Leakage current testing device for inverter

Abstract

The utility model relates to a leakage current testing device for an inverter. The input end of the device is connected with the direct current input end of the inverter, the output end of the device is grounded, and the device comprises a resistance adjusting circuit, a capacitance adjusting circuit, a plurality of resistance circuits connected in parallel and a switch module. And the switch module is connected with the resistance adjusting circuit and the plurality of resistance circuits which are connected in parallel, and controls the resistance adjusting circuit and at least one of the resistance circuits to access to form a continuous leakage current test loop. The switch module is connected with the capacitance adjusting circuit, and controls the access of the capacitance adjusting circuit to form a leakage current threshold adjusting loop. And the switch module controls the access of at least one resistor circuit in the plurality of resistor circuits connected in parallel based on a leakage current threshold value to form a sudden rise leakage current test loop. The device is simple in loop and convenient to operate, can quickly adjust the magnitude of the leakage current, and realizes high-precision inverter leakage protection test.

Description

Technical Field

[0001] The present application relates to the technical field of inverters, and in particular to a leakage current testing device for inverters. Background Art

[0002] Leakage current in photovoltaic systems is caused by parasitic capacitance between the photovoltaic system and the earth. When a loop is formed between the parasitic capacitance, the photovoltaic system, and the power grid, a common-mode voltage generates a common-mode current on the parasitic capacitance. When a power-frequency transformer is installed in the photovoltaic system, the common-mode current generated by the common-mode voltage in the loop can be suppressed to a certain extent due to the relatively large impedance of the parasitic capacitance between the transformer windings. However, in a transformerless photovoltaic system, the loop impedance is relatively small, and the common-mode voltage generates a large common-mode current on the parasitic capacitance between the photovoltaic system and the earth, which is called leakage current.

[0003] The inverter of the existing photovoltaic system is provided with a leakage current protection device. When the leakage current on the parasitic capacitor is too large, the shutdown protection mechanism of the inverter will be triggered.

[0004] To test the inverter's leakage current protection device, existing technology typically uses a large sliding rheostat, manually rotating it to adjust the resistance value and generate the leakage current for testing. However, this manual rotation method significantly affects test efficiency, accuracy, and stability, which in turn affects the reliability of test results. Utility Model Content

[0005] Based on this, it is necessary to provide a leakage current testing device for an inverter that is easy to operate, can detect the leakage current threshold that the inverter can carry, and improve the accuracy of the inverter leakage current test to address the above technical problems.

[0006] In a first aspect, the present application provides a leakage current testing device for an inverter, wherein the input end thereof is connected to the DC input end of the inverter, and the output end thereof is grounded. The device comprises: a resistance adjustment circuit, a capacitance adjustment circuit, a plurality of resistance circuits connected in parallel, and a switch module;

[0007] The switch module is connected to the resistance adjustment circuit and the multiple resistance circuits connected in parallel, and controls the connection of the resistance adjustment circuit and at least one of the resistance circuits to form a continuous leakage current test loop;

[0008] The switch module is connected to the capacitance adjustment circuit to control the access of the capacitance adjustment circuit to form a leakage current threshold adjustment loop; the leakage current threshold of the leakage current threshold adjustment loop is determined by the size of the capacitance connected to the capacitance adjustment circuit;

[0009] The switch module controls at least one of the plurality of parallel-connected resistance circuits to be connected based on a leakage current threshold value, thereby forming a sudden leakage current test loop.

[0010] In one embodiment, the switch module includes a plurality of fixed switches and a resistance-adjustable switch.

[0011] Each of the fixed switches is connected in series with the corresponding resistance circuit, and the resistance adjustable switch is connected in series with the resistance adjustment circuit, controlling the connection of the resistance adjustment circuit and at least one of the resistance circuits to form a continuous leakage current test loop.

[0012] In one embodiment, the switch module further includes a capacitance adjustable switch connected in series with the capacitance adjustment circuit to control the access of the capacitance adjustment circuit to form a leakage current threshold adjustment loop.

[0013] In one embodiment, the apparatus further comprises:

[0014] A filtering digital display circuit is connected in parallel with the plurality of parallel-connected resistance circuits.

[0015] The switch module is connected to the filtering digital display circuit, controls the access of the filtering digital display circuit, and monitors the loop voltage generated by the continuous leakage current test loop, the leakage current threshold adjustment loop, or the sudden leakage current test loop.

