Electrically excited direct-current generator system

Abstract

An electro-magnetic direct-current generator system comprises an electro-magnetic direct-current motor and a full-wave rectification switching output circuit. A stator winding of the electro-magnetic direct current motor is composed of two sets of three-phase windings, and two neutral points of the two sets of three-phase windings are not connected with each other. The first winding is used for a high-rotating-speed use condition; the second winding is used for a low-rotating-speed use condition; the full-wave rectification switching output circuit comprises a full-wave rectification circuit and a switching circuit; the full-wave rectifier circuit comprises two three-phase rectifier bridges which are respectively connected with the two sets of three-phase windings; the switching circuit comprises three equivalent resistors in star connection with three phase lines of the motor, a frequency sensitive circuit used for outputting frequency sensitive signals, a frequency change circuit used for converting the frequency sensitive signals into frequency signals, and a switching execution circuit used for working winding switching according to the frequency signals. The motor is used for a fuel-powered unmanned aerial vehicle, and the output capacity at high and low rotating speeds is taken into account on the premise that the size of the motor is not changed.

Description

Technical Field

[0001] The invention belongs to the technical field of electrically excited direct current generators. Background Art

[0002] As UAV technology matures, UAVs are increasingly used in military and civilian fields. Except for small battery-driven UAVs, fuel-powered UAVs need to be equipped with dedicated generators. In order to meet the wide operating speed range of the engine, the permissible speed range of the generator must also be expanded. At the same time, the miniaturization and lightness of UAVs also put forward strict requirements on the size and weight of motors. Due to mission requirements, fuel-powered UAVs have more electrical equipment on board and greater power demand. Therefore, UAV generators require a wide speed range and large output capacity. The inventors have found that for the same motor, when the number of winding turns of the motor is large, the output capacity of the motor is better at low speed, while the output capacity is poor at high speed; when the number of turns of the motor is small, the output capacity of the motor is better at high speed, while the output capacity is poor at low speed. Generally, the requirements of the above-mentioned high and low speed output performance can be achieved by increasing the size of the motor, but for UAVs with restrictions on both volume and weight, the above scheme cannot simultaneously meet the UAV's power generation needs for the high and low speed range of the motor. Summary of the invention

[0003] The purpose of the present invention is to solve the above-mentioned deficiencies of the prior art and to provide a small-sized and light-weight electrically excited DC generator system for a fuel-powered UAV, which can achieve a balance between the output capacity of the motor at high and low speeds without changing the size of the motor.

[0004] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: an electrically excited DC generator system, including an electrically excited DC motor and a full-wave rectifier switching output circuit; the stator winding of the electrically excited DC motor is composed of two sets of three-phase windings, and the two neutral points of the two sets of three-phase windings are not connected to each other; the first set of windings has a small number of series turns and a thick equivalent wire diameter of the windings, and is used in high-speed operating conditions; the second set of windings has a large number of series turns and a thin equivalent wire diameter of the windings, and is used in low-speed operating conditions; the full-wave rectifier switching output circuit includes a full-wave rectifier circuit and a switching circuit; the full-wave rectifier circuit includes two three-phase rectifier bridges respectively connected to the two sets of three-phase windings; the switching circuit includes three equivalent resistors connected in star shape on the three-phase lines of the motor, and a switching circuit for A frequency sensitive circuit for comparing the neutral point voltage formed by the connecting point of the three equal-value resistors with any phase voltage of the first set of windings to output a frequency sensitive signal, a frequency changing circuit for converting the frequency sensitive signal into a frequency signal, and a switching execution circuit for switching the working winding according to the frequency signal; the switching execution circuit includes an N-channel field effect transistor Q13; the positive poles of the two three-phase rectifier bridges are directly connected as the output positive pole of the motor, the negative poles of the two three-phase rectifier bridges are connected through the N-channel field effect transistor Q13, and the drain end of the N-channel field effect transistor Q13 is used as the output negative pole of the motor to form a common positive output mode; the switching of the working rectifier bridge, that is, the working winding is realized by turning the N-channel field effect transistor Q13 on and off.

