Inverter sampling resistor short circuit prediction method, inverter, refrigerator and storage medium

Abstract

The present application provides a method for predicting a short circuit of a sampling resistor in an inverter, comprising applying a first pulse voltage having a pulse width less than or equal to a preset pulse width to an input end of the inverter; testing whether there is a voltage drop at the output end of the sampling resistor relative to the input end of the resistor within a time period corresponding to the preset pulse width; if there is a voltage drop, it is determined that the sampling resistor is not short-circuited; otherwise, it indicates a problem and further testing is required; the method for predicting a short circuit of a sampling resistor in an inverter of the present application uses a first pulse voltage having a pulse width less than or equal to a limit width at which the sampling resistor will not be damaged, thereby avoiding damage to power components in the event of a short circuit of the sampling resistor; and also avoiding equipment damage or safety issues caused by directly starting a motor without performing a short-circuit test on the sampling resistor.

Description

Technical Field

[0001] The present application relates to the technical field of electronic equipment fault testing, and in particular to a method for predicting a short circuit of a sampling resistor of an inverter, an inverter, a refrigerator, and a storage medium. Background Art

[0002] In sensorless vector control inverters, current and voltage sampling resistors are crucial components of motor startup and operation control, and they provide the sole basis for protections like overcurrent and short-circuit protection. Therefore, timely detection of sampling resistor failures not only affects the inverter's normal operation but also significantly impacts its safety and reliability.

[0003] If the sampling resistor in the inverter short-circuits, the motor cannot be started successfully. Furthermore, uncontrollable high currents are generated during startup, significantly damaging the power components. In severe cases, these components can burn out, explode, or damage the motor. High-speed flying fragments can even strike eyes or skin, causing serious injury and other safety concerns. The resulting noise, smoke, and odor can also cause significant fear and a negative user experience. Summary of the Invention

[0004] In some embodiments of the present application, a method for predicting a short circuit of a sampling resistor in an inverter is provided. A first pulse voltage having a pulse width less than or equal to a preset pulse width is applied to the sampling resistor. If the voltage across the sampling resistor reaches or exceeds the preset voltage, it indicates that the sampling resistor is not short-circuited and a load such as a motor can be started normally. Otherwise, a problem exists and further testing is required.

[0005] By applying a pulse voltage to the sampling resistor, damage caused by a short circuit of the sampling resistor can be avoided; equipment damage or safety problems caused by directly starting the motor without performing a short circuit test on the sampling resistor can also be avoided.

[0006] In some embodiments of the present application, by conducting between the input end of the inverter and the input end of the load, and between the output end of the load and the input end of the sampling resistor, the current flows through the load and then flows to the sampling resistor, further preventing a large current from flowing through the sampling resistor and causing damage to the sampling resistor.

[0007] In some embodiments of the present application, when the voltage on the sampling resistor is lower than the preset voltage as tested in the above embodiments, the voltage is bypassed by the load and directly applied to both ends of the sampling resistor for testing. On the one hand, it is possible to directly determine whether the sampling resistor is short-circuited by whether the voltage on the sampling resistor reaches or exceeds the preset voltage, and it is also possible to determine whether the load is open-circuited.

[0008] In some embodiments of the present application, if the voltage on the sampling resistor is lower than a preset voltage in one test, the test is repeated several times; if the ratio of the number of times the voltage generated on the sampling resistor is not lower than the preset voltage to the number of tests reaches or exceeds a predetermined value, it can be determined that the sampling resistor is short-circuited, thereby improving the accuracy of the test.

[0009] In some embodiments of the present application, if the voltage on the sampling resistor is lower than a preset voltage after applying a first pulse voltage and performing a test, a third pulse voltage having a pulse width greater than the first pulse voltage is applied to the sampling resistor, and the voltage on the sampling resistor is tested within a time corresponding to the pulse width of the third pulse voltage, thereby improving the probability and accuracy of testing that the voltage on the sampling resistor reaches or exceeds the preset voltage when the sampling resistor is not short-circuited.

[0010] In some embodiments of the present application, a preset time interval is set between two adjacent tests to avoid damage caused by continuous application of voltage.

[0011] In some embodiments of the present application, the pulse width of the first pulse voltage is less than or equal to 2 microseconds, thereby avoiding damage.

[0012] In some embodiments of the present application, a method for predicting a short circuit of a sampling resistor of an inverter is provided, comprising:

[0013] Applying a first pulse voltage less than or equal to a preset pulse width to the sampling resistor;

[0014] The controller in the frequency converter obtains the voltage on the sampling resistor within a time period corresponding to the pulse width of the first pulse voltage, and compares the voltage on the sampling resistor with a preset voltage;

[0015] If the voltage on the sampling resistor reaches or exceeds the preset voltage, it is determined that the sampling resistor is not short-circuited.

