A motor online insulation monitoring device and method

Abstract

The present invention discloses an online insulation monitoring device and method for a motor, which relates to the technical field of insulation monitoring of power equipment, and includes a power isolation transformer, a resistance detection circuit and an early warning circuit. The output end of the power isolation transformer is respectively connected to the resistance detection circuit and the early warning circuit, and the resistance detection circuit and the early warning circuit are photoelectrically isolated through a photoelectric coupler; the resistance detection circuit is used to detect the insulation resistance of the motor; the early warning circuit is used to issue an alarm prompt when the insulation resistance of the detected motor is lower than the pre-alarm resistance. The insulation resistance of the motor and the cable connected to the motor winding can be monitored online in real time. The resistance detection circuit can detect the decrease in the insulation resistance of the motor and the cable connected to the motor in the first time, and the early warning circuit can issue a pre-alarm signal or prohibit the equipment from starting, so that the equipment maintenance personnel can deal with it in time, nip the fault in the bud, and ensure the safe and reliable operation of the equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment insulation monitoring, and in particular to a motor online insulation monitoring device and method. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.

[0003] Equipment such as water pumps and fans used in urban rail transit stations operate intermittently, and some have long operating intervals. If the motor is not running for a long time and the environment is humid, the insulation resistance of the motor will decrease. If it is not discovered in time, it will cause faults such as switch tripping or motor burning during startup, seriously affecting the normal use of the equipment.

[0004] Due to the particularity of subway equipment, if equipment such as water pumps cannot start normally due to poor insulation resistance and cannot be discovered and handled in time, the equipment will lose its hot standby function and may even cause some serious problems. Ventilation equipment such as fans provide a comfortable riding or working environment for passengers, station staff, and equipment rooms, and play an important role in disease prevention and control, especially during special periods. Fans generally work according to pre-set modes. If the fan cannot be started or burns out due to poor insulation, the mode execution will fail, and all equipment corresponding to the mode will not be able to run automatically. Replacing fans, especially some large fans, is costly and time-consuming.

[0005] Most existing motor insulation monitoring methods use a megohmmeter to periodically shut down the power supply to test the insulation of the equipment. This requires a power outage, which can easily affect the normal use of the motor. It cannot monitor in real time and has a high monitoring cost, which is not suitable for the operation characteristics of equipment in the subway industry. In addition, existing motor insulation monitoring can only monitor a single threshold and cannot be flexibly set according to actual application scenarios, so it is less widely used. Summary of the invention

[0006] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a motor online insulation monitoring device and method, which can realize real-time monitoring of the insulation resistance of the motor and the cables connected to the motor windings, and can detect the decrease in the insulation resistance of the motor and the connected cables in the first time, and issue a pre-alarm signal or prohibit the equipment from starting, so that the equipment maintenance personnel can deal with it in time, nip the fault in the bud, and ensure the safe and reliable operation of the equipment.

[0007] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0008] In a first aspect, the present invention provides an online insulation monitoring device for a motor, comprising a power isolation transformer, a resistance detection circuit and an early warning circuit, wherein the output end of the power isolation transformer is connected to the resistance detection circuit and the early warning circuit respectively, and the resistance detection circuit and the early warning circuit are photoelectrically isolated through a photoelectric coupler;

[0009] The resistance detection circuit is used to detect the insulation resistance of the motor; the early warning circuit is used to issue an alarm prompt when the insulation resistance of the detected motor is lower than the pre-alarm resistance.

[0010] According to a further technical solution, the resistance detection circuit includes a first rectifier module, a voltage reduction and current limiting module, a photoelectric isolation module and a circuit protection module which are connected in sequence.

[0011] According to a further technical solution, the input end of the first rectifier module is connected to the output end of the power isolation transformer, and the negative pole of the circuit protection module is connected to the motor winding.

