Insulation resistance detection system of capacitor

Abstract

A capacitor insulation resistance detection system comprises a power supply circuit, a protection circuit and an insulation resistance detection circuit. The protection circuit comprises a plurality of protection switches. The insulation resistance detection circuit comprises a plurality of detection modules connected with the protection switch. Each detection module comprises an output terminal, a terminal to be detected, a differential amplifier, a first inverting amplifier and a second inverting amplifier. The output terminal comprises a first detection end and a second detection end to output a first voltage value and a second voltage value. The to-be-tested terminal is used for connecting a to-be-tested capacitor The output end of the second inverting amplifier is a first detection end, and the output end of the differential amplifier is a second detection end. The first voltage value and the second voltage value are used for calculating the insulation resistance value of the to-be-detected capacitor, and when the insulation resistance value of the to-be-detected capacitor of the detection module is smaller than a preset saturation resistance value, the protection circuit closes the detection module. Therefore, the influence on the measurement of other detection modules can be avoided, and the test voltage can be ensured to be actually applied to the to-be-tested capacitors on other detection modules.

Description

Technical Field

[0001] The present disclosure relates to a capacitor insulation resistance detection system, and more particularly to a capacitor insulation resistance detection system with a protection mechanism. Background Art

[0002] The insulation resistance of multi-layer ceramic capacitors (MLCCs) is often used as a key indicator in capacitor aging tests, assessing the capacitor's service life. A low insulation resistance indicates excessive leakage current, which can be used as a criterion for capacitor failure.

[0003] However, if the test voltage supplied by the power supply to the capacitor under test is not stable enough, the detection element in the detection circuit is not accurate enough, or the capacitor under test experiences changes in impedance due to temperature rise during testing, these may cause insulation resistance measurement errors, thereby affecting the capacitor life assessment results. Summary of the Invention

[0004] Therefore, the present disclosure provides an insulation resistance detection system for a capacitor, comprising a power supply circuit, a protection circuit, and an insulation resistance detection circuit. The protection circuit is electrically connected to the power supply circuit and comprises a plurality of protection switches. The insulation resistance detection circuit comprises a plurality of detection modules, and each of these detection modules is electrically connected to a corresponding one of these protection switches, wherein each of these detection modules comprises an output terminal, a terminal to be tested, a first inverting amplifier, a second inverting amplifier, and a differential amplifier. The output terminal comprises a first detection terminal and a second detection terminal, which are respectively used to output a first voltage value and a second voltage value. The terminal to be tested comprises a first terminal and a second terminal, and is configured to connect to a capacitor to be tested. The first inverting amplifier comprises a first inverting input terminal, a first non-inverting input terminal, and a first output terminal, wherein the first inverting input terminal is electrically connected to the second end of the terminal to be tested, and the first non-inverting input terminal is electrically connected to the ground potential. The second inverting amplifier includes a second inverting input, a second non-inverting input, and a second output. The second inverting input is electrically connected to the first output of the first inverting amplifier, the second non-inverting input is electrically connected to ground, and the second output serves as a first detection terminal. The differential amplifier includes a differential inverting input, a differential non-inverting input, and a differential output. The differential inverting input is electrically connected to the second end of the terminal under test, the differential non-inverting input is electrically connected to the protection circuit and the first end of the terminal under test, and the differential output serves as a second detection terminal. A first voltage value at the first detection terminal and a second voltage value at the second detection terminal are input to a programmable control system to calculate the insulation resistance of the capacitor under test. When the insulation resistance of the capacitor under test on one of the detection modules is less than a predetermined saturation resistance value of the first inverting amplifier, the protection circuit disables a corresponding one of the protection switches corresponding to the one of the detection modules.

[0005] According to one embodiment of the present disclosure, the insulation resistance of the capacitor under test serves as the input resistance of a first inverting amplifier, and the first inverting amplifier includes an operational amplifier and a feedback resistor. The operational amplifier includes an inverting terminal and a non-inverting terminal, wherein the non-inverting terminal is electrically connected to a ground potential. The feedback resistor is electrically connected between the inverting terminal of the operational amplifier and a first output terminal.

