Three-phase ac power open-phase detection circuit and method

Abstract

This invention relates to the field of circuit testing technology, and particularly to a three-phase AC phase loss detection circuit and method, comprising a current-limiting sampling circuit, a voltage clamping circuit, an opto-isolation circuit, and a status output circuit connected in sequence. The current-limiting sampling circuit includes an R-phase sampling circuit, an S-phase sampling circuit, and a T-phase sampling circuit. The current-limiting sampling circuit is used to collect the R-phase voltage signal, the S-phase voltage signal, and the T-phase voltage signal. The voltage clamping circuit is used to manage the R-phase voltage signal, the S-phase voltage signal, and the T-phase voltage signal to send a drive signal to the opto-isolation circuit. The opto-isolation circuit is used to generate a corresponding optical signal according to the drive signal, and to generate a low-level pulse signal or a high-level pulse signal according to the output mode of the optical signal, so as to output a three-phase normal status signal or a three-phase abnormal status signal through the status output circuit, enabling rapid and accurate detection of the three-phase AC status.

Description

Technical Field

[0001] This invention relates to the field of circuit testing technology, and in particular to a three-phase AC phase loss detection circuit and method. Background Technology

[0002] In modern industrial production systems, three-phase alternating current (AC) has become the core power source driving various large-scale equipment due to its significant advantages of high power transmission efficiency and strong power supply stability. From the roaring smelting units in steel plants to the precise operation of filling production lines in pharmaceutical workshops, and the efficient sorting automated equipment in logistics warehouses, three-phase motors, as the core component of power output, support the orderly operation of the entire industrial production process. According to relevant industry statistics, more than 90% of power equipment in the industrial sector relies on three-phase motors for drive, and their stable operation is directly related to production efficiency, product quality, and the economic benefits of enterprises.

[0003] However, in actual production, the problem of three-phase power loss is like a lurking "invisible killer," constantly threatening equipment safety and production continuity. Three-phase power loss refers to a fault state in a three-phase AC power system where any phase experiences voltage loss, low voltage, or a circuit break. Its causes are complex and varied. On the power supply side, issues such as blown fuses at the transformer output end, momentary voltage drops in the grid, or harmonic interference frequently occur. In the wiring connections, poor cable or socket contact, or loose terminals, can obstruct current transmission. Within the equipment itself, a short circuit or open circuit in one phase coil of a three-phase motor can cause a corresponding current loss. Regarding control switches, problems such as contactor contact erosion and switch aging can also trigger phase loss faults.

[0004] In the development of phase loss protection, early protection methods primarily relied on short-circuit and overload protection devices to indirectly ensure equipment safety. However, these traditional protection methods have significant limitations. Short-circuit protection mainly targets situations where the current in the circuit increases rapidly; it often cannot respond promptly to phase loss faults, where the current changes slowly and is unbalanced. Overload protection focuses on protecting motors from prolonged overload operation, but its action threshold and delay settings are difficult to accurately match the characteristics of phase loss faults, often triggering protection only when the motor has already suffered severe damage.

[0005] For most small and medium-sized motors, limited by cost and technological conditions, they have long been equipped only with short-circuit and overload protection, while dedicated phase loss protection devices are mostly used in the starting and running circuits of large motors. This imbalance in protection configuration has left a large number of small and medium-sized motors exposed to the risk of phase loss faults for a long time. According to statistics on industrial equipment failures, about 30% of three-phase motor failures are caused by single-phase operation, imposing a heavy economic burden on enterprises.

[0006] With the rapid development of electronic technology and the increasing demands for equipment reliability and safety in industrial production, specialized phase loss detection circuits have emerged. The core task of a phase loss detection circuit is to continuously monitor the current or voltage status of the three-phase power supply. When any phase is detected to be missing, the power supply is quickly cut off after a delay confirmation to prevent the motor from burning out due to the missing phase.

