Online motor insulativity detection device and method thereof

Abstract

The invention relates to the technical field of motor detection, and discloses an online motor insulativity detection device and method. The device comprises a detection circuit, a sampling circuit and a microcontroller, the detection circuit is electrically connected with a casing and a winding of the motor and is used for applying a high-voltage detection signal between the casing and the winding; the sampling circuit is used for collecting an initial voltage signal at a sampling resistor in the detection circuit, converting the initial voltage signal through an optocoupler and transmitting the converted initial voltage signal to the microcontroller; and the microcontroller is used for comparing the received voltage signal sampling value with a preset voltage reference value to judge whether the insulativity of the motor is good or not. The isolation degree between circuits is improved through the optocouplers, so that the detection safety is ensured, and the accuracy of a detection result is improved.

Description

Technical Field

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

[0002] During motor operation, especially in high-humidity, dusty, or corrosive environments like water pumps, the insulation between the windings and the housing can deteriorate due to aging, contamination, or moisture absorption, leading to safety hazards such as leakage and short circuits. Therefore, testing motor insulation is of great engineering significance.

[0003] Traditional insulation testing usually relies on manual shutdown and the use of equipment such as megohmmeters to measure insulation resistance. However, this method has poor real-time performance and low efficiency, making it difficult to meet the operation and maintenance requirements of continuously running systems.

[0004] To this end, some existing technologies have proposed online detection solutions. For example, the invention patent application with publication number CN115598528A discloses an automatic detection solution for motor insulation. A high-voltage signal is applied between the motor coil and the housing through a detection circuit, and a sampling resistor is set in the detection circuit to obtain a voltage signal. The insulation resistance of the motor is then calculated in combination with known circuit parameters to achieve quantitative analysis of the insulation performance. However, in its sampling circuit structure, the isolation of the electrical signal transmission path is low, and the risk of interference coupling between circuits is high. When faced with high-voltage detection signals, measurement errors or even safety hazards may occur, especially in high-noise or complex grounding environments. In addition, in actual applications, due to process fluctuations and individual differences in some components in the detection circuit, their electrical transmission characteristics often deviate from the theoretical value or nominal value, which may have a significant impact on the calculation results. Summary of the Invention

[0005] In order to solve the technical problems in the prior art that motor insulation detection has safety hazards and the detection results are not accurate due to low circuit isolation, the present invention provides an online motor insulation detection device and method.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention discloses an online motor insulation detection device, comprising: a detection circuit, a sampling circuit and a microcontroller; the detection circuit is electrically connected to the housing and winding of the motor respectively, and is used to apply a high-voltage detection signal between the housing and the winding; the sampling circuit is used to collect an initial voltage signal at a sampling resistor in the detection circuit, and then convert the initial voltage signal through an optical coupler to transmit it to the microcontroller; the microcontroller is used to judge whether the insulation of the motor is good by comparing the received voltage signal sampling value with a preset voltage reference value.

[0008] As a further improvement of the above solution, the microcontroller adopts a single-chip microcomputer, which is provided with four I / O interfaces IO1 to IO4, wherein the IO3 interface is used as an ADC sampling interface, and the single-chip microcomputer is powered by VCC; the detection circuit includes: transistor N1, diode D1, resistor R1, resistor R4, transformer T1 and relay RELAY1;

[0009] Among them, one end of the resistor R4 is connected to the VDD power supply, and the other end of the resistor R4 is connected to the negative end of the diode D1 and one end of the primary coil of the transformer T1 respectively; the positive end of the diode D1 is connected to the collector end of the transistor N1 and the other end of the primary coil of the transformer T1 respectively; the emitter end of the transistor N1 is grounded, and the base end of the transistor N1 is connected to the IO2 interface;

[0010] One end of the secondary coil of transformer T1 is connected to the casing through a knife switch of relay RELAY1, and the other end of the secondary coil of transformer T1 is connected to one end of resistor R1 through another knife switch of relay RELAY1; resistor R1 serves as a sampling resistor, and its other end is connected to any phase winding of the motor.

