Motor winding turn-to-turn short circuit and interphase short circuit fault diagnosis device and method

Abstract

The invention discloses a motor winding turn-to-turn short circuit and interphase short circuit fault diagnosis device and method. The device comprises a phase detection unit, an interphase short circuit detection unit, a winding short circuit sound-light alarm unit, an interphase short circuit positioning indication unit, a microcontroller and an execution driving unit. The method comprises the following steps: S1, signal acquisition; s2, winding short circuit detection and indication; s3, inter-phase short circuit judgment and indication; s4, fault types are distinguished; s5, performing protection action; and S6, fault recording. The device is simple in structure, low in cost, high in response speed and high in sensitivity, can clearly distinguish and indicate the types and phases of turn-to-turn short circuit and interphase short circuit faults, and achieves the rapid detection and protection of the early short circuit fault of the low-voltage motor winding.

Description

Technical Field

[0001] This invention relates to the field of motor fault diagnosis and protection technology, specifically to a device and method for detecting inter-turn short circuits and phase-to-phase short circuits in the stator windings of a low-voltage motor. Background Technology

[0002] As a core power unit, electric motors are widely used in many fields such as industrial manufacturing, transportation, construction engineering, and new energy power generation. The reliability and safety of their operation are of paramount importance. Inter-turn short circuits and phase-to-phase short circuits in the stator windings are common electrical faults in electric motors. If they are not detected and dealt with in a timely manner, they can easily lead to local overheating of the motor, accelerated deterioration of insulation performance, and in severe cases, even safety accidents such as fires or explosions.

[0003] Currently, the commonly used protection devices for motors mainly include thermal relays, fuses, and electromagnetic circuit breakers. These traditional protection methods are primarily designed for overload, locked rotor, and severe phase-to-phase short-circuit faults. Their operating characteristics are often based on current amplitude detection, which is severely insufficient for early, minor turn-to-turn short-circuit faults, resulting in a protection dead zone. Furthermore, these devices have a slow operating speed, typically requiring hundreds of milliseconds or even several seconds to activate, making it difficult to meet the requirement of rapid fault isolation.

[0004] To improve the detection capability of inter-turn short-circuit faults, various methods have been proposed in existing technologies, such as monitoring negative-sequence current, detecting the composite magnetic field at the stator ends, and analyzing the zero-sequence voltage component. However, these methods are more commonly used in high-voltage motor protection, and their promotion in the field of low-voltage motors faces significant obstacles: First, low-voltage motors are usually not equipped with dedicated current and voltage transformers, and installing such sensors is costly and complex; second, methods based on negative-sequence current are susceptible to grid asymmetry and external two-phase short-circuit interference, making setting difficult; third, some methods can only detect inter-turn short circuits and cannot simultaneously detect phase-to-phase short circuits and phase loss faults. Therefore, developing a general-purpose motor protection device and method that is simple in structure, low in cost, has a rapid response, and can simultaneously detect inter-turn and phase-to-phase short-circuit faults has significant engineering practical value. Summary of the Invention

[0005] To overcome the shortcomings of existing motor protection technologies, such as low sensitivity, slow speed, limited functionality, and high cost in diagnosing early winding short-circuit faults, this invention provides a device and method for diagnosing inter-turn and phase-to-phase short-circuit faults in motor windings based on reed switches and phase angle monitoring. This device eliminates the need for traditional current transformers, directly utilizing reed switches as current sensing and logic triggering elements. It diagnoses inter-turn short circuits by monitoring abnormal phase angles between the three-phase currents of the motor, and reliably identifies internal phase-to-phase short circuits using an innovative differential reed switch structure, thereby achieving fast, accurate, and low-cost multi-fault protection.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A fault diagnosis device for inter-turn short circuits and phase-to-phase short circuits in motor windings includes a phase detection unit, a phase-to-phase short circuit detection unit, a winding short circuit audible and visual alarm unit, a phase-to-phase short circuit location indicator unit, a microcontroller, and an execution drive unit.

[0008] The phase detection unit includes a first reed switch, a second reed switch, and a third reed switch. Each of the first, second, and third reed switches is provided with a single winding, namely a first winding on the first reed switch, a second winding on the second reed switch, and a third winding on the third reed switch. The first winding is connected in series with the motor A-phase input line, the second winding is connected in series with the motor B-phase input line, and the third winding is connected in series with the motor C-phase input line.