[0006] According to an embodiment of the present disclosure, the feedback resistance of the first inverting amplifier is smaller than a standard value of the insulation resistance of the capacitor to be measured.

[0007] According to one embodiment of the present disclosure, estimating the insulation resistance of the capacitor under test based on a first voltage value at a first detection terminal and a second voltage value at a second detection terminal further includes calculating a voltage difference between the first voltage value at the first detection terminal and the second voltage value at the second detection terminal. When the voltage difference between the first detection terminal and the second detection terminal is lower than a preset voltage difference, the protection circuit turns off a corresponding one of the protection switches corresponding to one of the detection modules.

[0008] According to an embodiment of the present disclosure, the program control system receives the first voltage value and the second voltage value measured by the first detection end and the second detection end of the output terminal, and provides control signals to the protection switches according to the insulation resistance value.

[0009] According to an embodiment of the present disclosure, the protection circuit further includes a plurality of optical coupling circuits, each of which is electrically connected between the power supply circuit and each of the protection switches.

[0010] According to one embodiment of the present disclosure, the second inverting amplifier further includes an operational amplifier, an input resistor, and a feedback resistor. The operational amplifier includes an inverting terminal and a non-inverting terminal, wherein the non-inverting terminal is connected to a ground potential. The input resistor is electrically connected between the first output terminal and the inverting terminal of the operational amplifier. The feedback resistor is electrically connected between the input resistor and the second output terminal.

[0011] According to one embodiment of the present disclosure, the differential amplifier further includes an operational amplifier, a voltage divider circuit, an input resistor, and a feedback resistor. The operational amplifier includes an inverting terminal and a non-inverting terminal. The voltage divider circuit is electrically connected between a first terminal of the terminal to be measured and the non-inverting terminal of the operational amplifier. The input resistor is electrically connected between a second terminal of the terminal to be measured and the inverting terminal of the operational amplifier. The feedback resistor is electrically connected between the input resistor and the differential output terminal.

[0012] According to an embodiment of the present disclosure, the second inverting amplifier further includes a Zener diode electrically connected between the second output terminal of the second inverting amplifier and the ground potential.

[0013] According to an embodiment of the present disclosure, the differential amplifier further includes a Zener diode electrically connected between the differential output terminal of the differential amplifier and the ground potential.

[0014] The beneficial effects of the present disclosure are at least that, by using an insulation resistance detection circuit formed by connecting multiple operational amplifiers and a protection circuit connected to multiple detection modules in the insulation resistance detection circuit, not only can the accuracy of the aging test be improved, but also the following effects can be achieved: (1) real-time monitoring of the test results of each capacitor to be tested, and ensuring that each capacitor to be tested is independent and not affected by each other during measurement; (2) when expanding the connection of different numbers of capacitors to be tested, ensuring that the input voltage can maintain a stable output; (3) when the capacitor to be tested measured by the detection module is short-circuited, the insulation resistance is too low, or it is damaged, the detection module can be turned off in time to avoid circuit burnout or the test voltage cannot be accurately applied to the capacitors to be tested on other detection modules, thereby affecting the detection results of other detection modules. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] To make the above and other objects, features, advantages and embodiments of the present disclosure more clearly understood, the accompanying drawings are described as follows:

[0016] Figure 1 A schematic diagram of a capacitor insulation resistance detection system according to an embodiment of the present disclosure;

[0017] Figure 2 is an internal schematic diagram of a detection module according to an embodiment of the present disclosure; and

[0018] Figure 3 FIG. 1 is a wiring diagram of a first inverting amplifier, a second inverting amplifier, and a differential amplifier according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0019] Figure 1 This is a schematic diagram of a capacitor insulation resistance testing system 100 according to an embodiment of the present disclosure. Capacitor insulation resistance testing system 100 is suitable for aging testing of multilayer ceramic capacitors or any application requiring the insulation resistance of a capacitor. The system utilizes the connection and characteristics of multiple operational amplifiers (OPAs) to ensure that the test voltage applied to each capacitor under test is maintained, thereby improving the accuracy of insulation resistance measurements. Furthermore, the addition of a protection circuit ensures that each capacitor under test is measured independently and safely, without any impact on the other capacitors due to a short circuit, low insulation resistance, or damage to one of the capacitors under test.

