A motor current monitoring circuit

Abstract

The application discloses a motor current monitoring circuit, which comprises a single-chip microcomputer U1; the single-chip microcomputer U1 is connected with a power supply VCC; the inner holes of current transformers CT1, CT2 and CT3 are used for penetrating through the A-phase, B-phase and C-phase electric wires of a motor respectively; the current transformers CT1, CT2 and CT3 are used for outputting full-wave current analog signals corresponding to the A-phase, B-phase and C-phase electric wires respectively; rectifier bridges Z1, Z2 and Z3 are connected with the current transformers CT1, CT2 and CT3 respectively; sampling resistors R4, R5 and R6 are connected with the rectifier bridges Z1, Z2 and Z3 respectively; the single-chip microcomputer U1 is connected with the sampling resistors R4, R5 and R6 and is used for obtaining the current effective values flowing through the A-phase, B-phase and C-phase electric wires through analysis and calculation. The motor current on the vehicle speed reducer can be safely and reliably monitored, the motor current monitoring circuit does not directly contact with the power supply cable of the motor, and the safety is higher.

Description

Technical Field

[0001] This invention relates to the field of current acquisition and railway track transportation technology, and in particular to a motor current monitoring circuit. Background Technology

[0002] Rail transit is an important form of transportation. The diversion of freight rail transit depends on the operation of hump yards, and vehicle decelerators are one of the core pieces of equipment in hump yards.

[0003] A vehicle speed reducer is a device that uses two brake rails to clamp the sides of a railway vehicle's wheels and reduces speed through friction. The motor on the speed reducer provides power to the brake rails.

[0004] With the rapid development of my country's rail transit and the large-scale construction of hump yards, freight transport capacity and volume are constantly increasing, placing higher demands on vehicle reducers. Currently, given that the output power of the three-phase motors installed on vehicle reducers varies under different braking levels, it is necessary to monitor the current (specifically, the magnitude of the current) of the three-phase motors in the vehicle reducer in order to better monitor the braking status of the vehicle reducer under different braking levels.

[0005] However, there is currently no technology that can safely and reliably monitor the current of the motor in a vehicle's gearbox. Summary of the Invention

[0006] The purpose of this invention is to address the technical deficiencies of existing technologies by providing a motor current monitoring circuit.

[0007] Therefore, the present invention provides a motor current monitoring circuit, including a microcontroller U1, a power supply VCC, current transformers CT1 to CT3, a rectifier bridge Z1 to Z3, and sampling resistors R4 to R6;

[0008] The microcontroller U1 is connected to the power supply VCC;

[0009] VCC power supply is used to provide operating power for the microcontroller U1.

[0010] The microcontroller U1 is connected to the current transformers CT1, CT2 and CT3 through rectifier bridges Z1, Z2 and Z3 respectively;

[0011] The inner holes of current transformers CT1, CT2 and CT3 are used to pass through the A-phase, B-phase and C-phase wires of a three-phase motor, respectively.

[0012] Current transformers CT1, CT2, and CT3 are used to output three full-wave current analog signals corresponding to the A-phase, B-phase, and C-phase wires of a three-phase motor, respectively, when AC current flows through the A-phase, B-phase, and C-phase wires.

[0013] The rectifier bridges Z1, Z2 and Z3 are connected to the current transformers CT1, CT2 and CT3 respectively, and are used to convert the three full-wave current analog signals output by the current transformers CT1, CT2 and CT3 into three half-wave current analog signals, which are then output to the sampling resistors R4, R5 and R6 respectively.

[0014] Sampling resistors R4, R5, and R6 are connected to rectifier bridges Z1, Z2, and Z3 respectively, and are used to convert the three half-wave current analog signals output by rectifier bridges Z1, Z2, and Z3 into three half-wave voltage analog signals, which are then output to the microcontroller U1.

[0015] The microcontroller U1 is connected to sampling resistors R4, R5, and R6. It is used to convert the three half-wave voltage analog signals output by sampling resistors R4, R5, and R6 into voltage digital signals, and through analysis and calculation, obtain the effective values ​​of the current flowing through the A-phase, B-phase, and C-phase wires of the three-phase motor.

[0016] As can be seen from the technical solution provided by the present invention above, compared with the prior art, the present invention provides a motor current monitoring circuit, which is scientifically designed and can safely and reliably monitor the current of the motor on the vehicle reducer.

[0017] The circuit of this invention adopts a non-contact monitoring method, which does not directly contact the power supply cable of the motor, making it safer and more reliable. It can avoid the vehicle reducer itself being affected by damage to the monitoring equipment, ensuring the safe use of the vehicle reducer and providing higher safety.

[0018] After testing, the circuit provided by this invention is an interface circuit with strong anti-interference ability, high safety and stable output signal, which can be reliably applied to vehicle reducer monitoring equipment in the railway industry.

[0019] Furthermore, the circuit of this invention can also realize functions such as external communication and automatic restart in case of failure, with high precision and significant practical value. Attached Figure Description

[0020] Figure 1 The schematic diagram of the first part of a motor current monitoring circuit provided by the present invention has been omitted, and the unused pins of the microcontroller U1 have been omitted.

[0021] Figure 2 A schematic diagram of the second part of a motor current monitoring circuit provided by the present invention;

[0022] Depend on Figure 1 and Figure 2 Together, they form the overall schematic diagram of the entire motor current monitoring circuit. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] In the description of this patent, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this patent according to the specific circumstances.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0026] See Figure 1 , Figure 2 The present invention provides a motor current monitoring circuit, including a microcontroller U1, a power supply VCC, current transformers CT1 to CT3, a rectifier bridge Z1 to Z3, and sampling resistors R4 to R6;

[0027] The microcontroller U1 is connected to the power supply VCC;

[0028] VCC power supply is used to provide power for the microcontroller U1.

