Performance evaluation system of ultrahigh frequency partial discharge test equipment

Abstract

The utility model discloses a performance evaluation system of ultrahigh frequency partial discharge test equipment. The performance evaluation system is composed of an upper computer module, a radio frequency signal emission module, a pulse source acquisition module and a partial discharge tester to be evaluated. In the pulse source acquisition module, a plurality of coils are wound and connected in series to imitate a connection structure in a three-phase stator, and a high-voltage relay short circuit mode is adopted between every two coils to simulate a damage structure between opposite phases, so that the working condition of poor insulation between the opposite phases of the motor stator is simulated; the defect that performance evaluation for the pulse output source in the motor stator phase-to-phase test is lacked in the prior art is overcome, actual use and operation are facilitated, and evaluation requirements of various different devices can be met.

Description

Technical Field

[0001] The utility model belongs to the technical field of motor testing, and specifically relates to a test system for ultra-high frequency partial discharge equipment. Background Technique

[0002] With the continuous development of the new energy vehicle market, the EV (Electric Vehicle) motors used to drive electric vehicles are beginning to transfer from the 400V platform to the 800V platform. The increase in the drive voltage and frequency of the motor makes the partial discharge phenomenon of the motor stator insulation non-negligible, thus promoting the rapid development of motor stator partial discharge testing equipment. Among them, the ultra-high frequency partial discharge detection technology (Ultra High Frequence, abbreviated as UHF) is more suitable for production line use due to its strong anti-interference ability, and is favored by many OEMs and vehicle manufacturers.

[0003] The partial discharge tester using the ultra-high frequency detection technology generally includes two parts: the excitation source output part and the ultra-high frequency signal acquisition part. Among them, the excitation source output generally has two forms. One is a pulse excitation source for the relative phases of the motor stator, and the other is an AC voltage source for the relative ground of the motor stator. As Figure 1 shown, it shows a schematic diagram of using a UHF device to test a motor stator product, where the A end is connected to the motor stator housing, the B, C, and D ends are respectively connected to the U, V, and W phases of the motor stator, the E end represents the antenna probe for receiving partial discharge electromagnetic wave signals, and the F represents the electromagnetic wave signal emitted outward by the motor stator.

[0004] During the partial discharge test of the motor stator relative to the ground, the partial discharge tester applies an AC voltage source to the B, C, and D ends, and the A end is used as the tester loop. At this time, partial discharge signals will be generated between the three-phase windings and the housing of the motor stator. During the generation process of the partial discharge signals, electromagnetic wave signals F will be radiated outward, and these signals will be collected by the antenna probe E of the partial discharge tester.

[0005] During the partial discharge test of the motor stator relative to the phase, the partial discharge tester applies pulse voltage sources to the B-C, C-D, and D-B ends respectively, that is, B is the high end and C is the loop. At this time, partial discharge signals will be generated between the three-phase windings of the motor stator. During the generation process of the partial discharge signals, electromagnetic wave signals F will be radiated outward, and these signals will be collected by the antenna probe E of the partial discharge tester

[0006] Based on the actual application of the above ultra-high frequency partial discharge test equipment in the motor testing industry, relevant teams have already carried out research on how to test the performance of ultra-high frequency partial discharge test equipment and designed relevant solutions. Generally, it is aimed at two aspects. One is the test and evaluation of the excitation source voltage signal, and the other is the test and evaluation of the ultra-high frequency signal detection ability.

[0007] Figure 2 and Figure 3 shows the test and evaluation of the excitation source voltage signal in the existing solution. Figure 2 represents the voltage signal measurement of the AC voltage source. The high end of the probe is connected to point D, and the low end of the probe is connected to point A. Figure 3 represents the voltage signal measurement of the pulse voltage source. The high end of the probe is connected to point D, and the low end of the probe is connected to point B. After completing the connection as above, read the actual voltage output by the tester on the oscilloscope to evaluate the deviation between the output voltage and the set voltage value.