[0009] The phase-to-phase short-circuit detection unit includes a first differential reed switch, a second differential reed switch, and a third differential reed switch. Each of these switches has two windings: a fourth and a fifth winding on the first differential reed switch, a sixth and a seventh winding on the second differential reed switch, and an eighth and a ninth winding on the third differential reed switch. The fourth, sixth, and eighth windings are wound in reverse order of the fifth, seventh, and ninth windings. The fourth, sixth, and eighth windings are connected in series to the current loops on the A, B, and C phase power supply sides, respectively, while the fifth, seventh, and ninth windings are connected in series to the current loops on the neutral point side on the A, B, and C phases, respectively.

[0010] The input terminals of the microcontroller are electrically connected to the first reed switch, the second reed switch, the third reed switch, the first differential reed switch, the second differential reed switch, and the third differential reed switch, respectively.

[0011] The execution drive unit includes a drive mechanism, the input end of which is electrically connected to the output end of the microcontroller;

[0012] The winding short-circuit audible and visual alarm unit includes a winding short-circuit audible and visual alarm, which is connected to the output of the microcontroller via a drive mechanism.

[0013] The phase-to-phase short circuit positioning indicator unit includes a winding phase-to-phase short circuit indicator light group. The winding phase-to-phase short circuit indicator light group includes three indicator lights corresponding to phases A, B, and C of the motor, respectively. These indicator lights are connected to the corresponding first differential reed switch, second differential reed switch, and third differential reed switch through three independent indicator light driving units, or directly connected to the corresponding output terminal of the microcontroller.

[0014] As a preferred embodiment of the present invention, the parameters and specifications of the first reed switch, the second reed switch and the third reed switch are the same.

[0015] As a preferred technical solution of the present invention: the magnetic induction intensity generated by the two windings of the differential reed switch of the same phase is equal in magnitude and opposite in direction at its sensitive element, and the combined magnetic induction intensity is less than its action threshold. Only when a phase-to-phase short circuit occurs inside the motor, causing a fundamental change in the current relationship between the power supply side and the neutral point side of the fault phase, will the combined magnetic induction intensity of the differential reed switch of the corresponding phase exceed the threshold, so that its contacts can operate reliably.

[0016] As a preferred embodiment of the present invention: the microcontroller integrates the following:

[0017] Multiple timers are used to measure the time interval between the trigger signals of each reed switch;

[0018] The logic comparison unit is used to calculate the phase angle based on the time interval and compare it with a preset threshold.

[0019] The memory is used to store threshold parameters, delay logic, and fault records.

[0020] As a preferred technical solution of the present invention: the microcontroller has a built-in start-up lockout logic unit. At the moment the motor starts, the microcontroller initiates a short delay, during which the inter-turn short circuit judgment function is temporarily disabled.

[0021] As a preferred embodiment of the present invention, the indicator light driving unit includes:

[0022] A PNP transistor with its emitter connected to a +5V power supply;

[0023] A light-emitting diode, whose anode is connected to the collector of a corresponding PNP transistor through a current-limiting resistor, and whose cathode is grounded;

[0024] A base resistor is connected between the contact of the corresponding reed switch and the base of the corresponding PNP transistor;

[0025] A current-limiting resistor;

[0026] A pull-up resistor;

[0027] In each differential reed switch, one end of the contact is grounded, and the other end is connected to a +5V power supply through a corresponding pull-up resistor, and is also connected to the corresponding input pin and the corresponding base resistor of the microcontroller.

[0028] A method for diagnosing inter-turn short circuits and phase-to-phase short circuits in motor windings includes the following steps:

[0029] S1, Signal Acquisition:

[0030] The zero-crossing or amplitude trigger signal of the three-phase current of the motor is collected in real time through the first reed switch, the second reed switch and the third reed switch;

[0031] S2. Winding short circuit detection and indication:

[0032] The microcontroller calculates the phase angle between the currents of each phase of the motor based on the time difference of the trigger signals of the reed switches of each phase detection. If any phase angle deviates from the rated symmetry value of 120° by more than the first preset threshold and the duration meets the condition, it is determined that a winding short circuit has occurred. At this time, the winding short circuit audible and visual alarm unit starts to alarm.

[0033] S3. Phase-to-phase short circuit detection and indication:

[0034] The microcontroller monitors the contact states of the first differential reed switch, the second differential reed switch, and the third differential reed switch:

[0035] If the first differential reed switch and the second differential reed switch are closed at the same time, it is determined that a short circuit between phases A and B has occurred, and the corresponding indicator lights of phase A and phase B are controlled to light up.

[0036] If the second differential reed switch and the third differential reed switch are closed at the same time, it is determined that a short circuit between phases B and C has occurred, and the indicator lights corresponding to phases B and C are controlled to light up.

