Isolated tachometer for a starter generator

Abstract

This utility model discloses an isolated speed measurement device for a starter generator, comprising a voltage sampling circuit, a clamping protection circuit, an isolated comparator circuit, a signal processing circuit, and a controller. The voltage sampling circuit includes two voltage sampling branches connected in parallel. Each voltage sampling branch includes a resistor voltage divider acquisition circuit and a low-pass filter circuit. The two voltage sampling branches are connected to any two phase windings of the starter generator's three phases (U, V, and W) to perform voltage division sampling and filtering on the voltage signals of any two phase windings of the starter generator. The clamping protection circuit limits the voltage of the filtered first and second voltage divider signals. The input terminal of the isolated comparator circuit receives the first and second voltage divider signals and converts them into square wave pulse signals. The signal processing circuit amplifies and filters the square wave pulse signals before transmitting them to the controller, so that the controller can obtain the motor speed based on the square wave pulse signals.

Description

Technical Field

[0001] This utility model relates to the field of generator electronic control technology, and in particular to an isolated speed measuring device for generators. Background Technology

[0002] In the field of turbojet engines, starter generators are mostly three-phase permanent magnet synchronous motors, and the motor rotor speed and inertial stopping time are among the important indicators of turbojet engines. Currently, the rotor speed of the motor is mostly measured using non-contact measurement methods such as laser sensors and Hall sensors. However, some turbojet engine starter generators use non-magnetic materials such as aerospace aluminum due to considerations such as weight reduction, structural optimization, and heat dissipation, making it impossible to use Hall sensors. Installing laser sensors would affect the intake and overall structure of the turbojet engine, and considering structural optimization, electromagnetic interference, and high engine temperatures, laser sensors cannot be used either. In addition, these non-contact speed measurement devices also increase costs and installation space, and are more susceptible to interference from the external environment, leading to reduced measurement accuracy. Moreover, after turbojet engines start, the speed can reach tens of thousands of revolutions per minute, and the starter generator transforms into a generator. The voltage induced by the starter generator is determined by the speed; the higher the speed, the greater the voltage amplitude. Driven by the turbine, the starter generator induces a high voltage of hundreds of volts. Current speed measurement devices are mostly non-isolated, which can easily cause crosstalk to the downstream low-voltage acquisition circuit. Utility Model Content

[0003] To solve the above-mentioned technical problems, this utility model provides a low-cost isolated speed measurement device for starter generators.

[0004] The present invention adopts the following technical solution:

[0005] An isolated speed measurement device for a generator includes a voltage sampling circuit, a clamping protection circuit, an isolated comparator circuit, a signal processing circuit, and a controller connected in sequence. The voltage sampling circuit includes a first voltage sampling branch and a second voltage sampling branch connected in parallel. The first voltage sampling branch includes a first resistor voltage divider acquisition circuit and a first low-pass filter circuit. The second voltage sampling branch includes a second resistor voltage divider acquisition circuit and a second low-pass filter circuit.

[0006] The first and second resistance voltage divider acquisition circuits are respectively connected to any two phases of the U, V, and W phases of the generator windings to perform voltage divider sampling on the voltage signals of any two phases of the generator windings to obtain the first voltage divider signal and the second voltage divider signal.

[0007] The first low-pass filter circuit is used to filter the first voltage divider signal, and the second low-pass filter circuit is used to filter the second voltage divider signal.

[0008] The clamping protection circuit is used to limit the voltage of the filtered first and second voltage divider signals to ensure the stability of the signal voltage of the input isolation comparator circuit.

[0009] The first input terminal of the isolated comparator circuit is connected to the output terminal of the first voltage sampling branch, and the second input terminal is connected to the output terminal of the second voltage sampling branch. It is used to convert the filtered first voltage divider signal and the second voltage divider signal into square wave pulse signals.

[0010] The signal processing circuit is connected to the output of the isolated comparator circuit and is used to amplify and filter the square wave pulse signal;

[0011] The controller is connected to the signal processing circuit and is used to obtain the motor speed based on the amplified and filtered square wave pulse signal.

[0012] The clamping protection circuit includes a first diode and a second diode. The anode of the first diode is connected to the output terminal of the first resistor voltage divider acquisition circuit, the cathode of the first diode is connected to the output terminal of the second resistor voltage divider acquisition circuit, the anode of the second diode is connected to the output terminal of the second resistor voltage divider acquisition circuit, and the cathode of the second diode is connected to the output terminal of the first resistor voltage divider acquisition circuit.

