase rectification/three-phase auxiliary excitation control high-speed induction generator as claimed in claim 1, 2 or 3 is characterized in that: in the m-phase uncontrollable rectification device, every two three The DC side of the three-phase rectifier bridge connected to the phase winding is connected to the phase-to-phase balancing reactor, and then output in parallel or series-parallel to reduce the harmonic component of the power winding current and improve the power factor and efficiency of the generator. 5. The m-phase rectification/three-phase auxiliary excitation control high-speed induction generator as claimed in one of claims 1 to 4, characterized in that: In order to reduce the harmonic current and voltage of the auxiliary excitation control winding, the three-phase rectification/inversion bidirectional converter adopts a cascaded multi-level pulse width modulation PWM converter main circuit, and the DC side of each power unit of the converter is connected in parallel There are capacitors that can be charged and discharged, and no DC power supply is installed; according to the excitation control strategy formulated on the basis of the dynamic model of this type of multi-winding induction generator, digital directional control technology is adopted to automatically follow the frequency and phase of the stator winding voltage to adjust the auxiliary excitation The current of the winding keeps the voltage of the parallel capacitors connected to the DC side of each power unit constant, and maintains the m-phase rectified output voltage stable, or adjusts the rectified output voltage in a multi-machine parallel power supply system to change the output power of a single generator. 6. The m-phase rectification/three-phase auxiliary excitation control high-speed induction generator according to one of claims 1 to 5, characterized in that: the uncontrollable rectification device is replaced by the m-phase controllable rectification device, so that the rectification The conduction angle of the element greatly changes the setting value of the rectified output voltage. 7. The m-phase rectification/three-phase auxiliary excitation control high-speed induction generator according to any one of claims 1 to 6, characterized in that: the rotor is a fully solid rotor with an annular narrow groove or the outer surface is equipped with binding straps or high Ordinary laminated squirrel-cage rotors reinforced with strength material retaining rings replace composite rotors composed of rotor cores with annular narrow grooves and squirrel-cage windings.

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