[0012] According to a further technical solution, the early warning circuit includes a photoelectric isolation module, a control module, a signal amplification module, an alarm prompt module and a second rectifier module which are connected in sequence.

[0013] According to a further technical solution, the control module is also connected in parallel with a pre-alarm resistance adjustment module.

[0014] According to a further technical solution, the pre-alarm resistance adjustment module includes an adjustable potentiometer.

[0015] According to a further technical solution, the alarm prompt module includes a relay and an LED indicator light connected in parallel.

[0016] According to a further technical solution, the normally open contact of the relay is connected to an external alarm signal, and the normally closed contact is connected to a motor stop interlocking control circuit.

[0017] In a second aspect, the present invention provides a method for online insulation monitoring of a motor, comprising:

[0018] Detect the insulation resistance of the motor to be tested;

[0019] When the insulation resistance is higher than the pre-alarm resistance, the current in the resistance detection circuit is less than the conduction current of the photoelectric coupler, the photoelectric coupler is not saturated and turned on, and the alarm circuit does not operate;

[0020] When the insulation resistance is lower than the pre-alarm resistance, the current in the resistance detection circuit is greater than the conduction current of the photoelectric coupler, the photoelectric coupler is turned on, and the alarm circuit is activated to issue an alarm prompt.

[0021] According to a further technical solution, the pre-alarm resistance value is set as required within a set range.

[0022] One or more of the above technical solutions have the following beneficial effects:

[0023] The present invention can realize online real-time monitoring of the insulation resistance of the motor and the cables connected to the motor windings. The resistance detection circuit can detect the decrease of the insulation resistance of the motor and the cables connected to the motor in the first time, and send out a pre-alarm signal or prohibit the equipment from starting through the early warning circuit, so that the equipment maintenance personnel can deal with it in time, nip the fault in the bud, and ensure the safe and reliable operation of the equipment.

[0024] The present invention changes the traditional operation mode of using a megohmmeter to periodically shut down the power to test the insulation of the equipment. It does not require power outages and does not affect the normal use of the equipment. It solves the current problem of lack of effective online insulation monitoring devices for motors and their connecting cables, and no longer requires manual special operations.

[0025] The present invention is a special single-body device, the pre-alarm resistance value can be adjusted, the pre-alarm resistance value range is large, and can be set as needed within the range of 0-50MΩ.

[0026] The device of the present invention has strong functions. When the insulation of the measured equipment is lower than the set value, it can not only give an alarm but also prohibit the linkage functions such as equipment startup and signal remote transmission. It has a simple structure and high cost performance.

[0027] The present invention has low power consumption, and the working current value of the whole device is about 25mA, which is lower than the safety current of the human body, thereby ensuring the safety of the tested equipment and the safety of personnel using it.

[0028] The present invention can realize the insulation resistance pre-alarm function of the motor and its connecting cables, which is of great significance to special important equipment such as water pumps in the subway industry. The device of the present invention can be used not only in motor insulation monitoring scenarios, but also in all scenarios where insulation monitoring is required, and has a wide range of applications.

[0029] The invention has the advantages of high circuit integration, small size, convenient installation, low power consumption, high sensitivity, safety and reliability, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0031] Figure 1 This is a functional block diagram of a motor online insulation monitoring device according to an embodiment of the present invention;

[0032] Figure 2 is a circuit diagram of a motor online insulation monitoring device according to an embodiment of the present invention;

[0033] Figure 3Schematic diagram of an online insulation monitoring device for a motor according to an embodiment of the present invention;

[0034] Figure 4 It is a connection diagram of a motor online insulation monitoring device according to an embodiment of the present invention.

[0035] Among them, 1-insulation test box, 2-base, 3-fixing hole, 4-power cord terminal, 5-control signal output terminal, 6-motor insulation test terminal, 7-LED indicator, 8-insulation alarm resistance adjustment knob. DETAILED DESCRIPTION

[0036] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0037] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0038] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0039] Terminology explanation: Unsaturated conduction: When the optocoupler is turned on, if the input signal (current) is not sufficient to drive the light-emitting diode to reach the maximum brightness, the output signal will not reach the maximum value. This phenomenon is called unsaturated conduction.