[0029] The microcontroller U1 is connected to the current transformers CT1, CT2 and CT3 through rectifier bridges Z1, Z2 and Z3 respectively;

[0030] The inner holes of current transformers CT1, CT2 and CT3 are used to pass through the A-phase, B-phase and C-phase wires of the three-phase motor (without contact with the wires);

[0031] Current transformers CT1, CT2 and CT3 are used to output three full-wave current analog signals (i.e. induce AC current) corresponding to the A-phase, B-phase and C-phase wires of a three-phase motor when AC current flows through them.

[0032] The rectifier bridges Z1, Z2 and Z3 are connected to the current transformers CT1, CT2 and CT3 respectively, and are used to convert the three full-wave current analog signals output by the current transformers CT1, CT2 and CT3 into three half-wave current analog signals, which are then output to the sampling resistors R4, R5 and R6 respectively.

[0033] Sampling resistors R4, R5, and R6 are connected to rectifier bridges Z1, Z2, and Z3 respectively, and are used to convert the three half-wave current analog signals output by rectifier bridges Z1, Z2, and Z3 into three half-wave voltage analog signals, which are then output to the microcontroller U1.

[0034] The microcontroller U1 is connected to sampling resistors R4, R5, and R6. It is used to convert the three half-wave analog voltage signals output by sampling resistors R4, R5, and R6 into digital voltage signals, and through analysis and calculation, obtain the effective values ​​of the current flowing through the A-phase, B-phase, and C-phase wires of the three-phase motor (i.e., the effective values ​​of the current signals input by the current transformer).

[0035] In this invention, specifically regarding the connection between the microcontroller U1 and the power supply VCC, the specific circuit structure design is as follows:

[0036] The VLCD port (pin 1), VDDA port (pin 13), and four VDD ports (pins 48, 32, 19, and 64) of the microcontroller U1 converge at node A, which is connected to the power supply VCC.

[0037] The four VSS ports of the microcontroller U1 (i.e., pins 47, 18, 31, and 63) are connected to the power ground terminal GND;

[0038] The VSSA port (pin 12) of the microcontroller U1 is connected to one end of the resistor R1;

[0039] The other end of resistor R1 is connected to the power supply ground terminal GND;

[0040] Node A is connected to one end of capacitors C1 through C6 respectively;

[0041] The other end of capacitors C1 to C6 is connected to the power supply ground terminal GND;

[0042] It should be noted that capacitors C1, C2, C3, C4, C5, and C6 should be placed close to the VLCD port (pin 1), VDDA port (pin 13), and four VDD ports (pins 48, 32, 19, and 64) of the microcontroller U1. Their function is to decouple the input power supply of the microcontroller.

[0043] In this invention, specifically, the microcontroller U1 is also connected to the crystal oscillator X1;

[0044] Regarding the connection between the microcontroller U1 and the crystal oscillator X1, the specific circuit structure design is as follows:

[0045] The OSC_IN port (pin 5) of the microcontroller U1 is connected to one end of the crystal oscillator X1 and one end of the capacitor C7, respectively.

[0046] The other end of capacitor C7 is connected to the power supply ground terminal GND;

[0047] The OSC_OUT port (pin 6) of the microcontroller U1 is connected to the other end of the crystal oscillator X1 and one end of the capacitor C8, respectively.

[0048] The other end of capacitor C8 is connected to the power supply ground terminal GND.

[0049] In this invention, specifically, the BOOT0 port (i.e., pin 60) of the microcontroller U1 is connected to the power ground terminal GND through resistor R2.

[0050] In this invention, specifically, the microcontroller U1 is connected to the watchdog chip U2;

[0051] In terms of specific implementation, the circuit structure design for connecting the microcontroller U1 and the watchdog chip U2 is as follows:

[0052] The NRST pin (pin 7) of the microcontroller U1 is connected to the RESET pin (pin 1) of the watchdog chip U2;

[0053] The PB3 terminal (pin 55) of the microcontroller U1 is connected to the WDI terminal (pin 4) of the watchdog chip U2.

[0054] Furthermore, the NRST terminal (i.e., pin 7) of the microcontroller U1 is also connected to one end of resistor R3 and capacitor C9, respectively;

[0055] The other end of resistor R3 is connected to the power supply VCC;

[0056] The other end of capacitor C9 is connected to the power supply ground terminal GND;

[0057] Furthermore, the VDD terminal (i.e., pin 5) of the watchdog chip U2 is connected to the power supply VCC;

[0058] The GND terminal of the watchdog chip U2 is connected to the power ground terminal GND;

[0059] Furthermore, the VDD terminal (i.e., pin 5) of the watchdog chip U2 is also connected to one end of capacitor C10;

[0060] The other end of capacitor C10 is connected to the power supply ground terminal GND.

[0061] Furthermore, the MR terminal of the watchdog chip U2 is connected to a button (i.e., a manual reset button);

[0062] It should be noted that the MR terminal of the watchdog chip U2 is an external reset signal terminal, which can be connected to a button, for example.

[0063] It should be noted that one end of the button (i.e., the manual reset button) is connected to the MR terminal of the watchdog chip U2, and the other end of the button (i.e., the manual reset button) is grounded.

