CN113419169A - High-voltage motor stator insulation detection system and method thereof - Google Patents
High-voltage motor stator insulation detection system and method thereof Download PDFInfo
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Abstract
The invention relates to a high-voltage motor stator insulation detection system and a method thereof, wherein the system comprises a main controller, a current detection unit, a direct-current high-voltage generator and a high-voltage switching device, wherein the main controller is respectively connected with the current detection unit, the direct-current high-voltage generator and the high-voltage switching device; and processing to obtain a plurality of insulation parameters of the to-be-tested sample according to the polarization current and depolarization current data of the to-be-tested sample measured by the current detection unit, wherein the plurality of insulation parameters comprise insulation resistance, equivalent capacitance, absorption ratio, polarization index and dielectric loss. Compared with the prior art, the invention can realize the nondestructive detection of the motor stator, obtain richer insulation parameters and improve the accuracy of an insulation detection result.
Description
Technical Field
The invention relates to the technical field of motor insulation detection, in particular to a high-voltage motor stator insulation detection system and a method thereof.
Background
At present, the insulation state of a motor is mostly detected through a voltage withstand test, wherein the alternating current voltage withstand test is very strict in insulation test, dangerous concentrated defects can be effectively found, and meanwhile, a test object can be greatly damaged; compared with the alternating current withstand voltage test, the direct current withstand voltage test has the advantages that the test equipment is light and local defects of the equipment are easy to find, and compared with the alternating current withstand voltage test, the main defect of the direct current withstand voltage test is that because the voltage distribution inside the insulation under alternating current and direct current is different, the test of the direct current withstand voltage test on the insulation is not as practical as that under alternating current.
In the existing direct current withstand voltage test, detection is usually performed based on single insulation information, such as insulation resistance, absorption ratio or polarization index, wherein whether a local short circuit phenomenon occurs in the motor can be detected based on the insulation resistance, but the test time is long; the mode based on the absorption ratio or the polarization index can only detect whether the area connectivity of the motor is affected with damp, but cannot detect local damp. And direct current withstand voltage test can produce certain destruction to insulating material equally moreover, in addition, in the actual test process, receives influence such as external strong power frequency electric field, power frequency current, stray current and corona discharge of going into ground, leads to insulating testing result inaccurate easily.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a high-voltage motor stator insulation detection system and a method thereof so as to realize nondestructive detection of a motor stator and improve the accuracy of an insulation detection result.
The purpose of the invention can be realized by the following technical scheme: a high-voltage motor stator insulation detection system comprises a main controller, a current detection unit, a direct-current high-voltage generator and a high-voltage switching device, wherein the main controller is respectively connected with the current detection unit, the direct-current high-voltage generator and the high-voltage switching device;
the current detection unit is used for measuring the polarization current and depolarization current of a to-be-detected sample;
the main controller is used for respectively controlling the working states of the direct-current high-voltage generator and the high-voltage switching device; and processing to obtain a plurality of insulation parameters of the to-be-tested sample according to the polarization current and depolarization current data of the to-be-tested sample, wherein the plurality of insulation parameters comprise insulation resistance, equivalent capacitance, absorption ratio, polarization index and dielectric loss.
Further, the current detection Unit includes a differential input Amplifier module, a PGA (Programmable Gain Amplifier) differential module, an analog-to-digital conversion module, and an MCU (micro controller Unit) connected in sequence, where the differential input Amplifier module is connected to the sample to be tested, the MCU is connected to the main controller, and the differential input Amplifier module is used to amplify a weak voltage signal from the sample to be tested;
the PGA difference module is used for adjusting the amplification factor;
the analog-to-digital conversion module is used for converting the amplified voltage signal into a corresponding digital signal;
and the MCU is used for controlling the working state of the analog-to-digital conversion module and transmitting the digital signal to the main controller.
Further, the differential input amplifier module is connected to a test object through a current detection resistor, and the current detection resistor is used for converting a weak current signal flowing through the test object into a voltage signal.