[0037] If the first differential reed switch and the third differential reed switch are closed at the same time, it is determined that an AC phase-to-phase short circuit has occurred, and the indicator lights corresponding to phase A and phase C are controlled to light up.

[0038] S4. Fault Type Differentiation:

[0039] If the winding short circuit audible and visual alarm unit alarms and no indicator light in the winding phase-to-phase short circuit indicator group is lit, the fault is determined to be an inter-turn short circuit. If the winding short circuit audible and visual alarm unit alarms and any indicator light in the winding phase-to-phase short circuit indicator group is lit, the fault is determined to be a phase-to-phase short circuit of the corresponding type.

[0040] S5, Protective Actions:

[0041] When a winding short circuit is detected, the microcontroller controls the execution drive unit to drive the contactor to open and cut off the motor power supply.

[0042] S6. Fault Record:

[0043] The microcontroller stores the time, type, and phase information of the fault in its memory.

[0044] As a preferred technical solution of the present invention: In step S1:

[0045] At the moment the motor starts, the microcontroller activates the start-up lockout logic unit, which initiates a short-delay lockout period during which the inter-turn short-circuit judgment logic is suspended to prevent malfunctions caused by the start-up current surge.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] 1. High sensitivity and speed: Directly monitors phase angle changes, and can generate significant detection signals for early winding inter-turn short circuits. The entire fault clearing time of the device can be controlled in milliseconds, achieving true fast protection.

[0048] 2. High reliability: It adopts a physically isolated reed switch as a sensor, which has strong anti-electromagnetic interference capability; the differential phase-to-phase short circuit detection principle fundamentally avoids false operation caused by external short circuits and power grid imbalance, resulting in high reliability.

[0049] 3. Multifunctional integration: One device can simultaneously detect and protect against inter-turn short circuits, phase-to-phase short circuits, and phase loss (considered as extreme phase angle anomalies), providing comprehensive functionality.

[0050] 4. Low cost and easy implementation: It eliminates the need for expensive current transformers, signal conditioning circuits, and analog-to-digital converters, resulting in extremely low core sensor costs. Its modular design allows for easy installation on existing motors, similar to replacing a junction box cover, leading to low retrofit costs and easy adoption.

[0051] 5. Compact structure: All components can be integrated into a compact module, which is easy to install.

[0052] 6. High versatility: The core principle of the device and method of this invention is based on the destruction of the electrical symmetry of the motor windings, which is applicable to all types of three-phase AC motors and is not limited to specific voltage or power levels, thus having wide applicability. Attached Figure Description

[0053] Figure 1 The electrical principle structure diagram for diagnosing inter-turn short circuits and phase-to-phase short circuits in motor windings;

[0054] Figure 2 Wiring diagram for motor protection;

[0055] Figure 3 This is a connection diagram of the winding phase-to-phase short-circuit indicator group and the differential reed switch;

[0056] Figure 4 This is a connection diagram for directly connecting the winding phase-to-phase short circuit indicator group to the microcontroller.

[0057] List of reference numerals in the attached diagram:

[0058] 1. First reed switch; 11. First winding; 2. Second reed switch; 21. Second winding; 3. Third reed switch; 31. Third winding; 4. First differential reed switch; 41. Fourth winding; 42. Fifth winding; 5. Second differential reed switch; 51. Sixth winding; 52. Seventh winding; 6. Third differential reed switch; 61. Eighth winding; 62. Ninth winding; 7. Microcontroller; 8. Drive mechanism; 9. Winding short circuit audible and visual alarm; 10. Winding phase-to-phase short circuit indicator light group. Detailed Implementation

[0059] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0060] like Figure 1-4 As shown, the present invention proposes a fault diagnosis device for inter-turn short circuit and phase-to-phase short circuit in motor windings, comprising a phase detection unit, a phase-to-phase short circuit detection unit, a winding short circuit audible and visual alarm unit, a phase-to-phase short circuit location indication unit, a microcontroller, and an execution drive unit.

[0061] The phase detection unit includes a first reed switch 1, a second reed switch 2, and a third reed switch 3. Each of the first reed switch 1, the second reed switch 2, and the third reed switch 3 is provided with a single winding, namely a first winding 11 provided on the first reed switch 1, a second winding 21 provided on the second reed switch 2, and a third winding 31 provided on the third reed switch 3. The first winding 11 is connected in series with the motor A-phase input line, the second winding 21 is connected in series with the motor B-phase input line, and the third winding 31 is connected in series with the motor C-phase input line.

