Device and method for detecting inter-phase short circuit fault of separately excited three-phase alternating current motor

Abstract

The invention provides a device and a method for detecting an inter-phase short-circuit fault of a separately excited three-phase alternating current motor. The device comprises an impedance device, an excitation winding, a magnet, a detection winding and an identification circuit, an electrical wiring terminal of a to-be-detected motor is connected with the impedance device, the impedance device is connected with the excitation winding, the excitation winding and the detection winding are installed on the magnet, and the detection winding is connected with the identification circuit. Wherein the impedance device is used for limiting the current of the excitation winding; the excitation winding is used for generating a magnetic field in the magnet; the detection winding is used for detecting a magnetic field in the magnet; and the identification circuit identifies whether an interphase short circuit fault occurs according to the voltage difference generated by the detection winding. According to the structure, detection and identification can be carried out under the isolated operation condition of a generator with a motor and a power loop disconnected, and full-condition protection is realized; detection and identification can be carried out only through the voltage of the electrical wiring terminal of the motor, and no extra working power supply is needed. The method is completely realized by a hardware structure and has higher reliability.

Description

Technical Field

[0001] The present application relates to the field of electrical engineering, and in particular to a detection device and method for a phase-to-phase short circuit fault of a separately excited three-phase AC motor. Background Art

[0002] Separately excited three-phase AC motors include permanent magnet excited three-phase AC motors and electrically excited three-phase AC motors. Such motors are widely used due to their advantages in efficiency, power factor and mechanical properties. Separately excited three-phase AC motors usually generate magnetic poles on the rotor. The electrical terminals of the motor are connected to a symmetrical three-phase AC voltage, which forms a rotating magnetic field inside the motor through the stator winding. The rotor with magnetic poles rotates under the action of the rotating magnetic field to achieve mechanical energy output, which is called the motor operating condition. On the contrary, when the rotor of the separately excited three-phase AC motor is dragged to rotate and the magnetic poles cannot or cannot be cancelled, the rotor with magnetic poles rotates inside the motor, and the periodically changing magnetic field induces a symmetrical three-phase AC voltage through the stator winding, and the mechanical energy is converted into electrical energy, which is called the generator operating condition. When the separately excited three-phase AC motor is in the generator operating condition and is disconnected from the external circuit, it is called the generator isolated operating condition. For simplicity, separately excited three-phase AC motors are uniformly referred to as motors in this article.

[0003] The motor stator winding may have a phase-to-phase short circuit fault. After the phase-to-phase short circuit fault occurs, the motor will have a voltage and current that exceed the rated range. Continuing to run will cause the motor temperature to rise and the insulation material performance to deteriorate, further exacerbating the spread of the fault. In extreme cases, there is a risk of fire. Therefore, it is necessary to set up the detection and identification of the phase-to-phase short circuit fault of the motor under all operating conditions, including the motor operating conditions and the generator operating conditions, especially the generator isolated operating conditions. When the motor has a phase-to-phase short circuit fault in the motor operating condition, the voltage of the motor's electrical terminal will change and show characteristics, among which the notable characteristics are: three-phase voltage vector, the short-circuited phase voltage is zero; the other two phase voltages are opposite in phase and have the same amplitude. When the motor has a phase-to-phase short circuit fault in the generator operating condition, the voltage of the motor's electrical terminal will change and show characteristics, among which the notable characteristics are: three-phase voltage vector, the short-circuited phase voltage is zero; the other two phase voltages are opposite in phase and have the same amplitude, and the voltage waveform is distorted, as shown in Figure 2. FIG2(a) shows the short-circuited phase-to-phase voltage, and FIG2(b) and FIG2(c) show the two non-short-circuited phase-to-phase voltages.

[0004] It can be seen that when the motor has a phase-to-phase short circuit fault in the motor operating condition and the generator operating condition, the voltage characteristics of the motor's electrical terminal are similar: the short-circuited phase voltage in the three-phase voltage vector is zero; the other two phase voltages are opposite in phase and have the same amplitude. The current common motor phase-to-phase short circuit fault detection and identification methods: Method 1 is to install a current sensor in the motor's power supply circuit, and the control system detects the negative sequence current component of the circuit for identification; Method 2 is to install an overcurrent protection device in the motor's power supply circuit, and the protection action occurs when the circuit current reaches the threshold; Method 3 is to use a voltage sensor to detect the voltage of the motor's electrical terminal, and then use an electronic circuit to process the voltage signal and transmit it to the control system, and then use software in the control system to identify the voltage waveform according to the voltage characteristics of the motor phase-to-phase short circuit fault. Disadvantages of the existing technology: Methods 1 and 2 cannot detect and identify when the motor is disconnected from the power supply circuit, and cannot protect when the generator is in isolated operation; Method 3 requires the configuration of additional working power, voltage sensor and control system, and the structure is complex; the control system cannot identify the fault when it is abnormal, and there is a fault identification loophole. Summary of the invention

[0005] The purpose of the present application is to provide a detection device and method for interphase short-circuit faults of a separately excited three-phase AC motor, so as to realize the detection and identification of interphase short-circuit faults under all operating conditions without relying on a control system.