[0008] Figure 4 shows the test and evaluation of the detection ability for UHF signals. The RF signal generator is used to emit electromagnetic wave signals with adjustable center frequency and variable amplitude through probe B. The detection ability for UHF signals is evaluated by comparing the values of the partial discharge tester with the amplitude emitted by the RF signal generator.

[0009] The existing technical solutions can, to a certain extent, reflect the performance of the UHF partial discharge tester and can evaluate the basic functions of the test equipment. However, the above solutions focus on the test and evaluation of UHF signals. For the evaluation of the performance of the excitation source, static parameters such as the voltage amplitude are measured by an oscilloscope. Essentially, it is a measurement of the accuracy of the output source and cannot fully reflect the performance characteristics of the output source of the partial discharge tester.

[0010] This is mainly because for the transformer and insulation material industries, only the insulation between a single winding and the shell needs to be evaluated. According to the national standard requirements, applying an AC source below 50 - 400 Hz for a certain period of time can charge the entire product with sufficient energy. Therefore, there is no need to consider the performance of the relative phase excitation source. However, the special feature of the motor stator field is that the relative phase test requirements need to be increased, which is a key insulation assessment item.

[0011] Taking a conventional three - phase stator as an example, the three phases are connected together by star connection or delta connection, resulting in the inability to use the AC source required by the national standard for excitation, which will cause a short - circuit and abnormal testing. The existing solution is to use the short - time pulse source mentioned above for excitation. However, due to the influence of factors such as traveling wave theory and stator load, different characteristic pulse sources acting on the same stator product will generate different field strength distributions inside the stator. As Figure 5 shown in the winding diagram of a certain three - phase stator, a short - circuit between point A and point B is generally referred to as poor insulation between the same phase, and a short - circuit between point A and point C is generally referred to as poor insulation between different phases. Identifying the short - circuit between point A and point B requires higher pulse source performance than that between point A and point C.

[0012] Factors such as energy, rise time, fall time, or impact frequency will affect the field strength distribution inside the stator, inevitably resulting in different voltage gradients. The essence of insulation detection is that sufficient field strength needs to be applied to the insulator to generate corresponding discharge, breakdown, and other phenomena.

[0013] Taking the rise time as an example, a short and sharp rise time in the voltage signal means that the voltage changes rapidly from low to high. This rapid change will cause a larger voltage gradient in the circuit. The voltage gradient generally refers to the voltage difference or change rate between different positions in the circuit. When a sharp rise time signal is applied to the stator, since the inside of the stator can be regarded as a series-parallel model of capacitance, inductance, and resistance, corresponding voltage differences will be generated locally. When the signal passes through the equivalent capacitance circuit, the sharp rise time will cause the capacitor to charge rapidly. Since the capacitor charging process takes time, the rapidly changing voltage will increase the voltage gradient across the capacitor. After the equivalent inductor experiences a sharp rise time, it will cause a rapid change in the current in the inductor. This rapidly changing current will also generate a reverse induced voltage across the inductor, which will also increase the voltage gradient.

[0014] Similarly, greater energy and higher frequency will make it easier for charges to accumulate inside the motor stator, be able to penetrate deeper into the motor stator, and detect insulation defects deeper. It can be seen that the different performances of the pulse excitation source directly affect the partial discharge test of the motor stator, which cannot be reflected by simply measuring the voltage accuracy. However, the above pulse source characteristics cannot be specifically quantified so far and can only be evaluated through the actual effects on the motor stator products.