[0005] The frequency sensitive circuit includes a charge-discharge circuit and a differential amplifier circuit; the charge-discharge circuit is composed of an optocoupler U4, a resistor R32, and a capacitor C18, and the motor neutral point voltage and the phase voltage are connected through the charge-discharge circuit to obtain a sawtooth wave whose period varies with the speed; the differential amplifier circuit is composed of resistors R33-R35, R38-R40 and an operational amplifier U5A, and the differential amplifier circuit improves the sensitivity of the frequency sensitive circuit by intercepting the peak part of the sawtooth wave, thereby ensuring the stability of the system.

[0006] The frequency change circuit receives the frequency sensitive signal output by the frequency sensitive circuit. The frequency sensitive signal obtains a high-quality DC voltage through the filtering circuit in the frequency change circuit. The voltage changes with the change of the motor speed. When the motor speed decreases, the DC voltage increases, and the operational amplifier U5B in the frequency change circuit outputs a low level; when the motor speed increases, the DC voltage decreases, and U5B in the frequency change circuit outputs a high level, and after a delay, the execution circuit outputs a frequency signal.

[0007] The switching execution circuit includes an optocoupler U3; the N-channel field effect transistor Q13 is turned on by the optocoupler U3 to achieve level isolation, and plays the role of switching between two rectifier bridges in the circuit; when the operational amplifier U5B outputs a low level, the optocoupler U3 is turned off, the field effect transistor Q13 is turned on, the second set of windings works, and the motor is in a low-speed working mode; when the operational amplifier U5B outputs a high level, the optocoupler U3 is turned on, the field effect transistor Q13 is turned off, the first set of windings works, and the motor is in a high-speed working mode.

[0008] When the motor speed is lower than the set threshold, the conduction time of the optocoupler U4 is short, the voltage of the capacitor C18 is higher than the threshold, the output voltage of the operational amplifier U5A is higher than the threshold, the operational amplifier U5B outputs a low level, the optocoupler U3 is cut off, the gate voltage of the field effect transistor Q13 is higher than the source voltage, the field effect transistor Q13 is turned on, the second set of windings works, and the motor is in a low-speed working mode; when the motor speed is higher than the set threshold, the conduction time of the optocoupler U4 is long, the voltage of the capacitor C18 is lower than the threshold, the output voltage of the operational amplifier U5A is lower than the threshold, the operational amplifier U5B outputs a high level, the optocoupler U3 is turned on, the gate voltage of the field effect transistor Q13 is lower than the source voltage, the field effect transistor Q13 is cut off, the first set of windings works, and the motor is in a high-speed working mode.

[0009] The full-wave rectifier switching output circuit also includes a filter circuit and a sampling voltage regulation circuit; the filter circuit is used to filter out ripples in the rectifier output voltage to improve the quality of the DC voltage; the sampling voltage regulation circuit is used to sample and regulate the DC voltage to control the output voltage of the motor.

[0010] The first set of windings has n series turns per phase and 2m parallel conductors; the second set of windings has 2n series turns per phase and m parallel conductors.

[0011] The three equal value resistors are connected to the three-phase lines of the first set of windings.

[0012] The three-phase rectifier bridge includes six field effect tubes.

[0013] The A-phase outgoing wires of the first set of windings are respectively connected to the gate of the field effect transistor Q1, the source of the field effect transistor Q1 and the drain of the field effect transistor Q4; the B-phase outgoing wires are respectively connected to the gate of the field effect transistor Q2, the source of the field effect transistor Q2 and the drain of the field effect transistor Q5; the C-phase outgoing wires are respectively connected to the gate of the field effect transistor Q3, the source of the field effect transistor Q3 and the drain of the field effect transistor Q6; the U-phase outgoing wires of the second set of windings are respectively connected to the gate of the field effect transistor Q7, the source of the field effect transistor Q7 and the drain of the field effect transistor Q10; the V-phase outgoing wires are respectively connected to the gate of the field effect transistor Q8, the source of the field effect transistor Q8 and the drain of the field effect transistor Q11; the W-phase outgoing wires are respectively connected to the gate of the field effect transistor Q9, the source of the field effect transistor Q9 and the drain of the field effect transistor Q12; the drains of the field effect transistors Q1 to Q6 are connected; the gates and sources of the field effect transistors Q4, Q5, Q6, Q10, Q11 and Q12 are simultaneously connected to a common ground.