[0064] In this invention, specifically, the microcontroller U1 is also connected to the connector J2;

[0065] In terms of specific implementation, the circuit structure design for connecting the microcontroller U1 to the connector J2 is as follows:

[0066] The PA13 terminal (pin 46) of the microcontroller U1 is connected to the SWDIO terminal (pin 3) of the connector J2;

[0067] The PA14 terminal (pin 49) of the microcontroller U1 is connected to the SWCLK terminal (pin 2) of the connector J2;

[0068] The GND terminal (i.e., pin 1) of connector J2 is connected to the power ground terminal GND;

[0069] It should be noted that connector J2 is the programming port for microcontroller U1.

[0070] In this invention, specifically, the microcontroller U1 can be directly connected to an external SOC chip (system-on-a-chip).

[0071] In specific implementation, when the microcontroller U1 is connected to an external SOC chip (system-on-a-chip, specifically the SOC chip with model number MYC-Y6ULY2-256N256D-50-I), the PB11 terminal (i.e., pin 30) of the microcontroller U1 is used as the data transmission terminal TXD for UART communication and is connected to the pin on the SOC chip that has the data reception terminal RXD function for UART communication.

[0072] The PB10 pin (pin 29) of the microcontroller U1 is used as the data receiver RXD for UART communication and is connected to the pin on the SOC chip that has the data transmitter TXD function for UART communication.

[0073] The GND pin of the SOC chip is connected to the ground terminal GND in this invention.

[0074] It should be noted that the external SOC chip, such as the MYC-Y6ULY2-256N256D-50-I chip produced by MYR Technology Co., Ltd., can summarize and analyze other information collected from monitoring the vehicle reducer and motor current information, and transmit it to the host computer via the network.

[0075] In addition, the microcontroller U1 can also be connected to a UART to RS-485 chip, which is used to convert UART signals to RS-485 signals;

[0076] The UART to RS-485 chip can be, for example, the RS-485 differential driver chip SN65LBC184DR manufactured by Yutai Semiconductor.

[0077] In addition, the microcontroller U1 can also be connected to a UART to CAN chip, which is used to convert UART signals to CAN signals.

[0078] The UART to CAN chip can be, for example, the SIT1050 high-speed CAN bus transceiver manufactured by Coretronic.

[0079] In this invention, specifically, the microcontroller U1 is connected to the current transformer CT1 through the rectifier bridge Z1;

[0080] In terms of specific implementation, the specific circuit structure design is as follows:

[0081] The SA1 and SA2 terminals of the current transformer CT1 are connected to the IN1 terminal (i.e., pin 2) and IN2 terminal (i.e., pin 4) of the rectifier bridge Z1, respectively.

[0082] The positive terminal (pin 1) of rectifier bridge Z1 is connected to the PB0 terminal (pin 26) of microcontroller U1.

[0083] The - terminal (i.e., pin 3) of rectifier bridge Z1 is connected to the power ground terminal GND.

[0084] Furthermore, the positive terminal (i.e., pin 1) of rectifier bridge Z1 is also connected to one end of capacitors C11 and C12;

[0085] The other ends of capacitors C11 and C12 are connected to the - end (i.e., pin 3) of rectifier bridge Z1.

[0086] Furthermore, the positive terminal (i.e., pin 1) of the rectifier bridge Z1 is connected to one end of the sampling resistor R4;

[0087] The other end of the sampling resistor R4 is connected to the power supply ground terminal GND.

[0088] In this invention, specifically, the microcontroller U1 is connected to the current transformer CT2 through the rectifier bridge Z2;

[0089] In terms of specific implementation, the specific circuit structure design is as follows:

[0090] The SB1 and SB2 terminals of the current transformer CT2 are connected to the IN1 terminal (i.e., pin 2) and IN2 terminal (i.e., pin 4) of the rectifier bridge Z2, respectively.

[0091] The positive terminal (pin 1) of rectifier bridge Z2 is connected to the PB1 terminal (pin 26) of the microcontroller.

[0092] The - terminal (i.e., pin 3) of rectifier bridge Z2 is connected to the power supply ground terminal GND;

[0093] Furthermore, the positive terminal (i.e., pin 1) of rectifier bridge Z2 is connected to one end of capacitors C13 and C14;

[0094] The other ends of capacitors C13 and C14 are connected to the - end (i.e., pin 3) of rectifier bridge Z2.

[0095] Furthermore, the positive terminal (i.e., pin 1) of rectifier bridge Z2 is connected to one end of sampling resistor R5;

[0096] The other end of the sampling resistor R5 is connected to the power supply ground terminal GND.

[0097] In this invention, specifically, the microcontroller U1 is also connected to the current transformer CT3 through the rectifier bridge Z3;

[0098] In terms of specific implementation, the specific circuit structure design is as follows:

[0099] The SC1 and SC2 terminals of the current transformer CT3 are connected to the IN1 terminal (i.e., pin 2) and IN2 terminal (i.e., pin 4) of the rectifier bridge Z3, respectively.

[0100] The positive terminal (pin 1) of rectifier bridge Z3 is connected to the PA3 terminal (pin 17) of the microcontroller.

[0101] The - terminal (i.e., pin 3) of rectifier bridge Z3 is connected to the power supply ground terminal GND;

[0102] Furthermore, the positive terminal (i.e., pin 1) of rectifier bridge Z3 is connected to one end of capacitors C15 and C16;

[0103] The other ends of capacitors C15 and C16 are connected to the - end (i.e., pin 3) of rectifier bridge Z3.

[0104] Furthermore, the positive terminal (i.e., pin 1) of rectifier bridge Z3 is connected to one end of sampling resistor R6;

[0105] The other end of the sampling resistor R6 is connected to the power supply ground terminal GND.