[0006] To achieve the above-mentioned purpose, the detection device for phase-to-phase short-circuit fault of a separately excited three-phase AC motor provided in the present application specifically comprises an impedance device, an excitation winding, a magnet, a detection winding and an identification circuit; the electrical terminal of the motor to be detected is connected to the impedance device, the impedance device is connected to the excitation winding, the excitation winding and the detection winding are installed on the magnet, and the detection winding is connected to the identification circuit; wherein the impedance device is used to limit the current of the excitation winding; the excitation winding is used to generate a magnetic field in the magnet; the detection winding is used to detect the magnetic field in the magnet; and the identification circuit identifies whether a phase-to-phase short-circuit fault occurs based on the voltage difference generated by the detection winding.

[0007] In the above-mentioned detection device for interphase short-circuit fault of separately excited three-phase AC motor, optionally, the impedance device includes a first impedance device, a second impedance device and a third impedance device; the excitation winding includes a first excitation winding, a second excitation winding and a third excitation winding; wherein, one end of the first impedance device, the second impedance device and the third impedance device are respectively connected to the first terminal, the second terminal and the third terminal of the electrical connection of the motor, and the other end is respectively connected to the head end of the first excitation winding, the second excitation winding and the third excitation winding.

[0008] In the above-mentioned detection device for phase-to-phase short-circuit fault of the separately excited three-phase AC motor, optionally, the device further includes: when the excitation winding connection mode is star connection, the head ends of the first excitation winding, the second excitation winding and the third excitation winding are respectively connected to the first impedance device, the second impedance device and the third impedance device, and the ends of the first excitation winding, the second excitation winding and the third excitation winding are connected to each other.

[0009] In the above-mentioned detection device for interphase short-circuit fault of separately excited three-phase AC motor, optionally, the device further includes: when the excitation winding connection mode is delta connection, the first ends of the first excitation winding, the second excitation winding and the third excitation winding are respectively connected to the first impedance device, the second impedance device and the third impedance device; the end of the first excitation winding is connected to the beginning of the second excitation winding, the end of the second excitation winding is connected to the beginning of the third excitation winding, and the end of the third excitation winding is connected to the beginning of the first excitation winding.

[0010] In the above-mentioned detection device for interphase short circuit fault of separately excited three-phase AC motor, optionally, the identification circuit includes a first rectifier unit, a second rectifier unit, a first capacitor, a second capacitor, a first resistor, a second resistor and an indicator device; wherein, the first and second ends of the first detection winding are connected to the first capacitor through the first rectifier unit, and the first and second ends of the second detection winding are connected to the capacitor through the second rectifier unit; the first resistor is connected in parallel with the first capacitor, and the second resistor is connected in parallel with the second capacitor; when the negative electrode of the first capacitor is connected to the negative electrode of the second capacitor, the two ends of the indicator device are respectively connected to the positive electrode of the first capacitor and the positive electrode of the second capacitor; when the positive electrode of the first capacitor is connected to the positive electrode of the second capacitor, the two ends of the indicator device are respectively connected to the negative electrode of the first capacitor and the negative electrode of the second capacitor. In the above-mentioned detection device for interphase short-circuit fault of separately excited three-phase AC motor, optionally, the first rectifier unit includes a first diode, a second diode, a third diode and a fourth diode; the second rectifier unit includes a fifth diode, a sixth diode, a seventh diode and an eighth diode; the head end of the first detection winding is connected to the positive electrode of the first diode and the negative electrode of the third diode; the end of the first detection winding is connected to the positive electrode of the second diode and the negative electrode of the fourth diode; the negative electrode of the first diode and the negative electrode of the second diode are connected to the positive electrode of the first capacitor; the positive electrode of the third diode and the positive electrode of the fourth diode are connected to the negative electrode of the first capacitor; the head end of the second detection winding is connected to the positive electrode of the fifth diode and the negative electrode of the seventh diode; the end of the second detection winding is connected to the positive electrode of the sixth diode and the negative electrode of the eighth diode; the negative electrode of the fifth diode and the negative electrode of the sixth diode are connected to the positive electrode of the second capacitor; the positive electrode of the seventh diode and the positive electrode of the eighth diode are connected to the negative electrode of the second capacitor.