[0062] The parameters and specifications of the first reed switch 1, the second reed switch 2 and the third reed switch 3 are the same. The operating ampere-turns of the reed switches are selected so that they can reliably engage when the motor phase current reaches N times (adjusted according to actual needs, such as 1.2 times) of the rated current. The normally open contacts of each switch are connected to the input port of the microcontroller 7.

[0063] The phase-to-phase short-circuit detection unit includes a first differential reed switch 4, a second differential reed switch 5, and a third differential reed switch 6. Each of the first, second, and third differential reed switches has a double winding: a fourth winding 41 and a fifth winding 42 on the first differential reed switch 4; a sixth winding 51 and a seventh winding 52 on the second differential reed switch 5; and an eighth winding 61 and a ninth winding 62 on the third differential reed switch 6. The fourth winding 41, sixth winding 51, and eighth winding 61 are wound in reverse order with the fifth winding 42, seventh winding 52, and ninth winding 62. The fourth winding 41, sixth winding 51, and eighth winding 61 are connected in series to the current loops on the A, B, and C phase power supply sides, respectively. The fifth winding 42, seventh winding 52, and ninth winding 62 are connected in series to the current loops on the neutral point side on the A, B, and C phases, respectively.

[0064] The winding connection method of the three differential detection reed switches ensures that when the motor is running normally, starting, operating asymmetrically externally, or short-circuited externally, the magnetic induction intensity generated by the two windings of the differential reed switch of the same phase is equal in magnitude and opposite in direction at its sensitive element, and the combined magnetic induction intensity is less than its action threshold. Only when a phase-to-phase short circuit occurs inside the motor, causing a fundamental change in the current relationship between the power supply side and the neutral point side of the fault phase, will the combined magnetic induction intensity of the differential reed switch of the corresponding phase exceed the threshold, allowing its contacts to operate reliably.

[0065] Taking the first differential reed switch 4 connected to phase A as an example, it includes two independent windings with opposite directions: a fourth winding 41 and a fifth winding 42. The fourth winding 41 is connected in series to the power supply side of phase A, and the fifth winding 42 is connected in series to the neutral point side of phase A. During normal operation, the currents flowing through the fourth winding 41 and the fifth winding 42 are equal in magnitude and in the same direction. However, because the windings are in opposite directions, the magnetic fields they generate cancel each other out at the reed switch's contact point, resulting in a zero combined magnetic induction intensity. Therefore, the first differential reed switch 4 remains normally open. Similarly, the structure and connection method of the second differential reed switch 5 and the third differential reed switch 6 are the same as those of the reed switch 4.

[0066] The input terminals of the microcontroller 7 are electrically connected to the first reed switch 1, the second reed switch 2, the third reed switch 3, the first differential reed switch 4, the second differential reed switch 5, and the third differential reed switch 6, respectively, and are used to receive switch trigger signals, calculate the phase angle between phase currents, and determine winding short-circuit faults.

[0067] The microcontroller 7 integrates the following:

[0068] Multiple timers are used to measure the time interval between the trigger signals of each reed switch;

[0069] The logic comparison unit is used to calculate the phase angle based on the time interval and compare it with a preset threshold.

[0070] The memory is used to store threshold parameters, delay logic, and fault records.

[0071] The microcontroller 7 has a built-in start-up lockout logic unit. At the moment the motor starts, the microcontroller 7 initiates a short delay, during which the inter-turn short circuit detection function is temporarily disabled.

[0072] The internal logic of the microcontroller 7 includes:

[0073] The phase angle calculation module calculates the phase difference between the currents of each phase by measuring the time interval between the closing of different reed switch contacts;

[0074] The fault diagnosis module compares the calculated phase angle with the rated value of 120°. If the deviation continues to exceed the preset threshold, it is determined that the winding is short-circuited.

[0075] Meanwhile, the fault diagnosis module continuously monitors the contact status of the differential reed switch. Once the contact is closed, it immediately determines that a phase-to-phase short circuit has occurred inside the motor; otherwise, it determines that an inter-turn short circuit has occurred.

[0076] Microcontroller 7 uses an embedded microcontroller, whose internal programming implements the following functions:

[0077] (1) Timer capture function: accurately records the moment when the three input pins of the first reed switch 1, the second reed switch 2 and the third reed switch 3 change (close the contact).

[0078] (2) Phase angle calculation: Let the time difference between the closing of the first reed switch 1 and the second reed switch 2 be . Then the phase difference between the currents in phases A and B is:

[0079] ;

[0080] in, This is the operating frequency of the motor; similarly, it can be calculated. and .