[0106] It should be noted that the current transformers CT1, CT2 and CT3 are existing mature electronic components, and the TA1420-M type current transformers of the Bingzi brand produced by Beijing Xinchuang Sifang Electronics Co., Ltd. can be used.

[0107] In this invention, specifically, the current transformers CT1, CT2 and CT3 each have a first wire from PA1 to PA2, a second wire from PB1 to PB2 and a third wire from PC1 to PC2, which are respectively the A phase, B phase and C phase wires of the motor, and all of them are through wires (i.e. wires that pass through the inner hole of the current transformer).

[0108] In other words, the inner holes of current transformers CT1, CT2 and CT3 are used to pass through the A-phase, B-phase and C-phase wires of the motor (three-phase motor), respectively.

[0109] Current transformers CT1, CT2 and CT3 are used to output three full-wave current analog signals (i.e. induce AC current) corresponding to the A-phase, B-phase and C-phase wires of the motor (three-phase motor) when AC current flows through the A-phase, B-phase and C-phase wires respectively.

[0110] It should be noted that for current transformers CT1, CT2 and CT3, since the through-core wire carries alternating current, alternating current will also be induced from SA1 to SA2 of current transformer CT1, from SB1 to SB2 of current transformer CT2 and from SC1 to SC2 of current transformer CT3.

[0111] Among them, for current transformers CT1, CT2 and CT3, the input range between P1 and P2 of these three current transformers (specifically including: PA1 to PA2, PB1 to PB2, PC1 to PC2) is 0 to 10A, and the output range between S1 and S2 of these three current transformers (specifically including: SA1 to SA2, SB1 to SB2, SC1 to SC2) is 0 to 5mA, forming a linear relationship.

[0112] The correspondence between input and output (i.e., the correspondence between current input and output of the current transformer) is as follows:

[0113]

[0114] In formula (1): I inI represents the current in one direction of the motor, i.e., the input current of the current transformer (i.e., the motor current). When the current transformer is selected as TA1420-M, I in The range is AC 0-10A;

[0115] I out The output current (i.e., induced current) induced by the current transformer, when the current transformer is selected as TA1420-M, I in The range is AC 0-5mA;

[0116] M is the ratio of the input current to the output current of the current transformer (i.e., the linear multiple of the input current to the output current). When the current transformer is selected as TA1420-M, M is 2000.

[0117] It should be noted that formula (1) is the relationship between the input current (motor current) and the output current (induced current) of the current transformer, with the unit being A. When the input current is 0 to 10A, the induced current is 0 to 5mA. The input current and the output current are linearly related.

[0118] In this invention, specifically, the rectifier bridges Z1, Z2 and Z3 all function to convert the three full-wave current analog signals output by the current transformers CT1, CT2 and CT3 into three half-wave current analog signals, and then output them to the sampling resistors R4, R5 and R6 respectively.

[0119] It should be noted that rectifier bridges Z1, Z2, and Z3 are existing and mature electronic components. For example, the ABS10A-13 rectifier bridge from Dahl Technologies can be used.

[0120] In this invention, specifically, sampling resistors R4, R5 and R6 are used to convert the three half-wave current analog signals output by rectifier bridges Z1, Z2 and Z3 into three half-wave voltage analog signals, which are then output to the microcontroller U1.

[0121] It should be noted that resistors R4, R5, and R6 are all sampling resistors used to convert the half-wave current analog signal into a half-wave voltage analog signal, so that the microcontroller U1 can directly read the signal. When the current transformers CT1, CT2, and CT3 are TA1420-M type current transformers, the resistance values ​​of sampling resistors R4, R5, and R6 are 500Ω.

[0122] In this invention, specifically, the microcontroller U1 is used to convert the analog signals output by rectifier bridges Z1, Z2 and Z3 into digital signals; specifically, it is used to convert the half-wave voltage analog signals output by rectifier bridges Z1, Z2 and Z3 through sampling resistors R4, R5 and R6 into voltage digital signals.

[0123] It should be noted that the microcontroller U1 is a mature electronic component with existing technology. For example, the STM32L151RET6 microcontroller manufactured by STMicroelectronics can be used.

[0124] In this invention, by utilizing the analog signal acquisition function of the microcontroller U1, the half-wave voltage analog signal can be converted into a digital signal (i.e., a digital signal).

[0125] The microcontroller U1 is used to convert the real-time value of the acquired half-wave voltage signal (i.e., the analog half-wave voltage signal) into the effective value of the voltage signal through root mean square (RMS) calculation. The formula for the RMS calculation is as follows:

[0126]

[0127] In formula (2): U rms This is the effective value of the voltage, which is a calculated value.

[0128] u k The k-th real-time voltage value within a sampling period is obtained by the microcontroller U1 through AD acquisition.

[0129] n is the number of real-time voltage values ​​within the acquisition period, which is a natural number greater than 0 and is preset by the microcontroller U1.

[0130] It should be noted that formula (2) is the formula for calculating the effective value of voltage. Given n real-time voltage values ​​within a sampling period, the effective value of voltage for this sampling period is calculated through root mean square operation.

[0131] In this invention, the microcontroller U1 is also used to calculate the effective value of the current signal output by the current transformer based on the effective value of the voltage signal and the resistance value of the sampling resistor.

[0132] It should be noted that, according to Ohm's law, the effective value of the current signal is the effective value of the voltage signal divided by the resistance of the sampling resistor. In this invention, the effective value I of the current signal output by the current transformer... rms The calculation formula is as follows:

[0133]

[0134] In formula (3): I rms This is the effective value of the current output by the current transformer;

[0135] U rms R is the effective value of the voltage, which can be calculated using formula (2); R is the sampling resistor, i.e., the resistance value of R4, R5 or R6, specifically equal to 500Ω.