Further, the direct current high voltage generator comprises a direct current high voltage power supply and a high voltage detection module, two ends of the direct current high voltage power supply are respectively connected with the main controller and a test object to be detected, two ends of the high voltage detection module are respectively connected with the test object to be detected and the main controller, the direct current high voltage power supply outputs direct current high voltage to the test object to be detected according to a control signal output by the main controller, and the high voltage detection module is used for measuring a voltage value of the test object to be detected and returning the voltage value to the main controller.
Further, the direct current high voltage power supply comprises an inverter, a high frequency transformer and a voltage doubling rectifier module which are connected in sequence, the inverter is connected with a low voltage direct current power supply, the inverter is used for inverting the direct current low voltage output by the low voltage direct current power supply into high frequency alternating current, the high frequency transformer is used for boosting the high frequency alternating current into alternating current high voltage, and the voltage doubling rectifier module is used for rectifying the alternating current high voltage into direct current high voltage.
Further, high pressure auto-change over device is including interconnect's isolation module, disturbance prevention module, high voltage switch module and protection module in proper order, isolation module still is connected with main control unit, the disturbance prevention module is used for preventing to produce the disturbance to the current detection unit when high pressure auto-change over device switches over the action, high voltage switch module is used for switching polarization return circuit and depolarization return circuit, protection module is used for preventing polarization return circuit and depolarization return circuit to switch on simultaneously.
Further, the high-voltage switch module comprises two high-voltage reed relays corresponding to the polarization loop and the depolarization loop respectively.
Further, the high-voltage reed relay is specifically HVR12-1A 15-150.
Furthermore, the protection module adopts a NAND gate structure.
A high-voltage motor stator insulation detection method comprises the following steps:
s1, the main controller controls the direct current generator to output direct current high voltage, controls the high voltage switching device to conduct the polarization loop, applies the direct current high voltage to the test object to be tested, and starts the polarization test;
s2, the current detection unit collects the polarization current of the tested object in real time and transmits the collected polarization current data to the main controller;
s3, after the polarization test of the preset polarization time is completed, the main controller controls the high-voltage switching device to conduct the depolarization loop, and the test object discharges the bound charges formed in the polarization process to start the depolarization test;
s4, the current detection unit collects depolarization current of the test sample to be detected in real time and transmits collected depolarization current data to the main controller;
and S5, based on the received polarization current data and depolarization current data, the main controller obtains the equivalent resistance and equivalent capacitance of each branch in the motor insulation equivalent model through curve fitting, and further calculates to obtain the absorption ratio, the polarization index and the dielectric loss.
Compared with the prior art, the invention has the following advantages:
according to the invention, the main controller, the current detection unit, the direct current high voltage generator and the high voltage switching device are arranged, the main controller is utilized to respectively control the direct current high voltage generator to output direct current high voltage to a sample to be tested, and control the switching-over state of the polarization loop and the depolarization loop of the aunt high switching device, so that the sample to be tested is respectively subjected to polarization test and depolarization test, the current detection unit is combined to measure polarization current and depolarization current in real time, the main controller can analyze and obtain a plurality of insulation parameters of the sample to be tested based on polarization current and depolarization current data, the whole test process can not damage the sample to be tested, and more insulation characteristic parameters can be obtained, so that the accuracy of the insulation test is improved.
The current detection unit is provided with the differential input amplifier module, weak signals can be accurately identified by adopting differential signals, the reference voltage is controlled in the differential circuit, so that the interference caused by inconsistent grounding can be avoided, and the differential signals can reduce EMI electromagnetic interference to the maximum extent, so that the accuracy of the detection result is further improved.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention;
FIG. 2 is a schematic diagram illustrating the structural connection of the current detecting unit;
FIG. 3 is a schematic structural connection diagram of a DC high voltage generator;
FIG. 4 is a schematic structural connection diagram of the high-voltage switching device;
FIG. 5 is a schematic view of the detection principle of the present invention;
FIG. 6 is a graph showing the change of polarization current and depolarization current;
FIG. 7 is a plot of the polarization current and depolarization current of the stator bars of the example;
the notation in the figure is: 1. the device comprises a main controller, 2, a current detection unit, 3, a direct current high voltage generator, 4, a high voltage switching device, 5, a to-be-tested sample, 201, a differential input amplifier module, 202, a PGA differential module, 203, an analog-to-digital conversion module, 204, an MCU, 301, a direct current high voltage power supply, 302, a high voltage detection module, 401, an isolation module, 402, an anti-disturbance module, 403, a high voltage switch module, 404 and a protection module.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments.
