A single-phase AC / DC excitation system for aviation three-stage starter generator

Abstract

The embodiment of the present invention discloses a single-phase AC / DC excitation system for an aviation three-stage starter generator, and relates to the technical field of aviation three-stage starter generators. In the starting stage, the exciter is connected to a single-phase constant voltage and frequency AC power supply, and the phase shifting effect of two capacitors that match the exciter parameters is used to achieve approximate symmetry of the three-phase winding current of the exciter, and an approximately circular rotating magnetic field is formed inside the exciter. In the power generation stage, when the power generation speed is reached, the exciter is connected to the generator control unit to obtain a DC excitation power supply. In the DC excitation mode, the capacitor is naturally disconnected, and the three-phase windings are connected in series to form a single-phase winding. The present invention only adds two capacitors, and can simultaneously realize the use of a three-phase AC excitation mode in the starting stage and a single-phase DC excitation mode in the power generation stage, taking into account the advantages of the two excitation modes, and can realize the switching between three-phase AC excitation and single-phase DC excitation without the need for an additional winding switching switch.

Description

Technical Field

[0001] The invention relates to the technical field of aviation three-stage starter generators, and in particular to a single-phase AC / DC excitation system for aviation three-stage starter generators. Background Art

[0002] The three-stage motor has been widely used in the aviation field as the main power source of aircraft. Its basic structure is as follows: Figure 1 As shown. With the development of aircraft electrification, the three-stage motor also integrates the starting function, that is, it runs as an electric motor to drive the aircraft engine to start. In the power generation state, the engine drives the three-stage motor, and the permanent magnet exciter provides a controllable DC excitation current to the exciter through the rectifier circuit inside the generator control unit. The exciter provides excitation to the main motor, and the main motor outputs electrical energy to the outside. In the starting state, the starting controller injects current into the main motor, so that the main motor generates enough torque to drive the engine to start. At this time, the exciter still runs as a generator to provide excitation current to the main motor. However, the traditional three-stage motor designed mainly to meet the power generation function has the problem of difficulty in excitation in the starting state: in the starting state, the three-stage motor is in a stationary or low-speed state, and the stator of the exciter is a single-phase DC excitation winding, which cannot provide sufficient excitation power for the main motor at low speed.

[0003] In view of the above problems, in the current solution, during the starting stage, the motor speed is low, and the exciter must use AC excitation. The energy transmission efficiency of the three-phase AC excitation method is higher than that of the single-phase AC excitation method, but the three-phase AC excitation requires a special excitation controller, and the excitation voltage amplitude and frequency need to be controlled, which is more complicated to control. Single-phase AC excitation has lower requirements for the excitation power supply, and a constant voltage and frequency single-phase AC power supply can be used. In the power generation stage, the motor is in a medium and high speed state, and the traditional DC excitation control is simple and convenient to adjust the voltage. However, the excitation current output by the exciter in the three-phase AC excitation method varies greatly with the speed, and the control is more complicated.

[0004] Therefore, the new design goal is to take into account the advantages of three-phase AC excitation and DC excitation without adding a large number of new structural parts, and it also needs to have high winding utilization, no need for a dedicated winding switching switch, and reduce the requirements for excitation power supply to reduce the difficulty of control. How to design and improve a single-phase AC / DC excitation system with the above design goals that can be applied to aviation three-stage starter generators has become a topic that requires in-depth research. Summary of the invention

[0005] An embodiment of the present invention provides a single-phase AC / DC excitation system for an aviation three-stage starter generator, which can take into account the advantages of three-phase AC excitation and DC excitation, and also has a high winding utilization rate, does not require a dedicated winding switching switch, and can reduce the requirements for the excitation power supply, thereby reducing the difficulty of control.

[0006] To achieve the above object, the embodiments of the present invention adopt the following technical solutions:

[0007] A single-phase AC / DC excitation system for an aviation three-stage starter generator comprises: a main motor (1), a rotating rectifier (2), an exciter (3), a permanent magnet exciter (4), a generator control unit (5) and a single-phase constant voltage and constant frequency AC power supply (6); the rotor part of the exciter (3) is a three-phase armature winding, the stator part of the exciter (3) comprises a three-phase symmetrical winding formed by an A phase (31), a B phase (32) and a C phase (33), the windings of each of the A phase (31), the B phase (32) and the C phase (33) are all open winding structures, and the two ports of each phase winding are led out by wires; the windings of each of the A phase (31), the B phase (32) and the C phase (33) are respectively connected to a phase shift capacitor C1 (34) and a phase shift capacitor C2 (35).