[0081] (3) Winding short-circuit fault judgment: Set the phase angle fault threshold to 120°±10°. If multiple consecutive cycles detect... , , If any value continuously exceeds this range, a winding short circuit is determined to have occurred. The microcontroller 7 sets the winding short circuit flag and drives the output pin to output a high level, illuminating the winding phase-to-phase short circuit indicator group 10 and triggering the winding short circuit audible and visual alarm 9. Simultaneously, the microcontroller 7 continuously monitors the contact status (input pin level) of the three differential reed switches.

[0082] (4) Phase-to-phase short circuit detection: The microcontroller continuously monitors the status of the three contacts on the first differential reed switch 4, the second differential reed switch 5, and the third differential reed switch 6. If any two contacts are detected to be closed simultaneously, a phase-to-phase short circuit is determined. The specific type is determined based on the combination:

[0083] If the first differential reed switch 4 and the second differential reed switch 5 are closed, there will be a short circuit between phases A and B, and the short circuit indicator lights of phases A and B will be lit through the circuit.

[0084] If the second differential reed switch 5 and the third differential reed switch 6 are closed, there will be a short circuit between phases B and C, and the short circuit indicator lights of phases B and C will be lit through the circuit.

[0085] If the first differential reed switch 4 and the third differential reed switch 6 are closed, there will be a short circuit between AC phases, and the short circuit indicator lights of phases A and C will be lit through the circuit.

[0086] (5) Fault type differentiation:

[0087] If the winding short circuit audible and visual alarm 9 sounds, and the winding phase-to-phase short circuit indicator group 10 does not light up, it is determined to be an inter-turn short circuit.

[0088] If the winding short circuit audible and visual alarm 9 sounds, and any two of the winding phase-to-phase short circuit indicator lights in the winding phase-to-phase short circuit indicator group 10 are lit, then it is determined to be a phase-to-phase short circuit, and the specific fault location is indicated by the lit short circuit indicator lights.

[0089] The execution drive unit includes a drive mechanism 8, the input end of which is electrically connected to the output end of the microcontroller 7, and is used to drive the motor main circuit contactor to operate according to the fault command.

[0090] The drive mechanism 8 is a small intermediate relay KA. When the microcontroller 7 detects a fault, its output pin outputs a high level, energizing the coil of relay KA through the circuit. The normally closed contact of KA is connected in series to the coil circuit of the motor main circuit contactor KM, causing KM to trip instantaneously.

[0091] The winding short circuit audible and visual alarm unit includes a winding short circuit audible and visual alarm 9, which is connected to the output terminal of the microcontroller 7 via a drive mechanism 8, and is used to light up an indicator light and issue an alarm when a winding short circuit is detected.

[0092] The phase-to-phase short circuit positioning indicator unit includes a winding phase-to-phase short circuit indicator light group 10. The winding phase-to-phase short circuit indicator light group 10 includes three indicator lights corresponding to phases A, B, and C of the motor, respectively. These indicator lights are connected to the corresponding first differential reed switch 4, second differential reed switch 5, and third differential reed switch 6 through three independent indicator light driving units, or directly connected to the corresponding output terminals of the microcontroller 7.

[0093] The indicator light driving unit includes:

[0094] A PNP transistor with its emitter connected to a +5V power supply;

[0095] A light-emitting diode, whose anode is connected to the collector of a corresponding PNP transistor through a current-limiting resistor, and whose cathode is grounded;

[0096] A base resistor is connected between the contact of the corresponding reed switch and the base of the corresponding PNP transistor;

[0097] A current-limiting resistor;

[0098] A pull-up resistor;

[0099] In each differential reed switch, one end of the contact is grounded, and the other end is connected to a +5V power supply through a corresponding pull-up resistor, and is also connected to the corresponding input pin and the corresponding base resistor of the microcontroller 7.

[0100] The differential reed switch controls the base potential of the PNP transistor to drive the corresponding LED to light up. Even if the microcontroller 7 fails, the short-circuit indicator light can still be lit to achieve fault warning. The second solution is to connect the winding phase-to-phase short-circuit indicator light 10 to the three output terminals of the microcontroller 7 respectively. When the microcontroller 7 detects the low-level signal of the differential reed switch, it outputs a high level on the corresponding pin to drive the corresponding short-circuit indicator light.

[0101] The present invention proposes a method for diagnosing inter-turn short circuits and phase-to-phase short circuits in motor windings, comprising the following steps:

[0102] S1, Signal Acquisition:

[0103] The zero-crossing or amplitude trigger signal of the three-phase current of the motor is collected in real time through the first reed switch 1, the second reed switch 2 and the third reed switch 3.