[0007] Compared with traditional protection methods, phase loss detection circuits have advantages such as fast response speed, high detection accuracy, and strong targeting. They can capture subtle changes in three-phase power in real time, issuing alarms or cutting off power in the early stages of a phase loss fault, minimizing damage. Today, phase loss detection circuits have evolved from simple voltage and current detection to intelligent detection systems integrating microprocessors and digital processing technology, possessing multiple functions such as delayed confirmation, remote monitoring, and data logging, enabling them to better adapt to complex and changing industrial production environments.

[0008] With the trend of industrial automation and intelligentization, three-phase phase loss detection circuits have not only become an important protection feature for three-phase motors (especially critical equipment), but also a key technology for ensuring the safe, stable, and efficient operation of industrial production. By installing phase loss detection circuits, enterprises can effectively reduce the phase loss failure rate of three-phase motors, reduce equipment maintenance costs and production downtime, and improve overall production efficiency. Summary of the Invention

[0009] The embodiments of the present invention provide a three-phase AC phase loss detection circuit and method, which can quickly and accurately detect the state of three-phase AC power.

[0010] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions: Firstly, a three-phase AC phase loss detection circuit is provided, comprising: The current-limiting sampling circuit, voltage clamping circuit, opto-isolation circuit, and status output circuit are connected in sequence. The current-limiting sampling circuit includes an R-phase sampling circuit, an S-phase sampling circuit, and a T-phase sampling circuit. The current-limiting sampling circuit is used to collect the R-phase voltage signal, the S-phase voltage signal, and the T-phase voltage signal. The voltage clamping circuit is used to manage the R-phase voltage signal, the S-phase voltage signal, and the T-phase voltage signal to send a drive signal to the opto-isolation circuit. The opto-isolation circuit is used to generate a corresponding optical signal according to the driving signal, and to generate a low-level pulse signal or a high-level pulse signal according to the output mode of the optical signal, so as to output a three-phase normal state signal or a three-phase abnormal state signal through the state output circuit.

[0011] According to a second aspect of the present invention, a three-phase alternating current phase loss detection method is provided, for implementing a three-phase alternating current phase loss detection circuit as described in any one of the first aspects, comprising: The R-phase voltage signal, S-phase voltage signal, and T-phase voltage signal are acquired, and the R-phase voltage signal, S-phase voltage signal, and T-phase voltage signal are stepped down. When the R-phase voltage signal, S-phase voltage signal, and T-phase voltage signal have a high-low relationship that meets a predetermined standard, the light-emitting diode in the circuit is forward-biased to activate the light-emitting diode and generate a light signal. When any one of the R-phase voltage signal, S-phase voltage signal, and T-phase voltage signal is missing, the LED in the circuit is cut off and does not generate a light signal. The light signals generated by the light-emitting diodes are periodically identified to output low-level pulse signals or high-level pulse signals; When the servo driver detects a low-level pulse signal, it determines that the three-phase power supply is normal; when it detects a high-level pulse signal, it determines that the three-phase power supply is missing or abnormal.

[0012] This invention provides a three-phase AC phase loss detection circuit and method. The phase loss detection circuit features fast response speed, high detection accuracy, and strong targeting, capable of capturing subtle changes in three-phase power in real time. It can promptly issue alarms or cut off power supply in the early stages of a phase loss fault, minimizing fault losses. It has evolved from simple voltage and current detection to an intelligent detection system integrating microprocessor and digital processing technology, possessing multiple functions such as delayed confirmation, remote monitoring, and data recording, adapting to complex industrial production environments. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of a three-phase AC phase loss detection circuit provided in an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the steps of a three-phase AC phase loss detection method provided in an embodiment of the present invention; Figure reference numerals: R1-first resistor, R2-second resistor, R3-third resistor, R4-fourth resistor, R5-fifth resistor, R6-sixth resistor, R7-seventh resistor, R8-eighth resistor, R9-ninth resistor, D1-first dual-channel bidirectional TVS diode array, D2-second dual-channel bidirectional TVS diode array, D3-third dual-channel bidirectional TVS diode array, C1-filter capacitor, ZD1-Zenyl regulator diode, U1-opto-isolation circuit. Detailed Implementation

[0015] 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.