[0040] Embodiment 1

[0041] like Figure 1 As shown, this embodiment discloses an online insulation monitoring device for a motor, including a power isolation transformer, a resistance detection circuit and an early warning circuit, wherein the output end of the power isolation transformer is connected to the resistance detection circuit and the early warning circuit respectively, and the resistance detection circuit and the early warning circuit are photoelectrically isolated through a photoelectric coupler;

[0042] The resistance detection circuit is used to detect the insulation resistance of the motor; the early warning circuit is used to issue an alarm prompt when the insulation resistance of the detected motor is lower than the pre-alarm resistance.

[0043] In this embodiment, the resistance detection circuit includes a first rectifier module, a voltage reduction and current limiting module, a photoelectric isolation module and a circuit protection module which are connected in sequence.

[0044] The input end of the power isolation transformer is connected to the power supply, which adopts an AC 380V power supply. The output end of the power isolation transformer is connected to the input end of the first rectifier module, that is, the primary side of the power isolation transformer is connected to the 380V power supply, the secondary side is connected to the first rectifier module, and the other secondary side is connected to the second rectifier module.

[0045] like Figure 2 As shown, the first rectifier module is a bridge rectifier Q1, which is used to convert AC power into DC power for use in the subsequent resistance detection circuit; the step-down and current limiting module is a first resistor R1, which is used to reduce the voltage of the DC power output from the bridge rectifier Q1 and limit the current to protect the subsequent circuit components from the impact of large voltage or current; the photoelectric isolation module is a photoelectric coupler D5, which is used to achieve photoelectric isolation between the resistance detection circuit and the early warning circuit, ensuring that the signal transmission between the two circuits is stable and reliable, while avoiding electrical interference; the circuit protection module is a first diode D1, because it is connected to the motor, the motor power supply is AC power, there are fluctuations, to prevent the reverse current of the motor from entering the resistance detection circuit, and protect the circuit from damage by reverse voltage or excessive current. The photoelectric coupler D5 includes a light source and a light receiver, the light source is a light emitting diode, and the light receiver is a photosensitive transistor, which is used to achieve photoelectric isolation of the circuit.

[0046] Specifically, Figure 2 As shown, the input end of the bridge rectifier Q1 is connected to the first secondary side of the power isolation transformer, the output end is connected to the first end of the first resistor R1, the second end of the first resistor R1 is connected to the positive electrode of the light-emitting diode of the photoelectric coupler D5, the negative electrode of the light-emitting diode is connected to the positive electrode of the first diode D1, the negative electrode of the first diode D1 is connected to the motor winding, and the output ground end of the bridge rectifier Q1 is connected to the motor housing.

[0047] The bridge rectifier Q1 is also connected in parallel to the first capacitor C1 and then grounded to reduce the ripple at the output end of the bridge rectifier Q1, making the output DC power smoother and more stable; and filtering out harmonics to further obtain a smooth DC voltage, thereby improving the stability of the entire circuit through filtering and voltage stabilization.

[0048] In this embodiment, the early warning circuit includes a photoelectric isolation module, a control module, a signal amplification module, an alarm prompt module and a second rectifier module connected in sequence. That is, the output end of the photoelectric isolation module is connected to the input end of the control module, the output end of the control module is connected to the input end of the signal amplification module, the output end of the signal amplification module is connected to the input end of the alarm prompt module, and the alarm prompt module is connected to the second rectifier module.