[0014] The two neutral points of the two sets of windings of the present invention are not connected to each other. The first set of windings has a small number of series turns, so that the output capacity of the motor is high when the motor is at high speed; the second set of windings has a large number of series turns, so that the output capacity of the motor is high when the motor is at low speed; the rectifier circuits of the two sets of windings respectively use six N-channel field effect transistors, whose source and gate are directly connected, and the body diode inside is used to achieve the purpose of rectification. The structure is compact and highly integrated, and can effectively save space; the positive poles of the two three-phase rectifier bridges are directly connected as the output positive pole of the motor, and the negative poles of the two rectifier bridges are connected through the N-channel field effect transistor Q13, and the drain end of the field effect transistor Q13 is used as the output negative pole of the motor, forming The output mode of forming a common positive pole; three equal value resistors are connected in star shape on the three-phase line of the motor, and the connection point of the three resistors is used to form a neutral point. The voltage of a certain phase of the winding is compared with the voltage of the neutral point, and the unidirectional conductivity of the light-emitting diode inside the optocoupler is used to obtain a square wave signal. After the square wave signal passes through the RC charging and discharging circuit, the differential amplification circuit and the filtering circuit, a DC voltage with an amplitude proportional to the speed can be obtained. The DC voltage is compared with the reference voltage to obtain a switch switching signal at a certain speed corresponding to the reference voltage. The signal controls the on-off operation of the N-channel field effect transistor Q13 to realize the free switching of high and low speeds of the motor.

[0015] Compared with the prior art, the present invention, under the premise of unchanged volume, unchanged weight and unchanged copper usage, achieves a balance between the output capacity of the motor at high and low speeds by adopting a design of two sets of windings combined with changes in the control part (although the number of control elements has increased, the components such as field effect transistors used are small in size and light in weight, and the overall volume and weight of the motor remain basically unchanged). BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The circuit diagram of the full-wave rectifier switching output circuit.

[0017] Figure 2 The circuit diagram of the full-wave rectifier circuit.

[0018] Figure 3 This is the circuit diagram of the first set of windings and the first rectifier bridge.

[0019] Figure 4 This is the circuit diagram of the second set of windings and the second rectifier bridge.

[0020] Figure 5 A circuit diagram of a switching circuit.

[0021] Figure 6 This is the circuit diagram of the frequency sensitive circuit.

[0022] Figure 7 This is the circuit diagram of the frequency changing circuit.

[0023] Figure 8 The circuit diagram of the switching execution circuit. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without carrying out creative work are within the scope of protection of the present invention.

[0025] Technologies, methods, and apparatus known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, such technologies, methods, and apparatus should be considered part of the authorization specification.

[0026] For the convenience of description, an existing motor is used as an example to illustrate the implementation method. It should be noted that the following implementation method is not the only one and its implementation parameters are not fixed. Assuming that the existing motor has 2n turns of series winding per phase and each winding has 2m parallel conductors, the motor has a high low-speed output capability, and naturally its high-speed output capability is poor. At this time, the motor can be designed into two sets of windings. The number of series turns of each phase of the first set of windings is reduced to n, but the number of parallel conductors of the windings is still 2m; the number of series turns of each phase of the second set of windings is still 2n, but the number of parallel conductors of the windings is reduced to m. At the same time, the two neutral points of the two sets of windings remain unconnected. In this way, after the two sets of windings are embedded in the motor, the motor slot full rate still maintains the original slot full rate unchanged, but the motor can have two output capabilities without changing its volume. Through the speed switching circuit in the circuit design, the motor is connected to the second set of windings at low speed, thereby closing the first set of windings and working through the second set of windings. At high speed, the second set of windings is cut off and working through the first set of windings. At this time, it is possible to retain the advantages of the original motor's low-speed output capacity and improve the motor's high-speed output capacity, thereby meeting the operating conditions of the drone.

[0027] In the circuit implementation scheme, two sets of independent windings are respectively connected to two three-phase rectifier bridges. The positive poles of the two three-phase rectifier bridges are directly connected as the positive output pole of the motor. The negative poles of the two rectifier bridges are connected through the N-channel field effect transistor Q13 (the field effect transistor Q13 is used to realize the switching of the two rectifier bridges). The drain end of the field effect transistor Q13 serves as the negative output pole of the motor, forming a common positive output mode. Of course, a common negative output mode can also be formed through a P-channel field effect transistor.