[0008] The stator input port of the exciter (3) is connected to the excitation power supply via a switching switch (36), and the exciter (3) provides excitation current for the main motor (1) during the starting stage and the power generation stage of the aviation three-stage starter generator;

[0009] In the starting stage, the switch (36) is connected to the single-phase constant voltage and constant frequency AC power supply (6), and when the speed of the aviation three-stage starter generator reaches the engine disconnecting speed, the switch (36) is disconnected;

[0010] In the power generation stage, when the speed of the aviation three-stage starter generator reaches the power generation speed, the switch (36) is connected to the generator control unit (5).

[0011] The single-phase AC / DC excitation system for an aviation three-stage starter generator provided in an embodiment of the present invention can meet the excitation requirements of the aviation three-stage starter generator in two different working modes: starting and power generation. In the starting stage, the exciter is connected to a single-phase constant voltage and frequency AC power supply, and the phase shifting effect of two capacitors that match the exciter parameters is used to achieve approximate symmetry of the three-phase winding current of the exciter, and an approximately circular rotating magnetic field is formed inside the exciter, thereby achieving efficient transmission of the exciter energy, and the excitation effect is close to three-phase AC excitation. When the disconnection speed is reached, the exciter cuts off the single-phase AC power supply. In the power generation stage, when the power generation speed is reached, the exciter is connected to the generator control unit to obtain the DC excitation power supply. In the DC excitation mode, the capacitor is naturally disconnected, and the three-phase windings are connected in series to form a single-phase winding, realizing the DC excitation mode required in the power generation stage. Compared with the traditional single-phase excitation or three-phase excitation system, the present invention only adds two capacitors to simultaneously realize the use of three-phase AC excitation in the starting stage and single-phase DC excitation in the power generation stage, taking into account the advantages of both excitation methods, and without the need for an additional winding switching switch, the switching between three-phase AC excitation and single-phase DC excitation can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 It is a schematic diagram of the principle of an existing three-stage motor;

[0014] Figure 2 A schematic diagram of the principle of a single-phase AC / DC excitation system provided in an embodiment of the present invention;

[0015] Figure 3 A schematic diagram of a system connection method when AC excitation is used in the starting phase provided by an embodiment of the present invention;

[0016] Figure 4 A schematic diagram of a system mode when DC excitation is used in the power generation stage provided by an embodiment of the present invention;

[0017] Figure 5 A vector diagram of the magnetic potential of the stator winding of the exciter (3) when DC excitation is used in the power generation stage provided in an embodiment of the present invention;

[0018] Figure 6 A schematic diagram of a simulation model of an exciter (3) provided in an embodiment of the present invention;

[0019] Figure 7A schematic diagram of an external circuit of an exciter (3) provided in an embodiment of the present invention;

[0020] Figure 8 A schematic diagram of current waveforms of the three-phase excitation winding of an exciter (3) when a single-phase constant voltage and constant frequency AC power source (6) is used for power supply during the starting phase provided by an embodiment of the present invention;

[0021] Fig. 9 A schematic diagram of the output current of the exciter (3) provided in an embodiment of the present invention within a rotation speed range of 0 to 6800 rpm;