[0016] In one embodiment, the filtering digital display circuit includes a resistor R12, a capacitor C1 and a voltmeter U1. The resistor R12 is connected in series with the capacitor C1, and the voltmeter U1 is connected in parallel across the capacitor C1.

[0017] In one embodiment, the switch module further includes:

[0018] The first digital display control switch is connected in series with the resistor R12 and the capacitor C1 to control the filtering digital display circuit to be connected to the continuous leakage current test circuit, the leakage current threshold adjustment circuit, or the sudden leakage current test circuit.

[0019] In one embodiment, the apparatus further comprises:

[0020] a current digital display circuit connected to the plurality of parallel-connected resistance circuits via the resistance adjustment circuit;

[0021] The switch module is connected to the current digital display circuit, controls the access of the current digital display circuit, and monitors the loop current generated by the continuous leakage current test loop, the leakage current threshold adjustment loop, or the sudden leakage current test loop.

[0022] In one embodiment, the current digital display circuit includes an ammeter A1, and the switch module includes a second digital display control switch. The second digital display control switch is connected in series with the ammeter A1 to control the access of the current digital display circuit.

[0023] In one embodiment, the switch module further includes:

[0024] The first short-circuit switch is connected in parallel with the plurality of resistance circuits connected in parallel, and controls the plurality of resistance circuits connected in parallel to be short-circuited.

[0025] In one embodiment, the switch module further includes:

[0026] The second short-circuit switch is connected in parallel with the resistance adjustment circuit and the capacitance adjustment circuit, and controls the resistance adjustment circuit to be short-circuited, or controls the capacitance adjustment circuit to be short-circuited.

[0027] The above-mentioned leakage current test device for an inverter performs both continuous and sudden leakage current testing of the inverter by controlling the connection between the switch module, the resistance adjustment circuit, the capacitance adjustment circuit, and multiple parallel-connected resistance circuits. It features a simple circuit, convenient operation, and the ability to quickly adjust the test leakage current. Furthermore, through the sophisticated series and parallel combination of resistance circuits, precise control of the leakage current test environment is achieved, effectively reducing test errors and ensuring the reliability of test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present application or related technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 1 is a structural block diagram of a leakage current testing device for an inverter according to an embodiment;

[0030] Figure 2 is a connection block diagram of a switch module in one embodiment;

[0031] Figure 3 A connection block diagram of a switch module in another embodiment;

[0032] Figure 4 is a structural block diagram of a leakage current testing device for an inverter in another embodiment;

[0033] Figure 5 is a structural block diagram of a leakage current testing device for an inverter in yet another embodiment;

[0034] Figure 6 is a connection block diagram of a switch module in yet another embodiment;

[0035] Figure 7 FIG. 4 is a circuit diagram of a leakage current testing device for an inverter in a preferred embodiment. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0037] Unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by a person of ordinary skill in the technical field to which this application belongs. The words "one", "a", "the" and the like used in this application do not indicate a limit on quantity and may indicate the singular or plural. The terms "include", "comprise", "have" and any variations thereof used in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units that are inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The word "multiple" used in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the objects before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in this application are only used to distinguish similar objects and do not represent a specific order for the objects.

[0038] like Figure 1 As shown, a leakage current test device for an inverter is provided. The inverter is connected to the power grid via a DC / AC converter. The input end of the leakage current test device is connected to the DC input end of the inverter, and the output end of the device is grounded. The device includes: a resistance adjustment circuit 10, a capacitance adjustment circuit 20, a plurality of resistance circuits 30 connected in parallel, and a switch module 40. The switch module includes a switch S1, one end of which is connected to the DC input end of the inverter and the other end is connected to the resistance adjustment circuit 10, and is used to control the input of the DC voltage of the inverter.

[0039] The switch types of the switch module 40 include but are not limited to manual switches, rocker switches, single-pole switches, contactors and other devices with single-control functions.

[0040] The switch module 40 is connected to the resistance adjustment circuit 10 and the plurality of resistance circuits 30 connected in parallel, and controls the connection of the resistance adjustment circuit 10 and at least one of the resistance circuits 30 to form a continuous leakage current test loop.