[0028] When the motor is working, the polarity of any phase voltage of the motor will change alternately from positive to negative relative to the neutral point. By utilizing the unidirectional conductivity of the light-emitting diode inside the optocoupler, the phase voltage of a phase of the winding (such as phase A) is connected to the base of the optocoupler and the neutral point is connected to the emitter of the optocoupler to obtain a square wave signal with a frequency proportional to the motor speed. The square wave signal passes through an RC charging and discharging circuit composed of a transistor, a resistor and a capacitor to obtain a sawtooth wave whose period changes with the speed. After passing through an amplification circuit and a filtering circuit, a DC voltage with an amplitude proportional to the speed can be obtained. By comparing the DC voltage with the reference voltage, a switch switching signal at a certain speed corresponding to the reference voltage can be obtained. The signal controls the on-off operation of the N-channel field effect transistor Q13, thereby realizing the switching of the working rectifier bridge, that is, the working winding.

[0029] Whether the first set of windings or the second set of windings is used to extract the speed signal does not affect the realization of the above functions, but because the terminal voltage of the first set of windings will double when switching to the second set of windings, in order to reduce the withstand voltage requirements of components, the present invention adopts the first set of windings for sampling.

[0030] There are at least one circuit implementation scheme using the comparison between a certain phase voltage of the winding and the neutral point voltage. The first is a three-phase four-wire system, which requires the motor to lead out a fourth lead wire as a neutral point, which increases the manufacturing complexity in structure. Another scheme is to connect three equal-value resistors in a star shape on the three-phase line of the motor, and use the connection point of the three resistors to form a neutral point. This scheme is relatively simple in structure, and the present invention adopts this scheme. The third scheme is to connect two voltage-dividing resistors with the same resistance in series between the positive and negative poles of the motor, and the connection point of the two voltage-dividing resistors is the neutral point of the motor.

[0031] Generally, three-phase rectifier bridges are implemented by power diodes, but existing power diodes are all packaged in relatively large volumes, making it difficult to achieve miniaturized design of products. The present invention utilizes the body diode inside the field effect tube to replace the diode of the field effect tube by short-circuiting the gate and source of the N-channel field effect tube, and utilizes the miniaturized packaging of the field effect tube to achieve miniaturization of the three-phase rectifier bridge, thereby achieving the effect of arranging two three-phase rectifier bridges in a limited space.

[0032] The motor stator winding is composed of two sets of three-phase windings, and the two neutral points of the two sets of three-phase windings are not connected to each other. The first set of windings has a small number of series turns and a thick equivalent wire diameter, and is used in high-speed operating conditions; the second set of windings has a large number of series turns and a thin equivalent wire diameter, and is used in low-speed operating conditions.

[0033] Each set of three-phase windings of the motor uses six field effect tubes to form a three-phase full-wave rectifier circuit. When an N-channel field effect tube is used, the source and gate of the field effect tube are directly connected, and the body diode inside the field effect tube is used to achieve the purpose of rectification. Generally, three-phase rectifier bridges are implemented using power diodes. Compared with diodes, the field effect tube solution used in the present invention has a small size, a compact structure, a high degree of integration, and can save space.

[0034] The positive poles of the two three-phase rectifier bridges are directly connected as the output positive pole of the motor, the negative poles of the two rectifier bridges are connected through the N-channel field effect tube Q13, and the drain terminal of the field effect tube Q13 is used as the output negative pole of the motor, forming a common positive pole output mode. The output mode of the P-channel field effect tube can also be used: the negative poles of the two three-phase rectifier bridges are directly connected as the output negative pole of the motor, and the positive poles of the two rectifier bridges are connected through the P-channel field effect tube, and the source terminal of this field effect tube is used as the output positive pole of the motor, forming a common negative pole output mode. The present invention adopts the solution of the N-channel field effect tube.

[0035] The full-wave rectifier switching output circuit compares a phase voltage of the winding with the neutral point voltage, and uses the unidirectional conductivity of the light-emitting diode inside the optocoupler to obtain a square wave signal. After passing through the RC charging and discharging circuit, the amplification circuit, and the filtering circuit, the square wave signal can obtain a DC voltage with an amplitude proportional to the speed. By comparing the DC voltage with the set reference voltage, a switch switching signal at a certain speed corresponding to the reference voltage can be obtained. The signal controls the on-off operation of the N-channel field effect transistor Q13 to realize the switching of the working winding.