[0011] As a further improvement of the above solution, the sampling circuit includes: a resistor R2, a resistor R3, an optical coupler O1, a capacitor C1 and a diode D2;

[0012] Among them, one end of the resistor R3 is connected to one end of the resistor R1 connected to the relay RELAY1 knife switch, and the other end of the resistor R3 is respectively connected to the positive end of the emission source of the optocoupler O1 and the negative end of the diode D2; the positive end of the diode D2 is respectively connected to the negative end of the emission source of the optocoupler O1 and one end of the resistor R1 connected to the motor winding; the emitter end of the receiver of the optocoupler O1 is respectively connected to one end of the capacitor C1 and grounded, and the collector end of the receiver of the optocoupler O1 is respectively connected to one end of the resistor R2, the other end of the capacitor C1 and the ADC sampling interface; the other end of the resistor R2 is connected to the VCC power supply.

[0013] As a further improvement of the above solution, the diode D2 is a reverse voltage stabilizing diode.

[0014] As a further improvement of the above scheme, the detection device also includes a motor control circuit; the motor control circuit is used to power the three-phase winding of the motor in a timing sequence according to the motor control signal sent by the single-chip microcomputer to drive the motor to rotate; wherein, the UVW three-phase interface of the motor control circuit is respectively connected to the three-phase winding of the motor through the three-phase knife switch of the relay RELAY2.

[0015] As a further improvement of the above scheme, the detection device further comprises a relay control circuit; the relay control circuit comprises a transistor N2, a diode D3, a transistor N3 and a diode D4;

[0016] Wherein, the base end of the transistor N2 is connected with the IO1 interface, and the emitter end of the transistor N2 is grounded; the collector end of the transistor N2 is connected with the positive end of the diode D3 and one end of the coil of the relay RELAY1 respectively; the negative end of the diode D3 is connected with the VDD power supply and the other end of the coil of the relay RELAY1 respectively.

[0017] The base end of the transistor N3 is connected with the IO4 interface, and the emitter end of the transistor N4 is grounded; the collector end of the transistor N4 is connected with the positive end of the diode D4 and one end of the coil of the relay RELAY2 respectively; the negative end of the diode D4 is connected with the VDD power supply and the other end of the coil of the relay RELAY2 respectively.

[0018] The application further discloses an online motor insulation detection method, which applies the online motor insulation detection device.

[0019] S1, the relay RELAY2 is controlled to be disconnected to separate the motor from the motor control circuit, and after a time delay, the relay RELAY1 is controlled to be connected to connect the motor to the detection circuit;

[0020] S2, a pulse signal with a set frequency and duty cycle is output to the detection circuit through the IO2 interface, so that the secondary coil of the transformer T1 generates a high-voltage detection signal;

[0021] S3, the voltage signal sampling value is obtained through the ADC sampling interface, and then the output of the IO2 interface is stopped, and the relay RELAY1 is disconnected;

[0022] S4, according to the received voltage signal sampling value and a preset voltage reference value, whether the motor insulation is qualified is judged by comparison.

[0023] As a further improvement of the above scheme, in step S3, the voltage signal is sampled and converted for multiple times to obtain multiple voltage signal sampling values; a voltage signal sampling mean value is obtained by mean processing of the multiple voltage signal sampling values;

[0024] In step S4, when the voltage signal sampling mean value is lower than the voltage reference value, it is determined that the motor insulation is unqualified and step S5 is executed, otherwise, it is qualified and step S6 is executed; wherein, the quality of the motor insulation is positively correlated with the voltage signal sampling mean value.

[0025] S5, an alarm signal is generated;

[0026] S6, control the relay RELAY2 to turn on to restore the motor drive.