[0104] S2. Winding short circuit detection and indication:

[0105] The microcontroller 7 calculates the phase angle between the currents of each phase of the motor based on the time difference of the trigger signals of the reed switches of each phase detection. If any phase angle deviates from the rated symmetry value of 120° by more than the first preset threshold and the duration meets the condition, it is determined that a winding short circuit has occurred. At this time, the winding short circuit audible and visual alarm unit starts to alarm.

[0106] S3. Phase-to-phase short circuit detection and indication:

[0107] The microcontroller 7 monitors the contact states of the first differential reed switch 4, the second differential reed switch 5, and the third differential reed switch 6:

[0108] If the first differential reed switch 4 and the second differential reed switch 5 are closed at the same time, it is determined that a short circuit between phases A and B has occurred, and the indicator lights corresponding to phases A and B are controlled to light up.

[0109] If the second differential reed switch 5 and the third differential reed switch 6 are closed at the same time, it is determined that a short circuit between phases B and C has occurred, and the indicator lights corresponding to phases B and C are controlled to light up.

[0110] If the first differential reed switch 4 and the third differential reed switch 6 are closed at the same time, it is determined that an AC phase-to-phase short circuit has occurred, and the indicator lights corresponding to phase A and phase C are controlled to light up.

[0111] S4. Fault Type Differentiation:

[0112] If no indicator light in the winding phase-to-phase short circuit indicator light group 10 is lit when the winding short circuit audible and visual alarm unit alarms, the fault is determined to be an inter-turn short circuit. If any indicator light in the winding phase-to-phase short circuit indicator light group 10 is lit at the same time as the winding short circuit audible and visual alarm unit alarms, the fault is determined to be a phase-to-phase short circuit of the corresponding type.

[0113] S5, Protective Actions:

[0114] When a winding short circuit is detected, the microcontroller 7 controls the execution drive unit to drive the contactor to open and cut off the motor power supply;

[0115] S6. Fault Record:

[0116] The microcontroller 7 stores the time, type, and phase information of the fault in its memory.

[0117] In step S1: At the moment the motor starts, the microcontroller 7 activates the start-up lockout logic unit to initiate a short-term delay lockout period, during which the inter-turn short-circuit judgment logic is suspended to prevent malfunctions caused by the start-up current surge.

[0118] The specific process is as follows:

[0119] (1) Initialization and start-up interlock: When the device is powered on, the microcontroller 7 is initialized. When a motor start signal is received (or the current is detected to increase from zero to one), a delay timer is started (set according to the motor start time, for example, 0.5s). During this period, the phase angle fault judgment logic is shielded to prevent false judgment caused by the start-up inrush current.

[0120] (2) Real-time monitoring:

[0121] Phase angle monitoring: The microcontroller 7 captures the operating edges of the first reed switch 1, the second reed switch 2, and the third reed switch 3 in real time. When a short circuit fault occurs in the motor windings, including inter-turn short circuit faults and phase-to-phase short circuit faults, the equivalent impedance of the faulty phase changes, which will lead to an imbalance in the three-phase winding impedance. This will cause φ_AB, φ_CA, or φ_BC to deviate from the normal value. The microcontroller 7 calculates and finds that it continuously exceeds the threshold range and the duration exceeds the set value (e.g., 4 power cycles, to avoid false operation).

[0122] (2) Phase-to-phase short circuit monitoring: The microcontroller 7 continuously reads the status of the first reed switch 1, the second reed switch 2, and the third reed switch 3. Assuming the fault is an inter-turn short circuit, the first reed switch 1, the second reed switch 2, and the third reed switch 3 all remain in the open state.

[0123] Fault diagnosis, indication and action:

[0124] 1) When the microcontroller 7 determines that a winding short circuit has occurred, the short circuit indicator light is lit and the winding short circuit audible and visual alarm 9 is activated.

[0125] 2) The microcontroller 7 detected that the first differential reed switch 4, the second differential reed switch 5, and the third differential reed switch 6 were not activated.

[0126] 3) Comprehensive judgment: Since the winding short circuit fault alarm is triggered and no short circuit indicator light is lit, the microcontroller 7 determines that it is "inter-turn short circuit".

[0127] 4) The microcontroller 7 immediately drives the relay KA to trip, causing the main contact of the contactor KM to trip and the motor to be de-energized.

[0128] 5) The fault information "inter-turn short circuit" is recorded in the memory.