[0013] This also includes an ESD electrostatic protection circuit connected between the signal processing circuit and the controller;

[0014] The ESD electrostatic protection circuit is implemented using a TVS diode. The anode of the TVS diode is grounded, and the cathode is connected to the output terminal of the signal processing circuit.

[0015] The signal processing circuit includes a level conversion circuit and a third low-pass filter circuit.

[0016] The input terminal of the level conversion circuit is connected to the output terminal of the isolated comparator circuit, and is used to amplify the square wave pulse signal.

[0017] The input of the third low-pass filter circuit is connected to the output of the level conversion circuit, and is used to filter the amplified square wave pulse signal.

[0018] The level conversion circuit includes resistors R1, R4, and R8, and transistor Q1. The base of transistor Q1 is connected to the output of the isolated comparator circuit, the emitter of transistor Q1 is grounded, the collector of transistor Q1 is connected in series with resistor R1 and then connected to a preset signal processing power supply, resistor R4 is connected between the base and collector of transistor Q1, resistor R8 is connected between the base and emitter of transistor Q1, and the collector of transistor Q1 serves as the output of the level conversion circuit and is connected to the input of the third low-pass filter circuit.

[0019] The third low-pass filter circuit includes a resistor R5 and a capacitor C13. The resistor R5 and the capacitor C13 form a first-order low-pass filter. One end of the resistor R5 is connected to the output of the level conversion circuit, and the other end of the resistor R5 is connected to the controller through a connector.

[0020] It also includes a first power supply circuit located on the high-voltage measurement side of the isolated comparator circuit and a second power supply circuit located on the signal comparison side of the isolated comparator circuit.

[0021] The first power supply circuit uses a DC-DC step-down isolation chip to prevent high-voltage crosstalk;

[0022] The second power supply circuit is implemented using a linear voltage regulator chip.

[0023] Compared with the prior art, the main advantages of this utility model are as follows:

[0024] The generator isolated speed measuring device provided by this utility model does not require a complex optocoupler isolation design. It can realize generator isolated speed measurement through voltage sampling circuit, clamping protection circuit, isolated comparator circuit, signal processing circuit and controller. It not only has low circuit implementation cost, but also has the advantages of high voltage isolation, accurate measurement, ultra-high response speed and wide measurement range.

[0025] The above description is merely an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this utility model more obvious and understandable, specific embodiments of this utility model are given below. Attached Figure Description

[0026] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0027] Figure 1 Structural block diagram of the generator isolated speed measuring device provided in the embodiment of this utility model;

[0028] Figure 2 Circuit diagram of the generator isolated speed measuring device provided in this embodiment of the utility model;

[0029] Figure 3 A schematic diagram of the electric motor speed measurement method provided in this embodiment of the utility model;

[0030] Figure 4 This is a schematic diagram of a generator speed measurement method provided in an embodiment of the present invention. Detailed Implementation

[0031] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0032] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art and should not be interpreted in an idealized or overly formal sense unless specifically defined.

[0033] Reference Figure 1-2 The generator isolated speed measuring device provided in this embodiment includes a voltage sampling circuit 10, a clamping protection circuit 20, an isolated comparator circuit 30, a signal processing circuit 40, and a controller 50 connected in sequence. The voltage sampling circuit 10 includes a first voltage sampling branch and a second voltage sampling branch connected in parallel. The first voltage sampling branch includes a first resistor voltage divider acquisition circuit 101 and a first low-pass filter circuit 102. The second voltage sampling branch includes a second resistor voltage divider acquisition circuit 103 and a second low-pass filter circuit 104.

[0034] The first resistor voltage divider acquisition circuit 101 and the second resistor voltage divider acquisition circuit 103 are respectively connected to any two phases of the U, V and W phases of the generator winding, and are used to perform voltage divider sampling on the voltage signal of any two phases of the generator winding, so as to convert the voltage signal of the winding into the voltage range of the chip through the resistor voltage divider method to obtain the first voltage divider signal and the second voltage divider signal.

[0035] The first low-pass filter circuit 102 is connected to the output terminal of the first resistor voltage divider acquisition circuit 101 to filter the first voltage divider signal. The second low-pass filter circuit 104 is connected to the output terminal of the second resistor voltage divider acquisition circuit 103 to filter the second voltage divider signal, so as to filter out noise in the first voltage divider signal and the second voltage divider signal and obtain a cleaner signal.