[0027] As a further improvement of the above-mentioned solution, before step S1, the method further comprises the following steps:

[0028] Upon receiving a detection instruction, the single-chip microcomputer is initialized, and then the saved learning flag is read to determine whether parameter learning is needed according to whether the number of learned times reaches the set number of rounds; if parameter learning is needed, the learning-needed flag FLG is set to 1, and then step S1 is executed; if parameter learning is not needed, step S1 is directly executed;

[0029] After step S3, the method further comprises the following steps:

[0030] It is determined whether the learning-needed flag FLG is set to 1; if the learning-needed flag FLG is not set to 1, an actual detection phase is entered, i.e., step S4 is executed; if the learning-needed flag FLG is set to 1, the current voltage signal sampling average is saved as a learning result, and a learning flag is saved to complete a parameter learning, and then it is determined whether the parameter learning is completed according to whether the number of learned times reaches the set number of rounds;

[0031] If the parameter learning is completed, the learning results of all rounds are processed by removing extreme values and taking averages, so as to obtain an effective voltage reference value, and step S6 is executed, and subsequent periodic calibration of the voltage reference value is performed according to a set motor service period; if the parameter learning is not completed, step S6 is executed.

[0032] As a further improvement of the above-mentioned solution, in step S4, the insulation resistance of the motor is calculated by the following formula:

[0033]

[0034] In the formula, R 绝缘 is the insulation resistance of the motor winding to the motor shell; ADC is the voltage signal sampling average; VCC is the supply voltage of the single-chip microcomputer; V1 is the output voltage of the transformer T1; R1, R2 and R3 are the resistance values of the resistors R1, R2 and R3, respectively; k is a constant; and N is the conversion bit number of the ADC module in the single-chip microcomputer.

[0035] Compared with the prior art, the beneficial effects of the present application are:

[0036] 1. The online motor insulation detection device disclosed in the present application realizes automatic online qualitative analysis of motor insulation by integrating a microcontroller, a detection circuit and a sampling circuit, avoids downtime operation and the risk of manual electric shock compared with the traditional manual measurement method, and improves the safety and real-time performance of detection.

[0037] In addition, since a high-voltage detection signal needs to be applied between the motor winding and the shell during detection, if the sampling circuit and the microcontroller are not effectively electrically isolated, error accumulation or even safety hazards may occur due to coupling between different potentials. The present application introduces an optical coupling element with isolation capability to reliably isolate the high-voltage detection part from the low-voltage control part, thereby effectively preventing short circuits, voltage interference and other problems, improving the measurement stability and electrical safety of the system, and being suitable for more complex or harsh industrial environments.

[0038] 2、The online motor insulation detection method disclosed in the present application can automatically detect the insulation state on a regular basis or as needed by applying the above-mentioned circuit structure and designing the control logic of the single-chip microcomputer, thereby effectively improving the reliability of motor operation and the intelligent level of maintenance.

[0039] The present application also combines a parameter learning mechanism in the detection method to realize qualitative identification of the insulation state, avoids dependence on device parameters such as optical coupling transmission ratio, and improves the universality and stability of the detection scheme. Since the transmission characteristics (such as transmission ratio) of isolation elements such as optical coupling devices vary from batch to batch, temperature, and aging conditions, if the nominal parameters of the elements are directly used for calculation and analysis of the insulation resistance, detection errors are likely to occur. The present application introduces a parameter learning mechanism to collect multiple sampling values in the initial service state of the motor, extracts the stable value as a reference voltage value, and only needs to compare with the reference value in subsequent regular detection to judge the change trend of the insulation performance, thereby realizing qualitative analysis. This method effectively avoids dependence on the precision of optical coupling elements, and improves the adaptability and engineering practicability of the detection method.

[0040] 3、The detection method of the present application also provides a calculation formula based on known parameters in the detection circuit on the basis of the above-mentioned qualitative analysis, which can be used to deduce the insulation resistance between the motor winding and the shell, has a certain quantitative analysis capability, helps to make more intuitive numerical evaluation of the insulation state, and is also beneficial to trend judgment and fault analysis by maintenance personnel. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 It is the circuit principle diagram of the online motor insulation detection device in embodiment 1 of the present application.

[0042] Figure 2 It is the flowchart of the online motor insulation detection method in embodiment 1 of the present application. DETAILED DESCRIPTION

[0043] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of the present application.