Examples
As shown in fig. 1, a high-voltage motor stator insulation detection system includes a main controller 1, a current detection unit 2, a dc high-voltage generator 3 and a high-voltage switching device 4, where the main controller 1 is connected to the current detection unit 2, the dc high-voltage generator 3 and the high-voltage switching device 4 respectively, the dc high-voltage generator 3 is connected to the high-voltage switching device 4, the current detection unit 2 and the high-voltage switching device 4 are connected to a test article 5 to be tested respectively, and the high-voltage switching device 4 is used for switching a connection state between the dc high-voltage generator 3 and the test article 5 to be tested;
the current detection unit 2 is used for measuring the polarization current and depolarization current of the sample 5 to be tested;
the main controller 1 is used for respectively controlling the working states of the direct-current high-voltage generator 3 and the high-voltage switching device 4; and processing to obtain a plurality of insulation parameters of the sample 5 to be tested according to the polarization current and depolarization current data of the sample 5 to be tested, wherein the plurality of insulation parameters comprise insulation resistance, equivalent capacitance, absorption ratio, polarization index and dielectric loss.
Specifically, as shown in fig. 2, the current detection unit 2 includes a differential input amplifier module 201, a PGA differential module 202, an analog-to-digital conversion module 203, and an MCU204, which are connected in sequence, where the differential input amplifier module 201 is connected to the sample 5 to be tested, the MCU204 is connected to the main controller 1, and the differential input amplifier module 201 is configured to amplify a weak voltage signal from the sample 5 to be tested;
the PGA difference block 202 is used to adjust the amplification factor;
the analog-to-digital conversion module 203 is configured to convert the amplified voltage signal into a corresponding digital signal;
the MCU204 is configured to control the operating state of the analog-to-digital conversion module 203 and transmit the digital signal to the main controller 1.
In practical applications, the differential input amplifier module 201 is connected to the sample 5 to be tested through a current detection resistor, and the current detection resistor is used for converting a weak current signal flowing through the sample 5 to be tested into a voltage signal.
As shown in fig. 3, the dc high voltage generator 3 includes a dc high voltage power supply 301 and a high voltage detection module 302, two ends of the dc high voltage power supply 301 are respectively connected to the main controller 1 and the sample 5 to be tested, two ends of the high voltage detection module 302 are respectively connected to the sample 5 to be tested and the main controller 1, the dc high voltage power supply 301 outputs a dc high voltage to the sample 5 to be tested according to a control signal output by the main controller 1, the high voltage detection module 302 is used for measuring a voltage value of the sample 5 to be tested and returning the voltage value to the main controller 1, so as to form a closed loop negative feedback control.
In practical application, the dc high voltage power supply 301 includes an inverter, a high frequency transformer and a voltage-doubling rectifier module, which are connected in sequence, the inverter is connected to the low voltage dc power supply, the inverter is configured to invert the dc low voltage output by the low voltage dc power supply into a high frequency ac power, the high frequency transformer is configured to boost the high frequency ac power into an ac high voltage, and the voltage-doubling rectifier module is configured to rectify the ac high voltage into a dc high voltage.
As shown in fig. 4, the high-voltage switching device 4 includes an isolation module 401, an anti-disturbance module 402, a high-voltage switch module 403, and a protection module 404, which are sequentially connected to each other, the isolation module 401 is further connected to the main controller 1, the anti-disturbance module 402 is configured to prevent disturbance from occurring to the current detection unit 2 when the high-voltage switching device 4 performs a switching operation, the high-voltage switch module 403 is configured to switch a polarization loop and a depolarization loop, and the protection module 404 is configured to prevent the polarization loop and the depolarization loop from being simultaneously turned on.
In practical application, the high-voltage switch module 403 includes two high-voltage reed relays corresponding to the polarization loop and the depolarization loop, in this embodiment, the high-voltage reed relay is HVR12-1a15-150, and the protection module 404 employs a nand gate structure.