[0016] In some embodiments of the present application, applying a first pulse voltage having a width less than or equal to a preset pulse width to the sampling resistor includes:

[0017] Conducting between the input end of the frequency converter and the input end of the load, and conducting between the output end of the load and the input end of the sampling resistor;

[0018] A voltage is applied to the input end of the frequency converter and the output end of the sampling resistor, so as to apply the first pulse voltage to the sampling resistor.

[0019] In some embodiments of the present application, after the controller in the inverter obtains the voltage on the sampling resistor and compares it with the preset voltage within the time period corresponding to the preset pulse width, the method further includes:

[0020] If the voltage on the sampling resistor is lower than the preset voltage, conducting the input end of the inverter and the input end of the sampling resistor;

[0021] Applying a second pulse voltage less than or equal to the preset pulse width to the sampling resistor;

[0022] In a time period corresponding to the pulse width of the second pulse voltage, obtaining the voltage on the sampling resistor and comparing it with a preset voltage;

[0023] If the voltage on the sampling resistor reaches or exceeds the preset voltage, it is determined that the sampling resistor is not short-circuited and the load is open-circuited;

[0024] If the voltage on the sampling resistor is lower than the preset voltage, it is determined that the sampling resistor is short-circuited.

[0025] In some embodiments of the present application, if the voltage on the sampling resistor is lower than the preset voltage, determining that the sampling resistor is short-circuited includes:

[0026] Repeating applying a second pulse voltage less than or equal to the preset pulse width to the sampling resistor for a preset number of times, obtaining a voltage on the sampling resistor each time the second pulse voltage is applied and comparing the voltage with the preset voltage;

[0027] If the ratio of the number of times the voltage on the sampling resistor is lower than the preset voltage to the preset number of times reaches or exceeds a predetermined value, it is determined that the sampling resistor is short-circuited.

[0028] In some embodiments of the present application, the pulse width of the first pulse voltage is less than a preset pulse width; and after the controller in the inverter obtains the voltage on the sampling resistor within a time period corresponding to the preset pulse width and compares the voltage with the preset voltage, the method further includes:

[0029] If the voltage on the sampling resistor is lower than the preset voltage, a third pulse voltage is applied to the sampling resistor; the pulse width of the third pulse voltage is greater than the pulse width of the first pulse voltage and less than or equal to the preset pulse width;

[0030] The controller in the frequency converter obtains the voltage on the sampling resistor and compares it with a preset voltage within a time period corresponding to the pulse width of the third pulse voltage;

[0031] If the voltage on the sampling resistor reaches or exceeds the preset voltage, it is determined that the sampling resistor is not short-circuited.

[0032] In some embodiments of the present application, if the voltage on the sampling resistor is lower than the preset voltage, a third pulse voltage is applied to the sampling resistor; the pulse width of the third pulse voltage is greater than the pulse width of the first pulse voltage and less than or equal to the preset pulse width;

[0033] There is a preset time interval between the start of the third pulse voltage and the end of the first pulse voltage.

[0034] In some embodiments of the present application, the preset pulse width is 2 microseconds.

[0035] In some embodiments of the present application, a frequency converter is further provided for driving a load, the frequency converter comprising:

[0036] Sampling resistor;

[0037] The controller is configured to obtain a voltage on the sampling resistor when a first pulse voltage less than or equal to a preset pulse width is applied to the sampling resistor, and compare the voltage on the sampling resistor with a preset voltage, and determine that the sampling resistor is not short-circuited if the voltage on the sampling resistor reaches or exceeds the preset voltage.

[0038] In some embodiments of the present application, a refrigerator is further provided, comprising a compressor and the inverter described in the above embodiments, wherein the inverter is used to drive the compressor to operate.

[0039] In some embodiments of the present application, a storage medium is further provided, on which a computer program is stored. When the computer program is executed by a processor, the method described in any of the above embodiments is implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 1 is a schematic diagram of the steps of a method for predicting a short circuit of a sampling resistor of an inverter in one embodiment of the present application.

[0041] Figure 2 1 is a diagram showing the measured short-circuit protection current and the voltage waveform on the current sampling resistor in one embodiment of the present application.

[0042] Figure 3 This is a schematic diagram of the circuit structure in which the switch tube controls the current to flow through the load and the sampling resistor after the inverter is connected to the load in one embodiment of the present application.

[0043] Figure 4 This is a schematic diagram of a circuit structure in which the switch tube controls the current to flow through the sampling resistor instead of the load after the inverter is connected to the load in one embodiment of the present application.

[0044] Figure 5 This is a schematic diagram of a voltage test process in which a switch tube controls current to flow through a load and a sampling resistor in one embodiment of the present application.