[0049] like Figure 2As shown, the photoelectric isolation module is a photoelectric coupler D5; the control module is a control chip IT1, which receives the input signal from the photoelectric coupler D5, processes and judges the input signal, and outputs a high level when it detects that the insulation resistance of the motor is lower than the pre-alarm resistance, triggering the transistor D4 to turn on; the signal amplification module is a transistor D4, which is used to amplify the signal. When the control chip IT1 outputs a signal, the transistor D4 will amplify the signal to drive the subsequent alarm prompt module to ensure that the alarm prompt module can receive a sufficiently strong signal to issue a clear alarm prompt; the alarm prompt module includes a relay KJ and an LED indicator connected in parallel, the relay KJ plays the role of switch control, the relay triggers the contact, and the contact can drive other circuits or devices, such as starting a remote sound and light alarm, cutting off the power supply of the motor, starting a standby motor, etc., to achieve fault handling or safety protection; the LED indicator plays an intuitive alarm prompt role, and the LED indicator lights up to remind the operator that the insulation resistance of the motor is lower than the pre-alarm resistance and that corresponding measures need to be taken; the second rectifier module is a bridge rectifier Q2, which provides a stable DC voltage for each component in the alarm circuit.

[0050] In some implementations, the control chip uses a NE555 chip, which is the control core of the motor online insulation monitoring device.

[0051] Specifically, the emitter of the phototransistor of the photocoupler D5 is grounded, the collector of the phototransistor is connected to pins 6 and 2 of the control chip IT1, and pins 4 and 8 of the control chip IT1 are connected to the output end of the bridge rectifier Q2, that is, connected to the power supply; pin 3 of the control chip IT1 is connected to the base of the transistor D4, the emitter of the transistor D4 is grounded, and the collector of the transistor D4 is connected in series with the relay KJ and the LED indicator light respectively, and then connected to the output end of the bridge rectifier Q2; pin 1 of the control chip IT1 is grounded, and pin 5 is connected in series with the third capacitor C3 and then grounded; the input end of the bridge rectifier Q2 is connected to the second secondary side of the power isolation transformer, that is, connected to the power supply through the power isolation transformer.

[0052] Furthermore, the relay KJ includes a normally open contact, a normally closed contact and a COM contact. The normally open contact or the normally closed contact can be connected to an external alarm signal output, or connected to a corresponding control circuit to realize motor interlocking control, prohibit the motor from starting, and better ensure the safety of the equipment. The control circuit can use an existing control circuit to stop the motor, which will not be described in detail here.

[0053] Furthermore, the coil of the relay KJ is connected in parallel with a second diode D2 for protecting the circuit and eliminating reverse electromotive force, thereby improving the reliability and stability of the circuit and avoiding circuit failures caused by component damage.

[0054] Furthermore, the LED indicator light is connected in series with the fourth resistor R4 and then connected to the output end of the bridge rectifier Q2, which is used for current limiting and protection circuits, limiting the current passing through the LED indicator light to prevent the LED from burning out due to excessive current, and dividing the voltage with the LED indicator light to ensure that the LED indicator light can work normally under a suitable voltage. The current limiting and protection circuits help stabilize the working state of the circuit and prevent the brightness and stability of the LED indicator light from being affected by current or voltage fluctuations.

[0055] The early warning circuit also includes a pre-alarm resistance adjustment module, which is connected in parallel with the control module. The pre-alarm resistance adjustment module is an adjustable potentiometer R3, which is connected in series with the second resistor R2. R3 and R2 can be regarded as a resistor R, and R2 is the minimum value of the resistor R. Figure 2 As shown, the second end of the adjustable potentiometer R3 is respectively connected to the 6th and 2nd pins of the control chip IT1, the collector of the phototransistor, and the first end of the fourth capacitor C4, the second end of the fourth capacitor C4 is grounded, the first end of the adjustable potentiometer R3 is connected to the second end of the second resistor R2, and the first end of the second resistor R2 is respectively connected to the 4th and 8th pins of the control chip IT1 and the output end of the bridge rectifier Q2. Through the above modules, the device can adjust the pre-alarm resistance value by adjusting the resistance value of the adjustable potentiometer R3, and the adjustable setting range is 0-50MΩ. It is verified by experiments that the pre-alarm resistance value range is large.