[0036] Compare the voltage of a certain phase of the winding in the switching circuit with the voltage of the neutral point. Connect three equal resistors in a star shape on the three-phase line of the motor, and use the connection point of the three resistors to form a neutral point. Compare the voltage of a certain phase of the winding with the voltage of the neutral point to obtain the speed signal.

[0037] Alternatively, two voltage-dividing resistors with the same resistance value may be connected in series between the positive and negative poles of the motor, and the connection point of the two voltage-dividing resistors is the neutral point of the motor.

[0038] The present invention adopts three equal-value resistors connected in star shape on the three-phase lines of the first set of windings of the motor. Compared with the second set of windings, the first set of windings can reduce the voltage requirements of components.

[0039] The field effect tube Q13 is controlled to be turned on through the optocoupler U3 to achieve level isolation, and plays the role of switching of two rectifier bridges in the circuit, thereby achieving the function of winding switching, that is, speed switching.

[0040] The electrically excited direct current generator system provided in the embodiment of the present invention comprises an electrically excited direct current motor and a full-wave rectification switching output circuit.

[0041] The electromagnetically excited DC motor must have both high-speed and low-speed output capabilities. The motor winding is designed as two sets of windings. The two neutral points of the two sets of windings are not connected to each other. The first set of windings has a small number of series turns and a thick equivalent wire diameter, and is used in high-speed operating conditions; the second set of windings has a large number of series turns and a thin equivalent wire diameter, and is used in low-speed operating conditions.

[0042] Each set of motor windings uses six N-channel field effect transistors and the body diodes inside the field effect transistors to form a three-phase full-wave rectifier circuit. The volume of the field effect transistor is much smaller than that of a diode with the same voltage and current resistance. This design is compact and highly integrated. All connections with the motor are made by welding, which can greatly reduce the length and width. It can effectively solve the technical problems of complex physical structure and large size in the existing technology and can greatly save space.

[0043] The full-wave rectification switching output circuit includes a full-wave rectification circuit and a switching circuit; the full-wave rectification circuit includes two three-phase rectification bridges respectively connected to two sets of three-phase windings; the switching circuit includes three equal value resistors connected in star shape on the three-phase lines of the motor, a frequency sensitive circuit, a frequency change circuit, and a switching execution circuit.

[0044] The positive poles of the two three-phase rectifier bridges are directly connected as the output positive pole of the motor, and the negative poles of the two rectifier bridges are connected through the N-channel field effect transistor Q13. The drain end of the field effect transistor Q13 serves as the output negative pole of the motor, forming a common positive output mode.

[0045] Frequency sensitive circuit: three equal value resistors are connected in star shape on the three-phase line of the motor, and the connection point of the three resistors is used to form a neutral point. The voltage of any phase of the first set of windings (C phase is taken as an example in the present invention) is selected to compare with the neutral point voltage. When the motor is working, the polarity between the motor midpoint voltage and the phase voltage will change alternately, and the sawtooth wave whose period changes with the speed can be obtained through the RC charging and discharging circuit composed of the optical coupler U4, the resistor R32, and the capacitor C18. By selecting appropriate RC parameters, within the operating speed range, the higher the speed, the shorter the charging time of the capacitor C18, and the lower the sawtooth peak value of the C18 voltage, that is, the amplitude of the sawtooth wave is inversely correlated with the speed. Resistors R33~R35, R38-R40 and operational amplifier U5A constitute a differential amplifier circuit, which intercepts the peak part of the above sawtooth wave through the bias voltage of the inverting input end for subsequent comparison (the part below the bias voltage is discarded) to improve the sensitivity of the frequency sensitive circuit, and also improve the output impedance of the frequency sensitive circuit through the operational amplifier, thereby ensuring the stability of the system.

[0046] Frequency change circuit: The frequency sensitive signal obtains a DC voltage through the filter circuit composed of diode D18, resistor R41 and capacitor C19. When the motor speed decreases, the DC voltage increases, and this voltage is input to the inverting terminal of the operational amplifier U5B through resistor R47. When the potential of the inverting terminal of the operational amplifier U5B is higher than the set potential of the same phase terminal (corresponding to the switching speed), U5B outputs a low level. When the motor speed increases, the DC voltage decreases, and this voltage is input to the inverting terminal of the operational amplifier U5B through resistor R47. When the potential of the inverting terminal of the amplifier U5B is lower than the set potential of the same phase terminal (corresponding to the switching speed), U5B outputs a high level, and after a delay, the switching execution circuit outputs a frequency signal.