[0016] This invention provides a three-phase AC phase loss detection circuit, such as... Figure 1 As shown, it includes: The current limiting sampling circuit, voltage clamping circuit, opto-isolation circuit U1, and status output circuit are connected in sequence. The current-limiting sampling circuit includes an R-phase sampling circuit, an S-phase sampling circuit, and a T-phase sampling circuit. The current-limiting sampling circuit is used to collect the R-phase voltage signal, the S-phase voltage signal, and the T-phase voltage signal. The voltage clamping circuit is used to manage the R-phase voltage signal, the S-phase voltage signal, and the T-phase voltage signal to send a drive signal to the opto-isolation circuit. The opto-isolation circuit U1 is used to generate a corresponding optical signal according to the driving signal, and to generate a low-level pulse signal or a high-level pulse signal according to the output mode of the optical signal, so as to output a three-phase normal state signal or a three-phase abnormal state signal through the state output circuit.

[0017] This circuit is a three-phase AC phase loss / phase sequence detection and high-voltage / low-voltage isolation protection circuit. Its core uses optocouplers to achieve electrical isolation between the high-voltage three-phase signals and the low-voltage servo control side, ultimately outputting a PH signal to the servo driver to determine the three-phase power supply status. This three-phase AC phase loss detection circuit is as follows: Figure 1As shown, the voltage clamping circuit is composed of current-limiting resistors R1 / R2, R5 / R6, R8 / R9, dual diodes D1 / D2 / D3, filter capacitor C1, and Zener diode ZD1 (R3+ZD1). The core isolating optocoupler U1 contains an LED (pin 1 / 2) and a phototransistor (pin 3 / 4). The +5V / R4 is the pull-up power supply and resistor on the optocoupler output side. R7 is a current-limiting resistor that matches the input impedance of the PH pin of the servo driver to prevent overcurrent damage to the servo I / O port.

[0018] When the three phases are normal, there is a 120° phase difference between the three phases (R / S / T). Within the power frequency cycle, at any given moment, at least two phases have an effective voltage difference. The current-limiting resistors R1 / R2, R5 / R6, and R8 / R9 significantly reduce the high-voltage AC voltage of the three phases. The voltage limiting current is a low-voltage signal that the diodes can withstand. When the voltage of one phase is higher than another, the corresponding diode conducts forward (e.g., when the voltage of phase R is higher than phase S, D1 / D2 conducts). The voltage is then passed through capacitor C1 (which filters out the voltage ripple after three-phase rectification, preventing high-frequency interference from causing false triggering of the optocoupler and improving detection stability) to R3+ZD1 (Zenyl Regulator Diode ZD1), forming a voltage clamping circuit. ZD1 clamps the voltage on the optocoupler output side to a fixed value (e.g., 5~10V). When the three-phase voltage fluctuates, it ensures that the U1 optocoupler LED will only conduct when the voltage is higher than the ZD1 regulated voltage, preventing false triggering due to low voltage. When the LED at pin 2 of U1 is lit, it activates the phototransistor. Due to the alternating changes in the three-phase voltage, the three optocouplers are in a time-division alternating conduction state, and the phototransistor periodically turns on and off. The optocoupler output (pin 2 of U1) is a stable low-level pulse signal, and the PH signal output through R4 / R7 is a continuously effective level. The subsequent detection circuit determines that the three-phase power supply is normal and allows startup.