[0044] Embodiment 1

[0045] Please refer to Figure 1 The embodiment provides an online motor insulation detection device, which comprises a detection circuit, a sampling circuit and a microcontroller, and can further comprise a motor control circuit and a relay control circuit.

[0046] The detection circuit is electrically connected with the shell and the winding of the motor respectively, and is used for applying a high-voltage detection signal between the shell and the winding; the sampling circuit is used for collecting an initial voltage signal at a sampling resistor in the detection circuit, and then converting the initial voltage signal through an optical coupler to transmit to the microcontroller; and the microcontroller is used for judging whether the motor insulation is good or not by comparing a received voltage signal sampling value with a preset voltage reference value.

[0047] In the embodiment, the microcontroller can be a single-chip microcomputer, which is the core of the detection device. At present, most single-chip microcomputers can meet the requirements, such as ES7P169C, ES8P5066, etc. Four I / O interfaces IO1-IO4 are arranged on the single-chip microcomputer, wherein the IO3 interface is used as an ADC sampling interface, and the single-chip microcomputer is powered by VCC.

[0048] The detection circuit comprises a transistor N1, a diode D1, a resistor R1, a resistor R4, a transformer T1 and a relay RELAY1.

[0049] One end of the resistor R4 is connected with a VDD power supply, and the other end of the resistor R4 is connected with a negative electrode end of the diode D1 and one end of a primary coil of the transformer T1 respectively; a positive electrode end of the diode D1 is connected with a collector end of the transistor N1 and the other end of the primary coil of the transformer T1 respectively; an emitter end of the transistor N1 is grounded, and a base end of the transistor N1 is connected with the IO2 interface.

[0050] One end of a secondary coil of the transformer T1 is connected with the shell through one of the two switches of the relay RELAY1, and the other end of the secondary coil of the transformer T1 is connected with one end of the resistor R1 through the other switch of the relay RELAY1; the resistor R1 is used as a sampling resistor, and the other end of the resistor R1 is connected with any one winding of the motor.

[0051] The sampling circuit comprises a resistor R2, a resistor R3, an optical coupler O1, a capacitor C1 and a diode D2.

[0052] Among them, the optocoupler O1 is a linear optocoupler; one end of the resistor R3 is connected to the end of the resistor R1 connected to the relay RELAY1 knife switch, and the other end of the resistor R3 is respectively connected to the positive end of the emitter of the optocoupler O1 and the negative end of the diode D2; the positive end of the diode D2 is respectively connected to the negative end of the emitter of the optocoupler O1 and the end of the resistor R1 connected to the motor winding; the emitter end of the receiver of the optocoupler O1 is respectively connected to one end of the capacitor C1 and grounded, and the collector end of the receiver of the optocoupler O1 is respectively connected to one end of the resistor R2, the other end of the capacitor C1 and the ADC sampling interface; the other end of the resistor R2 is connected to the VCC power supply.

[0053] Transformer T1 of the present invention is used to generate a high-voltage detection signal. A single-chip microcontroller applies a pulse signal to transformer T1's primary coil via transistor N1, causing the secondary coil of transformer T1 to generate a high-voltage detection signal for motor insulation testing. Resistor R4 limits the primary current of transformer T1. Resistor R1, connected in series with the motor winding, divides the detection signal. The divided signal is detected by optocoupler O1 and then transmitted to the single-chip microcontroller. D2 is a reverse voltage stabilizing diode at the optocoupler input, ensuring that the signal does not exceed the permitted value at the optocoupler input.

[0054] When testing is required, relay RELAY2 opens, isolating the motor from the motor control circuit. Once the motor stops completely, relay RELAY1 closes, connecting the motor to the test circuit. At this point, because T1 is a high-ratio transformer, the microcontroller's IO2 interface outputs pulses with a certain frequency and duty cycle, which act on transistor N1. When transistor N1 is on, the primary coil of transformer T1 is charged. When transistor N1 is off, the stored energy in the primary coil of transformer T1 is released through diode D1. During this charging and discharging process, the secondary coil simultaneously generates a high-voltage signal.