[0020] The capacitor insulation resistance detection system 100 includes a power supply circuit 110, a protection circuit 120, and an insulation resistance detection circuit 130. The power supply circuit 110 is used to supply the AC voltage or DC voltage required by the protection circuit 120 and the insulation resistance detection circuit 130. The protection circuit 120 is electrically connected between the power supply circuit 110 and the insulation resistance detection circuit 130 and includes a plurality of protection switches S1 to S2. n The insulation resistance detection circuit 130 includes a plurality of detection modules M1 to M2. n , can be used to detect multiple capacitors to be tested at the same time, and in the detection module M1 ~ M n The output terminal of each of the o1 ~V on And the actual cross-voltage signal V DUT1 ~V DUTn .

[0021] Specifically, the detection modules M1 to M n Electrically connected to the protection switches S1~S n The corresponding one of them is used to protect the switches S1 to S n The corresponding detection modules M1 to M are turned on or off based on the conduction ofn In the embodiment disclosed herein, if the insulation resistance detection circuit 130 has n detection modules, the protection circuit 120 is correspondingly provided with n protection switches. For example, the protection switch S1 corresponds to the detection module M1, and is used to turn on / off the detection module M1 according to the on / off state of the protection switch S1. Similarly, the protection switch S1 corresponds to the detection module M1. n Also corresponds to the detection module M n , and according to the protection switch S n The detection module M is turned on / off by the on / off n In this way, each capacitor under test can be measured independently and safely in each detection module.

[0022] exist Figure 1 In the example shown, when the detection modules M1 to M n When the voltage difference between the measurement signal and the actual cross-voltage signal of one of the detection modules is lower than the preset voltage difference, the protection circuit 120 will turn off the protection switch corresponding to the detection module. For example, the detection module M1 is used to detect the capacitor DUT1 under test. When the measurement signal V o1 And the actual cross-voltage signal V DUT1 When the voltage difference between the two is lower than the preset voltage difference, it means that the insulation resistance of the capacitor DUT1 is too low, and the protection circuit 120 will be triggered to close the protection switch S1 corresponding to the detection module M1. More specifically, the measurement signal V o1 And the actual cross-voltage signal V DUT1 The insulation resistance value of the capacitor DUT1 can be calculated, and when the insulation resistance value of the capacitor DUT1 is less than the preset saturation resistance value, the protection circuit 120 is further triggered to close the protection switch S1 corresponding to the detection module M1.

[0023] In some embodiments, the capacitor insulation resistance detection system 100 further includes a program control system (not shown). The program control system is used to receive the detection modules M1-M n The measured signal V is obtained at the output of o1 ~V on And the actual cross-voltage signal V DUT1 ~V DUTn , and based on the measurement signal V o1 ~V on And the actual cross-voltage signal V DUT1 ~V DUTn Calculate each detection module M1~M n The insulation resistance value of the capacitor to be tested is measured. nWhen the insulation resistance value measured by one of the test modules is less than the preset saturation resistance value, the program control system is also used to provide a control signal to the protection circuit 120 to turn off the detection module by closing the corresponding protection switch. In some embodiments, the test module can also be directly controlled based on the measurement signal V o1 ~V on And the actual cross-voltage signal V DUT1 ~V DUTn To determine the insulation resistance of the capacitor under test. For example, if the voltage difference between the measured signal and the actual cross-voltage signal falls below a preset voltage difference, indicating that the insulation resistance of the capacitor under test is too low, the protection circuit will trigger the corresponding protection switch to close, thereby shutting down the corresponding detection module. This not only prevents interference with the measurements of other detection modules, but also ensures that the test voltage is applied to the capacitors under test in other detection modules.

[0024] The programmable control system consists of a programmable logic controller (PLC) and a computer. The analog module in the PLC captures the capacitor's measurement results and displays them on a human-machine interface. Furthermore, the measurement data can be transmitted to the computer via wired or wireless communication to serve as a historical record for subsequent query.