[0011] In the above-mentioned detection device for interphase short circuit fault of separately excited three-phase AC motor, optionally, the indicating device is a device without positive or negative polarity.

[0012] In the above-mentioned detection device for interphase short-circuit fault of separately excited three-phase AC motor, optionally, the magnet is a solid structure; wherein the first excitation winding, the second excitation winding and the third excitation winding are symmetrically installed; the first detection winding and the second detection winding are installed at positions with equal radial distances and different radial angles; the first detection winding and the second detection winding have equal numbers of turns and the same enclosed area.

[0013] In the above-mentioned detection device for interphase short-circuit fault of separately excited three-phase AC motor, optionally, the first excitation winding, the second excitation winding and the third excitation winding are symmetrically installed, including: the first excitation winding, the second excitation winding and the third excitation winding have equal number of turns, the same enclosed area, and are spatially distributed with an electrical angle difference of 120°.

[0014] The present application also provides a detection method for a detection device for the above-mentioned separately excited three-phase AC motor interphase short-circuit fault, the method comprising: using the AC voltage of the motor to form a periodically changing magnetic field in a magnet through an excitation winding; obtaining a periodically changing induced potential generated by the magnetic field change at the location through detection windings at different positions in the magnet; and identifying the interphase short-circuit fault condition of the separately excited three-phase AC motor by comparing the induced potential change range of the detection windings at different positions.

[0015] The beneficial technical effects of the present application are: detection and identification can be performed under the isolated operating condition of the generator with the motor disconnected from the power supply circuit, thereby realizing full operating condition protection; detection and identification can be performed with only the voltage of the motor's electrical terminal, without the need for an additional working power supply, and with a simple structure; it is completely implemented by a hardware structure, without the need for software and its operating carrier, and has higher reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present application, constitute a part of the present application, and do not constitute a limitation of the present application. In the drawings:

[0017] Figure 1 It is a structural schematic diagram of a detection device for interphase short circuit fault of a separately excited three-phase AC motor;

[0018] FIG2(a) is a schematic diagram of the short-circuited phase-to-phase voltage waveform when a motor has a phase-to-phase short-circuit fault;

[0019] FIG2(b) and FIG2(c) are schematic diagrams of two non-short-circuited phase-to-phase voltage waveforms when a motor phase-to-phase short-circuit fault occurs;

[0020] FIG3( a ) is a schematic diagram of the connection mode of the excitation winding using star connection;

[0021] FIG3( b ) is a schematic diagram of the connection mode of the excitation winding using a delta connection;

[0022] FIG4( a ) is a connection diagram of the identification circuit of the indicator device at the positive electrode;

[0023] FIG4( b ) is a connection diagram of the identification circuit of the indicator device at the negative pole;

[0024] Figure 5(a) shows the motor AB is short-circuited and U BC Positive U CA is negative, the current relationship and magnetic field distribution of the star-connected excitation winding;

[0025] Figure 5(b) shows that the motor AB is short-circuited and U BC Negative U CA is positive, the current relationship and magnetic field distribution of the star-connected excitation winding;

[0026] Figure 5(c) shows that the motor AB is short-circuited and U BC Positive U CA is negative, current relationship and magnetic field distribution of delta-connected excitation winding;

[0027] Figure 5(d) shows that the motor AB is short-circuited and U BC Negative U CA is positive, current relationship and magnetic field distribution of delta-connected excitation winding;

[0028] Figure 6(a) shows the motor BC short circuit, U CA Positive U AB is negative, current relationship and magnetic field distribution of the excitation winding in star connection;

[0029] Figure 6(b) shows the motor BC short circuit, U CA Negative U AB is positive, current relationship and magnetic field distribution of the excitation winding in star connection;

[0030] Figure 6(c) shows the motor BC short circuit and U CA Positive U AB is negative, the current relationship and magnetic field distribution of the excitation winding in delta connection;

[0031] Figure 6(d) shows the motor BC short circuit, U CA Negative U AB is positive, the current relationship and magnetic field distribution of the excitation winding in delta connection;

[0032] Figure 7(a) shows the motor CA short circuit and U AB Positive U BC is negative, current relationship and magnetic field distribution of the excitation winding in star connection;

[0033] Figure 7(b) shows the motor CA short circuit and U AB Negative UBC is positive, current relationship and magnetic field distribution of the excitation winding in star connection;

[0034] Figure 7(c) shows the motor CA short circuit and U AB Positive U BC is negative, the current relationship and magnetic field distribution of the excitation winding in delta connection;

[0035] Figure 7(d) shows the motor CA short circuit and U AB Negative U BC is positive, the current relationship and magnetic field distribution of the delta-connected excitation winding. DETAILED DESCRIPTION

[0036] The following will describe the implementation methods of the present application in detail in conjunction with the accompanying drawings and embodiments, so that the implementation process of how the present application applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that as long as there is no conflict, the various embodiments in the present application and the various features in the embodiments can be combined with each other, and the technical solutions formed are all within the protection scope of the present application.