[0019] When a three-phase phase is missing or abnormal, if any phase (such as phase R) is missing, the corresponding diode D1 will not be driven by current and will be cut off; however, the S / T phase will still have voltage, and theoretically, the front-end node may still be pulled low. After a phase loss, the phase balance of the three-phase voltage is disrupted, and the combined pulsating voltage of the three phases will experience a significant drop / phase distortion, causing the voltage clamped by ZD1 to be unable to continuously drive the front-end optocoupler. The front-end common node will periodically switch between high and low levels → the LED of U1 will intermittently conduct → the phototransistor of U1 will intermittently cut off → the PH pin will output a high level (or pulse signal). The servo driver detects the high-level / abnormal pulse, determines that the three-phase phase is missing / abnormal, and immediately executes protection (such as shutdown, alarm) to prevent the servo driver from burning out due to phase loss operation.

[0020] Furthermore, the R-phase sampling circuit includes a first resistor R1, a second resistor R2 and a first dual-channel bidirectional TVS diode array D1 connected in series; the S-phase sampling circuit includes a fifth resistor R5, a sixth resistor R6 and a second dual-channel bidirectional TVS diode array D2 connected in series; and the T-phase sampling circuit includes an eighth resistor R8, a ninth resistor R9 and a third dual-channel bidirectional TVS diode array D3 connected in series. The first dual-channel bidirectional TVS diode array D1, the second dual-channel bidirectional TVS diode array D2, and the third dual-channel bidirectional TVS diode array D3 each have a first pin, a second pin, and a third pin. The first pins of the first dual-channel bidirectional TVS diode array D1, the second dual-channel bidirectional TVS diode array D2, and the third dual-channel bidirectional TVS diode array D3 are electrically connected to each other, the second pins are electrically connected to each other, and they are respectively electrically connected to the second resistor R2, the sixth resistor R6, and the ninth resistor R9 through the third pin.

[0021] It consists of a first resistor R1, a second resistor R2, and a first dual-channel bidirectional TVS diode array D1 connected in series. The first resistor R1 and the second resistor R2 serve to divide the voltage and limit the current, converting the high voltage signal of the R phase into a low voltage signal suitable for subsequent circuit processing. The first dual-channel bidirectional TVS diode array D1 is used to protect the circuit and prevent transient overvoltages in the R phase from damaging subsequent components.

[0022] The S-phase sampling circuit also consists of the fifth resistor R5, the sixth resistor R6, and the second dual-channel bidirectional TVS diode array D2 connected in series. Its function is similar to that of the R-phase sampling circuit, sampling and protecting the S-phase voltage. The T-phase sampling circuit consists of the eighth resistor R8, the ninth resistor R9, and the third dual-channel bidirectional TVS diode array D3 connected in series, realizing the sampling and protection of the T-phase voltage.

[0023] Each dual-channel bidirectional TVS diode array has a first pin, a second pin, and a third pin. These pins perform different functions in the circuit. The first pins of the first dual-channel bidirectional TVS diode array D1, the second dual-channel bidirectional TVS diode array D2, and the third dual-channel bidirectional TVS diode array D3 are electrically connected to each other. This connection is to connect them to a common reference potential, such as ground, to ensure that in the event of a transient overvoltage, the overvoltage can be guided to the reference potential, thereby protecting the circuit.

[0024] The second pins of these three dual-channel bidirectional TVS diode arrays are also electrically connected to each other to connect them to a common power or signal line for unified voltage protection. The third pins are electrically connected to the second resistor R2, the sixth resistor R6, and the ninth resistor R9, respectively. Through this connection, the TVS diode array can protect the voltage signal after voltage division by resistors. When a transient overvoltage occurs, the TVS diodes will quickly conduct, limiting the overvoltage to a safe range and protecting subsequent circuit components.

[0025] Through the aforementioned sampling circuit and TVS diode array connection method, the circuit can effectively sample the three-phase power and provide protection against transient overvoltages. This ensures that subsequent detection and control circuits can operate stably and reliably, avoiding damage caused by transient overvoltages. Simultaneously, through the voltage division effect of the resistors, the high voltage of the three-phase power can be converted into a low-voltage signal suitable for subsequent circuit processing, facilitating further analysis and processing.