[0022] Fig.10 The output current I of the exciter (3) when DC excitation is used at a power generation speed of 8200 rpm provided in the embodiment of the present invention F and input excitation current I ef Schematic diagram of the relationship between them. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention will be described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention. It can be understood by those skilled in the art that, unless specifically stated, the singular forms "one", "one", "said" and "the" used herein may also include plural forms. It should be further understood that the term "including" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups. It should be understood that when we say that an element is "connected" or "coupled" to another element, it can be directly connected or coupled to other elements, or there may also be intermediate elements. In addition, the "connection" or "coupling" used here may include wireless connection or coupling. The term "and / or" used herein includes any unit and all combinations of one or more associated listed items. It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as generally understood by those of ordinary skill in the art to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0024] At present, the main solutions at home and abroad are: 1. Without changing the original structure of the exciter, a single-phase AC is passed through the stator winding of the exciter during the starting stage to generate a pulsating magnetic field. The exciter is equivalent to a rotating transformer, which can provide excitation for the main motor at low speed. When the motor reaches the power generation speed, it will switch to DC excitation. This solution does not need to change the existing exciter structure, but only needs to switch different excitation power supplies at different stages. However, the energy transmission efficiency of the pulsating magnetic field is low, and the excitation power provided by the exciter to the main motor is limited during single-phase AC excitation. 2. Add a set of auxiliary three-phase windings to the stator of the exciter. Use the auxiliary three-phase windings during the starting stage, pass three-phase AC, form a circular rotating magnetic field, so that the exciter rotor armature winding can also generate induced current at low speed; when the motor reaches a certain speed, the auxiliary three-phase winding is cut off and replaced with the original single-phase excitation winding of the exciter, and single-phase DC excitation is adopted. Compared with the single-phase AC excitation method, the three-phase AC excitation method has high energy transmission efficiency and can provide greater excitation power. However, this solution adds an additional excitation winding, which increases the size and weight of the motor, making the excitation machine structure more complicated, and the two sets of windings cannot be reused, resulting in low utilization. 3. The stator single-phase excitation winding of the traditional excitation machine is changed to a three-phase excitation winding, and a single-pole double-throw switch is set at the neutral point of the three-phase winding. Three-phase AC excitation control is adopted in the starting stage. When the motor reaches a certain speed, the three-phase excitation winding is connected in series to a single-phase winding for DC excitation control using a single-pole double-throw switch. This solution improves the utilization rate of the excitation winding, but the coordinated control of the three-phase AC excitation control and the single-pole double-throw switch increases the complexity of AC and DC excitation switching. 4. The stator of the excitation machine is a three-phase excitation winding, and the single-pole double-throw switch is cancelled. There is no need to switch the excitation method. Three-phase AC excitation is used throughout the starting and power generation stages. This solution overcomes the shortcomings of Solution 3, but fails to take advantage of the simplicity of DC excitation control in the medium and high speed stages.

[0025] The design goal of this embodiment is to take into account the advantages of three-phase AC excitation and DC excitation without adding a large number of new structural parts, and also to have a high winding utilization rate, without the need for a dedicated winding switching switch, and to reduce the requirements for the excitation power supply, thereby reducing the difficulty of control.

[0026] The basic structure of a traditional three-stage motor is as follows: Figure 1 As shown, it includes: a main motor, a rotating rectifier (2), an exciter (3), a permanent magnet exciter (4) and an external generator control unit (5). The main motor is an electrically excited synchronous motor, the exciter (3) is a rotating armature type electrically excited synchronous generator, and the permanent magnet exciter (4) is a permanent magnet synchronous generator. The exciter (3) and the rotating rectifier (2) realize the brushless excitation of the main motor. An embodiment of the present invention provides a single-phase AC / DC excitation system for an aviation three-stage starter generator, such as Figure 2As shown, it comprises: a main motor (1), a rotating rectifier (2), an exciter (3), a permanent magnet exciter (4), a generator control unit (5) and a single-phase constant voltage and constant frequency AC power supply (6);

[0027] The rotor part of the exciter (3) is a three-phase armature winding, and the stator part of the exciter (3) includes a three-phase symmetrical winding formed by an A phase (31), a B phase (32) and a C phase (33). The windings of the A phase (31), the B phase (32) and the C phase (33) are all open winding structures, and two ports of each phase winding are led out by wires.

[0028] The windings of phase A (31), phase B (32) and phase C (33) are connected to phase shift capacitors C1 (34) and C2 (35) according to Figure 2 Connect in the same way.

[0029] The stator input port of the exciter (3) is connected to the excitation power supply via a switching switch (36), and the exciter (3) provides excitation current for the main motor (1) during both the starting stage and the power generation stage of the aviation three-stage starter generator.

[0030] The single-phase AC / DC excitation system provided in this embodiment is used for an aviation three-stage starter generator. During the starting stage of the aviation three-stage starter generator, a switching switch (36) is connected to a single-phase constant voltage and constant frequency AC power source (6). When the speed of the aviation three-stage starter generator reaches the engine disconnection speed, the switching switch (36) is disconnected. By selecting appropriate phase-shifting capacitors C1 (34) and C2 (35), the three-phase winding currents of phase A (31), phase B (32) and phase C (33) are approximately symmetrical, thereby forming an approximately circular rotating magnetic field, and the excitation effect is close to that of efficient three-phase AC excitation. The system is connected as follows: Figure 3 When the three-stage motor reaches the engine disconnecting speed, the switch (36) is disconnected.

[0031] In the power generation stage, when the speed of the aviation three-stage starter generator reaches the power generation speed, the switch (36) is connected to the generator control unit (5) to obtain a DC excitation power supply.