[0037] In addition, the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be performed in an order different from that shown here.

[0038] The detection device for phase-to-phase short-circuit fault of a separately excited three-phase AC motor provided in the present application specifically comprises an impedance device, an excitation winding, a magnet, a detection winding and an identification circuit; the electrical terminal of the motor to be detected is connected to the impedance device, the impedance device is connected to the excitation winding, the excitation winding and the detection winding are mounted on the magnet, and the detection winding is connected to the identification circuit; wherein the impedance device is used to limit the current of the excitation winding; the excitation winding is used to generate a magnetic field in the magnet; the detection winding is used to detect the magnetic field in the magnet; and the identification circuit identifies whether a phase-to-phase short-circuit fault occurs based on the voltage difference generated by the detection winding.

[0039] Specifically, in the above embodiment, the impedance device includes a first impedance device, a second impedance device and a third impedance device; the excitation winding includes a first excitation winding, a second excitation winding and a third excitation winding; wherein, one end of the first impedance device, the second impedance device and the third impedance device are respectively connected to the first terminal, the second terminal and the third terminal of the electrical connection of the motor, and the other end is respectively connected to the head end of the first excitation winding, the second excitation winding and the third excitation winding.

[0040] For details, please refer to Figure 1 to Figure 4(b)As shown, the impedance device includes: a first impedance device Z1, a second impedance device Z2 and a third impedance device Z3; the magnet includes: a magnet G; the excitation winding includes: a first excitation winding Q1, a second excitation winding Q2 and a third excitation winding Q3; the detection winding includes: a first detection winding K1 and a second detection winding K2; the identification circuit includes: a first rectifier unit RT1 and a second rectifier unit RT2, a first capacitor C1 and a second capacitor C2, a first resistor R1 and a second resistor R2, and an indicator device IDX. The rectifier unit RT1 includes a first diode D11, a second diode D12, a third diode D13 and a fourth diode D14, and the rectifier unit RT2 includes a fifth diode D21, a sixth diode D22, a seventh diode D23 and an eighth diode D24. The indicator device IDX is a device without positive or negative polarity.

[0041] The first excitation winding Q1, the second excitation winding Q2 and the third excitation winding Q3 have their head ends U1, V1 and W1 respectively, and their tail ends U2, V2 and W2 respectively; the first detection winding K1 and the second detection winding K2 have their head ends L11 and L21 respectively, and their tail ends L12 and L22 respectively. One end of the first impedance device Z1, the second impedance device Z2 and the third impedance device Z3 are respectively connected to the first terminal A, the second terminal B and the third terminal C of the electrical connection of the motor, and the other end is respectively connected to the head ends U1, V1 and W1 of the first excitation winding Q1, the second excitation winding Q2 and the third excitation winding Q3.

[0042] In one embodiment of the present application, the device further comprises: when the excitation winding connection mode is star connection, the first end of the first excitation winding, the second excitation winding and the third excitation winding are respectively connected to the first impedance device, the second impedance device and the third impedance device, and the ends of the first excitation winding, the second excitation winding and the third excitation winding are connected to each other. When the excitation winding connection mode is delta connection, the first end of the first excitation winding, the second excitation winding and the third excitation winding are respectively connected to the first impedance device, the second impedance device and the third impedance device; the end of the first excitation winding is connected to the first end of the second excitation winding, the end of the second excitation winding is connected to the first end of the third excitation winding, and the end of the third excitation winding is connected to the first end of the first excitation winding.

[0043] For details, please refer to FIG3(a): When the excitation winding connection mode is star connection, the first end U1, V1 and W1 of the excitation winding are respectively connected to the first impedance device Z1, the second impedance device Z2 and the third impedance device Z3; the end U2, V2 and W2 of the excitation winding are connected to each other. Please refer to FIG3(b): When the excitation winding connection mode is delta connection, the first end U1, V1 and W1 of the excitation winding are respectively connected to the first impedance device Z1, the second impedance device Z2 and the third impedance device Z3; the end U2, V2 and W2 of the excitation winding are respectively connected to V1, W1 and U1.