[0015] In summary, compared with the traditional partial discharge detection technology based on the pulse current method, there is no mature and reliable national standard document to regulate the requirements for the ultra-high frequency partial discharge detection technology. Customers cannot evaluate the actual performance of the ultra-high frequency partial discharge detection equipment. And the partial discharge detection equipment is often a key workstation in the production process of motor stator products. Once the test performance of the partial discharge detection equipment does not meet the requirements, it will bring huge hidden dangers to the quality of the motor stator products. Summary of the Invention

[0016] The purpose of the present utility model is to provide an evaluation system for an ultra-high frequency partial discharge test equipment applicable to the field of motor stators. By imitating the internal connection structure of the three-phase stator and the working conditions of relative phase insulation defects through the structure of coil winding in series and high-voltage relay short circuit, it makes up for the deficiency in the existing technical solutions that lack the performance evaluation of the pulse output source in the relative phase test of the motor stator.

[0017] The present utility model is implemented by adopting the following technical solutions:

[0018] A performance evaluation system for a very high frequency partial discharge test device is proposed, which consists of a host computer module, a radio frequency signal transmitting module, a pulse source acquisition module, and a partial discharge tester to be evaluated; among them;

[0019] The host computer module is connected to the radio frequency signal transmitting module, the pulse source acquisition module, and the partial discharge tester to be evaluated through a communication bus;

[0020] The radio frequency signal transmitting module internally integrates a radio frequency signal generator and externally transmits radio frequency signals through a radio frequency signal transmitting antenna;

[0021] The pulse source acquisition module is composed of a coil short - circuit switching circuit and a pulse voltage trigger acquisition circuit connected in parallel and then connected in series with an ARM main control core circuit; the high - voltage input of the partial discharge tester to be evaluated acts on the coil short - circuit switching circuit. After the pulse voltage trigger acquisition circuit triggers the acquisition, the ARM main control core circuit acquires the voltage output from the coil short - circuit switching circuit; the coil short - circuit switching circuit is composed of multiple coils wound in series, and high - voltage relays are connected in parallel between two coils, and two coils are short - circuited by the high - voltage relay to simulate a relative - phase breakage structure;

[0022] The pulse voltage trigger acquisition circuit is composed of a sampling circuit, a rising - edge trigger circuit, and an FPGA processor; the sampling circuit acquires the high - voltage input of the partial discharge tester to be evaluated and outputs it to the FPGA processor, and the FPGA processor transfers it to the ARM main control core circuit through a data bus; the rising - edge trigger circuit converts the high - voltage input from the partial discharge tester to be evaluated into a high - level square - wave signal and sends it to the FPGA processor and the ARM main control core circuit; after the ARM main control core circuit captures the rising edge, it reads the analog voltage data from the FPGA processor and sends it to the host computer module.

[0023] In some embodiments of the present invention, the sampling circuit is composed of an operational amplifier amplification circuit, an offset modulation circuit, and an ADC acquisition circuit connected in series.

[0024] In some embodiments of the present invention, the offset modulation circuit is composed of a first - stage operational amplifier, a second - stage operational amplifier, and a differential signal conversion chip.

[0025] In some embodiments of the present invention, the pulse source acquisition module further includes a resistor - capacitor voltage - dividing circuit; the high - voltage input of the partial discharge tester to be evaluated is divided by the resistor - capacitor voltage - dividing circuit and then transmitted to the conversion circuit and the rising - edge trigger circuit respectively.

[0026] In some embodiments of the present utility model, a high-voltage relay is connected in series between the output of the partial discharge tester to be evaluated and the pulse source acquisition module.

[0027] Compared with the prior art, the advantages and positive effects of the present utility model are as follows: In the evaluation system of the ultra-high frequency partial discharge test equipment proposed by the present utility model, a connection structure inside the three-phase stator is simulated by winding and connecting multiple coils in series. A damaged structure between opposite phases is simulated by short-circuiting with a high-voltage relay between two coils, thereby simulating the working condition of poor insulation between opposite phases of the motor stator. This makes up for the deficiency in the prior art solution that lacks the performance evaluation of the pulse output source in the test of opposite phases of the motor stator, provides a structural basis for quantitatively solving the problem that the performance of the original pulse source cannot be quantitatively evaluated through the comparison of the standard waveform and the test waveform, is convenient for actual use and operation, and can meet the evaluation requirements of a variety of different devices.