[0136] Then, based on the current input-output correspondence of the current transformer, for example, according to the above formula (1), the effective value of the actual motor current (i.e. the effective value of the current signal input by the current transformer) can be obtained.

[0137] In this invention, specifically, the power supply VCC is a 3.3V DC power supply, which is an integrated power supply.

[0138] In this invention, specifically, the watchdog chip U2 is a mature electronic component with existing technology, such as the TPS3828-33DBVR chip from Texas Instruments.

[0139] In terms of specific implementation, the watchdog chip U2 plays the following role:

[0140] The watchdog chip U2 is used to control the microcontroller U1 to reset itself when the microcontroller U1 fails to continuously send PWM waves (pulse width modulation waves) to the watchdog chip U2 due to a fault, that is, when the level change time reaches 1.6 seconds. Specifically, the watchdog chip U2 controls its RESET terminal (i.e., pin 1) to send a reset signal to the NRST terminal (i.e., pin 7) of the microcontroller U1, and the microcontroller U1 then restarts.

[0141] In addition, the watchdog chip U2 is also used to prevent the microcontroller U1 from starting when the voltage of the microcontroller U1 is low (i.e., when the voltage of the power supply VCC is lower than 2.93V). The watchdog chip U2 continuously pulls down the level of the NRST terminal (i.e., pin 7) of the microcontroller U1 until the power supply voltage returns to normal.

[0142] It should be noted that the microcontroller U1 sends a PWM wave to the watchdog chip U2 to prove that the microcontroller U1 is operating normally and has not been stuck due to a fault.

[0143] It should be noted that when the voltage between the VDD terminal (pin 5) and the GND terminal (pin 2) of the watchdog chip U2 (i.e., the voltage of the power supply VCC) is lower than 2.93V, the WDI terminal (pin 4) of the watchdog chip U2 will output a low level.

[0144] In this invention, specifically, capacitors C1, C2, C3, C4, C5, C6, C9, C10, C12, C14 and C16 are all 0.1uF ceramic capacitors;

[0145] In practice, both capacitors C7 and C8 are 18pF ceramic capacitors.

[0146] In practice, capacitors C11, C13, and C15 are all 0.1uF ceramic capacitors;

[0147] In practice, resistor R1 is a 0Ω resistor (i.e., a zero-ohm resistor, also known as a bridging resistor);

[0148] In practice, resistor R2 is a 10kΩ resistor;

[0149] In practice, resistor R3 is a 1kΩ resistor;

[0150] In practice, crystal oscillator X1 is an 8MHz crystal oscillator.

[0151] In this invention, it should be noted that the microcontroller U1 can specifically be an STM32L151RET6 microcontroller manufactured by STMicroelectronics.

[0152] The four VDD ports of the microcontroller U1 (i.e., pins 48, 32, 19, and 64) are the power input terminals of the microcontroller U1, used to provide power to the microcontroller.

[0153] The VDDA port (i.e., pin 13) is the power input terminal for the microcontroller's AD acquisition function, used to provide power for the microcontroller's AD acquisition function.

[0154] The VLCD port (i.e., pin 1) is the power input terminal for the microcontroller's LCD function and requires a 3.3V power supply.

[0155] The four VSS ports (i.e., pins 18, 31, 47, and 63) are the digital ground of the microcontroller and need to be connected to GND.

[0156] The VSSA port (i.e., pin 12) is the analog ground of the microcontroller and needs to be connected to GND through a 0Ω resistor.

[0157] The OSC-IN port (pin 5) and OSC-OUT port (pin 6) are the clock oscillator input terminals, which are used to connect the crystal oscillator and provide a clock for the microcontroller U1.

[0158] The BOOT0 port (i.e., pin 60) is the microcontroller's boot mode pin. The microcontroller U1 can only operate normally when this pin is grounded through a 10kΩ resistor.

[0159] The NRST port (i.e., pin 7) is the microcontroller reset pin. When this pin is high, the microcontroller is running normally, and when this pin is high, the microcontroller is reset.

[0160] The PB3 port (i.e., pin 55) is the PWM wave output pin of the microcontroller, and its function is to output PWM waves.

[0161] Port PA13 (i.e., pin 46) is the microcontroller's programming data pin, which is used to receive programming data from the ARM emulator.

[0162] Port PA14 (i.e., pin 49) is the microcontroller's programming clock pin, which is used to receive the programming clock from the ARM emulator.

[0163] The PB11 port (i.e., pin 30) is the UART serial asynchronous transceiver data receive pin of the microcontroller, and its function is to receive data from the external UART serial asynchronous transceiver.

[0164] The PB10 port (i.e., pin 29) is the data transmission pin of the microcontroller's UART serial asynchronous transceiver, and its function is to send data to an external UART serial asynchronous transceiver.

[0165] The PB0 port (i.e., pin 26) is the microcontroller's AD acquisition pin, which is used by the microcontroller to convert the analog signal acquired by this port into a digital signal.

[0166] The PB1 port (i.e., pin 27) is the microcontroller's AD acquisition pin, which is used by the microcontroller to convert the analog signal acquired by this port into a digital signal.

[0167] Port PA3 (i.e., pin 17) is the microcontroller's AD acquisition pin, which is used by the microcontroller to convert the analog signal acquired by this port into a digital signal.

[0168] It should be noted that, except Figure 1 Apart from the multiple pins shown above that are already in use, the other pins of the microcontroller U1 are idle and not used.