The system is applied to the insulation detection of the high-voltage motor stator, and the process mainly comprises the following steps:
s1, the main controller controls the direct current generator to output direct current high voltage, controls the high voltage switching device to conduct the polarization loop, applies the direct current high voltage to the test object to be tested, and starts the polarization test;
s2, the current detection unit collects the polarization current of the tested object in real time and transmits the collected polarization current data to the main controller;
s3, after the polarization test of the preset polarization time is completed, the main controller controls the high-voltage switching device to conduct the depolarization loop, and the test object discharges the bound charges formed in the polarization process to start the depolarization test;
s4, the current detection unit collects depolarization current of the test sample to be detected in real time and transmits collected depolarization current data to the main controller;
and S5, based on the received polarization current data and depolarization current data, the main controller obtains the equivalent resistance and equivalent capacitance of each branch in the motor insulation equivalent model through curve fitting, and further calculates to obtain the absorption ratio, the polarization index and the dielectric loss.
In this embodiment, the technical scheme of the present invention is applied to perform insulation test on a stator bar, and a dc high voltage generator is designed as a dc high voltage excitation circuit with adjustable output voltage, wherein the dc high voltage excitation source has the design indexes of: voltage output type: d, direct current high voltage;
rated output voltage: 1-5 kV;
rated output current: 1 mA;
rated output power: 5W.
The current detection unit is designed into a weak current signal detection circuit with high resolution and wide measurement range, wherein the weak current measurement indexes are as follows: current measurement range: -1mA to 1 mA;
resolution ratio: 10 nA;
sampling rate: 25 sps.
The main controller adopts an embedded digital controller, and has the advantages of rich software resources and strong network function. The main controller adopts an Intel Sayboard J1900 processor with an x86 architecture, so that the power consumption is low, the fan-free design is realized, the work is stable, and the interface expansion is rich; the Linux system is adopted, so that the software resources are rich; various network protocols are supported, and the network function is strong.
The insulation state of the motor can be analyzed and evaluated from the electrical characteristic perspective by researching the method based on the time domain medium response theory.
Fig. 5 is a basic schematic diagram of insulation test by PDC method, which is to firstly turn on the switch S to K2 and turn off the switch K1, and then apply a dc voltage to polarize the insulation sample, and the measured current is the polarization current of the insulation resistance under the dc voltage. After the polarization time, the switch S is turned on to K2, and K1 is turned off, at this time, the insulation sample discharges the bound charges formed in the polarization process, the measured current is a depolarized current, which is a depolarization process, and the polarization current and depolarization circuit formed in the whole test process are shown in fig. 6. Parameters of each branch element in an equivalent model of motor insulation can be fitted according to the polarization current and depolarization current curves, and the motor insulation can be evaluated according to the model parameters.
When current detection is carried out, the invention provides a weak current signal detection mode, wherein weak current refers to a current signal with a very small current signal amplitude and is characterized by being easily submerged by noise. The invention designs a low-noise differential input amplifier circuit to amplify the polarization current and the depolarization current of an insulation sample, and adopts an analog-to-digital converter (ADC) and a multi-level capacitor (MUC) to acquire amplified data and transmit the data to a main controller. And a current detection resistor is selected to convert the weak current into a voltage signal and amplify the weak signal. In addition, the weak current detection circuit designed by the fully differential and three-layer PCB is designed in the embodiment, and the interference in the weak current measurement is effectively solved by starting from the aspects of circuit optimization and device model selection.
For internal noise interference, the following scheme is adopted for solving the problem:
the current detection resistor adopts a four-pin resistor with larger resistance value. The unipolar weak current detection adopts a scheme that a precise low-resistance current detection resistor is matched with a high amplification factor, and experiments show that although the problem of the amplification factor is solved by multi-stage amplification, new noise is introduced into each stage of amplification circuit, weak direct current bias in each stage of amplification circuit is amplified and superposed, and great interference is caused to the measurement of effective signals. Because the current values of the polarization current and the depolarization current are small, and the insulation resistance value of the motor is large, the sampling is performed by adopting the current detection resistor with relatively large resistance value, the amplification factor of the current detection resistor on the measured direct current signal is increased, and the series of multi-stage amplification is reduced. The current detection resistor is a four-pin resistor, so that the measurement precision is improved.