[0056] Furthermore, the second resistor R2 is connected in series with the adjustable potentiometer R3 to protect the circuit. The adjustable potentiometer R3 and the second resistor R2 are the load resistors of the phototransistor collector. R2 protects the circuit from being damaged when R3 is adjusted to 0 resistance. Adjusting R3 means adjusting the voltage drop of the collector to meet the IT1 trigger threshold. Adjusting R3 also means adjusting the control sensitivity.

[0057] Furthermore, the fourth capacitor C4 mainly plays the role of filtering and voltage clamping.

[0058] The early warning circuit also includes a current protection module and a voltage protection module. The current protection module includes a fuse FU1 and a fifth resistor R5. The fuse FU1 is used to protect the circuit from overload and short circuit; the fifth resistor R5 plays a role in current limiting and voltage reduction protection. The voltage protection module includes a second capacitor C2, a voltage stabilizing diode D3 and a sixth diode D6, which are used to stabilize the circuit voltage.

[0059] Specifically, the first end of the fuse FU1 is connected to the output end of the bridge rectifier Q2 and the first end of the second capacitor C2, the second end of the second capacitor C2 is grounded, and the second end of the fuse FU1 is connected in series with the fifth resistor R5 and then connected to the cathode of the voltage stabilizing diode D3 and the 4th and 8th pins of the control chip IT1. The second end of the fuse FU1 is connected to the alarm prompt module, the control module, and the pre-alarm resistance adjustment module respectively. In other words, the fuse FU1 is connected in series between the bridge rectifier Q2 and other modules for overload protection and short circuit protection.

[0060] Specifically, the second capacitor C2 is connected in parallel with the bridge rectifier Q2 for filtering and shaping; the cathode of the voltage stabilizing diode D3 is connected to the second end of the fuse FU1, the anode of the voltage stabilizing diode D3 is connected to the anode of the sixth diode D6, and the cathode of the sixth diode D6 is grounded. The voltage stabilizing diode D3 is used for voltage stabilization and overvoltage protection. By utilizing the reverse breakdown characteristics of the voltage stabilizing diode D3, when the power supply voltage is too high, D3 will be broken down and turned on, thereby limiting the increase in voltage and protecting other components in the circuit from damage by high voltage. The sixth diode D6 is used to assist in voltage stabilization and protection circuits. D6 cooperates with D3 to jointly maintain voltage stability in the circuit. When the power supply voltage fluctuates, D6 can assist D3 in absorbing or releasing excess electrical energy, thereby maintaining a constant output voltage; in some cases, D6 can also be used as a protection element to prevent damage to the circuit caused by excessive current or excessive voltage.

[0061] In this embodiment, if Figure 3 , Figure 4 As shown, the structure and wiring method of the motor online insulation monitoring device are demonstrated.

[0062] like Figure 3 As shown, the motor online insulation monitoring device includes an insulation test box, which is fixed above a base. A plurality of fixing holes are provided around the base for fixing the base.

[0063] The insulation test box is fixedly equipped with a power isolation transformer, a resistance detection circuit and an early warning circuit; one side of the insulation test box is provided with a power cord terminal for connecting to an AC 380V power supply; the other side is provided with a control signal output terminal and a motor insulation test terminal. The control signal output terminal is used to connect to a relay, and the motor insulation test terminal is used to connect to the motor to be tested.

[0064] The top of the insulation test box is equipped with an LED indicator and an insulation alarm resistance adjustment knob. The insulation alarm resistance adjustment knob is an adjustable potentiometer R3. The resistance of R3 can be adjusted by turning the knob to adjust the size of the pre-alarm resistance. Figure 3The range of 0-15 of the insulation alarm resistance adjustment knob is only for illustration, and does not limit the adjustable setting range of the pre-alarm resistance in this embodiment to 0-50MΩ. The knob scale can be flexibly set in actual application.