[0025] In some embodiments, the protection circuit 120 further includes a plurality of optical coupling circuits (not shown). The optical coupling circuits are electrically connected to the power supply circuit 110 and the protection switches S1 to S2. n Between each of them, it is used to protect the switches S1 to S n Each of the detection modules M1 to M2 is electrically isolated from the power supply circuit 110. When the control signal output by the program control system is an on signal, the test voltage provided by the power supply circuit 110 can be applied to the capacitor under test in the detection module. Conversely, when the control signal output by the program control system is an off signal, the test voltage provided by the power supply circuit 110 cannot be applied to the capacitor under test in the detection module. In this way, each detection module M1 to M2 is electrically isolated from the power supply circuit 110. When the control signal output by the program control system is an on signal, the test voltage provided by the power supply circuit 110 can be applied to the capacitor under test in the detection module. n Can be independent and not affect each other.

[0026] Figure 2 The internal structure of the detection module M1 of the embodiment of the present disclosure is further illustrated. It should be understood that although only the internal structure of the detection module M1 is illustrated here, the other detection modules M2 to M n Since they have similar or identical internal structures, the following description will only take the detection module M1 as an example.

[0027] like Figure 2As shown, the detection module M1 includes a terminal to be tested 131, a first inverting amplifier 132, a second inverting amplifier 133, a differential amplifier 134 and an output terminal 135. The terminal to be tested 131 includes a first terminal T1 and a second terminal T2, and is configured to connect to the capacitor to be tested DUT1. The output terminal 135 includes a first detection terminal T1 as the output terminal of the detection module M1. M1 And the second detection terminal T M2 The first inverting amplifier 132 includes a first inverting input terminal T 11 , the first non-inverting input terminal T 12 and the first output terminal T o1 The first inverting input terminal T 11 The second terminal T2 electrically connected to the terminal to be tested 131, the first non-inverting input terminal T 12 is electrically connected to the ground potential G. The second inverting amplifier 133 comprises a second inverting input terminal T 21 , the second non-inverting input terminal T 22 And the second output terminal T o2 The second inverting input terminal T 21 is electrically connected to the first output terminal T of the first inverting amplifier 132 o1 , the second non-inverting input terminal T 22 is electrically connected to the ground potential G, and wherein the second output terminal T o2 The first detection terminal T as the output terminal 135 M1 The differential amplifier 134 includes a differential inverting input terminal T 31 , differential non-inverting input terminal T 32 And the differential output terminal T o3 Differential inverting input terminal T 31 The second terminal T2 electrically connected to the terminal to be tested 131, the differential non-inverting input terminal T 32 is electrically connected to the protection switch S1 and the first terminal T1 of the terminal to be tested 131, and the differential output terminal T o3 The second detection terminal T as the output terminal 135 M2 .

[0028] The first inverting amplifier 132 and the second inverting amplifier 133 are connected in a negative feedback configuration and are connected in series so that the first detection terminal T M1 The measured signal V o1 In this way, the program control system can more quickly and conveniently measure the signal V o1 The differential amplifier 134 is used to adjust the voltage value across the capacitor DUT1 to a desired value so that the second detection terminal T M2 The actual cross-voltage signal V DUT1Comply with the voltage range that the programmable control system can accept.

[0029] Under normal circumstances, the protection switch S1 is always on, so the power supply circuit 110 ( Figure 2 (not shown) can apply the test voltage to the capacitor DUT1 connected to the test terminal 131 through the protection switch S1, and M1 and the second detection terminal T M2 The measurement signal V o1 And the actual cross-voltage signal V DUT1 When the measurement signal V o1 And the actual cross-voltage signal V DUT1 When the calculated insulation resistance of the capacitor DUT1 does not meet the preset standard (for example, the insulation resistance is too low), the protection switch S1 is triggered to be turned off, thereby shutting down the detection module M1. In this case, the other detection modules M2 to M3 are turned off. n It can still maintain operation without affecting the test voltage applied by the power supply circuit 110 to other capacitors under test, and will not affect other detection modules M2 to M n The measurement results.