[0041] Wherein, in the continuous leakage current test loop, the resistance adjustment circuit 10 is connected in series with the multiple resistance circuits 30 connected in parallel. The resistance of each resistance circuit on the multiple resistance circuits 30 connected in parallel can be the same or different. The resistance adjustment circuit 10 is controlled by the switch module 40, and can adjust the size of the variable resistor connected to the continuous leakage current test loop in real time. The multiple resistance circuits 30 connected in parallel are controlled by the switch module 40, and can adjust the size of the fixed resistor connected to the continuous leakage current test loop in real time. The variable resistor and the fixed resistor constitute the total resistance on the continuous leakage current test loop. The total resistance on the continuous leakage current test loop simulates the parasitic capacitance between the inverter, the power grid and the earth, and the total current simulates the leakage current generated by the parasitic capacitance to test whether the leakage protection of the inverter is normal.

[0042] The switch module 40 is connected to the capacitance adjustment circuit 20 to control the capacitance adjustment circuit 20 to connect and form a leakage current threshold adjustment loop. The leakage current threshold of the leakage current threshold adjustment loop is determined by the size of the capacitance connected to the capacitance adjustment circuit 20.

[0043] In the leakage current threshold adjustment loop, the capacitance value of the capacitor adjustment circuit 20 connected to the leakage current threshold adjustment loop is gradually increased, and a gradually increasing continuous leakage current is generated in the leakage current threshold adjustment loop until the continuous leakage current exceeds the original leakage current threshold of the inverter, triggering the leakage protection of the inverter and disconnecting the inverter from the power grid. Then, the capacitance value of the capacitor adjustment circuit 20 is gradually lowered, so that the continuous leakage current in the leakage current threshold adjustment loop gradually decreases until it drops to a value greater than the sudden leakage current value of the preliminary test, which can be n times the sudden leakage current value of the preliminary test, where n>1. At this time, the inverter is restarted, and the original leakage current threshold of the inverter is adjusted to n times the sudden leakage current value.

[0044] The switch module 40 controls the connection of at least one resistor circuit 30 based on the leakage current threshold to form a sudden leakage current test loop.

[0045] Specifically, based on the sudden leakage current value of the preliminary test, at least one resistance circuit to be connected to the sudden leakage current test circuit is determined, and the switch module 40 controls the sudden connection of the at least one resistance circuit to generate a sudden leakage current in the sudden leakage current test circuit, and tests whether the inverter can trigger the leakage protection in time and disconnect from the power grid after the sudden leakage current is connected.

[0046] The above-described leakage current test device for an inverter performs both continuous and sudden leakage current testing of the inverter by controlling the connection between the switch module, the resistance adjustment circuit, the capacitance adjustment circuit, and multiple parallel-connected resistance circuits. This simple circuit design allows for convenient operation and rapid adjustment of the test leakage current. Furthermore, through sophisticated serial and parallel combinations of resistance circuits, precise control of the leakage current test environment is achieved, effectively reducing test errors and ensuring the reliability of test results.

[0047] In one embodiment, Figure 2 As shown, the switch module 40 includes a plurality of fixed switches S i And the resistance adjustable switch S ri ,

[0048] Each of the fixed switches S i Connected in series with the corresponding resistance circuit, the resistance adjustable switch S ri It is connected in series with the resistance adjustment circuit 10, controls the resistance adjustment circuit 10 and at least one resistance circuit therein to be connected, and forms a continuous leakage current test loop.

[0049] The resistance adjustment circuit 10 includes at least one adjustable resistor R L .

[0050] Specifically, if the rated output of the inverter is less than or equal to 30 kVA, the leakage current threshold of the inverter is 300 mA. Before the inverter is started, the fixed switch S corresponding to at least one resistor circuit 30 is closed. i , connect the at least one resistance circuit 30 to the continuous leakage current test loop, and close the adjustable resistance switch S at the same time ri Set the adjustable resistor R L Connect to the continuous leakage current test circuit. Start the inverter and gradually adjust the adjustable resistor R L Adjust the resistance until the leakage current in the continuous leakage current test circuit reaches 300mA. Observe whether the inverter leakage protection is activated.

[0051] Optionally, if the rated output of the inverter is greater than 30kVA, for example, 50kVA, the leakage current threshold of the inverter is 500mA. By the same operation as in the above specific method, the adjustable resistor R is gradually adjusted. LThe resistance value is adjusted until the leakage current in the continuous leakage current test circuit reaches 500 mA. Observe whether the leakage protection of the inverter is activated.