[0047] Switching execution circuit: When the operational amplifier U5B outputs a low level, the optocoupler U3 is turned off, the gate voltage of the field effect tube Q13 is higher than the conduction voltage, Q13 is turned on, the second rectifier bridge is connected to close the first rectifier bridge and work through the second rectifier bridge, the second set of windings works, and the motor is in low-speed working mode. When the operational amplifier U5B outputs a high level, the optocoupler U3 is turned on, the gate voltage of the field effect tube Q13 is at the same potential as the source voltage, Q13 is turned off, the second rectifier is cut off and work through the first rectifier bridge, the first set of windings works, and the motor is in high-speed working mode.

[0048] like Figure 1-Figure 8 As shown, the full-wave rectification switching output circuit provided by the present invention includes a full-wave rectification circuit and a switching circuit; the full-wave rectification circuit includes two three-phase rectification bridges respectively connected to two sets of three-phase windings; the switching circuit includes three equivalent resistors connected in a star shape on the three-phase lines of the motor, a frequency sensitive circuit, a frequency change circuit, and a switching execution circuit.

[0049] The first rectifier bridge includes field effect transistors Q1 to Q6.

[0050] The second rectifier bridge includes field effect transistors Q7 to Q12.

[0051] The frequency sensitive circuit includes a resistor R31, a diode D21, an optocoupler U4, a resistor R32, a capacitor C18, a resistor R33, a resistor R35, a resistor R34, a resistor R38, a resistor R39, a resistor R40, an operational amplifier U5A, and a capacitor C14.

[0052] The frequency variation circuit includes resistor R45, resistor R44, resistor R41, resistor R43, resistor R42, resistor R47, resistor R48, variable resistor R46, operational amplifier U5B, diode D18, diode D20, and capacitor C19.

[0053] The switching execution circuit includes a resistor R23, an optical coupler U3, a resistor R24, a resistor R22, a voltage regulator D17, a field effect transistor Q13, a capacitor C15, and a resistor R27.

[0054] The first set of winding A phase outgoing wires are respectively connected to the gate of field effect transistor Q1, the source of field effect transistor Q1 and the drain of field effect transistor Q4. The winding B phase outgoing wires are respectively connected to the gate of field effect transistor Q2, the source of field effect transistor Q2 and the drain of field effect transistor Q5. The C phase outgoing wires are respectively connected to the gate of field effect transistor Q3, the source of field effect transistor Q3 and the drain of field effect transistor Q6.

[0055] The U-phase outgoing wires of the second set of windings are respectively connected to the gate of the field effect transistor Q7, the source of the field effect transistor Q7 and the drain of the field effect transistor Q10. The V-phase outgoing wires of the windings are respectively connected to the gate of the field effect transistor Q8, the source of the field effect transistor Q8 and the drain of the field effect transistor Q11. The W-phase outgoing wires are respectively connected to the gate of the field effect transistor Q9, the source of the field effect transistor Q9 and the drain of the field effect transistor Q12.

[0056] The drains of the field effect transistors Q1 to Q6 are connected, and the gates and sources of the field effect transistors Q4, Q5, Q6, Q10, Q11, and Q12 are grounded at the same time.

[0057] Select any phase voltage of a winding to compare with the midpoint voltage. At this time, select the C phase voltage of the low voltage winding to compare with the midpoint voltage.

[0058] The sources of field effect transistors Q1, Q2, and Q3 are connected to the first ends of resistors R28, R25, and R26 respectively, and the second ends of resistors R28, R25, and R26 are simultaneously connected to the anode of diode D21. The output line of phase C of low voltage winding is connected to the first end of resistor R31, and the second end of resistor R31 is connected to the cathode of diode D21.

[0059] The cathode of the diode D21 is connected to the positive electrode of the optocoupler U4, the anode of the diode D21 is connected to the negative electrode of the optocoupler U4, the collector of the optocoupler U4, the first end of the resistor R32, the first end of the capacitor C18 and the first end of the resistor R38 are connected together, the second end of the resistor R32, the first end of the resistor R33, the positive power supply of the operational amplifier U5A and the first end of the capacitor C14 are connected together. The second end of the capacitor C14 is grounded.