[0030] Figure 3 The first inverting amplifier 132, the second inverting amplifier 133 and the differential amplifier 134 of the embodiment of the present disclosure are further illustrated. The first inverting amplifier 132 includes an operational amplifier OPA1 and a feedback resistor R S The operational amplifier OPA1 includes an inverting terminal (-) and a non-inverting terminal (+), wherein the non-inverting terminal (+) is the first non-inverting input terminal T 12 , connected to the ground potential G. Feedback resistor R S is electrically connected to the inverting terminal (-) of the operational amplifier OPA1 and the first output terminal T o1 The second inverting amplifier 133 includes an operational amplifier OPA2, an input resistor R1, and a feedback resistor R2. The operational amplifier OPA2 includes an inverting terminal (-) and a non-inverting terminal (+), and the non-inverting terminal (+) is the second non-inverting input terminal T 22 , connected to the ground potential G. The input resistor R1 is electrically connected to the first output terminal T o1 The feedback resistor R2 is electrically connected between the input resistor R1 and the second output terminal T o2 between.

[0031] Based on the connection method of the capacitor DUT1, the first inverting amplifier 132 and the second inverting amplifier 133, it can be known that the insulation resistance R of the capacitor DUT1 is DUT1 As the input resistance of the first inverting amplifier 132, the second output terminal To2 (ie the first detection end T M1 ) The measured signal V o1 It can be expressed by the following equation:

[0032]

[0033] From the above equation, we can see that the measured signal V o1 The insulation resistance R of the capacitor DUT1 to be tested can be DUT1 , the feedback resistor R of the first inverting amplifier 132 S , the input resistance R1 of the second inverting amplifier 133 and the feedback resistance R2 are calculated. in is the test voltage applied to the capacitor under test DUT1 , ie, the voltage supplied via the power supply circuit 110 and the protection switch S1 of the conductive protection circuit 120 .

[0034] In circuit design, the feedback resistor R S Designed to be smaller than the insulation resistance R of the capacitor DUT1 under test DUT1 Therefore, the insulation resistance R DUT1 If the insulation resistance R of the capacitor DUT1 is less than 0.01, the first inverting amplifier 132 will not be saturated, so that the circuit can operate normally. DUT1 Does not meet the preset standards (for example, insulation resistance R DUT1 is lower than the preset saturation resistance value), the first inverting amplifier 132 is close to saturation, and the protection circuit 120 is prompted to shut down the detection module to ensure that the test voltage can still be applied to the capacitors under test on other detection modules. In other words, even if one of the detection modules is damaged by the insulation resistance R DUT1 When a module is shut down due to failure to meet preset standards, other detection modules can still perform measurements without being affected.

[0035] The differential amplifier 134 includes an operational amplifier OPA3, a voltage divider circuit 134a, an input resistor R3, and a feedback resistor R5. The operational amplifier includes an inverting terminal (-) and a non-inverting terminal (+). The voltage divider circuit 134a is electrically connected between the first terminal T1 of the terminal to be tested 131 and the non-inverting terminal (+) of the operational amplifier OPA3. The input resistor R3 is electrically connected between the second terminal T2 of the terminal to be tested 131 and the inverting terminal (-) of the operational amplifier OPA3. The feedback resistor R5 is electrically connected between the input resistor R3 and the differential output terminal T o3 From the connection mode of the differential amplifier 134, it can be seen that at the differential output terminal T o3 (ie the second detection end T M2 ) The actual cross-voltage signal VDUT1 It can be expressed by the following equation:

[0036]

[0037] From the above equation, we can know that the actual cross-voltage signal V DUT1 It can be calculated by the feedback resistor R5 and the input resistor R3 of the differential amplifier 134, where V in The same test voltage is applied to the capacitor under test DUT1. In the circuit design, the input resistor R3 is designed to be the same as the voltage divider resistor R4 in the voltage divider circuit 134a, and the feedback resistor R5 is designed to be the same as the voltage divider resistor R6 in the voltage divider circuit 134a, thereby obtaining the above equation. For example, but not limited to this, the feedback resistor R5 is designed to be 1 kiloohm (kΩ), and the input resistor R3 is designed to be 240kΩ. Therefore, the second detection terminal T M2 The voltage across the capacitor DUT1 under test, which is reduced by 240 times, can be obtained as the actual voltage signal V DUT1 . Through the actual cross-voltage signal V DUT1 The actual cross voltage on the capacitor DUT1 to be tested can be monitored in time to ensure that the actual cross voltage on the capacitor DUT1 to be tested is consistent with the required test voltage, thereby avoiding the insulation resistance R of the capacitor DUT1 to be tested due to the error of the applied test voltage. DUT1 measurement error.