[0045] Figure 6 This is a schematic diagram of a voltage test process in which a switch tube controls the current to flow through a sampling resistor instead of a load in an embodiment of the present application.

[0046] Reference numerals:

[0047] a. Sampling resistor;

[0048] b. Switching tube;

[0049] c. Controller;

[0050] d. Level boost and current amplification circuit;

[0051] e. Input terminal of the frequency converter;

[0052] f. Load;

[0053] g. Switch tube control line;

[0054] h. Sampling voltage measurement line. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0056] In the description of this application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0057] In the embodiments shown in the accompanying drawings, directional indications (such as up, down, left, right, front, and back) used to explain the structure and movement of various components of the present application are not absolute but relative. These descriptions are applicable when these components are in the positions shown in the accompanying drawings. If the descriptions of the positions of these components are changed, the directional indications will also change accordingly.

[0058] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. Throughout this application, unless otherwise specified, "plurality" means two or more.

[0059] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0060] In sensorless vector control inverters, current and voltage sampling resistors are crucial components of motor startup and operation control, and they provide the sole basis for protections like overcurrent and short-circuit protection. Therefore, timely detection of sampling resistor failures not only affects the inverter's normal operation but also significantly impacts its safety and reliability.

[0061] When the inverter is operating, if a power component or current sampling resistor fails, a large current surge will be generated, often preventing the protection circuit from responding in time, causing explosive damage to the power component, rectifier bridge, electrolytic capacitor, or fuse. Not only will the crackling sound or black smoke alarm the user, but improper protective film can also cause fragments to fly, endangering the user's personal safety. Even if the protection function works, the delay in protection (to prevent misjudgment) can still generate currents of more than ten or even dozens of amperes, potentially damaging the power component and shortening its service life.

[0062] Therefore, if it is possible to predict in advance whether the sampling resistor in the inverter is short-circuited, and then perform timely repairs when the sampling resistor short-circuit fault occurs, it can avoid equipment damage, extend the service life of the equipment, and improve safety in use.

[0063] The maximum current of a typical multimeter is only a dozen milliamperes. Because the current sampling resistor has a relatively small resistance, typically below 150 milliohms, or even tens of milliohms, even manual testing without specialized tools (such as a milliohmmeter) can make it difficult to accurately determine whether the current sampling resistor is short-circuited.

[0064] Reference Figure 1 In some embodiments of the present application, a method for predicting a short circuit of a sampling resistor of an inverter is provided, the method comprising:

[0065] Step S1, applying a first pulse voltage less than or equal to a preset pulse width to a sampling resistor;

[0066] Step S2, the controller in the frequency converter obtains the voltage on the sampling resistor within a time period corresponding to the preset pulse width, and compares the voltage on the sampling resistor with a preset voltage;

[0067] In step S3 , if the voltage on the sampling resistor reaches or exceeds a preset voltage, it is determined that the sampling resistor is not short-circuited.

[0068] As described in step S1 above, a first pulse voltage having a pulse width less than or equal to a preset pulse width is applied to the sampling resistor of the inverter.

[0069] The sampling resistor may specifically be a current sampling resistor. The first pulse voltage may be generated by causing a large current to flow through a drive circuit of the inverter. The large current may specifically be the current flowing when the inverter is driving a load such as a compressor or a motor. The drive circuit may be a current loop connected in series with the load or a current loop formed when the load is short-circuited.

[0070] For example, a voltage is applied to the power input terminal and the loop output terminal of the inverter, and a sampling resistor is connected in series in the driving circuit, so that a voltage is generated across the two ends of the sampling resistor when the sampling resistor is not short-circuited.

[0071] The first pulse voltage can be specifically generated by applying voltage to the power input terminal and the loop output terminal of the inverter. When the circuit is normal, the conduction time of the circuit is controlled by the switch tube in the circuit, such as only being turned on for 1.5 microseconds, so that the first pulse voltage with a width of 1.5 microseconds will inevitably be generated at both ends of the sampling resistor that is not short-circuited.

[0072] In some embodiments, the first pulse voltage may be generated by applying a pulse voltage to the power input and circuit output of the inverter. Therefore, when the circuit is normal, a pulse voltage is generated across the sampling resistor (the output and input terminals). The pulse voltage generated across the sampling resistor is the first pulse voltage.

[0073] The resistance of the current sampling resistor is relatively small, generally below 150 milliohms, or even tens of milliohms. A large current (e.g., 20 amps) flowing through the inverter's drive circuit can cause a significant voltage drop across the unshorted sampling resistor, making it easier to detect.

[0074] The specific value of the preset pulse width is a maximum pulse width at which the sampling resistor is not damaged by the first pulse voltage, such as 2 microseconds. When the preset pulse width is 2 microseconds, the pulse width of the first pulse voltage is less than or equal to 2 microseconds, for example, the pulse width of the first pulse voltage is 1.5 microseconds.