[0055] In actual applications, different transformer ratios are used for transformer T1 in different applications. For example, for a single-phase 220V motor, a ratio of 20 is used. For a three-phase 380V power supply, a ratio of 40 is used.

[0056] When a high-voltage signal is applied between the motor winding and the housing, if the motor insulation is normal, no voltage will be generated across resistor R1, or a very small voltage will be generated, insufficient to illuminate the optocoupler O1's light-emitting terminal. When the motor insulation deteriorates, the current in the detection circuit increases, generating a higher voltage across resistor R1. When the voltage reaches a certain value, the optocoupler O1's light-emitting terminal begins to emit faintly. The worse the insulation, the higher the voltage across resistor R1, and the stronger the light-emitting terminal's emission. When the light-emitting terminal begins to emit light, the optocoupler O1's light-receiving terminal begins to generate a signal, and the transistor at this terminal begins to conduct weakly. The worse the insulation, the higher the conduction level. The signal generated by the optocoupler O1's light-receiving terminal is sent to the microcontroller's ADC sampling interface via resistors R2 and C1. The microcontroller detects the changes in the ADC and obtains the current insulation status.

[0057] According to the circuit principle, when the insulation of the motor is worse, it means the insulation resistance is smaller, then the current of the detection circuit (the circuit corresponding to the secondary of the transformer) will be greater. The greater the current, the higher the voltage generated on the resistor R1. The higher the voltage on R1, the stronger the light intensity of the light-emitting end of the optocoupler, and the more strongly the light-receiving end is turned on. In other words, the voltage drop between CE of the light-receiving end of the optocoupler is lower, and the ADC samples the voltage corresponding to the light-receiving end of the optocoupler, so the ADC sampling value is smaller.

[0058] The motor control circuit is configured to supply power to the motor's three-phase windings in a timed sequence based on motor control signals transmitted by the microcontroller to drive the motor. The three-phase UVW interfaces of the motor control circuit are connected to the motor's three-phase windings via the three-phase knife switches of relay RELAY2. The specific structure of the motor control circuit varies depending on the selected motor type, but is not the focus of this disclosure and is not further described.

[0059] The relay control circuit is used to control the on and off of relays RELAY1 and RELAY2. The relay control circuit includes transistor N2, diode D3, transistor N3 and diode D4;

[0060] Among them, the base terminal of the transistor N2 is connected to the IO1 interface, and the emitter terminal of the transistor N2 is grounded; the collector terminal of the transistor N2 is respectively connected to the positive terminal of the diode D3 and one end of the relay RELAY1 coil; the negative terminal of the diode D3 is respectively connected to the VDD power supply and the other end of the relay RELAY1 coil.

[0061] The base terminal of transistor N3 is connected to the IO4 interface, and the emitter terminal of transistor N4 is grounded; the collector terminal of transistor N4 is respectively connected to the positive terminal of diode D4 and one end of the relay RELAY2 coil; the negative terminal of diode D4 is respectively connected to the VDD power supply and the other end of the relay RELAY2 coil.

[0062] In this embodiment, transistors are used to drive relays for on-off switching. The driving principles of the two relays are the same, with the difference being that RELAY1 has two poles and RELAY2 has three poles. Taking RELAY1 as an example, when the base of transistor N2 is high, the transistor conducts, powering the drive coil of RELAY1 and closing the contacts of RELAY1.

[0063] The present invention takes into account that different optocouplers have different electrical characteristics. Therefore, the detection device needs to learn parameters in the initial stage (i.e., the first application) to obtain baseline parameters. The data with good consistency of multiple detection results over a period of time is used as the benchmark. If valid data cannot be obtained, an alarm will be issued and the user will be asked to handle it. Of course, in the subsequent detection process, it is also necessary to save the data over a period of time for comparison. If the data change is not obvious, it means that the insulation has not changed. Otherwise, it is considered that there is a change, and an alarm will remind the user to handle it. The specific method is introduced later.