[0038] Based on the above two equations, the insulation resistance R of the capacitor DUT1 on the module M1 is finally detected. DUT1 It can be integrated into the following equation:

[0039]

[0040] In some embodiments, the second inverting amplifier 133 further includes a Zener diode Z1. The Zener diode Z1 is electrically connected to the second output terminal T of the second inverting amplifier 133. o2 and the ground potential G. In some embodiments, the differential amplifier 134 further includes a Zener diode Z2. The Zener diode Z2 is electrically connected to the differential output terminal T of the differential amplifier 134. o3 and the ground potential G. In those embodiments including the Zener diode, the Zener diode can be o2 And the differential output terminal T o3 It can realize voltage stabilization function and protect the program-controlled system from damage caused by surge current and static electricity.

[0041] According to the capacitor insulation resistance detection system disclosed herein, the insulation resistance detection circuit formed by connecting multiple operational amplifiers and the protection circuit connected to multiple detection modules in the insulation resistance detection circuit can not only improve the accuracy of the aging test, but also achieve the following effects: (1) real-time monitoring of the test results of each capacitor to be tested, and ensuring that each capacitor to be tested is independent and not affected by each other during measurement; (2) when expanding and connecting different numbers of capacitors to be tested, ensuring that the input voltage can maintain a stable output; (3) when the capacitor to be tested measured by the detection module is short-circuited, the insulation resistance is too low, or it is damaged, the detection module can be turned off in time to avoid circuit burnout or the test voltage cannot be accurately applied to the capacitor to be tested on other detection modules, thereby affecting the detection results of other detection modules. Overall, the capacitor insulation resistance detection system disclosed herein not only solves the problem of insufficient voltage stability of the test voltage, but also improves the measurement accuracy of the aging test.

[0042] Although the present disclosure has been disclosed above with various embodiments, they are not intended to limit the present disclosure. Any person skilled in the art may make slight changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be determined by the appended claims.

[0043]

Explanation of symbols

[0044] 100:Capacitor insulation resistance detection system

[0045] 110: Power supply circuit

[0046] 120: Protection circuit

[0047] 130: Insulation resistance detection circuit

[0048] 131: Terminal to be tested

[0049] 132: First inverting amplifier

[0050] 133: Second inverting amplifier

[0051] 134: Differential Amplifier

[0052] 134a: Voltage divider circuit

[0053] 135: Output terminal

[0054] T1: First end

[0055] T2: Second end

[0056] T 11 : First inverting input

[0057] T 12 : First non-inverting input

[0058] T o1 :First output terminal

[0059] T 21 : Second inverting input

[0060] T 22 : Second non-inverting input

[0061] T o2 : Second output terminal

[0062] T 31 : Differential inverting input

[0063] T 32 : Differential non-inverting input

[0064] T o3 : Differential output

[0065] T M1 :First detection end

[0066] T M2 : Second detection end

[0067] DUT1: Capacitor under test

[0068] G: Ground potential

[0069] S1,S2,S n :Protection switch

[0070] M1,M2,M n :Detection module

[0071] V o1 ,V o2 ,V on :Measurement signal

[0072] V DUT1 ,V DUT2 ,V DUTn : Actual cross-voltage signal

[0073] OPA1, OPA2, OPA3: Operational Amplifiers

[0074] R1, R3: input resistance

[0075] R2,R S ,R5: Feedback resistor

[0076] R4, R6: voltage divider resistors

[0077] R DUT1 :Insulation resistance.