[0036] The clamping protection circuit 20 is used to limit the voltage of the filtered first and second voltage divider signals to ensure the stability of the signal voltage of the input isolation comparator circuit.

[0037] The first input terminal of the isolated comparator circuit 30 is connected to the output terminal of the first voltage sampling branch, and the second input terminal is connected to the output terminal of the second voltage sampling branch. It is used to convert the filtered first voltage divider signal and the second voltage divider signal into square wave pulse signals. The main function of the isolated comparator circuit 30 is to provide electrical isolation and signal comparison functions in the circuit, ensure potential isolation between different circuits, avoid interference, and achieve high-precision signal detection and control.

[0038] The signal processing circuit 40 is connected to the output of the isolated comparator circuit 30 and is used to amplify and filter the square wave pulse signal. After the square wave pulse signal output by the isolated comparator is amplified and filtered, high-frequency noise in the signal is filtered out, making the signal quality more reliable.

[0039] The controller 50 is connected to the signal processing circuit 40 and is used to obtain the motor speed based on the amplified and filtered square wave pulse signal.

[0040] In one specific embodiment, such as Figure 2 As shown, the isolated comparator circuit 30 can be implemented using an isolated comparator chip U3, such as the AMC23C10DWVR. The isolated comparator chip uses electrical isolation technology to physically separate the high-voltage side signal detection from the low-voltage side control circuit, while simultaneously performing threshold judgment and signal transmission. The isolation is specifically achieved by using highly insulating materials such as silicon dioxide to block the direct electrical connection between the high-voltage and low-voltage circuits. After the high-voltage side input signal is judged by the internal comparator, it is transmitted to the low-voltage side via a radio frequency signal across the isolation layer, and demodulated back to a logic level at the receiving end, avoiding common-mode noise interference and ensuring stable signal transmission in a strong electromagnetic environment. It is understood that this embodiment is only used to explain the technical solution and does not limit the specific model of the isolated comparator chip.

[0041] OUT1 of the isolated comparator chip U3 is the open-drain output pin of the isolated comparator, which outputs a logic level square wave signal that is compared by the comparator and then input to the MCU.

[0042] VCC1 and VCC2 of the isolated comparator chip U3 are the power supplies for the high voltage measurement side and the signal comparison output side of the isolated comparator, respectively.

[0043] The INP and INN terminals of the isolated comparator chip U3 are the input terminals of the isolated comparator.

[0044] In one specific embodiment, the first low-pass filter circuit and the second low-pass filter circuit can be implemented using RC low-pass filters.

[0045] Figure 2As shown, the first resistor voltage divider acquisition circuit 101 includes resistors R2 and R6, and the first low-pass filter circuit 102 includes resistor R3, capacitor C11, and capacitor C12. Resistor R3, capacitor C11, and capacitor C12 form a second-order low-pass filter. Resistor R2 and resistor R6 are connected in series. The other end of resistor R2 is connected to any one of the three phase windings (U, V, W) of the generator through a connector. The other end of resistor R6 is grounded. The connection node of resistors R2 and R6 serves as the output terminal of the first resistor voltage divider acquisition circuit 101 and is connected to the input terminal of the first low-pass filter circuit. The output terminal of the first low-pass filter circuit is connected to one input terminal of the isolated comparator circuit 30.

[0046] Figure 2 As shown, the second resistor voltage divider acquisition circuit 103 includes resistors R9 and R11, and the second low-pass filter circuit 104 includes resistor R10, capacitor C14, and capacitor C15. Resistor R10, capacitor C14, and capacitor C15 form a second-order low-pass filter. Resistor R9 and resistor R11 are connected in series. The other end of resistor R9 is connected to another phase winding of the generator's three phases (U, V, W) through a connector. The other end of resistor R11 is grounded. The connection node of resistors R9 and R11 serves as the output terminal of the second resistor voltage divider acquisition circuit 103 and is connected to the input terminal of the second low-pass filter circuit. The output terminal of the second low-pass filter circuit is connected to the other input terminal of the isolated comparator circuit 30.

[0047] In one specific embodiment, such as Figure 2 As shown, the clamping protection circuit 20 includes a first diode D1 and a second diode D2. The anode of the first diode D1 is connected to the output terminal of the first resistor voltage divider acquisition circuit, and the cathode of the first diode D1 is connected to the output terminal of the second resistor voltage divider acquisition circuit. The anode of the second diode D2 is connected to the output terminal of the second resistor voltage divider acquisition circuit, and the cathode of the second diode D2 is connected to the output terminal of the first resistor voltage divider acquisition circuit.