[0064] See also Figure 2 This embodiment also provides an online motor insulation detection method using the above detection device, comprising the following steps:

[0065] When a detection instruction is received, the microcontroller is initialized, and then the saved learning flag is read to determine whether parameter learning is required based on whether the number of learning times has reached the set rounds; if parameter learning is required, the learning flag FLG=1 is set, and then step S1 is executed; if parameter learning is not required, step S1 is directly executed.

[0066] It should be noted that the regular issuance of detection instructions can be achieved through a program preset in the microcontroller, so that after the detection device and the motor are assembled and put into service for the first time, regular online insulation testing can be achieved as needed.

[0067] S1, control relay RELAY2 is disconnected to separate the motor from the motor control circuit, and after a delay, control relay RELAY1 is connected to connect the motor to the detection circuit.

[0068] S2 outputs a pulse signal with set frequency and duty cycle to the detection circuit through the IO2 interface, so that the secondary coil of the transformer T1 generates a high-voltage detection signal.

[0069] S3. Obtain the voltage signal sampling value through the ADC sampling interface, then stop the output of the IO2 interface and disconnect the relay RELAY1.

[0070] In step S3, the voltage signal is sampled and converted multiple times to obtain multiple voltage signal sampling values; and a voltage signal sampling mean is obtained by performing mean processing on the multiple voltage signal sampling values.

[0071] Determine whether the learning flag FLG=1 is set; if the learning flag FLG=1 is not set, enter the actual detection phase, that is, execute step S4; if the learning flag FLG=1 is set, save the current voltage signal sampling mean as the learning result, and save the learning flag to complete one parameter learning, and then determine whether the parameter learning is completed based on whether the number of learning times reaches the set rounds;

[0072] If parameter learning is completed, the learning results of all rounds are devalued and averaged to obtain a valid (consistency-compliant) voltage reference value, and step S6 is executed. Subsequently, the voltage reference value is periodically calibrated according to the set motor service cycle; if parameter learning is not completed, step S6 is executed.

[0073] S4. Determine whether the insulation of the motor is qualified by comparing the received voltage signal sampling value with a preset voltage reference value.

[0074] In step S4, when the voltage signal sampling mean value is lower than the voltage reference value, the motor insulation is determined to be unqualified and step S5 is executed; otherwise, it is qualified and step S6 is executed; wherein, the quality of the motor insulation is positively correlated with the voltage signal sampling mean value.

[0075] S5. Generate an alarm signal to remind relevant personnel to pay attention to motor safety.

[0076] S6. Control relay RELAY2 to turn on to resume motor drive and wait for the next detection instruction to be issued.

[0077] Since the present invention uses an optocoupler device, in actual applications, there is a high probability that the actual current transfer ratio of the optocoupler will be different from the nominal current transfer ratio at the time of shipment. Therefore, there are individual differences in the current transfer ratio of the same type of optocoupler. Although it is possible to conduct experiments on each optocoupler separately to obtain parameters such as the actual transmission ratio, it is time-consuming and labor-intensive and is not suitable for large-scale applications. Therefore, the present invention introduces the link of parameter learning, which performs parameter learning for a set number of times for a new motor and optocoupler, determines a reference value based on the mean value of the voltage signal sampling with good consistency in the early stage, and judges whether the insulation of the motor has deteriorated based on the reference value, thereby achieving qualitative analysis. Of course, in the subsequent use process, the learning process can also be re-run periodically (for example, once a year). If the difference between the learning result and the first learning result is too large, it indicates that there is a problem, and an alarm can be issued to remind manual intervention. The present invention uses "parameter learning" to replace the precise parameter dependence in the traditional quantitative calculation method, which significantly improves the adaptability and engineering practicality of the detection device.

[0078] Example 2

[0079] This embodiment provides an online motor insulation detection method. Based on the detection method in Example 1, in step S4, this embodiment can also calculate the motor insulation resistance to achieve quantitative analysis. The calculation formula is as follows:

[0080]

[0081] Where R 绝缘 is the insulation resistance of the motor winding to the motor housing; ADC is the sampling mean value of the voltage signal; ACC is the power supply voltage of the microcontroller; V S is the output voltage of transformer T1; R1, R2 and R3 are the resistance values ​​of resistors R1, R2 and R3 respectively; k is a constant; N is the number of conversion bits of the ADC module (i.e., analog-to-digital converter) in the microcontroller (which determines the conversion accuracy). For example, if a 12-bit ADC is used, then N = 12.