[0129] Another scenario: If an AC phase-to-phase short circuit occurs inside the motor:

[0130] 1) The microcontroller 7 determines that a winding short circuit has occurred by monitoring the phase angle, lights up the short circuit indicator light, and triggers the winding short circuit audible and visual alarm 9.

[0131] 2) The microcontroller 7 detects that the first differential reed switch 4 and the third differential reed switch 6 are closed at the same time.

[0132] 3) When the first differential reed switch 4 and the third differential reed switch 6 are closed, they respectively output low level to drive the short circuit indicator lights of phase A and phase C. The microcontroller 7 determines that there is a short circuit between phases A and C.

[0133] 4) Comprehensive judgment: When the short circuit indicator lights of phase A and phase C are lit at the same time, it indicates "short circuit between phases A and C".

[0134] 5) The microcontroller 7 drives the relay KA to trip.

[0135] 6) The fault information "AC phase-to-phase short circuit" was recorded.

[0136] Fault logging: The microcontroller 7 stores information such as fault type and occurrence time in its internal EEPROM for easy troubleshooting and analysis.

[0137] The scope of protection of this invention is not limited to the above embodiments. Any equivalent substitutions or modifications made according to the technical solution of this invention, such as using other types of magnetic latching relays or Hall switch arrays to achieve similar functions, replacing the microcontroller with a programmable logic device (PLD, FPGA), or applying diagnostic algorithms to other types of motors such as doubly-fed motors and permanent magnet synchronous motors, should be covered within the scope of the claims of this invention.

Claims

1. A fault diagnosis device for inter-turn short circuit and phase-to-phase short circuit in motor windings, characterized in that, It includes a phase detection unit, a phase-to-phase short circuit detection unit, a winding short circuit audible and visual alarm unit, a phase-to-phase short circuit location indicator unit, a microcontroller, and an execution drive unit. The phase detection unit includes a first reed switch (1), a second reed switch (2), and a third reed switch (3). The first reed switch (1), the second reed switch (2), and the third reed switch (3) are each provided with a single winding, namely a first winding (11) provided on the first reed switch (1), a second winding (21) provided on the second reed switch (2), and a third winding (31) provided on the third reed switch (3). The first winding (11) is connected in series with the motor A-phase input line, the second winding (21) is connected in series with the motor B-phase input line, and the third winding (31) is connected in series with the motor C-phase input line. The phase-to-phase short-circuit detection unit includes a first differential reed switch (4), a second differential reed switch (5), and a third differential reed switch (6). The first differential reed switch (4), the second differential reed switch (5), and the third differential reed switch (6) are each equipped with a double winding: a fourth winding (41) and a fifth winding (42) on the first differential reed switch (4), a sixth winding (51) and a seventh winding (52) on the second differential reed switch (5), and a third winding on the third differential reed switch (6). (6) The eighth winding (61) and the ninth winding (62) on the fourth winding (41), the sixth winding (51) and the eighth winding (61) and the fifth winding (42), the seventh winding (52) and the ninth winding (62) are wound in reverse; wherein the fourth winding (41), the sixth winding (51) and the eighth winding (61) are connected in series to the current loops of the A phase, B phase and C phase power supply side respectively, and the fifth winding (42), the seventh winding (52) and the ninth winding (62) are connected in series to the current loops of the A phase, B phase and C phase on the neutral point side respectively; The input terminals of the microcontroller (7) are electrically connected to the first reed switch (1), the second reed switch (2), the third reed switch (3), the first differential reed switch (4), the second differential reed switch (5), and the third differential reed switch (6), respectively. The execution drive unit includes a drive mechanism (8), the input end of which is electrically connected to the output end of the microcontroller (7); The winding short circuit audible and visual alarm unit includes a winding short circuit audible and visual alarm (9), which is connected to the output terminal of the microcontroller (7) via a drive mechanism (8). The phase-to-phase short circuit positioning indicator unit includes a winding phase-to-phase short circuit indicator light group (10). The winding phase-to-phase short circuit indicator light group (10) includes three indicator lights corresponding to phases A, B and C of the motor, respectively. They are connected to the corresponding first differential reed switch (4), second differential reed switch (5) and third differential reed switch (6) respectively through three independent indicator light driving units, or directly connected to the corresponding output terminal of the microcontroller (7).

2. The fault diagnosis device for inter-turn short circuit and phase-to-phase short circuit in motor windings according to claim 1, characterized in that, The parameters and specifications of the first reed switch (1), the second reed switch (2) and the third reed switch (3) are the same.