[0060] The second end of the resistor R33, the first end of the resistor R34, and the first end of the resistor R35 are connected together.

[0061] The second end of resistor R34 and the first end of resistor R40 are connected to the inverting input terminal of operational amplifier U5A, the second end of resistor R38 and the second end of resistor R39 are connected to the non-inverting input terminal of operational amplifier U5A, the negative pole of the power supply of operational amplifier U5A is grounded, and the output terminal of U5A is connected to the second end of resistor R40 and the anode of diode D18.

[0062] The emitter of the optical coupler U4, the second end of the capacitor C18, the second end of the resistor R35 and the second end of the resistor R39 are connected to a common ground.

[0063] The cathode of the diode D18 is connected to the first end of the resistor R41, and the second end of the capacitor R41, the first end of C19, the first end of the resistor R42 and the first end of the resistor R47 are connected together.

[0064] The second end of the capacitor C19 and the second end of the resistor R42 are connected to a common ground.

[0065] The second end of resistor R27 is connected to the reverse input terminal of operational amplifier U5B, the output terminal of B5B is connected to the anode of diode D20 and the first end of resistor R48, the second end of resistor R48 is connected to the non-inverting input terminal of operational amplifier U5B and the first end of resistor R43, the second end of resistor R43 is connected to the adjustment end of variable resistor R46, the first end of resistor R46 is connected to the first end of resistor R44, the second end of R44 is connected to +15V, the second end of variable resistor R46 is connected to the first end of resistor R45, and the second end of R45 is grounded.

[0066] The cathode of diode D20 is connected to the first end of resistor R23, the second end of R23 is connected to the positive electrode of optocoupler U3, the negative electrode of optocoupler U3 is grounded, and the collector of U3, the first end of resistor R24, the first end of resistor R22, the negative electrode of Zener diode D17, and the gate of field effect transistor Q13 are connected together.

[0067] The source of the field effect transistor Q13 and the first end of the resistor R27 are connected to a common ground, the second end of the resistor R27 is connected to the first end of the capacitor C15, and the second end of C15 and the drain of the field effect transistor Q13 are connected to a common ground.

[0068] The emitter of the optocoupler U3, the second end of the resistor R22, and the positive electrode of the voltage regulator D17 are grounded.

[0069] The electrically excited DC generator system provided by the present invention not only solves the problem that the motor cannot simultaneously take into account the output capabilities of high and low speeds, but also realizes automatic switching between high and low speeds.

Claims

1. An electrically excited DC generator system, characterized in that: It includes an electrically excited DC motor and a full-wave rectifier switching output circuit; the stator winding of the electrically excited DC motor is composed of two sets of three-phase windings, and the two neutral points of the two sets of three-phase windings are not connected to each other; the first set of windings has a small number of series turns and a thick equivalent wire diameter of the windings, and is used in high-speed operating conditions; the second set of windings has a large number of series turns and a thin equivalent wire diameter of the windings, and is used in low-speed operating conditions; the full-wave rectifier switching output circuit includes a full-wave rectifier circuit and a switching circuit; the full-wave rectifier circuit includes two three-phase rectifier bridges respectively connected to the two sets of three-phase windings; the switching circuit includes three equal-value resistors connected in star shape on the three-phase lines of the motor, and a neutral point formed by the connecting points of the three equal-value resistors. A frequency sensitive circuit for comparing the voltage at a point with the voltage of any phase of the first set of windings to output a frequency sensitive signal, a frequency changing circuit for converting the frequency sensitive signal into a frequency signal, and a switching execution circuit for switching the working winding according to the frequency signal; the switching execution circuit includes an N-channel field effect transistor Q13; the positive poles of the two three-phase rectifier bridges are directly connected as the output positive pole of the motor, the negative poles of the two three-phase rectifier bridges are connected through the N-channel field effect transistor Q13, and the drain end of the N-channel field effect transistor Q13 is used as the output negative pole of the motor, forming a common positive output mode; the switching of the working rectifier bridge, that is, the working winding is realized by turning the N-channel field effect transistor Q13 on and off.

2. The electrically excited DC generator system according to claim 1, characterized in that: The frequency sensitive circuit includes a charge and discharge circuit and a differential amplifier circuit; The charge-discharge circuit is composed of an optocoupler U4, a resistor R32, and a capacitor C18. The motor neutral point voltage and the phase voltage are connected through the charge-discharge circuit to obtain a sawtooth wave whose period changes with the speed. The differential amplifier circuit is composed of resistors R33-R35, R38-R40 and operational amplifier U5A. The differential amplifier circuit improves the sensitivity of the frequency sensitive circuit by intercepting the peak part of the sawtooth wave, thereby ensuring the stability of the system.