[0169] In this invention, it should be noted that the watchdog chip U2 can specifically be a Texas Instruments TPS3828-33DBVR chip.

[0170] In this invention, for the watchdog chip U2, the RESET terminal (i.e., pin 1) is a reset signal output pin used to control the level of the NRST pin of the microcontroller U1.

[0171] The VDD pin (i.e., pin 2) is used to ground the watchdog chip U2;

[0172] The MR pin (pin 3) is the external reset signal pin, used to allow the watchdog chip U2 to receive an external reset signal. When the level of this pin is pulled low, the RESET pin (pin 1) outputs a low level.

[0173] VDD (pin 5) is used to connect the power supply to the watchdog chip U2.

[0174] In this invention, the crystal oscillator X1 is a two-pin type. An 8MHz crystal oscillator is used to provide a clock for the microcontroller U1 during operation.

[0175] In this invention, for connector J2, its GND terminal (pin 1) is the ground terminal, which is used to maintain consistency with the ground of the ARM emulator. The SWCLK terminal (i.e., pin 2) is the programming clock line terminal, which provides a clock to the microcontroller when the ARM emulator is programming the microcontroller.

[0176] The SWDIO pin (pin 3) is the data line for programming, and its function is to transmit data to the microcontroller when programming the ARM emulator.

[0177] In practice, connector J2 uses a single-row pin header with a pin pitch of 2.54mm. Connector J2 and the ARM emulator are connected via DuPont wires. The GND terminal (pin 1) of connector J2 is connected to the GND terminal of the ARM emulator, the SWCLK terminal (pin 2) of connector J2 is connected to the SWCK terminal of the ARM emulator, and the SWDIO terminal (pin 3) of connector J2 is connected to the SWIO terminal of the ARM emulator.

[0178] In this invention, for current transformers CT1, CT2, and CT3, terminals PA1, PA2, PB1, PB2, PC1, and PC2 are current signal input terminals. Terminals PA1-PA2, PB1-PB2, and PC1-PC2 are actually through-core cables, i.e., the three-phase wires of a three-phase motor. Terminals S1 and S2 of the current transformer (specifically including terminals SA1 and SA2, SB1 and SB2, and SC1 and SC2) are induced current output terminals. When the current from P1 to P2 (specifically including terminals PA1 to PA2, PB1 to PB2, and PC1 to PC2) changes and a loop is formed from S1 to S2, an induced current occurs at terminals S1 to S2.

[0179] In this invention, for rectifier bridges Z1, Z2, and Z3, the IN1 terminal (pin 2) on each rectifier bridge is the first AC input terminal, and the IN2 terminal (pin 4) is the second AC input terminal. The AC signal requiring rectification is input from these two terminals. Furthermore, the + terminal (pin 1) on each rectifier bridge is the voltage output terminal, outputting the rectified DC signal. The - terminal (pin 3) on each rectifier bridge is the analog ground terminal and needs to be connected to analog ground.

[0180] To better understand the technical solution of this invention, the working principle of this invention will be explained below using phase A current acquisition and monitoring as an example.

[0181] I. Analog signal acquisition.

[0182] This invention uses a current transformer for data acquisition instead of a series ammeter, so that the use of the vehicle's reducer motor will not be affected in the event of a fault in the acquisition circuit.

[0183] In order to collect the A-phase current of a three-phase motor, when there is an alternating current in the first wire (i.e., the A-phase wire) of the PA1-PA2 terminals of the current transformer CT1, an induced current is generated at the SA1-SA2 terminals through electromagnetic induction.

[0184] The induced full-wave current signal is converted into a half-wave current signal after passing through the rectifier bridge Z1, and then converted into a half-wave voltage signal through the sampling resistor R4. The bypass capacitors C11 and C12 are used to remove high-frequency noise.

[0185] These are all passive components and do not require an external power supply to complete the data acquisition.

[0186] II. Digital-to-Analog Conversion and Calculation.

[0187] When the half-wave voltage signal output by the sampling resistor R4 flows into the PB0 terminal (i.e., pin 26) of the microcontroller U1, the analog signal can be converted into a digital signal through the ADC conversion function (i.e., analog-to-digital conversion function) of the microcontroller U1. The digital value at this time is the real-time value. According to formula (1), the real-time digital value collected by the ADC module of the microcontroller U1 is converted into the effective digital value through the root mean square operation.

[0188] The relationship between analog and digital quantities is as follows:

[0189]

[0190] In formula (4): u k The voltage is the analog signal acquired by the microcontroller U1.

[0191] V is the input power supply voltage of the microcontroller U1. When using the STM32L151RET6 microcontroller, it is 3.3V, which is equal to the voltage of the power supply VCC.

[0192] N represents the resolution of the ADC conversion function of microcontroller U1. When using the STM32L151RET6 microcontroller, it is 4096.

[0193] x k This refers to the digital output of the U1ADC converter in the microcontroller.

[0194] The microcontroller U1 can be configured with the real-time value acquisition frequency and the effective value calculation frequency.

[0195] For microcontroller U1, let x be the number of digital values ​​collected at a certain moment. kThe acquisition pin voltage of the ADC module of microcontroller U1 is u. k The induced current of the current transformer is i k The real-time value of the single-phase current of the motor is I. k The effective value of the single-phase current of the motor is I. rms The ADC module of microcontroller U1 has a sampling resolution of N, and the power supply voltage of microcontroller U1 is V. Each effective value is calculated by root mean square operation on n real-time values. n is a natural number greater than 1.