[0075] As described in step S2 above, the controller within the inverter acquires the voltage across the sampling resistor during the time period corresponding to the preset pulse width and compares the acquired voltage with the preset voltage. For example, if the pulse width of the first pulse voltage is 1.5 microseconds, the controller should measure the voltage across the sampling resistor within this 1.5 microsecond period. To avoid the rising and falling edges of the pulse, the controller can measure the voltage across the sampling resistor 1 microsecond after the first pulse voltage is applied.

[0076] This solution uses a controller within the inverter (such as a microcontroller (MCU)) to measure the voltage across a sampling resistor, enabling instantaneous voltage measurement. The controller obtains the voltage across the sampling resistor and compares it with a pre-set voltage.

[0077] The preset voltage may be a minimum voltage value generated by a current flowing through a sampling resistor in a normal inverter, which is measured or calculated in advance.

[0078] In some embodiments, the controller may also be an additional test element such as an MCU specifically configured to test whether there is voltage on the sampling resistor, which can also achieve the technical purpose.

[0079] As described in step S3 above, if the voltage across the sampling resistor reaches or exceeds the preset voltage, the sampling resistor is determined to be not short-circuited. In other words, if the controller detects that the voltage across the sampling resistor reaches or exceeds the preset voltage, it indicates that the sampling resistor is not short-circuited, the inverter is functioning normally, and loads such as compressors and motors can be started.

[0080] If the controller detects a voltage lower than the preset voltage across the sampling resistor, it indicates a circuit failure. Further testing and diagnosis are required to determine the specific cause of the failure. It is not recommended to start the load if the circuit is abnormal to avoid damage.

[0081] In some embodiments of the present application, the step S1 of applying a first pulse voltage having a width less than or equal to a preset pulse width to the sampling resistor includes:

[0082] Step S11, conducting between the input end of the inverter and the input end of the load, and conducting between the output end of the load and the input end of the sampling resistor;

[0083] Step S12: applying a voltage to the input end of the frequency converter and the output end of the sampling resistor, so as to apply the first pulse voltage to the sampling resistor.

[0084] As described in step S11 above, the input terminal of the inverter and the input terminal of the load (such as the refrigerator compressor) are connected, and the output terminal of the load and the input terminal of the sampling resistor are connected, thereby forming a loop connecting the load and the sampling resistor in series.

[0085] As described in the above step S12, a voltage is applied to the input terminal of the frequency converter and the output terminal of the sampling resistor, thereby achieving the purpose of applying the first pulse voltage to the sampling resistor.

[0086] The voltage applied to the input end of the inverter and the output end of the sampling resistor can be a continuous voltage. The conduction time of the circuit is controlled by the switching tube connected between the input end of the inverter and the input end of the load and the switching tube connected between the output end of the load and the input end of the sampling resistor, for example, it is only turned on for 1.5 microseconds, thereby generating a first pulse voltage with a width of 1.5 microseconds at both ends of the sampling resistor that is not short-circuited.

[0087] In some embodiments, the voltage applied to the input end of the inverter and the output end of the sampling resistor may also be a pulse voltage with the same pulse width as the first pulse voltage, so that after a certain degree of voltage division by the load, the first pulse voltage is generated on the sampling resistor that is not short-circuited.

[0088] After a certain degree of voltage division and current limiting by the load, a first pulse voltage is generated on the sampling resistor that is not short-circuited, which can prevent the voltage applied to the input end of the inverter and the output end of the sampling resistor from directly acting on the sampling resistor, thereby avoiding damage to the sampling resistor.

[0089] In some embodiments of the present application, after step S2 in which the controller in the inverter obtains the voltage on the sampling resistor and compares it with the preset voltage within the time period corresponding to the preset pulse width, the method further includes:

[0090] Step S21 , if the voltage on the sampling resistor is lower than the preset voltage, conducting the input end of the inverter and the input end of the sampling resistor;

[0091] Step S22, applying a second pulse voltage less than or equal to the preset pulse width to the sampling resistor;

[0092] Step S23, obtaining the voltage on the sampling resistor within a time period corresponding to the pulse width of the second pulse voltage and comparing it with a preset voltage;

[0093] Step S24: If the voltage on the sampling resistor reaches or exceeds the preset voltage, it is determined that the sampling resistor is not short-circuited, but the load is open-circuited.

[0094] In step S25 , if the voltage on the sampling resistor is lower than the preset voltage, it is determined that the sampling resistor is short-circuited.

[0095] The first pulse voltage is generated by applying voltage to the input terminal of the inverter and the output terminal of the sampling resistor after conducting the input terminal of the inverter and the input terminal of the load, and the output terminal of the load and the input terminal of the sampling resistor.