Claims

1. A capacitor insulation resistance detection system, characterized in that: Include: power supply circuit; a protection circuit electrically connected to the power supply circuit and comprising a plurality of protection switches; and The insulation resistance detection circuit includes a plurality of detection modules, and each of the plurality of detection modules is electrically connected to a corresponding one of the plurality of protection switches, wherein each of the plurality of detection modules includes: The output terminal includes a first detection terminal and a second detection terminal, respectively used to output a first voltage value and a second voltage value; A terminal to be tested, comprising a first end and a second end, and configured to be connected to a capacitor to be tested; a first inverting amplifier comprising a first inverting input terminal, a first non-inverting input terminal, and a first output terminal, wherein the first inverting input terminal is electrically connected to the second terminal of the terminal to be measured, and the first non-inverting input terminal is electrically connected to a ground potential; a second inverting amplifier comprising a second inverting input terminal, a second non-inverting input terminal, and a second output terminal, wherein the second inverting input terminal is electrically connected to the first output terminal of the first inverting amplifier, the second non-inverting input terminal is electrically connected to the ground potential, and the second output terminal serves as the first detection terminal; as well as a differential amplifier comprising a differential inverting input terminal, a differential non-inverting input terminal, and a differential output terminal, wherein the differential inverting input terminal is electrically connected to the second terminal of the terminal to be tested, the differential non-inverting input terminal is electrically connected to the protection circuit and the first terminal of the terminal to be tested, and the differential output terminal serves as the second detection terminal; The first voltage value of the first detection end and the second voltage value of the second detection end are input into a program control system to calculate the insulation resistance value of the capacitor to be tested, and when the insulation resistance value of the capacitor to be tested on one of the multiple detection modules is less than a preset saturation resistance value of the first inverting amplifier, the protection circuit turns off a corresponding one of the multiple protection switches corresponding to the one of the multiple detection modules.

2. The insulation resistance detection system according to claim 1, characterized in that: The insulation resistance of the capacitor to be measured serves as the input resistance of the first inverting amplifier, and the first inverting amplifier comprises: an operational amplifier comprising an inverting terminal and a non-inverting terminal, wherein the non-inverting terminal is electrically connected to the ground potential; and A feedback resistor is electrically connected between the inverting terminal and the first output terminal of the operational amplifier.

3. The insulation resistance detection system according to claim 2, characterized in that: The feedback resistance of the first inverting amplifier is smaller than a standard value of the insulation resistance of the capacitor to be measured.

4. The insulation resistance detection system according to claim 1, wherein: Calculating the insulation resistance of the capacitor to be tested according to the first voltage value of the first detection end and the second voltage value of the second detection end further includes: A voltage difference between the first voltage value of the first detection end and the second voltage value of the second detection end is calculated, and when the voltage difference between the first detection end and the second detection end is lower than a preset voltage difference, the protection circuit turns off a corresponding one of the multiple protection switches corresponding to one of the multiple detection modules.

5. The insulation resistance detection system according to claim 1, characterized in that: The program control system receives the first voltage value and the second voltage value measured by the first detection end and the second detection end of the output terminal, and provides control signals to the plurality of protection switches according to the insulation resistance value.

6. The insulation resistance detection system according to claim 5, characterized in that: The protection circuit further comprises: A plurality of optical coupling circuits are electrically connected between the power supply circuit and each of the plurality of protection switches.

7. The insulation resistance detection system according to claim 1, wherein: The second inverting amplifier further comprises: an operational amplifier comprising an inverting terminal and a non-inverting terminal, wherein the non-inverting terminal is connected to the ground potential; an input resistor electrically connected between the first output terminal and the inverting terminal of the operational amplifier; as well as The feedback resistor is electrically connected between the input resistor and the second output terminal.

8. The insulation resistance detection system according to claim 1, characterized in that: The differential amplifier further comprises: An operational amplifier, comprising an inverting terminal and a non-inverting terminal; a voltage divider circuit electrically connected between the first end of the terminal to be tested and the non-inverting end of the operational amplifier; an input resistor electrically connected between the second end of the terminal to be measured and the inverting terminal of the operational amplifier; as well as The feedback resistor is electrically connected between the input resistor and the differential output terminal.

9. The insulation resistance detection system according to claim 1, characterized in that: The second inverting amplifier further comprises: A Zener diode is electrically connected between the second output terminal of the second inverting amplifier and the ground potential.

10. The insulation resistance detection system according to claim 1, characterized in that: The differential amplifier further comprises: A Zener diode is electrically connected between the differential output terminal of the differential amplifier and the ground potential.

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