[0026] Furthermore, the voltage clamping circuit includes a filter capacitor C1, a Zener diode ZD1, and a third resistor R3; The two ends of the filter capacitor C1 are electrically connected to the first pin and the second pin respectively, and the end of the filter capacitor C1 that is electrically connected to the second pin is electrically connected to the third resistor R3, and the end of the filter capacitor C1 that is electrically connected to the first pin is electrically connected to the opto-isolation circuit U1. The cathode of the Zener diode ZD1 is electrically connected to the third resistor R3, and the anode of the Zener diode ZD1 is electrically connected to the opto-isolation circuit U1.

[0027] The main function of the voltage clamping circuit is to filter and clamp the input signal to ensure that the subsequent opto-isolation circuit U1 can receive a stable voltage signal within a safe range, thus avoiding damage or false triggering of the opto-isolation circuit U1 due to voltage fluctuations or excessive voltage.

[0028] The two ends of the filter capacitor C1 are electrically connected to the first pin and the second pin, respectively. The end of the filter capacitor C1 connected to the second pin is also electrically connected to the third resistor R3, while the end connected to the first pin is electrically connected to the opto-isolation circuit U1. The main function of the filter capacitor C1 is to filter out high-frequency noise and voltage ripple in the input signal. In applications such as three-phase AC sampling, the input signal is subject to various interferences, causing voltage fluctuations. The filter capacitor C1, by storing and releasing charge, smooths out voltage changes, making the voltage input to the opto-isolation circuit U1 more stable, reducing the impact of high-frequency interference on subsequent circuits, and improving the stability and reliability of the entire circuit.

[0029] The cathode of Zener diode ZD1 is electrically connected to the third resistor R3, and the anode is electrically connected to the opto-isolation circuit U1. The characteristic of Zener diode ZD1 is that it maintains a stable voltage in the reverse breakdown state. When the input voltage exceeds the Zener diode ZD1's regulation voltage, ZD1 enters the reverse breakdown state, clamping the voltage near its regulation voltage. In this circuit, the function of Zener diode ZD1 is to prevent excessively high voltage input to the opto-isolation circuit U1, protecting the components in the opto-isolation circuit U1 from damage by excessive voltage. Simultaneously, it ensures that the opto-isolation circuit U1 is only triggered when the input voltage is higher than its regulation voltage, avoiding false triggering due to low voltage fluctuations.

[0030] The third resistor, R3, is connected to the filter capacitor C1 and the cathode of the Zener diode ZD1. The third resistor R3 acts as a current limiter. When the Zener diode ZD1 enters reverse breakdown mode, a large current will flow. The third resistor R3 limits the magnitude of this current, preventing excessive current from damaging the Zener diode ZD1 and other components. It also adjusts the voltage distribution in the circuit, ensuring the normal operation of the entire circuit.

[0031] After the input signal is filtered by the filter capacitor C1, high-frequency interference and voltage ripple are removed. If the input voltage is lower than the Zener diode ZD1's voltage regulation value, ZD1 is in the off state, and the input signal is directly transmitted to the opto-isolation circuit U1. When the input voltage is higher than the Zener diode ZD1's voltage regulation value, ZD1 breaks down in reverse, clamping the voltage to its regulation value. The excess voltage drops across the third resistor R3, thus ensuring that the voltage received by the opto-isolation circuit U1 remains stable within a safe range.

[0032] Furthermore, the opto-isolation circuit U1 includes a light-emitting diode and a phototransistor; The anode of the light-emitting diode is electrically connected to the anode of the Zener diode ZD1, and the cathode of the light-emitting diode is electrically connected to the filter capacitor C1; The base of the phototransistor is coupled to the light-emitting diode via optical signal coupling, the collector of the phototransistor is electrically connected to the status output circuit, and the emitter of the phototransistor is grounded.

[0033] The core function of the opto-isolation circuit U1 is to achieve electrical isolation, transmitting the signal from the high-voltage side to the low-voltage side in the form of an optical signal, thus preventing electrical interference and potential dangers from the high-voltage side from affecting the circuit on the low-voltage side. At the same time, it completes the signal transmission and conversion, providing a suitable signal for the subsequent status output circuit.