[0096] As described in step S21 above, if the voltage across the sampling resistor is lower than the preset voltage, it indicates a circuit problem. Two possible causes of this problem are a load disconnection (e.g., a motor power line disconnection) or a short circuit in the sampling resistor. Further testing is required to determine the specific cause. It is not recommended to start the load if the circuit is abnormal to avoid damage.

[0097] Furthermore, in this step, the input end of the inverter and the input end of the sampling resistor are connected, thereby short-circuiting the load such as the motor or compressor driven by the inverter, and directly applying voltage to the sampling resistor. In this way, it is possible to detect whether the sampling resistor is short-circuited.

[0098] As described in step S22 above, a second pulse voltage less than or equal to a preset pulse width is applied to the sampling resistor.

[0099] The second pulse voltage applied to the sampling resistor can also be a continuous voltage applied to the input end of the inverter and the output end of the sampling resistor, and the conduction time of the switch tube controlled by the circuit in series between the input end of the inverter and the input end of the sampling resistor is controlled, for example, it is only turned on for 1.5 microseconds, thereby generating a second pulse voltage with a width of 1.5 microseconds at both ends of the sampling resistor that is not short-circuited.

[0100] In some embodiments, the second pulse voltage applied to the sampling resistor may also be generated by a pulse voltage with the same pulse width applied to the input terminal of the inverter and the output terminal of the sampling resistor.

[0101] The specific value of the preset pulse width is a maximum pulse width at which the sampling resistor is not damaged by the second pulse voltage, such as 2 microseconds. When the preset pulse width is 2 microseconds, the pulse width of the second pulse voltage is less than or equal to 2 microseconds, for example, the pulse width of the second pulse voltage is 1.5 microseconds.

[0102] As described in step S23 above, the voltage across the sampling resistor is acquired during the time period corresponding to the pulse width of the second pulse voltage and compared with the preset voltage. For example, if the pulse width of the second pulse voltage is 1.5 microseconds, the controller should acquire the voltage across the sampling resistor within 1.5 microseconds after the pulse begins. To avoid the rising and falling edges of the pulse, the controller can acquire the voltage across the sampling resistor 1 microsecond after the second pulse voltage is applied.

[0103] As described in step S24 , when the second pulse voltage is applied to the sampling resistor, if the controller detects that the voltage across the sampling resistor reaches or exceeds the preset voltage, it can be determined that the sampling resistor is not short-circuited.

[0104] In the above embodiment, after the inverter input and the load input are connected, and the load output and the sampling resistor input are connected, the inverter input, load, and sampling resistor are connected in series. If the sampling resistor is not short-circuited, and a voltage is applied between the inverter input and the sampling resistor output, but the controller does not detect a voltage across the sampling resistor or the detected voltage is lower than a preset voltage, this indicates that the load is short-circuited.

[0105] For example, if the power line driving the motor is broken, current cannot flow through the motor to the sampling resistor, and thus no voltage can be generated across the sampling resistor. Furthermore, in step S21, the input of the inverter and the input of the sampling resistor are directly connected, short-circuiting the load (motor). In this step, if the voltage across the sampling resistor reaches or exceeds a preset voltage, the controller can determine that the sampling resistor is not short-circuited and that the load is broken.

[0106] As described in step S25 , if the voltage across the sampling resistor measured by the controller in step S23 is lower than or greater than a preset voltage, it is determined that the sampling resistor is short-circuited.

[0107] In this step, since the second pulse voltage is directly generated by the voltage applied to the input end of the inverter and the output end of the sampling resistor without an intermediate load, if no voltage is measured at both ends of the sampling resistor or the measured voltage is lower than the preset voltage, it means that the sampling resistor is short-circuited.

[0108] In some embodiments of the present application, if the voltage on the sampling resistor is lower than the preset voltage, the step S25 of determining that the sampling resistor is short-circuited includes:

[0109] Step S251, repeatedly applying a second pulse voltage having a width less than or equal to the preset pulse width to the sampling resistor a preset number of times, obtaining a voltage across the sampling resistor each time the second pulse voltage is applied and comparing the voltage with a preset voltage;

[0110] In step S252 , if the ratio of the number of times the voltage on the sampling resistor is lower than the preset voltage to the preset number of times reaches or exceeds a predetermined value, it is determined that the sampling resistor is short-circuited.

[0111] As described in step S251 , the second pulse voltage having a width less than or equal to the preset pulse width is repeatedly applied to the sampling resistor for a preset number of times. Each time the second pulse voltage is applied, the controller obtains the voltage on one side of the sampling resistor and compares it with the preset voltage.

[0112] Each application of the second pulse voltage to the sampling resistor can be implemented in the same manner as in the above embodiments, namely, by applying a voltage between the input terminal of the inverter and the output terminal of the sampling resistor, and then generating the second pulse voltage on the sampling resistor that is not short-circuited through switching control or other methods. Each time the second pulse voltage is applied, the voltage across the sampling resistor is obtained and compared with a preset voltage.