[0082] It should be noted that in the process of motor safety monitoring, the main focus is on whether its insulation has changed significantly. The significant difference between the calculated motor insulation resistance and the reference value can be used as a basis for judgment. For example, in practical applications, a difference of more than 10% indicates a significant change in insulation.

[0083] In practical applications, ADC results are often used directly for comparison, without calculating the insulation resistance. However, there is a one-to-one correspondence between the insulation resistance and the ADC value. Some controllers with displays can also display the calculated resistance value for user reference.

[0084] In practical applications, it is necessary to determine the value of constant k. Constant k is related to optocoupler O1, resistor R1, resistor R2, and resistor R3 and is determined through experimentation. In this embodiment, k is set to 180. This constant can affect the accuracy of insulation resistance testing. Experiments have found that replacing different optocouplers O1, resistors R1, R2, and R3 has a total actual impact of less than 5%.

[0085] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. An online motor insulation detection device, comprising: Detection circuit, sampling circuit and microcontroller; The detection circuit is electrically connected to the motor casing and winding respectively, and is used to apply a high-voltage detection signal between the casing and the winding; it is characterized in that the sampling circuit is used to collect the initial voltage signal at the sampling resistor in the detection circuit, and then convert the initial voltage signal through an optical coupler for transmission to the microcontroller; the microcontroller is used to determine whether the insulation of the motor is good by comparing the received voltage signal sampling value with a preset voltage reference value.

2. An online motor insulation detection device according to claim 1, characterized in that: The microcontroller adopts a single chip microcomputer, which is provided with four I / O interfaces IO1 to IO4, wherein the IO3 interface is used as an ADC sampling interface, and the single chip microcomputer is powered by VCC; the detection circuit includes: a transistor N1, a diode D1, a resistor R1, a resistor R4, a transformer T1 and a relay RELAY1; Among them, one end of the resistor R4 is connected to the VDD power supply, and the other end of the resistor R4 is connected to the negative end of the diode D1 and one end of the primary coil of the transformer T1 respectively; the positive end of the diode D1 is connected to the collector end of the transistor N1 and the other end of the primary coil of the transformer T1 respectively; the emitter end of the transistor N1 is grounded, and the base end of the transistor N1 is connected to the IO2 interface; One end of the secondary coil of transformer T1 is connected to the casing through a knife switch of relay RELAY1, and the other end of the secondary coil of transformer T1 is connected to one end of resistor R1 through another knife switch of relay RELAY1; resistor R1 serves as a sampling resistor, and its other end is connected to any phase winding of the motor.

3. The online motor insulation detection device according to claim 2, characterized in that: The sampling circuit includes: a resistor R2, a resistor R3, an optical coupler O1, a capacitor C1 and a diode D2; Among them, one end of the resistor R3 is connected to one end of the resistor R1 connected to the relay RELAY1 knife switch, and the other end of the resistor R3 is respectively connected to the positive end of the emission source of the optocoupler O1 and the negative end of the diode D2; the positive end of the diode D2 is respectively connected to the negative end of the emission source of the optocoupler O1 and one end of the resistor R1 connected to the motor winding; the emitter end of the receiver of the optocoupler O1 is respectively connected to one end of the capacitor C1 and grounded, and the collector end of the receiver of the optocoupler O1 is respectively connected to one end of the resistor R2, the other end of the capacitor C1 and the ADC sampling interface; the other end of the resistor R2 is connected to the VCC power supply.

4. The online motor insulation detection device according to claim 3, characterized in that: Diode D2 is a reverse voltage zener diode.