[0028] After reading the detailed description of the embodiments of the present utility model in conjunction with the drawings, other features and advantages of the present utility model will become clearer. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings, as part of the present utility model, are used to provide a further understanding of the present utility model. The schematic embodiments and descriptions of the present utility model are used to explain the present utility model, but do not constitute an improper limitation to the present utility model. Obviously, the drawings in the following description are only some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative efforts.

[0030] Figure 1 Schematic diagram of the existing UHF equipment test;

[0031] Figure 2 Schematic diagram of the AC voltage source test;

[0032] Figure 3 Schematic diagram of the high-voltage source excitation test;

[0033] Figure 4 Schematic diagram of the ultra-high frequency signal test;

[0034] Figure 5 Schematic diagram of poor insulation between opposite phases of the three-phase stator;

[0035] Figure 6 Schematic diagram of the evaluation system of the ultra-high frequency partial discharge test equipment proposed by the present utility model;

[0036] Figure 7 Schematic diagram of the structure of the pulse source acquisition module in the present utility model;

[0037] Figure 8Schematic diagram of the coil short - circuit switching circuit in the present utility model;

[0038] Figure 9 Schematic diagram of the pulse - voltage - triggered acquisition circuit in the present utility model;

[0039] Figure 10 Schematic circuit diagram of the offset modulation circuit in the present utility model.

[0040] It should be noted that these drawings and textual descriptions are not intended to limit the scope of the concept of the present utility model in any way, but to illustrate the concept of the present utility model to those skilled in the art by referring to specific embodiments. Detailed implementation manners

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. The following embodiments are used to illustrate the present utility model but are not used to limit the scope of the present utility model.

[0042] The test system of the ultra - high - frequency partial - discharge equipment given in the embodiments of the present utility model, as Figure 6 shown, is composed of a host - computer module, a radio - frequency signal - transmitting module, a pulse - source acquisition module, a power - supply module, and a partial - discharge tester. In the figure, a and b respectively represent the high - voltage end and the loop end of the pulse excitation source output by the partial - discharge tester, and c and d respectively represent the acquisition antenna and the radio - frequency signal - transmitting antenna of the partial - discharge tester. The partial - discharge tester and the host - computer module have a communication - bus interface, which can support various communication methods such as serial ports and network ports.

[0043] The host - computer module is used to provide internal communication control, external content display, and a communication interface for connecting to an external partial - discharge tester. Among them, communication control and content display can be implemented using existing technologies according to actual needs, which are not the parts limited by the present utility model.

[0044] The radio - frequency signal - transmitting module internally integrates a radio - frequency signal generator, connects to the host - computer module through a communication bus, receives the set parameters issued by the host - computer module, and emits a radio - frequency signal with a variable center frequency and amplitude through the radio - frequency signal - transmitting antenna d. The radio - frequency signal - transmitting module can arbitrarily set the center frequency from 0.8 GHz to 6.5 GHz and arbitrarily adjust the amplitude from - 120 dBm to 20 dBm.

[0045] The pulse - source acquisition module is the core of this test system, as Figure 7It is divided into three parts, namely the coil short - circuit switching circuit, the pulse - voltage trigger acquisition circuit, and the ARM main - control core circuit. Among them, HV and RTN represent the high - voltage and return terminals from the partial - discharge tester. RY represents the high - voltage relay, which is used to isolate the high - voltage input of the partial - discharge tester and is controlled by the ARM main - control core circuit. The model of the ARM main - control core circuit is STM32F407VET.