[0052] In one embodiment, Figure 3 As shown, the switch module 40 also includes a capacitance adjustable switch S ci , connected in series with the capacitance adjustment circuit 20, controls the capacitance adjustment circuit 20 to be connected, and forms a leakage current threshold adjustment loop.

[0053] The capacitance adjustment circuit 20 includes at least one adjustable capacitor C L .

[0054] Specifically, after the inverter is started, the switch module 40 controls the capacitor adjustable switch S ci Close the adjustable capacitor C L Access the leakage current threshold adjustment loop.

[0055] In one embodiment, Figure 4 As shown, the device further includes: a filtering digital display circuit 50 connected in parallel with the multiple parallel-connected resistance circuits 30.

[0056] The switch module 40 is connected to the filter digital display circuit 50 to control the access of the filter digital display circuit 50 and monitor the loop voltage generated by the continuous leakage current test loop, the leakage current threshold adjustment loop, or the sudden leakage current test loop.

[0057] In detail, the filter digital display circuit includes a resistor R12, a capacitor C1 and a voltmeter U1. The switch module 40 also includes a first digital display control switch S n1 The resistor R12, the capacitor C1 and the first digital display control switch S n1 The voltmeter U1 is connected in parallel at both ends of the capacitor C1. n1 When closed, the filter digital display circuit is controlled to connect to the continuous leakage current test circuit, the leakage current threshold adjustment circuit, or the sudden leakage current test circuit. The voltmeter U1 displays the magnitude and waveform of the loop voltage in the loop in real time.

[0058] In one embodiment, Figure 5 As shown, the device further includes a current digital display circuit 60 connected in series with the plurality of parallel-connected resistance circuits 30 via the resistance adjustment circuit 10. The switch module 40 is connected to the current digital display circuit 60 to control access to the current digital display circuit 60 and monitor the loop current generated by the continuous leakage current test circuit, the leakage current threshold adjustment circuit, or the sudden leakage current test circuit.

[0059] In detail, the current digital display circuit 60 includes an ammeter A1, and the switch module 40 includes a second digital display control switch S n2 The second digital display control switch S n2 Connected in series with the ammeter A1, it controls the current digital display circuit 60 to connect to the continuous leakage current test circuit, the leakage current threshold adjustment circuit, or the sudden leakage current test circuit. The ammeter A1 displays the leakage current in the circuit in real time.

[0060] In one embodiment, Figure 6 As shown, the switch module 40 further includes: a first short-circuit switch S d1 , connected in parallel with the multiple parallel-connected resistance circuits 30, controlling the multiple parallel-connected resistance circuits to be short-circuited.

[0061] Specifically, since each parallel resistor circuit 30 is composed of a corresponding fixed switch S i After a leakage current test, the state of each fixed switch changes. To restore to the initial unconnected state, each fixed switch needs to be restored again. The operation is complicated and easy to miss. Therefore, a first short-circuit switch S is connected in parallel to the multiple parallel-connected resistance circuits 30. d1 , close the first short-circuit switch S d1 The short-circuit operation can be performed on multiple resistance circuits 30, and the operation is convenient.

[0062] In one embodiment, Figure 6 As shown, the switch module 40 further includes: a second short-circuit switch S d1 , connected in parallel with the resistance adjustment circuit 10 and the capacitance adjustment circuit 20, controlling the resistance adjustment circuit 10 to be short-circuited, or controlling the capacitance adjustment circuit 20 to be short-circuited, thereby improving the operation convenience of the device.

[0063] In a preferred embodiment, Figure 7 As shown, a circuit diagram of a leakage current test device for an inverter is provided, wherein the device includes an adjustable resistor R L The resistance adjustment circuit is composed of an adjustable capacitor C L The device comprises a capacitance adjustment circuit; a plurality of parallel resistance circuits formed by resistors R0 to R11; a switch module formed by fixed switches S7 to S18, an adjustable resistance switch S4, an adjustable capacitance switch S5, a first digital display control switch S0, a second digital display control switch S2, a first short-circuit switch S6, a second short-circuit switch S3, and a switch S1; a filter digital display circuit formed by resistor R1, capacitor C1, and voltmeter U1; and a current digital display circuit formed by ammeter A1. The switches in the switch module are manual toggle switches.