3. The electrically excited DC generator system according to claim 2, characterized in that: The frequency change circuit receives the frequency sensitive signal output by the frequency sensitive circuit. The frequency sensitive signal obtains a DC voltage through the filter circuit in the frequency change circuit. The voltage changes with the change of the motor speed. When the motor speed decreases, the DC voltage increases, and the operational amplifier U5B in the frequency change circuit outputs a low level; when the motor speed increases, the DC voltage decreases, and U5B in the frequency change circuit outputs a high level, and after a delay, the execution circuit outputs a frequency signal.

4. The electrically excited DC generator system according to claim 3, characterized in that: The switching execution circuit includes an optocoupler U3; the N-channel field effect transistor Q13 is turned on by the optocoupler U3 to achieve level isolation, and plays the role of switching between two rectifier bridges in the circuit; when the operational amplifier U5B outputs a low level, the optocoupler U3 is turned off, the field effect transistor Q13 is turned on, the second set of windings works, and the motor is in a low-speed working mode; when the operational amplifier U5B outputs a high level, the optocoupler U3 is turned on, the field effect transistor Q13 is turned off, the first set of windings works, and the motor is in a high-speed working mode.

5. The electrically excited DC generator system according to claim 4, characterized in that: When the motor speed is lower than the set threshold, the conduction time of the optocoupler U4 is short, the voltage of the capacitor C18 is higher than the threshold, the output voltage of the operational amplifier U5A is higher than the threshold, the operational amplifier U5B outputs a low level, the optocoupler U3 is cut off, the gate voltage of the field effect transistor Q13 is higher than the source voltage, the field effect transistor Q13 is turned on, the second set of windings works, and the motor is in a low-speed working mode; when the motor speed is higher than the set threshold, the conduction time of the optocoupler U4 is long, the voltage of the capacitor C18 is lower than the threshold, the output voltage of the operational amplifier U5A is lower than the threshold, the operational amplifier U5B outputs a high level, the optocoupler U3 is turned on, the gate voltage of the field effect transistor Q13 is lower than the source voltage, the field effect transistor Q13 is cut off, the first set of windings works, and the motor is in a high-speed working mode.

6. The electrically excited DC generator system according to claim 1, characterized in that: The full-wave rectification switching output circuit also includes a filtering circuit and a sampling voltage regulating circuit.

7. The electrically excited DC generator system according to claim 1, characterized in that: The first set of windings has n series turns per phase and 2m parallel conductors; the second set of windings has 2n series turns per phase and m parallel conductors.

8. The electrically excited DC generator system according to claim 1, characterized in that: The three equal value resistors are connected to the three-phase lines of the first set of windings.

9. The electrically excited DC generator system according to claim 1, characterized in that: The three-phase rectifier bridge includes six field effect tubes.

10. The electrically excited DC generator system according to claim 9, characterized in that: The A-phase outgoing wires of the first set of windings are respectively connected to the gate of the field effect transistor Q1, the source of the field effect transistor Q1 and the drain of the field effect transistor Q4; the B-phase outgoing wires are respectively connected to the gate of the field effect transistor Q2, the source of the field effect transistor Q2 and the drain of the field effect transistor Q5; the C-phase outgoing wires are respectively connected to the gate of the field effect transistor Q3, the source of the field effect transistor Q3 and the drain of the field effect transistor Q6; the U-phase outgoing wires of the second set of windings are respectively connected to the gate of the field effect transistor Q7, the source of the field effect transistor Q7 and the drain of the field effect transistor Q10; the V-phase outgoing wires are respectively connected to the gate of the field effect transistor Q8, the source of the field effect transistor Q8 and the drain of the field effect transistor Q11; the W-phase outgoing wires are respectively connected to the gate of the field effect transistor Q9, the source of the field effect transistor Q9 and the drain of the field effect transistor Q12; the drains of the field effect transistors Q1 to Q6 are connected; the gates and sources of the field effect transistors Q4, Q5, Q6, Q10, Q11 and Q12 are simultaneously connected to a common ground.

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