[0044] In one embodiment of the present application, the identification circuit includes a first rectifier unit, a second rectifier unit, a first capacitor, a second capacitor, a first resistor, a second resistor and an indicator device; wherein, the first and second ends of the first detection winding are connected to the first capacitor through the first rectifier unit, and the first and second ends of the second detection winding are connected to the second capacitor through the second rectifier unit; the first resistor is connected in parallel with the first capacitor, and the second resistor is connected in parallel with the second capacitor; when the negative electrode of the first capacitor is connected to the negative electrode of the second capacitor, the two ends of the indicator device are respectively connected to the positive electrode of the first capacitor and the positive electrode of the second capacitor; when the positive electrode of the first capacitor is connected to the positive electrode of the second capacitor, the two ends of the indicator device are respectively connected to the negative electrode of the first capacitor and the negative electrode of the second capacitor.

[0045] Wherein, the first rectifying unit includes a first diode, a second diode, a third diode and a fourth diode; the second rectifying unit includes a fifth diode, a sixth diode, a seventh diode and an eighth diode; the first end of the first detection winding is connected to the positive electrode of the first diode and the negative electrode of the third diode; the end of the first detection winding is connected to the positive electrode of the second diode and the negative electrode of the fourth diode; the negative electrode of the first diode and the negative electrode of the second diode are connected to the positive electrode of the first capacitor; the positive electrode of the third diode and the positive electrode of the fourth diode are connected to the negative electrode of the first capacitor; the first end of the second detection winding is connected to the positive electrode of the fifth diode and the negative electrode of the seventh diode; the end of the second detection winding is connected to the positive electrode of the sixth diode and the negative electrode of the eighth diode; the negative electrode of the fifth diode and the negative electrode of the sixth diode are connected to the positive electrode of the second capacitor; the positive electrode of the seventh diode and the positive electrode of the eighth diode are connected to the negative electrode of the second capacitor. The indicating device is a device without positive or negative polarity.

[0046] Specifically, please refer to FIG. 4(a) and FIG. 4(b). In actual operation, the head end L11 of the first detection winding K1 is connected to the anode of the first diode D11 and the cathode of the third diode D13; the end L12 of the first detection winding K1 is connected to the anode of the second diode D12 and the cathode of the fourth diode D14; the cathode of the first diode D11 and the cathode of the second diode D12 are connected to the anode of the first capacitor C1; the anode of the third diode D13 and the anode of the fourth diode D14 are connected to the cathode of the first capacitor C1; the head end L21 of the second detection winding K2 is connected to the anode of the fifth diode D21 and the cathode of the seventh diode D23; the end L22 of the second detection winding K2 is connected to the anode of the sixth diode D22 and the cathode of the eighth diode D24. The cathode of the fifth diode D21 and the cathode of the sixth diode D22 are connected to the anode of the second capacitor C2; the anode of the seventh diode D23 and the anode of the eighth diode D24 are connected to the cathode of the second capacitor C2; the first resistor R1 is connected in parallel with the first capacitor C1, and the second resistor R2 is connected in parallel with the second capacitor C2; when the cathode of the first capacitor C1 is connected to the cathode of the second capacitor C2, the two ends of the indicating device IDX are connected to the anode of the first capacitor C1 and the cathode of the second capacitor C2, as shown in FIG4(a); when the anode of the first capacitor C1 is connected to the cathode of the second capacitor C2, the two ends of the indicating device IDX are connected to the cathode of the first capacitor C1 and the cathode of the second capacitor C2, as shown in FIG4(b).

[0047] In one embodiment of the present application, the magnet is a solid structure; wherein the first excitation winding, the second excitation winding and the third excitation winding are symmetrically installed; the first detection winding and the second detection winding are installed at positions with equal radial distances and different radial angles; the first detection winding and the second detection winding have equal turns and the same enclosed area. Among them, the symmetrical installation of the first excitation winding, the second excitation winding and the third excitation winding includes: the first excitation winding, the second excitation winding and the third excitation winding have equal turns, the same enclosed area, and are 120° electrical angles apart in space distribution. Specifically, the magnet G is a solid structure. The first excitation winding Q1, the second excitation winding Q2 and the third excitation winding Q3 are symmetrically installed, that is, the first excitation winding Q1, the second excitation winding Q2 and the third excitation winding Q3 have equal turns, the same enclosed area, and are 120° electrical angles apart in space distribution. The first detection winding K1 and the second detection winding K2 are installed at positions with equal radial distances and different radial angles. The first detection winding K1 and the second detection winding K2 have the same number of turns and enclose the same area.