[0064] Fixed switches S7 to S18 are connected in series with corresponding resistors R0 to R11. L Connected in series with the adjustable resistor switch S4. Adjustable capacitor C L Connected in series with the capacitor adjustable switch S5. Resistor R1, capacitor C1 and the first digital display control switch S0 are connected in series, and voltmeter U1 is connected in parallel across capacitor C1. Ammeter A1 is connected in series with the second digital display control switch S2. The first short-circuit switch S6 is connected in parallel to the multiple parallel resistance circuits consisting of resistors R0 to R11. The second short-circuit switch S3 is connected in parallel to the adjustable resistor R L The switch S1 is connected in parallel to the ammeter A1 and the second digital display control switch S2.

[0065] Single closed fixed switch S7, R0 resistance is 12kΩ, leakage current is 30mA; single closed fixed switch S8, R1 resistance is 12kΩ, leakage current is 30mA; single closed fixed switch S9, R2 resistance is 4kΩ, leakage current is 90mA; single closed fixed switch S10, R3 resistance is 12kΩ, leakage current is 30mA; single closed fixed switch S11, R4 resistance is 12kΩ, leakage current is 30mA; single closed fixed switch S12, R5 resistance is 4kΩ, leakage current is 90mA; single closed fixed switch S1 3. The resistance of R6 is 3.6kΩ, and the leakage current is 100mA; for single closed S14, the resistance of R7 is 3.6kΩ, and the leakage current is 100mA; for single closed S15, the resistance of R8 is 600Ω, and the leakage current is 600mA; for single closed S16, the resistance of R9 is 1.4kΩ, and the leakage current is 257mA; for single closed S17, the resistance of R10 is 400Ω, and the leakage current is 900mA; R11 is a spare resistor and can be replaced according to actual needs. Its accuracy can reach one percent, and the manual switch greatly improves work efficiency.

[0066] In the first embodiment, a continuous leakage current test is performed on an inverter with a rated output less than or equal to 30 kVA as an example.

[0067] Step 11: Close the second digital display control switch S2, the adjustable resistance switch S4, and the fixed switches S7 to S12. After adjusting the adjustable resistor RL to the maximum resistance, start the inverter and connect it to the grid.

[0068] Step 12: Gradually adjust the adjustable resistor RL and observe the leakage current displayed on ammeter A1 until it reaches 300mA and the loop current measurement point waveform.

[0069] Step 13: Close the first digital display control switch S0 and observe the loop voltage and voltage waveform displayed on the voltmeter U1.

[0070] The above test can be repeated multiple times to observe whether the inverter triggers leakage protection and disconnects from the grid when the continuous leakage current reaches 300mA.

[0071] In the second embodiment, a sudden leakage current test is performed on an inverter with a rated output less than or equal to 30 kVA as an example.

[0072] The magnitude of the sudden leakage current and the corresponding response time of the inverter leakage protection are shown in Table 1 below:

[0073] Table 1

[0074] Serial number Current mutation mA The maximum time the inverter is disconnected from the grid 1 30 0.3 2 60 0.15 3 150 0.04

[0075] Assume the sudden leakage current to be tested is 30mA. Since the leakage protection threshold for inverters with a rated output of less than or equal to 30kVA is 300mA, it is necessary to test and adjust the leakage current threshold first to prevent the occurrence of continuous leakage current greater than the sudden leakage current to be tested due to operational errors during testing.

[0076] Step 21: Close the second digital display control switch S2, the capacitance adjustable switch S5 and the first short circuit switch S6. Gradually increase the adjustable capacitance C L The capacitance value is adjusted until ammeter A1 shows that the leakage current in the circuit is 300mA, and the inverter triggers the leakage protection and disconnects the grid.

[0077] Step 22: Gradually Lower the Adjustable Capacitor C L The capacitance value is adjusted until the ammeter A1 shows that the leakage current in the loop is 1.5 times the sudden leakage current to be tested, that is, 45 mA. The inverter is restarted, and the leakage current threshold of the inverter is now 45 mA.

[0078] Step 23: Close only the second digital control switch S2 (or switch S1), the second short-circuit switch S3, and the first digital control switch S0 to confirm stable inverter operation. Suddenly close fixed switch S7 and observe the time it takes for the current on ammeter A1 to drop from 30 mA to 0 to determine the time from the moment fixed switch S7 is closed to the moment the inverter disconnects from the grid.

[0079] If the time is less than 0.3s, it means that the inverter's leakage protection is normal when facing a sudden leakage current.