5. The online motor insulation detection device according to claim 3, characterized in that: It also includes a motor control circuit; the motor control circuit is used to power the three-phase winding of the motor in a timing sequence according to the motor control signal sent by the single-chip microcomputer to drive the motor to rotate; wherein the UVW three-phase interface of the motor control circuit is respectively connected to the three-phase winding of the motor through the three-phase knife switch of the relay RELAY2.

6. The online motor insulation detection device according to claim 5, characterized in that: Also includes a relay control circuit; the relay control circuit includes a transistor N2, a diode D3, a transistor N3 and a diode D4; Among them, the base terminal of transistor N2 is connected to the IO1 interface, and the emitter terminal of transistor N2 is grounded; the collector terminal of transistor N2 is respectively connected to the positive terminal of diode D3 and one end of the relay RELAY1 coil; the negative terminal of diode D3 is respectively connected to the VDD power supply and the other end of the relay RELAY1 coil; The base terminal of transistor N3 is connected to the IO4 interface, and the emitter terminal of transistor N4 is grounded; the collector terminal of transistor N4 is respectively connected to the positive terminal of diode D4 and one end of the relay RELAY2 coil; the negative terminal of diode D4 is respectively connected to the VDD power supply and the other end of the relay RELAY2 coil.

7. An online motor insulation detection method, characterized in that: The online motor insulation detection device according to claim 5 or 6 is used; the method comprises the following steps: S1, control relay RELAY2 to disconnect to separate the motor from the motor control circuit, and after a delay, control relay RELAY1 to connect the motor to the detection circuit; S2 outputs a pulse signal with set frequency and duty cycle to the detection circuit through the IO2 interface, so that the secondary coil of transformer T1 generates a high-voltage detection signal; S3, obtain the voltage signal sampling value through the ADC sampling interface, then stop the output of the IO2 interface and disconnect the relay RELAY1; S4. Determine whether the insulation of the motor is qualified by comparing the received voltage signal sampling value with a preset voltage reference value.

8. The online motor insulation detection method according to claim 7, characterized in that: In step S3, the voltage signal is sampled and converted multiple times to obtain multiple voltage signal sampling values; and a voltage signal sampling mean is obtained by averaging the multiple voltage signal sampling values. In step S4, if the voltage signal sampling mean value is lower than the voltage reference value, the motor insulation is determined to be unqualified and step S5 is executed; otherwise, the motor insulation is qualified and step S6 is executed; wherein, the quality of the motor insulation is positively correlated with the level of the voltage signal sampling mean value; S5, generating an alarm signal; S6, control relay RELAY2 to turn on to restore motor drive.

9. The online motor insulation detection method according to claim 8, characterized in that: Before step S1, the method further comprises the following steps: When a detection instruction is received, the single chip microcomputer is initialized, and then the saved learning flag is read to determine whether parameter learning is required based on whether the number of learning times reaches the set rounds; if parameter learning is required, the learning flag FLG is set to 1, and then step S1 is executed; if parameter learning is not required, step S1 is directly executed; After step S3, the method further comprises the following steps: Determine whether the learning flag FLG=1 is set; if the learning flag FLG=1 is not set, enter the actual detection phase, that is, execute step S4; if the learning flag FLG=1 is set, save the current voltage signal sampling mean as the learning result, and save the learning flag to complete one parameter learning, and then determine whether the parameter learning is completed based on whether the number of learning times reaches the set rounds; If parameter learning is completed, the learning results of all rounds are devalued and averaged to obtain a valid voltage reference value, and step S6 is executed. Subsequently, the voltage reference value is periodically calibrated according to the set motor service cycle; if parameter learning is not completed, step S6 is executed.

10. The online motor insulation detection method according to claim 8, characterized in that: In step S4, the motor insulation resistance is calculated using the following formula: Where R 绝缘 is the insulation resistance of the motor winding to the motor housing; ADC is the sampling mean value of the voltage signal; VCC is the power supply voltage of the microcontroller; V S is the output voltage of transformer T1; R1, R2 and R3 are the resistance values ​​of resistors R1, R2 and R3 respectively; k is a constant; N is the number of conversion bits of the ADC module in the microcontroller.

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