[0048] The present application also provides a detection method for a detection device for the above-mentioned separately excited three-phase AC motor interphase short-circuit fault, the method comprising: using the AC voltage of the motor to form a periodically changing magnetic field in a magnet through an excitation winding; obtaining a periodically changing induced potential generated by the magnetic field change at the location through detection windings at different positions in the magnet; and identifying the interphase short-circuit fault condition of the separately excited three-phase AC motor by comparing the induced potential change range of the detection windings at different positions.

[0049] Specifically, when a motor has an interphase short circuit fault in motor operation and generator operation, the voltage characteristics of the motor's electrical terminal blocks are similar. The present application performs detection and identification based on the characteristics of this voltage. The following describes the principles of detection and identification of motor interphase short circuit faults in two situations: when the motor is normal and when the motor has an interphase short circuit fault.

[0050] When the motor is normal, the voltage of its electrical terminals is a symmetrical three-phase AC voltage, the voltage after the impedance device is also symmetrical, and the exciting winding current is also symmetrical. According to the principle of three-phase AC motor, it is obvious that no matter whether the exciting winding connection mode is star connection or delta connection, the phase voltage U AB , U BC and U CA The effect produced is that a rotating magnetic field is formed in the magnet G, and a closed magnetic circuit of the magnetic field is formed in the magnet G. The rotating magnetic field causes the first detection winding K1 and the second detection winding K2 to pass through the changing magnetic field. The radial distances between the first detection winding K1 and the second detection winding K2 are equal, and the radial angles are different. At the same moment, the magnetic induction intensities at the positions of the first detection winding K1 and the second detection winding K2 are different, but within the period of the rotating magnetic field, the variation ranges of the magnetic induction intensities at the positions of the first detection winding K1 and the second detection winding K2 are the same, and the variation ranges of the magnetic flux passing through the first detection winding K1 and the second detection winding K2 are equal. Therefore, within the period of the rotating magnetic field, the induced potential ranges generated by the first detection winding K1 and the second detection winding K2 are the same, and the voltage generated on the first capacitor C1 after rectification by the first rectifier unit RT1 of the first detection winding K1 is equal to the voltage generated on the second capacitor C2 after rectification by the second rectifier unit RT2 of the second detection winding K2, and there is no voltage difference between the first capacitor C1 and the second capacitor C2, and no current passes through the indicating device IDX. The indicating device IDX is not activated, and it is identified that the motor has no phase-to-phase short circuit fault.

[0051] When a short circuit occurs between points AB in the motor, the phase-to-phase voltage U AB is zero, U BC with U CA The magnitudes are equal and the phases are opposite. The voltage characteristics are shown in Figure 2(a), Figure 2(b) and Figure 2(c).

[0052] When the excitation winding is connected in star connection: U BC Positive U CA When is negative, the current of the third excitation winding Q3 is the sum of the currents of the first excitation winding Q1 and the second excitation winding Q2. The current relationship of the excitation winding and the magnetic field distribution in the magnet G are shown in Figure 5(a); U BC Negative, U CA When is positive, the current relationship of the exciting winding and the magnetic field distribution in the magnet G are shown in Figure 5(b);

[0053] When the excitation winding is connected in delta connection: because U AB is zero, so the current of the first excitation winding Q1 is zero, and the current of the second excitation winding Q2 is equal to the current of the third excitation winding Q3, but in opposite directions. BC Positive U CA When U is negative, the current relationship of the exciting winding and the magnetic field distribution in the magnet G are shown in Figure 5(c); BC Negative U CA When is positive, the current relationship of the exciting winding and the magnetic field distribution in the magnet G are shown in Figure 5(d).

[0054] It can be seen that no matter whether the excitation winding is connected in star connection or delta connection, the phase-to-phase voltage U AB , U BC and U CA The effect produced is that a pulsating magnetic field is formed in the magnet G, and a closed magnetic circuit of the magnetic field is formed in the magnet G. The pulsating magnetic field causes the first detection winding K1 and the second detection winding K2 to pass through the changing magnetic field. The radial distances between the first detection winding K1 and the second detection winding K2 are equal, and the radial angles are different. The angles between the planes where the first detection winding K1 and the second detection winding K2 are located and the plane where the magnetic poles of the pulsating magnetic field are located are different. At the same time, the magnetic induction intensities at the positions where the first detection winding K1 and the second detection winding K2 are located are different, and within the period of the pulsating magnetic field, the angles of the planes where the magnetic poles of the pulsating magnetic field are located do not change (that is, the pulsating magnetic field does not rotate). The range of variation of the magnetic induction intensities at the positions where the first detection winding K1 and the second detection winding K2 are located are different, and the angles passing through the first detection winding K1 and the second detection winding K2 are different. The magnetic flux change range of the detection winding K2 is not equal, so the induced potential range generated by the first detection winding K1 and the second detection winding K2 is different within the period of the pulsating magnetic field. The voltage generated on the first capacitor C1 after the first detection winding K1 is rectified by the first rectifier unit RT1 is not equal to the voltage generated on the second capacitor C2 after the second detection winding K2 is rectified by the second rectifier unit RT2. There is a voltage difference between the first capacitor C1 and the second capacitor C2, and current passes through the indicating device IDX. The indicating device IDX is activated, and it is identified as a phase-to-phase short circuit fault in the motor.