[0048] In one specific embodiment, the generator isolated speed measuring device provided by this utility model further includes a first power supply circuit disposed on the high voltage measurement side of the isolated comparator circuit and a second power supply circuit disposed on the signal comparison side of the isolated comparator circuit.

[0049] like Figure 2 As shown, the first power supply circuit is implemented using a 24V to 5V DC-DC step-down isolation chip U1 to prevent high-voltage crosstalk; the second power supply circuit is implemented using a 24V to 5V linear regulator chip U2. This embodiment does not impose specific restrictions on the models of the DC-DC step-down isolation chip and the linear regulator chip, as long as they can achieve the corresponding functions.

[0050] Furthermore, a first decoupling circuit is provided at the output terminal of the first power supply circuit. The first decoupling circuit includes capacitor C7 and capacitor C8, which are connected in parallel between the high voltage measurement side power input terminal and the first power supply circuit.

[0051] Furthermore, a second decoupling circuit is provided at the output terminal of the second power supply circuit. The second decoupling circuit includes capacitors C9 and C10, which are connected in parallel between the power input terminal on the signal comparison side and the second power supply circuit.

[0052] In this embodiment, the clamping protection circuit ensures the voltage stability of the input comparator signal, and the DC-DC step-down isolation chip prevents high-voltage crosstalk. Together, they protect the isolated comparator.

[0053] Furthermore, the generator isolated speed measuring device provided by this utility model may also include a second power isolation circuit disposed at the low-voltage side power input terminal of the isolated comparator circuit. The second power isolation circuit includes capacitor C9 and capacitor C10, which are connected in parallel between the low-voltage side power input terminal and the power supply to prevent high-voltage crosstalk.

[0054] In one specific embodiment, such as Figure 2 As shown, the signal processing circuit 40 includes a level conversion circuit and a third low-pass filter circuit. The input terminal of the level conversion circuit is connected to the output terminal of the isolated comparator circuit 30 and is used to amplify the square wave pulse signal. The input terminal of the third low-pass filter circuit is connected to the output terminal of the level conversion circuit and is used to filter the amplified square wave pulse signal.

[0055] Specifically, the level conversion circuit includes resistors R1, R4, and R8, and transistor Q1. The base of transistor Q1 is connected to the output of the isolated comparator circuit 30, the emitter of transistor Q1 is grounded, and the collector of transistor Q1 is connected in series with resistor R1 and then connected to the 5V power supply for signal processing. Resistor R4 is connected between the base and collector of transistor Q1, and resistor R8 is connected between the base and emitter of transistor Q1. The collector of transistor Q1 serves as the output of the level conversion circuit and is connected to the input of the third low-pass filter circuit.

[0056] Specifically, the third low-pass filter circuit includes resistor R5 and capacitor C13. Resistor R5 and capacitor C13 form a first-order low-pass filter. One end of resistor R5 is connected to the output of the level conversion circuit, and the other end of resistor R5 is connected to the controller through a connector to transmit the filtered square wave pulse signal to the controller. The way the controller calculates the motor speed based on the received square wave pulse signal is a conventional technique in this field and does not involve any improvement to the method itself.

[0057] In one specific embodiment, such as Figure 2 As shown, the generator-isolated speed measuring device provided by this utility model also includes an ESD electrostatic protection circuit connected between the signal processing circuit and the controller. The ESD electrostatic protection circuit is implemented using a TVS diode D7. The anode of the TVS diode D7 is grounded, and the cathode is connected to the output terminal of the signal processing circuit, clamping the voltage between the two electrodes to a predetermined value. This effectively protects the precision components in the electronic circuit from damage by various surge pulses. The ESD electrostatic protection circuit can effectively protect the internal circuitry and prevent the effects of electrostatic discharge at the output terminal.

[0058] The following section uses the application of a generator in the field of turbojet engines as a specific example to explain in detail the implementation principle of the generator isolated speed measuring device provided by this utility model.

[0059] The three-phase permanent magnet synchronous motor is coaxial with the turbojet engine. The motor drives the turbojet rotor to rotate. The generator accelerates the rotor to the ignition speed, the motor stops driving, the turbojet engine reaches its self-sustaining speed, and the rotor drives the motor to rotate.