[0080] The above test process can be repeated multiple times to observe whether the inverter triggers leakage protection and disconnects from the grid when encountering a sudden leakage current of 30mA.

[0081] Similarly, when testing for a sudden leakage current of 60mA or 150mA, the method described in steps S21 and S22 can be used to adjust the inverter's leakage current threshold to the corresponding 90mA or 225mA. With switch S7 already closed in step 23, suddenly close switch S8 to complete the 60mA sudden leakage current test. With switches S7 and S8 already closed in step 23, suddenly close switch S9 to complete the 150mA sudden leakage current test.

[0082] The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0083] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A leakage current testing device for an inverter, wherein the input end thereof is connected to the DC input end of the inverter and the output end thereof is grounded, characterized in that: The device includes: a resistance adjustment circuit, a capacitance adjustment circuit, a plurality of resistance circuits connected in parallel, and a switch module; The switch module is connected to the resistance adjustment circuit and the multiple resistance circuits connected in parallel, and controls the connection of the resistance adjustment circuit and at least one of the resistance circuits to form a continuous leakage current test loop; The switch module is connected to the capacitance adjustment circuit to control the access of the capacitance adjustment circuit to form a leakage current threshold adjustment loop; the leakage current threshold of the leakage current threshold adjustment loop is determined by the size of the capacitance connected to the capacitance adjustment circuit; The switch module controls at least one of the plurality of parallel-connected resistance circuits to be connected based on a leakage current threshold value, thereby forming a sudden leakage current test loop.

2. The leakage current testing device for an inverter according to claim 1, characterized in that: The switch module includes a plurality of fixed switches and a resistance-adjustable switch. Each of the fixed switches is connected in series with the corresponding resistance circuit, and the resistance adjustable switch is connected in series with the resistance adjustment circuit, controlling the connection of the resistance adjustment circuit and at least one of the resistance circuits to form a continuous leakage current test loop.

3. The leakage current testing device for an inverter according to claim 1, characterized in that: The switch module further includes a capacitance adjustable switch connected in series with the capacitance adjustment circuit to control the capacitance adjustment circuit to be connected, thereby forming a leakage current threshold adjustment loop.

4. The leakage current testing device for an inverter according to claim 1, characterized in that: The device further comprises: A filtering digital display circuit is connected in parallel with the plurality of parallel-connected resistance circuits. The switch module is connected to the filtering digital display circuit, controls the access of the filtering digital display circuit, and monitors the loop voltage generated by the continuous leakage current test loop, the leakage current threshold adjustment loop, or the sudden leakage current test loop.

5. The leakage current testing device for an inverter according to claim 4, characterized in that: The filtering digital display circuit includes a resistor R12, a capacitor C1 and a voltmeter U1. The resistor R12 is connected in series with the capacitor C1 , and the voltmeter U1 is connected in parallel to both ends of the capacitor C1 .

6. The leakage current testing device for an inverter according to claim 5, characterized in that: The switch module further includes: The first digital display control switch is connected in series with the resistor R12 and the capacitor C1 to control the filtering digital display circuit to be connected to the continuous leakage current test circuit, the leakage current threshold adjustment circuit, or the sudden leakage current test circuit.

7. The leakage current testing device for an inverter according to claim 1, characterized in that: The device further comprises: a current digital display circuit connected to the plurality of parallel-connected resistance circuits via the resistance adjustment circuit; The switch module is connected to the current digital display circuit, controls the access of the current digital display circuit, and monitors the loop current generated by the continuous leakage current test loop, the leakage current threshold adjustment loop, or the sudden leakage current test loop.

8. The leakage current testing device for an inverter according to claim 7, characterized in that: The current digital display circuit includes an ammeter A1, and the switch module includes a second digital display control switch. The second digital display control switch is connected in series with the ammeter A1 to control the access of the current digital display circuit.

9. The leakage current testing device for an inverter according to claim 1, characterized in that: The switch module further includes: The first short-circuit switch is connected in parallel with the plurality of resistance circuits connected in parallel, and controls the plurality of resistance circuits connected in parallel to be short-circuited.

10. The leakage current testing device for an inverter according to claim 1, characterized in that: The switch module further includes: The second short-circuit switch is connected in parallel with the resistance adjustment circuit and the capacitance adjustment circuit, and controls the resistance adjustment circuit to be short-circuited, or controls the capacitance adjustment circuit to be short-circuited.

Images