[0055] When a short circuit occurs between two points BC in the motor, the phase voltage UBC is zero, U CA with U AB The magnitude is equal and the phase is opposite; the current relationship of the exciting winding and the magnetic field distribution in the magnet G are as follows Figure 6(a) to Figure 6(d) shown.

[0056] When a short circuit occurs between two points CA in the motor, the phase voltage U CA is zero, U AB with U BC The magnitude is equal and the phase is opposite. The current relationship of the exciting winding and the magnetic field distribution in the magnet G are as follows: Figure 7(a) to Figure 7(d) shown.

[0057] It can be seen that no matter the motor has a phase-to-phase short circuit fault at AB, BC or CA, no matter the connection mode of the excitation winding is star connection or delta connection, the phase-to-phase voltage U AB , U BC and U CA The effect produced is to form a pulsating magnetic field in the magnet G, the induced potential ranges generated by the first detection winding K1 and the second detection winding K2 are different, the voltage generated on the first capacitor C1 after the first detection winding K1 is rectified by the first rectifier unit RT1 and the voltage generated on the second capacitor C2 after the second detection winding K2 is rectified by the second rectifier unit RT2 are not equal, the first capacitor C1 and the second capacitor C2 have a voltage difference, and current passes through the indicating device IDX, the indicating device IDX is activated, and it is recognized that a phase-to-phase short circuit fault has occurred in the motor.

[0058] The indicating device IDX in the identification circuit may include but is not limited to: relay, bulb, light emitting diode, laser diode, buzzer, voltmeter / ammeter, etc. When a single device has positive and negative polarity, the indicating device IDX can be realized by two devices connected in reverse parallel without positive and negative polarity.

[0059] When the indicating device IDX is a relay, when the indicating device IDX is not activated, the coil of the relay has no current; when the indicating device IDX is activated, the control coil of the relay passes current;

[0060] When the indicator device IDX is a light-emitting device, when the indicator device IDX is not activated, the light-emitting device has no light; when the indicator device IDX is activated, the light-emitting device has light;

[0061] When the indicating device IDX is a buzzer, the buzzer has no sound when the indicating device IDX is not activated; the buzzer sounds when the indicating device IDX is activated;

[0062] When the indicating device IDX is a voltmeter / ammeter, when the indicating device IDX is not activated, the voltmeter / ammeter displays no voltage / current; when the indicating device IDX is activated, the voltmeter / ammeter displays voltage / current.

[0063] During the detection and identification process, the only input is the voltage of the motor terminals. No additional working power supply is required. Detection and identification can be performed during the full operating state of the motor.

[0064] The beneficial technical effects of the present application are: detection and identification can be performed under the isolated operating condition of the generator with the motor disconnected from the power supply circuit, thereby realizing full operating condition protection; detection and identification can be performed with only the voltage of the motor's electrical terminal, without the need for an additional working power supply, and with a simple structure; it is completely implemented by a hardware structure, without the need for software and its operating carrier, and has higher reliability.

[0065] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this specification should not be determined with reference to the above description, but should be determined with reference to the preceding claims and the full scope of equivalents to which these claims belong.

[0066] The above description is only the preferred embodiment of this specification and is not intended to limit this specification. For those skilled in the art, the embodiments of this specification may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this specification shall be included in the protection scope of this specification.

Claims

1. A detection device for interphase short circuit fault of a separately excited three-phase AC motor, characterized in that: The device comprises an impedance device, an exciting winding, a magnet, a detection winding and an identification circuit; The electrical terminal of the motor to be detected is connected to the impedance device, the impedance device is connected to the exciting winding, the exciting winding and the detecting winding are mounted on the magnet, and the detecting winding is connected to the identification circuit; Among them, the impedance device is used to limit the current of the excitation winding; the excitation winding is used to generate a magnetic field in the magnet; the detection winding is used to detect the magnetic field in the magnet; and the identification circuit identifies whether a phase-to-phase short circuit fault occurs based on the voltage difference generated by the detection winding.