[0046] Among them, the coil short - circuit switching circuit is as Figure 8 shown, and it is composed of multiple coils wound in series, used to imitate the internal connection structure of the three - phase stator. In the figure, A, B, C, and D represent the exposed copper points in the coil, that is, the damaged points. The label RYi in the figure represents that after the high - voltage relay is closed, the marked damaged points in the figure are short - circuited. The high - voltage relay can be manually controlled through the switch button or electronically controlled through the ARM main - control core circuit.

[0047] In actual operation, first, waveform sampling is carried out, that is, all high - voltage relays are disconnected, and waveform sampling is carried out and saved as the standard waveform. Then, according to the gear selection of the upper - computer module 1, the relevant high - voltage relays are closed, and then waveform sampling is carried out. The test waveform is compared with the standard waveform to judge whether the area and differential product are too different, so as to judge whether effective discharge occurs.

[0048] The pulse - voltage trigger acquisition circuit is as Figure 9 shown. The upper - computer module will send an instruction to wait for voltage input to the ARM main - control core circuit. After receiving the instruction, the ARM main - control core circuit enters the standby state. When the high - voltage inputs HV and RTN from the partial - discharge tester pass through the resistor - capacitor voltage - dividing circuit and enter the rising - edge trigger circuit, at this time, the circuit will detect that there is voltage input and will send a 100 - us high - level square - wave signal to the FPGA processor and the ARM main - control core circuit respectively, triggering the FPGA processor and the ARM main - control core circuit to start sampling. After the ARM main - control core circuit captures the rising edge, it starts to read data from the FPGA processor. Among them, the FPGA processor uses the PGL22G - 6CMBG324 model of Unisoc.

[0049] After sampling starts, the signal after resistor - capacitor voltage - dividing will be converted into an analog voltage range recognizable by the ADC through the operational amplifier and the offset modulation circuit. The AD9255BCPZ - 125 model is used in the ADC acquisition circuit, the sampling rate is 125M, and the accuracy is 14bit. The offset modulation circuit is as Figure 10In an embodiment shown, Vin is the original signal after resistor-capacitor voltage division. It is amplified by the first-stage operational amplifier and the signal polarity is adjusted. The second-stage operational amplifier adjusts the Analog signal output range to 0.3V - 0.9V. The operational amplifier signal uses LMH6714. Then, through the differential signal conversion chip U, the signal is converted from single-ended input to differential output, and at the same time, the reference voltage of the differential signal is lifted, and the lifting amplitude depends on VAVDD. The differential signal conversion chip uses AD8132.

[0050] The FPGA processor transfers the data collected by the ADC to the ARM main control core circuit through the data bus method, and then uploads it to the host computer module 1 through the network port.

[0051] The power supply module supplies power to the host computer module, the radio frequency signal transmission module, and the pulse source acquisition module, and the power supplies of the three are isolated from each other.

[0052] Based on the test system proposed in this application, the performance test process of the partial discharge tester is as follows:

[0053] 1. Connect the partial discharge tester to be evaluated according to the Figure 6 shown structure. After the connection is completed, start the partial discharge tester to be evaluated.

[0054] 2. Start the test process of the host computer module. The host computer module sends set parameters to the radio frequency signal transmission module, and the radio frequency signal source emits a radio frequency signal with a specified center frequency and specified amplitude.

[0055] 3. Read the magnitude of the radio frequency signal collected by the partial discharge tester to be evaluated, and record the transmitted and received values.

[0056] 4. The host computer module turns off the radio frequency signal source, turns on the pulse source acquisition module, and manually starts or communicates to start the partial discharge tester to be evaluated to output a high-voltage signal for the sampling stage until the host computer module completes the standard waveform storage.

[0057] 5. The host computer module sequentially selects the corresponding gears for evaluating waveform sampling, and respectively records the waveform results at different gears.

[0058] 6. Read the area and difference product values at each gear, complete the record, and evaluate the output performance of the pulse source.