[0065] The whole machine working current of the motor online insulation monitoring device is about 25mA. The working current is calculated according to Ohm's law and is lower than the human safety current, ensuring the safety of the equipment under test and the safety of personnel using it.

[0066] like Figure 4 As shown, the specific wiring method for testing the online insulation monitoring device of the motor is as follows: a two-core 1.0mm2 power line is connected to the AC incoming line 380V power circuit breaker to provide working power to the insulation monitoring device; one of the two-core 1.0mm2 insulation monitoring lines (i.e., the connecting line of the cathode of the first diode D1) is connected to the motor winding terminal, and one (i.e., the connecting line of the output grounding terminal of the bridge rectifier Q1) is connected to the ground terminal of the motor casing; three-core 1.0mm2 control signal output lines, one is connected to the normally open contact of relay KJ, which can be connected to an external alarm signal; one is connected to the COM contact of relay KJ; one is connected to the normally closed contact of relay KJ, which can be connected to the motor stop interlocking control; the alarm signal or the corresponding interlocking control can be connected according to the actual needs of the site.

[0067] Embodiment 2

[0068] This embodiment discloses a method for online insulation monitoring of a motor, comprising:

[0069] Detect the insulation resistance of the motor to be tested;

[0070] When the insulation resistance is higher than the pre-alarm resistance, the current in the resistance detection circuit is less than the conduction current of the photoelectric coupler, the photoelectric coupler is not saturated and turned on, and the alarm circuit does not operate;

[0071] When the insulation resistance is lower than the pre-alarm resistance, the current in the resistance detection circuit is greater than the conduction current of the photoelectric coupler, the photoelectric coupler is turned on, and the alarm circuit is activated to issue an alarm prompt.

[0072] In this embodiment, when the insulation resistance of the motor to be tested is higher than the pre-alarm resistance, the current in the resistance detection circuit is very small, which is smaller than the conduction current of the photocoupler. Only a tiny current flows through the light-emitting diode of the photocoupler, and the photocoupler is not saturated and turned on. Due to the setting value of the adjustable potentiometer R3, the phototransistor is not sufficient to trigger the control chip IT1 to operate. There is no high-level output at pin 3 of the control chip IT1, and the alarm circuit does not operate.

[0073] When the insulation resistance of the motor to be tested is lower than the pre-alarm resistance, the first diode D1 is equivalent to being directly connected to the motor housing and directly grounded. At this time, the current in the resistance detection circuit is relatively large (the conduction current becomes larger compared to the high insulation resistance), which is greater than the conduction current of the photocoupler. The current in the light-emitting diode of the photocoupler D5 changes and emits light. The phototransistor generates current when irradiated by the light, that is, the photocoupler D5 is turned on; the collector of the phototransistor outputs the current, that is, the electrical signal, to pin 2 of the control chip IT1. When the voltage of pin 2 is higher than When the power supply voltage (the output voltage of the bridge rectifier Q2) is lower than the power supply voltage (the output voltage of the bridge rectifier Q2), the output of the comparator is high, the output pin 3 outputs a low level, and the transistor D4 is not turned on; when the voltage of the pin 2 is lower than When the power supply voltage (the output voltage of the bridge rectifier Q2) is low, the output of the comparator is low, the output pin 3 is high, and the transistor D4 is turned on.

[0074] When transistor D4 is turned on, the received electrical signal is amplified to drive relay KJ to close. At the same time, the LED indicator light conducts current, making it easier for equipment maintenance personnel to inspect and discover.