[0113] For example, if the preset number of times is 5, that is, the second pulse voltage is applied to the sampling resistor a total of 5 times, then the controller also needs to test the voltage on the sampling resistor 5 times accordingly, and the timing of each test is within the time period corresponding to the pulse width of the corresponding second pulse voltage, thereby obtaining the test results corresponding to each second pulse voltage.

[0114] A preset time period may be provided between two adjacent tests. For example, if the preset time period is 5 seconds, then the second pulse voltage is applied to the sampling resistor and the controller obtains and compares the voltage on the sampling resistor twice, both with a 5-second interval.

[0115] As described in step S252 above, if the ratio of the number of times the voltage on the sampling resistor is lower than the preset voltage to the preset number of times reaches or exceeds a predetermined value, it is determined that the sampling resistor is short-circuited, for example:

[0116] The preset value is 0.8. According to the preset number of times (5), the second pulse voltage is applied to the sampling resistor a total of 5 times. The controller then tests the voltage on the sampling resistor 5 times accordingly. In 4 of the 5 tests, the voltage on the sampling resistor is lower than the preset voltage. That is, if the ratio of the number of times the voltage on the sampling resistor is lower than the preset voltage to the number of times the second pulse voltage is applied reaches the preset value of 0.8, it can be determined that the sampling resistor is short-circuited.

[0117] In some embodiments of the present application, the pulse width of the first pulse voltage is less than a preset pulse width. After step S2 in which the controller in the inverter obtains the voltage on the sampling resistor and compares it with the preset voltage within a time period corresponding to the preset pulse width, the method further includes:

[0118] Step S26: If the voltage on the sampling resistor is lower than the preset voltage, a third pulse voltage is applied to the sampling resistor; the pulse width of the third pulse voltage is greater than the pulse width of the first pulse voltage and less than or equal to the preset pulse width;

[0119] Step S27, the controller in the inverter obtains the voltage on the sampling resistor within a time period corresponding to the pulse width of the third pulse voltage and compares it with a preset voltage;

[0120] In step S28 , if the voltage on the sampling resistor reaches or exceeds the preset voltage, it is determined that the sampling resistor is not short-circuited.

[0121] As described in step S26 above, if the controller does not obtain the voltage on the sampling resistor or the obtained voltage is lower than the preset voltage in step S2, a third pulse voltage less than or equal to the preset pulse width is applied to the sampling resistor, and the pulse width of the third pulse voltage is greater than the pulse width of the first pulse voltage.

[0122] For example, if the pulse width of the first pulse voltage is 0.4 microseconds, the third pulse voltage may be selected to be 0.6 microseconds.

[0123] The third pulse voltage applied to the sampling resistor can be a continuous voltage applied to the input end of the inverter and the output end of the sampling resistor, and the conduction time of the switch tube controlled by the circuit in series between the input end of the inverter and the input end of the sampling resistor is controlled, for example, it is only turned on for 1.5 microseconds, thereby generating a third pulse voltage with a width of 1.5 microseconds at both ends of the sampling resistor that is not short-circuited.

[0124] In some embodiments, the third pulse voltage applied to the sampling resistor may also be generated by a pulse voltage with the same pulse width applied to the input terminal of the inverter and the output terminal of the sampling resistor.

[0125] As described in step S27 above, during the time period corresponding to the pulse width of the third pulse voltage, the controller acquires the voltage across the sampling resistor and compares it with the preset voltage. For example, if the pulse width of the third pulse voltage is 1 microsecond, the controller should acquire the voltage across the sampling resistor within 1 microsecond after the pulse begins. To avoid the rising and falling edges of the pulse, the controller can acquire the voltage across the sampling resistor 0.6 microseconds after the second pulse voltage is applied.

[0126] As described in step S28 above, if the voltage across the sampling resistor reaches or exceeds the preset voltage, the sampling resistor is determined to be not short-circuited. That is, if the controller detects that the voltage across the sampling resistor reaches or exceeds the preset voltage within the time period corresponding to the pulse width of the third pulse voltage, the controller determines that the sampling resistor is not short-circuited.

[0127] In this embodiment, since the pulse width of the third pulse voltage in step S26 is greater than the pulse width of the first pulse voltage in step S2, that is, compared with the first pulse voltage, the third pulse voltage prolongs the voltage application time, which can further improve the accuracy of the controller's voltage test on the sampling resistor.

[0128] In some embodiments, if the third pulse voltage is applied for the first time and the voltage on the sampling resistor is acquired by the controller, if the voltage on the sampling resistor is still not acquired or the acquired voltage on the sampling resistor is lower than a preset voltage, the third pulse voltage may be applied repeatedly multiple times, and the voltage on the sampling resistor is acquired and compared once each time the third pulse voltage is applied. Each repeated application of the third pulse voltage is separated from the previous application of the third pulse voltage by a preset time length, such as 3 seconds or 5 seconds.