Secondly, designing a circuit by adopting a differential circuit mode, using differential signals in the whole sampling process, and connecting the ground in the differential circuit with the ground. A differential signal is a signal representing the difference between two physical quantities, i.e. the voltage difference between two points in a circuit, by a value. The circuit mainly has the following two advantages by adopting differential signals:
1) small signals can be identified using differential signals. In single-ended signal measurement circuits, systems typically use "ground" as a reference voltage, and measurement accuracy depends on the consistency of "ground" within the system. The difference value of each point 'ground' in the weak current voltage test is larger than the weak current to be tested, and the measuring circuit can be greatly interfered. The differential source used in the weak current measuring circuit is the voltage difference between two ends of a four-pin sampling resistor, and the reference voltage is controlled in the differential circuit, so that the interference caused by ground inconsistency can be avoided;
2) and the EMI electromagnetic interference is reduced to the maximum extent by adopting differential signals. Because the acquired signal value is the voltage difference between the two ends, the influence of the same interference on the two ports of the differential signal is almost the same, so the differential signal can be adopted to ignore the same interference signal on the two ports, and the electromagnetic interference is effectively shielded.
And (III) reducing the amplification stage number and properly increasing the amplification factor of the single-stage amplification circuit. Because the resistance value of the current detection resistor is improved, the detection signal is amplified, and the total amplification factor of a subsequent amplifying circuit can be reduced. In order to reduce the noise in the amplifying circuit and reduce the DC bias voltage of each stage of amplification, the multistage amplification is reduced to one stage, and the amplification factor is set to be adjustable.
And (IV) double filtering is adopted to enhance the filtering of power frequency interference.
And (V) finally, the components in the preferred circuit.
For external noise interference, two solutions are proposed by adopting an isolation mode:
adopting three layers of circuit boards, circulating a measuring signal from the middle layer of PCB, and carrying out copper cladding operation on the upper layer of circuit board and the lower layer of circuit board to effectively isolate external interference;
and secondly, the ground of the test circuit board is connected with the ground, so that the influence of external interference on the circuit can be greatly reduced.
The invention adopts a direct-current high-voltage excitation power supply and an output closed-loop control mode, the direct-current high-voltage excitation circuit mainly comprises the direct-current high-voltage power supply, an output control circuit and a high-voltage signal detection circuit, the output control signal is output by a main controller to control the output voltage of the direct-current high-voltage power supply, and the negative feedback of the direct-current high-voltage detection circuit is realized. In this embodiment, the DC high-voltage power supply inverts the DC power supply voltage of 12V into a high-frequency ac power with a frequency of 30kHz through the inverter circuit, the high-frequency transformer boosts the ac input with an amplitude of 12V to 1.2kV, and finally, the voltage-doubler rectifier circuit boosts the ac power output from the transformer to a DC high voltage of 5 kV.
In addition, because the polarization loop and the depolarization loop need to be switched in the PDC method test of the motor insulating medium, the invention adopts a disturbance-free loop switching control mode, mainly comprising a main controller, an isolation circuit, a disturbance prevention circuit, a high-voltage switch and a protection circuit, wherein the high-voltage switch device selects two high-voltage reed relays HVR12-1A15-150, the maximum switchable voltage of the relay is 10kV, the breakdown voltage is up to 15kV, and the high-voltage reed relays are led out through a high-voltage lead; the disturbance prevention circuit isolates a control signal of the controller from a relay control loop by adopting an optical coupler, and prevents a switch loop from disturbing a weak current detection circuit; the protection circuit adopts the design of NAND gate, prevents effectively that polarization return circuit and depolarize the return circuit and switch on simultaneously, guarantees the security of device.