[0196] It should be noted that formula (4) is the digital-to-analog conversion formula of microcontroller U1. Dividing the 3.3V power supply by N (N is related to the microcontroller model, which is 4096 in this case) will give the unit reference voltage of the AD acquisition. When the microcontroller performs AD acquisition, the voltage is x times the unit reference voltage. The microcontroller U1 will record the value of this voltage as x, where x is a natural number with a maximum of N-1. The decimal part is directly discarded.

[0197] For formula (4), V is the input power supply of 3.3V, which is a fixed value; N is the microcontroller's AD acquisition resolution, which is a fixed value; u k x is the kth sampled voltage; k Collect digital values ​​for the k-th AD converter.

[0198] In this invention, as previously stated, the following formulas are known:

[0199]

[0200]

[0201]

[0202]

[0203] Substituting formula (2) into formula (3), we get the following formula (5):

[0204]

[0205] Then, substituting formula (4) into formula (5), we can obtain the following formula (6):

[0206]

[0207] Then I in formula (6) rms Substituting the output current (i.e., induced current) induced by the current transformer into formula (1) I out The effective value I of the input current (i.e., motor current) of the three-phase motor can be obtained. inThe calculation formula is as follows: the microcontroller U1 obtains the effective value I of the current flowing through the A-phase, B-phase, and C-phase wires of the three-phase motor according to the following calculation formula (7). in The details are as follows:

[0208]

[0209] In the above formula: x k This refers to the digital output of the ADC converter in microcontroller U1.

[0210] V is the voltage of the input power supply VCC of the microcontroller U1. When using the STM32L151RET6 microcontroller, it is 3.3V.

[0211] N represents the resolution of the ADC conversion function of microcontroller U1. When using the STM32L151RET6 microcontroller, it is 4096.

[0212] n is the number of real-time voltage values ​​acquired by the ADC acquisition cycle of microcontroller U1, which is set by the microcontroller program.

[0213] R is the sampling resistor. When the current transformer is selected as TA1420-M, the sampling resistor is 500Ω, that is, the resistance value of R4, R5 or R6 is 500Ω.

[0214] M is the ratio of the input current to the output current of the current transformer. When the current transformer is selected as TA1420-M, M is 2000.

[0215] III. Communication, monitoring and fault self-recovery.

[0216] The effective digital value information calculated by the microcontroller U1 is sent out through the UART port (i.e., the PB11 pin of the microcontroller U1). Alternatively, the UART port can be connected to an external SOC chip, and the acquired effective current value can be transmitted to the host computer via the SOC chip's network communication function. Alternatively, it can be connected to an RS-485 chip, communicating with the host computer via RS-485.

[0217] When the microcontroller U1 is stuck due to a fault, the PWM wave on the WDI terminal (pin 4) of the watchdog chip U2 disappears. Then, the watchdog chip U2 controls its RESET terminal (pin 1) to send a reset signal to the NRST terminal (pin 7) of the microcontroller U1, and the microcontroller U1 restarts.

[0218] In summary, compared with the prior art, the motor current monitoring circuit provided by the present invention is scientifically designed and can safely and reliably monitor the current of the motor on the vehicle reducer.

[0219] The circuit of this invention adopts a non-contact monitoring method, which does not directly contact the power supply cable of the motor, making it safer and more reliable. It can avoid the vehicle reducer itself being affected by damage to the monitoring equipment, ensuring the safe use of the vehicle reducer and providing higher safety.

[0220] After testing, the circuit provided by this invention is an interface circuit with strong anti-interference ability, high safety and stable output signal, which can be reliably applied to vehicle reducer monitoring equipment in the railway industry.

[0221] Furthermore, the circuit of this invention can also realize functions such as external communication and automatic restart in case of failure, with high precision and significant practical value.

[0222] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A motor current monitoring circuit, characterized in that, Includes microcontroller U1, power supply VCC, current transformers CT1 to CT3, rectifier bridges Z1 to Z3, and sampling resistors R4 to R6; The microcontroller U1 is connected to the power supply VCC; VCC power supply is used to provide operating power for the microcontroller U1. The microcontroller U1 is connected to the current transformers CT1, CT2 and CT3 through rectifier bridges Z1, Z2 and Z3 respectively; The inner holes of current transformers CT1, CT2 and CT3 are used to pass through the A-phase, B-phase and C-phase wires of a three-phase motor, respectively. Current transformers CT1, CT2, and CT3 are used to output three full-wave current analog signals corresponding to the A-phase, B-phase, and C-phase wires of a three-phase motor, respectively, when AC current flows through the A-phase, B-phase, and C-phase wires. The rectifier bridges Z1, Z2 and Z3 are connected to the current transformers CT1, CT2 and CT3 respectively, and are used to convert the three full-wave current analog signals output by the current transformers CT1, CT2 and CT3 into three half-wave current analog signals, which are then output to the sampling resistors R4, R5 and R6 respectively. Sampling resistors R4, R5, and R6 are connected to rectifier bridges Z1, Z2, and Z3 respectively, and are used to convert the three half-wave current analog signals output by rectifier bridges Z1, Z2, and Z3 into three half-wave voltage analog signals, which are then output to the microcontroller U1. The microcontroller U1 is connected to sampling resistors R4, R5, and R6. It is used to convert the three half-wave voltage analog signals output by sampling resistors R4, R5, and R6 into voltage digital signals, and through analysis and calculation, obtain the effective values ​​of the current flowing through the A-phase, B-phase, and C-phase wires of the three-phase motor.