[0129] The pulse width of the third pulse voltage is increased with each repetition. For example, the first application of the third pulse voltage is 0.6 microseconds, the second application of the third pulse voltage is 0.8 microseconds, the third application of the third pulse voltage is 1 microsecond, the fourth application of the third pulse voltage is 1.2 microseconds, and the fifth application of the third pulse voltage is 1.4 microseconds. However, the pulse width of the third pulse voltage cannot exceed a preset pulse width, such as a preset pulse width of 1.5 microseconds.

[0130] As long as the voltage obtained on the sampling resistor exceeds the preset voltage when the third pulse voltage is applied at a certain time, it can be determined that the sampling resistor is not short-circuited, and the test is not repeated.

[0131] In some embodiments of the present application, if the voltage across the sampling resistor is lower than a preset voltage, a third pulse voltage is applied to the sampling resistor. The pulse width of the third pulse voltage is greater than the pulse width of the first pulse voltage and less than or equal to the preset pulse width. The start of the third pulse voltage is separated from the end of the first pulse voltage by a preset time interval, such as 5 seconds, to avoid damage to the sampling resistor caused by the two pulse voltages being applied too close together.

[0132] In some embodiments of the present application, the preset pulse width is less than or equal to 2 microseconds. For example, the preset pulse width is preset to 1.5 microseconds, that is, the maximum pulse width of the first pulse voltage, the second pulse voltage, and the third pulse voltage in the above embodiment is 1.5 microseconds.

[0133] Reference Figure 2 , Figure 2 The waveform shown is a measured current waveform for load short-circuit protection. As can be seen from the figure, the current rises gradually during a load short-circuit. During a load short-circuit, no explosive damage occurs within 2 microseconds. Based on this test data, the maximum preset pulse width can be 2 microseconds.

[0134] A pulse voltage less than 2 microseconds is applied to the sampling resistor. Based on the conversion time of the MCU ADC, an appropriate sampling time is selected to sample the voltage on the current sampling resistor. If the sampled voltage drop is 0 or much smaller than the specified value, the current sampling resistor is determined to be short-circuited.

[0135] Reference Figure 3 and Figure 4 In some embodiments of the present application, a frequency converter is provided for driving a load such as a refrigerator compressor. The frequency converter includes a sampling resistor a, a switch b, a controller c, a level-boosting and current-amplifying circuit d, and wires.

[0136] Wires are used to electrically connect the inverter's input terminal e, the switch b, the sampling resistor a, the controller c, the level-boosting and current-amplifying circuit d, and the load f. These wires include the switch control line g and the sampling voltage measurement line h.

[0137] The two ends of the sampling resistor a can be respectively referred to as the input end and the output end of the sampling resistor. The sampling resistor a is connected in series in the current loop, and the output end of the sampling resistor a is grounded to form a loop.

[0138] The switch tube b can turn on or off the input end e of the inverter and the input end of the sampling resistor a, that is, the on and off of the circuit is controlled by the switch tube b.

[0139] Multiple switching transistors b can be provided. In this embodiment, six switching transistors b are provided. The six switching transistors b are labeled b1, b2, b3, b4, b5, and b6. Switches b1 and b2 form a half-bridge, switches b3 and b4 form a half-bridge, and switches b5 and b6 form a half-bridge. In other words, the six switching transistors b form three half-bridges in total.

[0140] Switch b controls the direction of current flow. For example, turning on switches b5 and b2 allows the current to flow through load f (the motor winding) and then to sampling resistor a. Turning on switches b3 and b4 allows the current to flow directly to sampling resistor a without passing through load f.

[0141] The level boosting and current amplifying circuit d is electrically connected to both ends of the sampling resistor a to boost the level and amplify the current.

[0142] The level-boosting and current-amplifying circuit d is connected to the controller c via the sample voltage measurement line h. This circuit transmits an amplified and filtered current signal corresponding to the voltage across the sampling resistor a to the controller c. Based on the current signal from the sample voltage measurement line h, the controller c determines whether there is a voltage across the sampling resistor a or whether the voltage has reached a preset voltage, thereby determining whether the sampling resistor a is short-circuited.

[0143] The controller c is also electrically connected to each switch tube b via a switch tube control line g, thereby controlling the on / off of each switch tube b. The controller c can be a control unit such as an MCU placed inside the inverter.