2. The detection device for interphase short circuit fault of a separately excited three-phase AC motor according to claim 1, characterized in that: The impedance device includes a first impedance device, a second impedance device and a third impedance device; the excitation winding includes a first excitation winding, a second excitation winding and a third excitation winding; Among them, one end of the first impedance device, the second impedance device and the third impedance device are respectively connected to the first terminal, the second terminal and the third terminal of the electrical connection of the motor, and the other end is respectively connected to the head end of the first excitation winding, the second excitation winding and the third excitation winding.

3. The detection device for interphase short circuit fault of a separately excited three-phase AC motor according to claim 2, characterized in that: The device also comprises: When the excitation winding connection mode is star connection, the first end of the first excitation winding, the second excitation winding and the third excitation winding are connected to the first impedance device, the second impedance device and the third impedance device respectively, and the ends of the first excitation winding, the second excitation winding and the third excitation winding are connected to each other.

4. The detection device for interphase short circuit fault of a separately excited three-phase AC motor according to claim 2, characterized in that: The device also comprises: When the connection mode of the excitation winding is delta connection, the head ends of the first excitation winding, the second excitation winding and the third excitation winding are connected to the first impedance device, the second impedance device and the third impedance device respectively; The end of the first excitation winding is connected to the beginning of the second excitation winding, the end of the second excitation winding is connected to the beginning of the third excitation winding, and the end of the third excitation winding is connected to the beginning of the first excitation winding.

5. The detection device for interphase short circuit fault of a separately excited three-phase AC motor according to claim 2, characterized in that: The identification circuit includes a first rectifying unit, a second rectifying unit, a first capacitor, a second capacitor, a first resistor, a second resistor and an indicating device; Wherein, the first and second ends of the first detection winding are connected to the first capacitor through a first rectifying unit, and the first and second ends of the second detection winding are connected to the second capacitor through a second rectifying unit; The first resistor is connected in parallel with the first capacitor, and the second resistor is connected in parallel with the second capacitor; When the negative electrode of the first capacitor is connected to the negative electrode of the second capacitor, the two ends of the indicating device are connected to the positive electrode of the first capacitor and the positive electrode of the second capacitor respectively; When the positive electrode of the first capacitor is connected to the positive electrode of the second capacitor, the two ends of the indicating device are connected to the negative electrode of the first capacitor and the negative electrode of the second capacitor respectively.

6. The detection device for interphase short circuit fault of a separately excited three-phase AC motor according to claim 5, characterized in that: The first rectifying unit includes a first diode, a second diode, a third diode and a fourth diode; the second rectifying unit includes a fifth diode, a sixth diode, a seventh diode and an eighth diode; The head end of the first detection winding is connected to the anode of the first diode and the cathode of the third diode; the end of the first detection winding is connected to the anode of the second diode and the cathode of the fourth diode; the cathode of the first diode and the cathode of the second diode are connected to the anode of the first capacitor; the anode of the third diode and the anode of the fourth diode are connected to the cathode of the first capacitor; The head end of the second detection winding is connected to the anode of the fifth diode and the cathode of the seventh diode; the end of the second detection winding is connected to the anode of the sixth diode and the cathode of the eighth diode; the cathode of the fifth diode and the cathode of the sixth diode are connected to the anode of the second capacitor; the anode of the seventh diode and the anode of the eighth diode are connected to the cathode of the second capacitor.

7. The detection device for interphase short circuit fault of a separately excited three-phase AC motor according to claim 5, characterized in that: The indicating device is a device without positive or negative polarity.

8. The detection device for interphase short circuit fault of a separately excited three-phase AC motor according to claim 2, characterized in that: The magnet is a solid structure; Wherein, the first excitation winding, the second excitation winding and the third excitation winding are symmetrically installed; The first detection winding and the second detection winding are installed at positions with equal radial distances and different radial angles; The first detection winding and the second detection winding have the same number of turns and enclose the same area.

9. The detection device for interphase short circuit fault of a separately excited three-phase AC motor according to claim 8, characterized in that: The first excitation winding, the second excitation winding and the third excitation winding are symmetrically installed and include: The first excitation winding, the second excitation winding and the third excitation winding have the same number of turns, the same enclosed area, and are spaced 120 degrees apart in electrical angle.

10. A detection method for a detection device for a phase-to-phase short circuit fault of a separately excited three-phase AC motor according to any one of claims 1 to 9, characterized in that: The method comprises: The AC voltage of the motor is used to form a periodically changing magnetic field in the magnet through the exciting winding; The detection windings at different positions in the magnet obtain the magnetic field changes at the positions to generate periodically changing induced potentials; By comparing the variation range of the induced potential of the detection winding at different positions, the interphase short circuit fault of the separately excited three-phase AC motor can be identified.

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