[0032] In the practical application of this embodiment, during the starting phase, the single-phase constant voltage and constant frequency AC power source (6) obtains power through a starting controller; or the single-phase constant voltage and constant frequency AC power source (6) is connected to an onboard three-phase AC power grid and obtains single-phase AC power.

[0033] In a preferred embodiment, the onboard three-phase AC power grid is 115V / 400Hz, and the single-phase constant voltage and constant frequency AC power supply (6) obtains single-phase AC power with a line voltage of 200V / 400Hz from the onboard three-phase AC power grid. The disconnection speed in the starting stage is 6800rpm. For example, in the starting stage, the excitation power supply in the external circuit model is set to a 200V / 400Hz single-phase constant voltage and constant frequency AC power supply (6). The speed of the three-stage motor increases from 0 to a disconnection speed of 6800rpm. Figure 8 When the exciter (3) is 0rpm, the three-phase current waveform of the stator winding is I efa ,I efb ,I efc , under the action of phase-shifting capacitors C1 and C2, the winding current is close to three-phase symmetry. Fig. 9 is the output excitation current I of the exciter (3) within the range of 0 to 6800 rpm F It can be seen that during the entire starting stage, the exciter (3) can output a relatively high excitation current I F , especially at the initial low speed of the starting output excitation current I F Larger.

[0034] In the practical application of this embodiment, during the power generation stage, the phase-shifting capacitor C1 (34) and the phase-shifting capacitor C2 (35) are naturally disconnected under the influence of DC excitation; and the three-phase windings of phase A (31), phase B (32) and phase C (33) are connected in series to form a single-phase winding structure; the synthetic magnetic field formed inside the exciter (3) after the three-phase windings of phase A (31), phase B (32) and phase C (33) are connected in series, thereby enabling the exciter (3) to achieve single-phase DC excitation. For example: the direction of the synthetic magnetic field is as follows: Figure 5 , is a constant magnetic field, and the exciter (3) realizes single-phase DC excitation. The system connection is as follows Figure 4 .

[0035] In the preferred embodiment, the power generation speed in the power generation stage is 8200 rpm. For example, in the power generation stage, the excitation power supply in the external circuit model is set to an adjustable DC current source, and the excitation current is I ef When the motor speed reaches the generating speed of 8200 rpm, the exciter (3) is connected to the DC excitation power supply. Fig.10 is the output current I of the exciter (3) at 8200 rpm F and input excitation current I ef The exciter (3) can provide a flexible and adjustable excitation current for the main motor in a DC excitation mode.

[0036] In this embodiment, the finite element + external circuit joint simulation can be used to verify the solution. A finite element simulation model of the exciter is built in Ansys Maxwell software, such as Figure 6 . Build an external circuit model, such as Figure 7 . Select capacitors C1 = 20.9 μF and C2 = 12.1 μF.

[0037] The capacitance value can be determined by the following method:

[0038] The goal of capacitor numerical design is to achieve approximate symmetry of the three-phase excitation current, so the optimization objective function f(C1, C2) = I n / I p , I n is the negative sequence component of the three-phase excitation current, I p is the positive sequence component of the three-phase excitation current, f(C1, C2) = I n / I p Represents the unbalance of the three-phase excitation current. The optimization variables are C1 and C2, and the optimization goal is to make the unbalance of the three-phase excitation current f(C1, C2) = I n / I p Minimum.

[0039] C2 has the most significant impact on the three-phase excitation effect. The value of C1 is related to C2. C1 = 1.727C2 can be selected to reduce the two-dimensional variable to a one-dimensional variable. Therefore, C1 can be parametrically simulated so that f(C1, C2) = I n / I p The minimum C1 is the required capacitance value.

[0040] The solution of this embodiment can take into account the advantages of three-phase AC excitation and DC excitation at the same time by simply adding two capacitors and using a specific connection method between the three-phase winding of the stator of the exciter (3) and the two capacitors. The winding utilization rate is high, no dedicated winding switching switch is required, the requirements for the excitation power supply are low, and the control is simple.