[0060] In the first stage, the motor drive circuit drives the three-phase permanent magnet synchronous motor to rotate and start the turbojet engine. In this stage, the voltage amplitude of the acquired signal is determined by the supply voltage. By connecting any two of the three phases (U, V, W) of the motor through the voltage sampling circuit, the square wave signal that can be processed by the microcontroller can be obtained after passing through the clamping protection circuit, the isolation comparator circuit, and the signal processing circuit. Finally, the microcontroller captures and processes the input signal and sends the speed value to the host computer for display in real time via 422 communication.

[0061] This is the method for measuring the motor speed of this device. The measurement scheme is as follows: Figure 3 As shown.

[0062] In the second stage, after the turbojet engine starts, the motor driver is disconnected by a relay to prevent high-voltage damage. Unlike the first stage of motor operation, the high-speed rotating motor stator coils generate electrical energy, and the U, V, and W three-phase power lines connected to the stator output induced current, which is rectified and stepped down to charge the battery. After the turbojet engine starts, the speed reaches tens of thousands of revolutions per minute, driving the three-phase permanent magnet synchronous motor to generate hundreds of volts of high voltage. In this stage, due to the excessively high sampling voltage, commonly used speed acquisition devices cannot accurately measure the motor speed. However, the generator-isolated speed measurement device provided by this invention can achieve level conversion through a voltage divider-type voltage sampling circuit and a high-low voltage isolated comparator circuit. The converted square wave signal is then processed by the MCU, and the accurate speed value is calculated using the following formula:

[0063] Rotational speed (RPM) = (Pulse frequency × 60) / Number of pole pairs (P)

[0064] In this embodiment, any two phases (e.g., U and V) of the generator winding are selected, and their output voltages are sine waves with a 120° phase difference. A resistor divider circuit reduces the high-voltage AC signal to a range acceptable to the isolated comparator, and an RC low-pass filter (cutoff frequency ≈ twice the generator's maximum frequency) is added to suppress high-frequency noise. The isolated comparator can convert the conditioned sine wave into a square wave pulse signal, and its output is electrically isolated to protect the downstream controller.

[0065] Finally, the speed information is sent to the host computer client via serial communication for real-time display, achieving accurate real-time speed acquisition. The above describes the generator speed measurement method for this device; the measurement scheme is as follows: Figure 4 As shown.

[0066] The engine's inertial stop time is one of the key performance indicators of a turbojet engine. When the turbojet engine shuts down, its inertial stop time needs to be measured. Therefore, from high speed down to a predetermined speed and finally until the motor stops rotating, the speed signal needs to be measured accurately in real time. The generator-isolated speed measurement device provided by this invention can measure amplitudes from hundreds of volts to millivolts. The input induced electromotive force can be processed into a 5V square wave signal recognizable by a microcontroller through an isolated comparator amplification circuit.

[0067] The generator isolated speed measuring device provided by this utility model does not require a complex optocoupler isolation design. It can realize generator isolated speed measurement through voltage sampling circuit, clamping protection circuit, isolated comparator circuit, signal processing circuit and controller. It not only has low circuit implementation cost, but also has the advantages of high voltage isolation, accurate measurement, ultra-high response speed and wide measurement range.

[0068] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the substance and scope of the present invention. Various modifications made to the above embodiments by those skilled in the art after reading this specification are all within the scope of protection of the present invention. The various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not further describe various possible combinations.

[0069] If the embodiments of this utility model involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

Claims

1. A generator isolated tachometer device, comprising: It includes a voltage sampling circuit, a clamping protection circuit, an isolated comparator circuit, a signal processing circuit, and a controller connected in sequence. The voltage sampling circuit includes a first voltage sampling branch and a second voltage sampling branch connected in parallel. The first voltage sampling branch includes a first resistor voltage divider acquisition circuit and a first low-pass filter circuit. The second voltage sampling branch includes a second resistor voltage divider acquisition circuit and a second low-pass filter circuit. The first and second resistance voltage divider acquisition circuits are respectively connected to any two phases of the U, V, and W phases of the generator windings to perform voltage divider sampling on the voltage signals of any two phases of the generator windings to obtain the first voltage divider signal and the second voltage divider signal. The first low-pass filter circuit is used to filter the first voltage divider signal, and the second low-pass filter circuit is used to filter the second voltage divider signal. The clamping protection circuit is used to limit the voltage of the filtered first and second voltage divider signals to ensure the stability of the signal voltage of the input isolation comparator circuit. The first input terminal of the isolated comparator circuit is connected to the output terminal of the first voltage sampling branch, and the second input terminal is connected to the output terminal of the second voltage sampling branch. It is used to convert the filtered first voltage divider signal and the second voltage divider signal into square wave pulse signals. The signal processing circuit is connected to the output of the isolated comparator circuit and is used to amplify and filter the square wave pulse signal; The controller is connected to the signal processing circuit and is used to obtain the motor speed based on the amplified and filtered square wave pulse signal.