[0034] The anode of the LED is electrically connected to the anode of the Zener diode ZD1, and the cathode is electrically connected to the filter capacitor C1. As an opto-isolated signal transmitter, the LED emits light when the voltage output from the voltage clamping circuit creates a suitable voltage difference across it. The intensity and state of its light emission depend on the input electrical signal, thus converting the electrical signal into a light signal.

[0035] The base of the phototransistor is optically coupled to the light-emitting diode (LED). When the LED emits light, the emitted light illuminates the base of the phototransistor, causing it to generate a photocurrent, thus converting the optical signal into an electrical signal. The collector of the phototransistor is electrically connected to the status output circuit. The phototransistor turns on or off according to the received optical signal, causing a corresponding change in the potential of its collector. This change in electrical signal is transmitted to the status output circuit for subsequent status judgment and processing. The emitter of the phototransistor is grounded, providing a reference potential for the circuit and ensuring its normal operation.

[0036] When the voltage output of the voltage clamping circuit meets the conduction condition of the LED, the LED emits light. The emitted light illuminates the base of the phototransistor, causing it to conduct. At this time, a path is formed between the collector and emitter of the phototransistor, and the collector potential changes. This change in potential is transmitted to the status output circuit. If the input signal changes and causes the LED to not emit light, the phototransistor will turn off, and the collector potential will change accordingly. In this way, the opto-isolation circuit U1 transmits the electrical signal from the high-voltage side to the low-voltage side in the form of an optical signal, while simultaneously achieving electrical isolation and signal conversion, providing a basis for subsequent status judgment.

[0037] Furthermore, the status output circuit includes a fourth resistor R4 and a seventh resistor R7. The fourth resistor R4 and the seventh resistor R7 are respectively electrically connected to the collector of the phototransistor. The fourth resistor R4 is electrically connected to a 5V voltage source, and the seventh resistor R7 is electrically connected to the PH pin of the servo driver.

[0038] The main function of the status output circuit is to convert the on or off state of the phototransistor in the opto-isolation circuit U1 into a suitable electrical signal and output the signal to the PH pin of the servo driver so that the servo driver can determine the status of the three-phase power supply based on the signal.

[0039] The fourth resistor, R4, is electrically connected at one end to the collector of the phototransistor and at the other end to a 5V voltage source. R4 acts as a pull-up resistor. When the phototransistor is off, no current flows through its collector, so the collector is connected to the 5V voltage source through R4, and its potential is approximately 5V. When the phototransistor is on, the collector potential is pulled low, and current flows through the phototransistor to ground. The pull-up resistor ensures a stable high-level signal at the collector when the phototransistor is off.

[0040] The seventh resistor R7 is electrically connected at one end to the collector of the phototransistor and at the other end to the PH pin of the servo driver. The seventh resistor R7 serves to limit current and match impedance. It limits the current flowing into the PH pin of the servo driver, preventing excessive current from damaging the servo driver's I / O port. Simultaneously, by appropriately selecting the value of the seventh resistor R7, the output impedance of the status output circuit can be matched with the input impedance of the PH pin of the servo driver, ensuring that the signal can be transmitted accurately and stably to the servo driver.

[0041] When the phototransistor is off, its collector potential is pulled up to 5V through the fourth resistor R4. After passing through the seventh resistor R7, the 5V high-level signal is transmitted to the PH pin of the servo driver. Upon detecting the high-level signal, the servo driver determines that there is an abnormality in the three-phase power supply and executes corresponding protection measures, such as shutdown or alarm.

[0042] When the phototransistor is turned on, its collector potential is pulled low, close to ground potential. After passing through resistor R7, the low-level signal is transmitted to the PH pin of the servo driver. Upon detecting the low-level signal, the servo driver determines that the three-phase power supply is normal and allows the equipment to start operating.