[0041] This embodiment can meet the excitation requirements of aviation three-stage starter generators in two different working modes: starting and power generation. In the starting stage, the exciter is connected to a single-phase constant voltage and frequency AC power supply. Through the phase shifting effect of two capacitors that match the exciter parameters, the approximate symmetry of the three-phase winding current of the exciter is achieved, and an approximately circular rotating magnetic field is formed inside the exciter, thereby achieving efficient transmission of the exciter energy, and the excitation effect is close to three-phase AC excitation. When the disconnection speed is reached, the exciter cuts off the single-phase AC power supply. In the power generation stage, when the power generation speed is reached, the exciter is connected to the generator control unit to obtain a DC excitation power supply. In the DC excitation mode, the capacitor is naturally disconnected, and the three-phase windings are connected in series to form a single-phase winding, realizing the DC excitation method required in the power generation stage. Compared with the traditional single-phase excitation or three-phase excitation system, the present invention only adds two capacitors to simultaneously realize the use of three-phase AC excitation in the starting stage and single-phase DC excitation in the power generation stage, taking into account the advantages of both excitation methods, and without the need for an additional winding switching switch, the switching between three-phase AC excitation and single-phase DC excitation can be realized.

[0042] In general, the advantages of this embodiment are mainly as follows: 1. This embodiment can simultaneously realize AC excitation in the starting stage and DC excitation in the power generation stage, and can take into account the advantages of the two excitation methods, and can achieve good excitation effects in both the starting and power generation stages; 2. The phase-shifting capacitor in this embodiment is naturally disconnected when switching between AC and DC excitation, and AC and DC excitation switching can be achieved without a special winding switching switch; 3. The stator three-phase winding of the excitation machine (3) of this embodiment can be fully reused in both AC excitation and DC excitation modes, and the winding utilization rate is high; 4. When AC excitation is adopted in the starting stage, this embodiment only needs a single-phase constant voltage and constant frequency AC power supply (6) to obtain an excitation effect similar to that of a three-phase AC power supply, and has low requirements for the excitation power supply and simple excitation control.

[0043] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. The above is only a specific implementation method of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A single-phase AC / DC excitation system for an aviation three-stage starter generator, characterized in that: include: A main motor (1), a rotating rectifier (2), an exciter (3), a permanent magnet exciter (4), a generator control unit (5) and a single-phase constant voltage and constant frequency AC power supply (6); The rotor part of the exciter (3) is a three-phase armature winding, and the stator part of the exciter (3) includes a three-phase symmetrical winding formed by an A phase (31), a B phase (32) and a C phase (33). The windings of the A phase (31), the B phase (32) and the C phase (33) are all open winding structures, and two ports of each phase winding are led out by wires; The windings of the A phase (31), the B phase (32) and the C phase (33) are respectively connected to the phase shifting capacitor C1 (34) and the phase shifting capacitor C2 (35); The stator input port of the exciter (3) is connected to the excitation power supply via a switching switch (36), and the exciter (3) provides excitation current to the main motor (1) during both the starting stage and the power generation stage of the aviation three-stage starter generator; In the starting phase, the switch (36) is connected to the single-phase constant voltage and constant frequency AC power supply (6), and when the speed of the aviation three-stage starter generator reaches the engine disconnecting speed, the switch (36) is disconnected; In the power generation stage, when the speed of the aviation three-stage starter generator reaches the power generation speed, the switch (36) is connected to the generator control unit (5); In the power generation stage, the phase-shifting capacitor C1 (34) and the phase-shifting capacitor C2 (35) are naturally disconnected under the influence of DC excitation; The three-phase windings of phase A (31), phase B (32) and phase C (33) are connected in series to form a single-phase winding structure.

2. The system according to claim 1, characterized in that During the starting phase, the single-phase constant voltage and constant frequency AC power source (6) obtains power through the starting controller; Alternatively, the single-phase constant voltage and constant frequency AC power source (6) is connected to the onboard three-phase AC power grid and obtains single-phase AC power.

3. The system according to claim 1, characterized in that The onboard three-phase AC power grid is 115V / 400Hz, and the single-phase constant voltage and constant frequency AC power source (6) obtains single-phase AC power with a line voltage of 200V / 400Hz from the onboard three-phase AC power grid.

4. The system according to claim 1, characterized in that The disengagement speed during the starting phase is 6800 rpm.

5. The system according to claim 1, characterized in that A synthetic magnetic field is formed inside the exciter (3) after the three-phase windings of phase A (31), phase B (32) and phase C (33) are connected in series, thereby enabling the exciter (3) to achieve single-phase DC excitation.

6. The system according to claim 5, characterized in that The power generation speed in the power generation stage is 8200 rpm.

7. The system according to claim 1, characterized in that The capacitance value of the phase shift capacitor C1 (34) is 20.9 μF, and the capacitance value of the phase shift capacitor C2 (35) is 12.1 μF.

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