2. The motor current monitoring circuit as described in claim 1, characterized in that, Regarding the connection between the microcontroller U1 and the power supply VCC, the specific circuit structure design is as follows: The VLCD port, VDDA port and four VDD ports of the microcontroller U1 converge at node A, which is connected to the power supply VCC. The four VSS ports of the microcontroller U1 are connected to the power ground terminal GND; The VSSA port of the microcontroller U1 is connected to one end of the resistor R1; The other end of resistor R1 is connected to the power supply ground terminal GND; Node A is connected to one end of capacitors C1 through C6 respectively; The other end of capacitors C1 to C6 is connected to the power supply ground terminal GND.

3. The motor current monitoring circuit as described in claim 1, characterized in that, The microcontroller U1 is also connected to the crystal oscillator X1; Regarding the connection between the microcontroller U1 and the crystal oscillator X1, the specific circuit structure design is as follows: The OSC_IN port of the microcontroller U1 is connected to one end of the crystal oscillator X1 and one end of the capacitor C7, respectively; The other end of capacitor C7 is connected to the power supply ground terminal GND; The OSC_OUT port of the microcontroller U1 is connected to the other end of the crystal oscillator X1 and one end of the capacitor C8, respectively. The other end of capacitor C8 is connected to the power supply ground terminal GND.

4. The motor current monitoring circuit as described in claim 1, characterized in that, The BOOT0 port of the microcontroller U1 is connected to the power ground terminal GND through resistor R2.

5. The motor current monitoring circuit as described in claim 1, characterized in that, The microcontroller U1 is connected to the watchdog chip U2; Regarding the connection between the microcontroller U1 and the watchdog chip U2, the specific circuit structure design is as follows: The NRST pin of the microcontroller U1 is connected to the RESET pin of the watchdog chip U2; The PB3 pin of the microcontroller U1 is connected to the WDI pin of the watchdog chip U2; The NRST terminal of the microcontroller U1 is also connected to one end of resistor R3 and capacitor C9, respectively; The other end of resistor R3 is connected to the power supply VCC; The other end of capacitor C9 is connected to the power supply ground terminal GND; The VDD terminal of the watchdog chip U2 is connected to the power supply VCC; The GND terminal of the watchdog chip U2 is connected to the power ground terminal GND; The VDD terminal of the watchdog chip U2 is also connected to one end of capacitor C10; The other end of capacitor C10 is connected to the power supply ground terminal GND.

6. The motor current monitoring circuit as described in claim 1, characterized in that, The microcontroller U1 is also connected to connector J2; Regarding the connection between the microcontroller U1 and connector J2, the specific circuit structure design is as follows: The PA13 pin of the microcontroller U1 is connected to the SWDIO pin of the connector J2; The PA14 pin of the microcontroller U1 is connected to the SWCLK pin of the connector J2; The GND terminal of connector J2 is connected to the power ground terminal GND.

7. The motor current monitoring circuit as described in any one of claims 1 to 6, characterized in that, The SA1 and SA2 terminals of the current transformer CT1 are connected to the IN1 and IN2 terminals of the rectifier bridge Z1, respectively. The positive terminal of rectifier bridge Z1 is connected to the PB0 terminal of microcontroller U1; The - terminal of rectifier bridge Z1 is connected to the power supply ground terminal GND; The positive terminal of rectifier bridge Z1 is also connected to one end of capacitors C11 and C12; The other ends of capacitors C11 and C12 are connected to one end of rectifier bridge Z1; The positive terminal of rectifier bridge Z1 is connected to one end of sampling resistor R4; The other end of the sampling resistor R4 is connected to the power supply ground terminal GND.

8. The motor current monitoring circuit as described in any one of claims 1 to 6, characterized in that, The SB1 and SB2 terminals of the current transformer CT2 are connected to the IN1 and IN2 terminals of the rectifier bridge Z2, respectively. The positive terminal of rectifier bridge Z2 is connected to the PB1 terminal of the microcontroller; The - terminal of rectifier bridge Z2 is connected to the power supply ground terminal GND; The positive terminal of rectifier bridge Z2 is connected to one end of capacitors C13 and C14; The other ends of capacitors C13 and C14 are connected to the - end of rectifier bridge Z2; The positive terminal of rectifier bridge Z2 is connected to one end of sampling resistor R5; The other end of the sampling resistor R5 is connected to the power supply ground terminal GND.

9. The motor current monitoring circuit as described in any one of claims 1 to 6, characterized in that, The SC1 and SC2 terminals of the current transformer CT3 are connected to the IN1 and IN2 terminals of the rectifier bridge Z3, respectively. The positive terminal of rectifier bridge Z3 is connected to the PA3 terminal of the microcontroller; The - terminal of rectifier bridge Z3 is connected to the power supply ground terminal GND; The positive terminal of rectifier bridge Z3 is connected to one end of capacitors C15 and C16; The other ends of capacitors C15 and C16 are connected to the - end of rectifier bridge Z3; The positive terminal of rectifier bridge Z3 is connected to one end of sampling resistor R6; The other end of the sampling resistor R6 is connected to the power supply ground terminal GND.

10. The motor current monitoring circuit as described in any one of claims 1 to 6, characterized in that, The microcontroller U1 obtains the effective value I of the current flowing through the A-phase, B-phase, and C-phase wires of the three-phase motor according to the following calculation formula (7). in ; In the above formula: x k This refers to the digital output of the ADC conversion of the microcontroller U1. V is the voltage of the input power supply VCC of the microcontroller U1; N represents the resolution of the ADC conversion function of the microcontroller U1; n is the number of real-time voltage values ​​acquired by the ADC of microcontroller U1 within a acquisition cycle; R is the resistance value of the sampling resistor; M is the ratio of the input current to the output current of the current transformer.

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