And finally, a motor insulation state detection system based on the PDC method is formed by a main controller, weak current detection, direct current high-voltage excitation and loop switching. After the test is started, the main controller controls the direct-current high-voltage generator to output direct-current high voltage, the switching device is switched to the polarization loop to start the polarization test, and the polarization current is collected through the current collection module. And after the polarization time is over, the switching devices are switched to a depolarization loop, the direct-current high-voltage power supply is closed, the weak current detection module collects depolarized current, and all the switching devices are disconnected after the test is finished.
In this example, the excitation voltage applied in the polarization stage was 5kV and the time was 5 minutes, and the polarization current was measured. And in the depolarization stage, the high-voltage dry reed relay switches the test loop to perform short-circuit discharge on the test sample for five minutes, and the depolarization current is measured. Fig. 7 shows the measurement result that under the excitation of 5kV direct voltage, the polarization current of the stator bar is positive, the maximum polarization current is about 2300nA, and then the polarization current starts to drop, and seven burrs appear on the dropping curve, and the polarization current is basically stabilized at 480nA in the fourth minute. And switching to a depolarization loop in the fifth minute to discharge the test sample, wherein the maximum depolarization current measured at the switching moment is about-4000 nA, then the depolarization current starts to decline, and the depolarization current stays at about 23nA in the eighth minute to basically finish discharging the test sample. The test is completed at the tenth minute and the current curve and measurement data are saved to a designated file for subsequent deeper data mining.
At present, a breakdown voltage characteristic parameter method is a unique and reliable standard for measuring the quality of the insulation performance of power equipment, but the breakdown voltage is a destructive parameter, so that the insulation material is damaged, and the breakdown voltage characteristic parameter method cannot be used for measuring the insulation state of the equipment in operation. Other electrical measurement methods, such as partial discharge, leakage current, dielectric loss under power frequency and insulation resistance lasting for 10min, provide single insulation information, and can be influenced by a strong power frequency electric field, power frequency current, ground-entering stray current, corona discharge and the like in an actual field. The invention adopts a polarization depolarization current method to detect the insulation state of the motor, and the detection method is based on a medium response theory and has the advantages of no damage to insulation materials, convenient detection, rich detection information and the like. In the embodiment, through multiple times of simulation and PCB experimental optimization, the design of a fully differential, multi-layer filtering and three-layer PCB is determined, and finally, the detection of the weak current signal with the resolution of 10nA is reliably realized.
In summary, the present invention deeply studies the insulation state automatic testing technology of the high voltage motor, selects a polarization depolarization current method (PDC) with rich diagnostic information and no damage to the insulation layer to test the main insulation of the motor among various insulation state analysis methods, and designs a set of insulation state automatic testing system of the high voltage motor by combining with the field practice of the motor, which mainly comprises weak current detection, a dc high voltage generator, a high voltage switching device and a corresponding processing and calculating method. Therefore, data mining and fusion can be carried out on the basis of acquiring a large amount of high-precision data, and more insulation special diagnosis parameters such as capacitance, dielectric loss angle and the like can be acquired; and the measurement and test are accurate, and the state evaluation of the insulation state can be more accurately carried out.
Claims (10)
1. The high-voltage motor stator insulation detection system is characterized by comprising a main controller (1), a current detection unit (2), a direct-current high-voltage generator (3) and a high-voltage switching device (4), wherein the main controller (1) is respectively connected with the current detection unit (2), the direct-current high-voltage generator (3) and the high-voltage switching device (4), the direct-current high-voltage generator (3) is connected with the high-voltage switching device (4), the current detection unit (2) and the high-voltage switching device (4) are respectively connected with a to-be-detected test article (5), and the high-voltage switching device (4) is used for switching the connection state of the direct-current high-voltage generator (3) and the to-be-detected test article (5);
the current detection unit (2) is used for measuring the polarization current and depolarization current of the to-be-detected sample (5);
the main controller (1) is used for respectively controlling the working states of the direct-current high-voltage generator (3) and the high-voltage switching device (4); and processing to obtain a plurality of insulation parameters of the to-be-tested sample (5) according to the polarization current and depolarization current data of the to-be-tested sample (5), wherein the plurality of insulation parameters comprise insulation resistance, equivalent capacitance, absorption ratio, polarization index and dielectric loss.