[0059] In view of the problem that the performance evaluation of ultra-high frequency partial discharge test equipment is lacking in the target motor stator market, it is found that the performance evaluation of the pulse output source in the relative phase test of the motor stator is lacking in the existing technical solutions. Therefore, by simulating the insulation defect conditions between the relative phases of the motor stator, the existing technical solutions are supplemented, making up for the deficiency of the lack of performance evaluation of the output source in the existing technical solutions. At the same time, the problem that the performance of the original pulse source cannot be quantitatively evaluated is quantitatively solved by comparing the standard waveform with the test waveform, which is convenient for actual use and operation and can meet the evaluation requirements of a variety of different devices.

[0060] It should be noted that although the technical description and test process of comparing the test waveform with the standard waveform are described in the embodiments of the present utility model, this part of the content is not the part defined by this application. This application provides a structural basis for the comparison and evaluation with the above-mentioned hardware architecture, and the means of comparison and evaluation are only used to illustrate how the evaluation system proposed in this application is applied.

[0061] It should be pointed out that the above description is not a limitation of the present utility model, and the present utility model is not limited to the above examples. Changes, modifications, additions or substitutions made by those of ordinary skill in the art within the essence of the present utility model should also fall within the protection scope of the present utility model.

Claims

1. A performance evaluation system for ultra-high frequency partial discharge test equipment, characterized in that: It consists of a host computer module, a radio frequency signal transmission module, a pulse source acquisition module and a partial discharge tester to be evaluated; in; The host computer module is connected to the radio frequency signal transmission module, the pulse source acquisition module and the partial discharge tester to be evaluated through a communication bus; The radio frequency signal transmitting module integrates a radio frequency signal generator internally and transmits radio frequency signals externally through a radio frequency signal transmitting antenna; The pulse source acquisition module is composed of a coil short-circuit switching circuit and a pulse voltage trigger acquisition circuit connected in parallel and connected in series with an ARM main control core circuit; the high voltage input of the partial discharge tester to be evaluated acts on the coil short-circuit switching circuit, and after the pulse voltage trigger acquisition circuit triggers acquisition, the ARM main control core circuit acquires the voltage output from the coil short-circuit switching circuit; the coil short-circuit switching circuit is composed of a plurality of coils wound in series, and a high-voltage relay is connected in parallel between the two coils, and the two coils are short-circuited by the high-voltage relay to simulate the relative phase damage structure; The pulse voltage trigger acquisition circuit is composed of a sampling circuit, a rising edge trigger circuit and an FPGA processor; The sampling circuit collects the high-voltage input of the partial discharge tester to be evaluated and outputs it to the FPGA processor, and the FPGA processor transmits it to the ARM main control core circuit through the data bus; the rising edge trigger circuit converts the high-voltage input from the partial discharge tester to be evaluated into a high-level square wave signal and sends it to the FPGA processor and the ARM main control core circuit; the ARM main control core circuit captures the rising edge, reads the analog voltage data from the FPGA processor, and sends it to the host computer module.

2. The evaluation system for ultra-high frequency partial discharge test equipment according to claim 1, characterized in that: The sampling circuit is composed of an operational amplifier circuit, an offset modulation circuit and an ADC acquisition circuit connected in series.

3. The evaluation system for ultra-high frequency partial discharge test equipment according to claim 1, characterized in that: The pulse source acquisition module also includes a resistor-capacitor voltage divider circuit; the high voltage input of the partial discharge tester to be evaluated is divided by the resistor-capacitor voltage divider circuit and then transmitted to the conversion circuit and the rising edge trigger circuit respectively.

4. The evaluation system for ultra-high frequency partial discharge test equipment according to claim 1, characterized in that: A high voltage relay is connected in series between the output of the partial discharge tester to be evaluated and the pulse source acquisition module.

5. The evaluation system for ultra-high frequency partial discharge test equipment according to claim 2, characterized in that: The offset modulation circuit is composed of a first-stage operational amplifier, a second-stage operational amplifier and a differential signal conversion chip.

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