[0043] Another embodiment of the present invention provides a three-phase AC phase loss detection method, which applies the three-phase AC phase loss detection circuit described in any one of the first aspects, such as... Figure 2 As shown, it includes: The R-phase voltage signal, S-phase voltage signal, and T-phase voltage signal are acquired, and the R-phase voltage signal, S-phase voltage signal, and T-phase voltage signal are stepped down. When the R-phase voltage signal, S-phase voltage signal, and T-phase voltage signal have a high-low relationship that meets a predetermined standard, the light-emitting diode in the circuit is forward-biased to activate the light-emitting diode and generate a light signal. When any one of the R-phase voltage signal, S-phase voltage signal, and T-phase voltage signal is missing, the LED in the circuit is cut off and does not generate a light signal. The light signals generated by the light-emitting diodes are periodically identified to output low-level pulse signals or high-level pulse signals; When the servo driver detects a low-level pulse signal, it determines that the three-phase power supply is normal; when it detects a high-level pulse signal, it determines that the three-phase power supply is missing or abnormal.

[0044] A resistor divider network is used to acquire and step down the voltage signals of the R-phase, S-phase, and T-phase. For example, a series-connected resistor (such as R1 / R2, R5 / R6, R8 / R9) can step down the high-voltage AC signal of the three-phase power supply to a low-voltage signal suitable for subsequent circuit processing. The voltage of three-phase power is usually high, while the components in the subsequent circuit (such as LEDs) can only withstand lower voltages. By stepping down the voltage, the high-voltage signal can be converted into a low-voltage signal within a safe range, protecting the subsequent components from damage by the high voltage.

[0045] When there is a high-low relationship between the voltage signals of phases R, S, and T, the corresponding diodes (such as D1 / D2 / D3) conduct in the forward direction, causing the LEDs to conduct in the forward direction and generate light signals. For example, when the voltage of phase R is higher than that of phase S, D1 / D2 conducts, and current flows through the LEDs, causing them to emit light. When a voltage signal of any phase is missing, the corresponding diode is cut off, and the LEDs are also cut off, not generating light signals. Since there is a 120° phase difference between the three phases, under normal circumstances, at least two phases have an effective voltage difference at any given time. Utilizing the unidirectional conductivity of diodes, the LEDs are turned on or off according to the high-low relationship of the three-phase voltages, thereby converting the state of the three-phase voltages into light signals.

[0046] A phototransistor is used for optical coupling with an LED. The phototransistor turns on or off based on the received light signal. When the LED emits light periodically, the phototransistor periodically turns on / off, outputting a low-level pulse signal; when the LED is off, the phototransistor is off, outputting a high-level pulse signal. This optical signal transmission achieves isolation between high-voltage and low-voltage circuits, preventing electrical interference from the high-voltage side from affecting the low-voltage side circuitry. Simultaneously, the on / off state of the phototransistor converts the optical signal into an electrical signal, facilitating subsequent detection and analysis.

[0047] The servo driver detects the output pulse signals. A low-level pulse signal indicates normal three-phase power supply; a high-level pulse signal indicates a phase loss or abnormality. When the three-phase power supply is normal, the three-phase voltages alternate, causing the LEDs to conduct alternately in a time-division multiplexing manner, and the phototransistors to periodically turn on and off, outputting low-level pulse signals. When a phase is missing, the phase balance of the three-phase voltages is disrupted, the LEDs cannot conduct properly, the phototransistors turn off, and a high-level pulse signal is output. Therefore, the three-phase power supply status can be determined by detecting the high and low levels of the pulse signals.