2. The high-voltage motor stator insulation detection system according to claim 1, wherein the current detection unit (2) comprises a differential input amplifier module (201), a PGA differential module (202), an analog-to-digital conversion module (203) and an MCU (204) which are connected in sequence, the differential input amplifier module (201) is connected with a sample (5) to be detected, the MCU (204) is connected with the main controller (1), and the differential input amplifier module (201) is used for amplifying a weak voltage signal from the sample (5) to be detected;
the PGA difference module (202) is used for adjusting the amplification factor;
the analog-to-digital conversion module (203) is used for converting the amplified voltage signal into a corresponding digital signal;
the MCU (204) is used for controlling the working state of the analog-to-digital conversion module (203) and transmitting the digital signal to the main controller (1).
3. The high-voltage motor stator insulation detection system as claimed in claim 2, wherein the differential input amplifier module (201) is connected to the test object (5) through a current detection resistor, and the current detection resistor is used for converting a weak current signal flowing through the test object (5) into a voltage signal.
4. The high-voltage motor stator insulation detection system according to claim 1, wherein the dc high-voltage generator (3) comprises a dc high-voltage power supply (301) and a high-voltage detection module (302), two ends of the dc high-voltage power supply (301) are respectively connected with the main controller (1) and the test object (5) to be detected, two ends of the high-voltage detection module (302) are respectively connected with the test object (5) to be detected and the main controller (1), the dc high-voltage power supply (301) outputs a dc high voltage to the test object (5) to be detected according to a control signal output by the main controller (1), and the high-voltage detection module (302) is used for measuring a voltage value of the test object (5) to be detected and returning the voltage value to the main controller (1).
5. The high-voltage motor stator insulation detection system according to claim 4, wherein the DC high-voltage power supply (301) comprises an inverter, a high-frequency transformer and a voltage-doubling rectification module, which are connected in sequence, the inverter is connected with a low-voltage DC power supply, the inverter is used for inverting a DC low voltage output by the low-voltage DC power supply into a high-frequency AC power, the high-frequency transformer is used for boosting the high-frequency AC power into an AC high voltage, and the voltage-doubling rectification module is used for rectifying the AC high voltage into a DC high voltage.
6. The high-voltage motor stator insulation detection system according to claim 1, wherein the high-voltage switching device (4) comprises an isolation module (401), an anti-disturbance module (402), a high-voltage switch module (403) and a protection module (404), which are sequentially connected with each other, the isolation module (401) is further connected with the main controller (1), the anti-disturbance module (402) is used for preventing disturbance to the current detection unit (2) during switching action of the high-voltage switching device (4), the high-voltage switch module (403) is used for switching a polarization loop and a depolarization loop, and the protection module (404) is used for preventing the polarization loop and the depolarization loop from being simultaneously conducted.
7. The high-voltage motor stator insulation detection system according to claim 6, characterized in that the high-voltage switch module (403) comprises two high-voltage dry reed relays corresponding to a polarization loop and a depolarization loop respectively.
8. The system of claim 7, wherein the high voltage reed relay is HVR12-1A 15-150.
9. The high-voltage motor stator insulation detection system according to claim 6, wherein the protection module (404) adopts a NAND gate structure.
10. An insulation detection method applying the high-voltage motor stator insulation detection system as claimed in any one of claims 1 to 9, characterized by comprising the following steps:
s1, the main controller controls the direct current generator to output direct current high voltage, controls the high voltage switching device to conduct the polarization loop, applies the direct current high voltage to the test object to be tested, and starts the polarization test;
s2, the current detection unit collects the polarization current of the tested object in real time and transmits the collected polarization current data to the main controller;
s3, after the polarization test of the preset polarization time is completed, the main controller controls the high-voltage switching device to conduct the depolarization loop, and the test object discharges the bound charges formed in the polarization process to start the depolarization test;
s4, the current detection unit collects depolarization current of the test sample to be detected in real time and transmits collected depolarization current data to the main controller;
and S5, based on the received polarization current data and depolarization current data, the main controller obtains the equivalent resistance and equivalent capacitance of each branch in the motor insulation equivalent model through curve fitting, and further calculates to obtain the absorption ratio, the polarization index and the dielectric loss.
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