[0075] In this embodiment, the adjustment of the adjustable potentiometer R3 (adjustment of the pre-alarm resistance) is to adjust the voltage drop of the collector of the phototransistor so that it meets the trigger threshold of the control chip IT1. The pre-alarm resistance is set as needed within the set range. In other words, the motor insulation pre-alarm resistance can be adjusted according to the insulation monitoring resistance corresponding scale according to the needs, and the adjustable potentiometer on the circuit board can be adjusted in the range of 0-50MΩ.

[0076] Take the setting of the pre-alarm resistance value of the insulation monitoring of the motor and its connecting cables as 1MΩ as an example: when the insulation resistance of the motor winding and its connecting cables to the ground is lower than 1MΩ, the phototransistor of the optoelectronic isolation device D5 is turned on, the control chip IT1 flips the output, the chip pin 3 changes from low level to high level output, the transistor D4 is turned on, the signal is amplified, the relay KJ is driven to attract, the relay normally open / normally closed contact is actuated, the normally open / normally closed contact can be connected to the alarm signal output, or to the corresponding control circuit to realize the motor interlocking control, prohibit the motor from starting, and better ensure the safety of the equipment. At the same time, the LED light-emitting diode is turned on, which is convenient for equipment maintenance personnel to patrol and find.

[0077] According to the circuit principle, the pre-alarm resistance range of the device is the insulation detection range, which can be further improved by increasing the resistors R2 and R3 to meet special application occasions. By changing the number of turns and insulation level of the transformer T coil, it can be used for equipment of all voltage levels, especially ultra-high voltage and super-ultra-high voltage equipment.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0079] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A motor online insulation monitoring device, characterized in that: It includes a power isolation transformer, a resistance detection circuit and an early warning circuit, wherein the output end of the power isolation transformer is connected to the resistance detection circuit and the early warning circuit respectively, and the resistance detection circuit and the early warning circuit are photoelectrically isolated through a photoelectric coupler; The resistance detection circuit is used to detect the insulation resistance of the motor; the early warning circuit is used to issue an alarm prompt when the insulation resistance of the detected motor is lower than the pre-alarm resistance.

2. A motor online insulation monitoring device as claimed in claim 1, characterized in that: The resistance detection circuit comprises a first rectifier module, a voltage reduction and current limiting module, a photoelectric isolation module and a circuit protection module which are connected in sequence.

3. A motor online insulation monitoring device as claimed in claim 2, characterized in that: The input end of the first rectifier module is connected to the output end of the power isolation transformer, and the negative pole of the circuit protection module is connected to the motor winding.

4. The motor online insulation monitoring device according to claim 1, characterized in that: The early warning circuit comprises a photoelectric isolation module, a control module, a signal amplification module, an alarm prompt module and a second rectification module which are connected in sequence.

5. The motor online insulation monitoring device according to claim 4, characterized in that: The control module is also connected in parallel with a pre-alarm resistance adjustment module.

6. A motor online insulation monitoring device as claimed in claim 5, characterized in that: The pre-alarm resistance adjustment module includes an adjustable potentiometer.

7. The motor online insulation monitoring device according to claim 4, characterized in that: The alarm prompt module includes a relay and an LED indicator light connected in parallel.

8. The motor online insulation monitoring device according to claim 7, characterized in that: The normally open contact of the relay is connected to an external alarm signal, and the normally closed contact is connected to a motor stop interlocking control circuit.

9. A method for online insulation monitoring of a motor, characterized in that: include: Detect the insulation resistance of the motor to be tested; When the insulation resistance is higher than the pre-alarm resistance, the current in the resistance detection circuit is less than the conduction current of the photoelectric coupler, the photoelectric coupler is not saturated and turned on, and the alarm circuit does not operate; When the insulation resistance is lower than the pre-alarm resistance, the current in the resistance detection circuit is greater than the conduction current of the photoelectric coupler, the photoelectric coupler is turned on, and the alarm circuit is activated to issue an alarm prompt.

10. A method for online insulation monitoring of a motor as claimed in claim 9, characterized in that: The pre-alarm resistance value is set as required within the set range.

Images