[0048] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A three-phase AC phase loss detection circuit, characterized in that, include: The current-limiting sampling circuit, voltage clamping circuit, opto-isolation circuit, and status output circuit are connected in sequence. The current-limiting sampling circuit includes an R-phase sampling circuit, an S-phase sampling circuit, and a T-phase sampling circuit. The current-limiting sampling circuit is used to collect the R-phase voltage signal, the S-phase voltage signal, and the T-phase voltage signal. The voltage clamping circuit is used to manage the R-phase voltage signal, the S-phase voltage signal, and the T-phase voltage signal to send a drive signal to the opto-isolation circuit. The opto-isolation circuit is used to generate a corresponding optical signal according to the driving signal, and to generate a low-level pulse signal or a high-level pulse signal according to the output mode of the optical signal, wherein the low-level pulse signal represents the normal state of the three phases, and the high-level pulse signal represents the three-phase loss or abnormal state.

2. The three-phase AC phase loss detection circuit as described in claim 1, characterized in that, The R-phase sampling circuit includes a first resistor, a second resistor, and a first dual-channel bidirectional TVS diode array connected in series; the S-phase sampling circuit includes a fifth resistor, a sixth resistor, and a second dual-channel bidirectional TVS diode array connected in series; and the T-phase sampling circuit includes an eighth resistor, a ninth resistor, and a third dual-channel bidirectional TVS diode array connected in series. The first dual-channel bidirectional TVS diode array, the second dual-channel bidirectional TVS diode array, and the third dual-channel bidirectional TVS diode array each have a first pin, a second pin, and a third pin. The first pins of the first dual-channel bidirectional TVS diode array, the second dual-channel bidirectional TVS diode array, and the third dual-channel bidirectional TVS diode array are electrically connected to each other, the second pins are electrically connected to each other, and they are respectively electrically connected to the second resistor, the sixth resistor, and the ninth resistor through the third pin.

3. The three-phase AC phase loss detection circuit as described in claim 2, characterized in that, The voltage clamping circuit includes a filter capacitor, a Zener diode, and a third resistor; The two ends of the filter capacitor are electrically connected to the first pin and the second pin respectively, and the end of the filter capacitor connected to the second pin is electrically connected to the third resistor, and the end of the filter capacitor connected to the first pin is electrically connected to the opto-isolation circuit. The cathode of the Zener diode is electrically connected to the third resistor, and the anode of the Zener diode is electrically connected to the opto-isolation circuit.

4. The three-phase AC phase loss detection circuit as described in claim 3, characterized in that, The opto-isolation circuit includes a light-emitting diode and a phototransistor; The anode of the light-emitting diode is electrically connected to the anode of the Zener diode, and the cathode of the light-emitting diode is electrically connected to the filter capacitor; The base of the phototransistor is coupled to the light-emitting diode via optical signal coupling, the collector of the phototransistor is electrically connected to the status output circuit, and the emitter of the phototransistor is grounded.

5. The three-phase AC phase loss detection circuit as described in claim 4, characterized in that, The status output circuit includes a fourth resistor and a seventh resistor. The fourth resistor and the seventh resistor are respectively electrically connected to the collector of the phototransistor. The fourth resistor is electrically connected to a 5V voltage source, and the seventh resistor is electrically connected to the PH pin of the servo driver.

6. A method for detecting phase loss in three-phase alternating current, characterized in that, The three-phase AC phase loss detection circuit according to any one of claims 1-5 includes: The R-phase voltage signal, S-phase voltage signal, and T-phase voltage signal are acquired, and the R-phase voltage signal, S-phase voltage signal, and T-phase voltage signal are stepped down. When the R-phase voltage signal, S-phase voltage signal, and T-phase voltage signal have a high-low relationship that meets a predetermined standard, the light-emitting diode in the circuit is forward-biased to activate the light-emitting diode and generate a light signal. When any one of the R-phase voltage signal, S-phase voltage signal, and T-phase voltage signal is missing, the LED in the circuit is cut off and does not generate a light signal. The light signals generated by the light-emitting diodes are periodically identified to output low-level pulse signals or high-level pulse signals; When the servo driver detects a low-level pulse signal, it determines that the three-phase power supply is normal; when it detects a high-level pulse signal, it determines that the three-phase power supply is missing or abnormal.

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