3. The fault diagnosis device for inter-turn short circuit and phase-to-phase short circuit in motor windings according to claim 1, characterized in that, The magnetic induction intensity generated by the two windings of the differential reed switch in the same phase is equal in magnitude and opposite in direction at its sensitive element. The combined magnetic induction intensity is less than its action threshold. Only when a phase-to-phase short circuit occurs inside the motor, causing a fundamental change in the current relationship between the power supply side and the neutral point side of the faulty phase, will the combined magnetic induction intensity of the differential reed switch of the corresponding phase exceed the threshold, enabling its contacts to operate reliably.

4. The fault diagnosis device for inter-turn short circuit and phase-to-phase short circuit in motor windings according to claim 1, characterized in that, The microcontroller (7) integrates the following: Multiple timers are used to measure the time interval between the trigger signals of each reed switch; The logic comparison unit is used to calculate the phase angle based on the time interval and compare it with a preset threshold. The memory is used to store threshold parameters, delay logic, and fault records.

5. The fault diagnosis device for inter-turn short circuit and phase-to-phase short circuit in motor windings according to claim 1, characterized in that, The microcontroller (7) has a built-in start-up lockout logic unit. At the moment the motor starts, the microcontroller (7) initiates a short delay, during which the inter-turn short circuit judgment function is temporarily disabled.

6. The fault diagnosis device for inter-turn short circuit and phase-to-phase short circuit in motor windings according to claim 1, characterized in that, The indicator light driving unit includes: A PNP transistor with its emitter connected to a +5V power supply; A light-emitting diode, whose anode is connected to the collector of a corresponding PNP transistor through a current-limiting resistor, and whose cathode is grounded; A base resistor is connected between the contact of the corresponding reed switch and the base of the corresponding PNP transistor; A current-limiting resistor; A pull-up resistor; In this case, one end of the contact of each differential reed switch is grounded, and the other end is connected to the +5V power supply through the corresponding pull-up resistor, and is also connected to the corresponding input pin and the corresponding base resistor of the microcontroller (7).

7. A method for diagnosing inter-turn short circuits and phase-to-phase short circuits in motor windings according to any one of claims 1-6, characterized in that, Includes the following steps: S1, Signal Acquisition: The zero-crossing or amplitude trigger signal of the three-phase current of the motor is collected in real time through the first reed switch (1), the second reed switch (2) and the third reed switch (3); S2. Winding short circuit detection and indication: The microcontroller (7) calculates the phase angle between the currents of each phase of the motor based on the time difference of the trigger signals of the reed switches of each phase detection. If any phase angle deviates from the rated symmetry value of 120° by more than the first preset threshold and the duration meets the condition, it is determined that a winding short circuit has occurred. At this time, the winding short circuit sound and light alarm unit starts to alarm. S3. Phase-to-phase short circuit detection and indication: The microcontroller (7) monitors the contact status of the first differential reed switch (4), the second differential reed switch (5), and the third differential reed switch (6): If the first differential reed switch (4) and the second differential reed switch (5) are closed at the same time, it is determined that a short circuit between phases A and B has occurred, and the indicator lights corresponding to phases A and B are controlled to light up. If the second differential reed switch (5) and the third differential reed switch (6) are closed at the same time, it is determined that a short circuit between phases B and C has occurred, and the indicator lights corresponding to phases B and C are controlled to light up. If the first differential reed switch (4) and the third differential reed switch (6) are closed at the same time, it is determined that a short circuit between AC phases has occurred, and the indicator lights corresponding to phase A and phase C are controlled to light up. S4. Fault Type Differentiation: If no indicator light in the winding phase-to-phase short circuit indicator light group (10) is lit when the winding short circuit audible and visual alarm unit alarms, the fault is determined to be an inter-turn short circuit. If any indicator light in the winding phase-to-phase short circuit indicator light group (10) is lit when the winding short circuit audible and visual alarm unit alarms, the fault is determined to be a phase-to-phase short circuit of the corresponding type. S5, Protective Actions: When a winding short circuit is detected, the microcontroller (7) controls the execution drive unit to drive the contactor to open and cut off the motor power supply; S6. Fault Record: The microcontroller (7) stores the time, type, and phase information of the fault in its memory.

8. The method for diagnosing inter-turn short circuits and phase-to-phase short circuits in motor windings according to claim 7, characterized in that, In step S1: At the moment the motor starts, the microcontroller (7) starts the start-up lockout logic unit, which initiates a short-term delay lockout period. During this period, the inter-turn short circuit judgment logic is suspended to prevent malfunction caused by the start-up current surge.

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