2. The generator isolated speed measuring device as described in claim 1, characterized in that, The clamping protection circuit includes a first diode and a second diode. The anode of the first diode is connected to the output terminal of the first resistor voltage divider acquisition circuit, the cathode of the first diode is connected to the output terminal of the second resistor voltage divider acquisition circuit, the anode of the second diode is connected to the output terminal of the second resistor voltage divider acquisition circuit, and the cathode of the second diode is connected to the output terminal of the first resistor voltage divider acquisition circuit.

3. The generator isolated speed measuring device as described in claim 1, characterized in that, It also includes an ESD electrostatic protection circuit connected between the signal processing circuit and the controller; The ESD electrostatic protection circuit is implemented using a TVS diode. The anode of the TVS diode is grounded, and the cathode is connected to the output terminal of the signal processing circuit.

4. The generator isolated speed measuring device as described in claim 1, characterized in that, The signal processing circuit includes a level conversion circuit and a third low-pass filter circuit; The input terminal of the level conversion circuit is connected to the output terminal of the isolated comparator circuit, and is used to amplify the square wave pulse signal. The input of the third low-pass filter circuit is connected to the output of the level conversion circuit, and is used to filter the amplified square wave pulse signal.

5. The generator isolated speed measuring device as described in claim 4, characterized in that, The level conversion circuit includes resistors R1, R4, and R8, and transistor Q1. The base of transistor Q1 is connected to the output of the isolated comparator circuit, the emitter of transistor Q1 is grounded, and the collector of transistor Q1 is connected in series with resistor R1 and then connected to a preset signal processing power supply. Resistor R4 is connected between the base and collector of transistor Q1, and resistor R8 is connected between the base and emitter of transistor Q1. The collector of transistor Q1 serves as the output of the level conversion circuit and is connected to the input of the third low-pass filter circuit.

6. The generator isolated speed measuring device as described in claim 4, characterized in that, The third low-pass filter circuit includes a resistor R5 and a capacitor C13. The resistor R5 and the capacitor C13 form a first-order low-pass filter. One end of the resistor R5 is connected to the output of the level conversion circuit, and the other end of the resistor R5 is connected to the controller through a connector.

7. The generator isolated speed measuring device as described in claim 1, characterized in that, It also includes a first power supply circuit located on the high-voltage measurement side of the isolated comparator circuit and a second power supply circuit located on the signal comparison side of the isolated comparator circuit; The first power supply circuit is implemented using a DC-DC step-down isolation chip; The second power supply circuit is implemented using a linear voltage regulator chip.

8. The generator isolated speed measuring device as described in claim 1, characterized in that, The first resistor voltage divider acquisition circuit includes resistors R2 and R6, which are connected in series. The other end of resistor R2 is connected to any one of the three phase windings (U, V, W) of the generator through a connector. The other end of resistor R6 is grounded. The connection point of resistors R2 and R6 serves as the output terminal of the first resistor voltage divider acquisition circuit and is connected to the input terminal of the first low-pass filter circuit. The output terminal of the first low-pass filter circuit is connected to one input terminal of an isolated comparator circuit. The second resistor voltage divider acquisition circuit includes resistors R9 and R11, which are connected in series. The other end of resistor R9 is connected to another phase winding of the generator's three phases (U, V, W) via a connector. The other end of resistor R11 is grounded. The connection point of resistors R9 and R11 serves as the output terminal of the second resistor voltage divider acquisition circuit and is connected to the input terminal of the second low-pass filter circuit. The output terminal of the second low-pass filter circuit is connected to the other input terminal of the isolated comparator circuit.

9. The generator isolated speed measuring device as described in claim 1, characterized in that, The first low-pass filter circuit includes resistor R3, capacitor C11 and capacitor C12, which together form a second-order low-pass filter. The second low-pass filter circuit includes resistor R10, capacitor C14, and capacitor C15, which together form a second-order low-pass filter.

Images