[0144] Based on the above settings and short-circuit prediction method, the following describes the working process of the inverter of this application using the refrigerator compressor as the load:

[0145] Continue to refer to Figure 3 and Figure 5 Before starting the refrigerator compressor, the power supply driving the inverter and the compressor applies voltage to the input terminal e of the inverter and the output terminal of the sampling resistor a. Then, the controller controls the switch tube b2 (corresponding to Figure 5 IGBT2) and switch tube b5 (corresponding to Figure 5 The IGBT5 is turned on for 0.4 microseconds, thereby generating a first pulse voltage with a pulse width of 0.4 microseconds at both ends of the sampling resistor a. Figure 3 The thick line and arrow from the input terminal e of the inverter to the output terminal (ground) of the sampling resistor a represent the current path.

[0146] Within 0.4 microseconds of the simultaneous conduction of switch tubes b2 and b5, the controller obtains the voltage across sampling resistor a. That is, AD sampling is started. The specific time point of AD sampling can be based on the start of the first pulse voltage as the timing starting point, and voltage sampling is performed after a predetermined delay. It is necessary to ensure that the moment of voltage sampling is within the time corresponding to the pulse width of the first pulse voltage, such as 0.2 microseconds after the start of the first pulse voltage. If a significant voltage reaching or exceeding the preset voltage is measured across sampling resistor a, it means that sampling resistor a is not short-circuited, and a test result is obtained that sampling resistor a is not short-circuited. Then, the refrigerator compressor can be started with confidence.

[0147] If the initial measurement shows no voltage across sampling resistor a or a voltage less than a preset voltage, switches b2 and b5 are simultaneously turned on for 0.6 microseconds, generating a third pulse voltage with a pulse width of 0.6 microseconds across sampling resistor a. Within 0.6 microseconds of applying the third pulse voltage, controller c measures the voltage across sampling resistor a. If the measured voltage across sampling resistor a reaches or exceeds the preset voltage, it is determined that sampling resistor a is not short-circuited, and the refrigerator compressor can be safely started.

[0148] If there is still no voltage across the two ends of sampling resistor a or the voltage is less than the preset voltage, switch tubes b2 and b5 can be controlled to apply a third pulse voltage with a pulse width of 0.8 microseconds to the two ends of sampling resistor a and perform the test. If the voltage still does not reach the preset voltage, after an interval of 10 seconds (preset duration), a third pulse voltage of 1 microsecond is applied again for testing. In this way, the pulse width of the third pulse voltage is gradually increased at each preset duration and the test is repeated. As long as the voltage across sampling resistor a reaches or exceeds the preset voltage in a certain test, it can be determined that sampling resistor a is not short-circuited and further testing is stopped.

[0149] If the pulse width of the third pulse voltage is close to or reaches the preset pulse width of 1.5 seconds, and the voltage measured at both ends of the sampling resistor a still does not reach the preset voltage, it means that there must be a problem with the circuit and the compressor cannot be started directly.

[0150] There are two possible reasons why no voltage is measured across sampling resistor A, or the measured voltage is less than the preset voltage: 1. A phase line (power line) in the compressor winding is open; 2. Sampling resistor A is short-circuited. Further testing can be performed using the following solution to obtain accurate test results.

[0151] Continue to refer to Figure 4 and Figure 6 , the controller controls the switch tube b3 (corresponding to Figure 6 IGBT3) and switch tube b4 (corresponding to Figure 6 The IGBT4 in the middle is turned on for 0.4 microseconds at the same time, thereby short-circuiting the compressor, and then a second pulse voltage with a pulse width of 0.4 microseconds is directly applied to the sampling resistor a. Figure 4 The bold line and arrow between the inverter input terminal e and the output terminal (ground) of sampling resistor a represent the current path. During the second pulse voltage application period, a voltage test is performed on sampling resistor a (i.e., AD sampling is initiated). If the measured voltage across sampling resistor a reaches or exceeds the preset voltage, it is determined that sampling resistor a is not short-circuited and the phase line of the compressor (load f) is disconnected. Therefore, the compressor can be started normally only after the phase line connection is repaired.

[0152] Similarly, if a single application of the second pulse voltage fails to detect a voltage across sampling resistor a that reaches or exceeds the preset voltage, a second pulse voltage with a larger pulse width can be applied again after a preset interval and tested again. Once the voltage across sampling resistor a reaches the preset voltage, it is determined that sampling resistor a is not short-circuited. If the pulse width of the second pulse voltage reaches or approaches the preset pulse width, but sampling resistor a still does not detect a voltage that reaches the preset voltage, sampling resistor a is determined to be short-circuited and must be repaired before the compressor can be started.

[0153] Some embodiments of the present application provide a refrigerator, which includes a compressor and the inverter described in the above embodiments, wherein the inverter is used to drive the compressor.

[0154] Some embodiments of the present application further provide a readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method of any of the above embodiments.

[0155] Although the present application has been described with reference to several exemplary embodiments, it should be understood that the terms used are illustrative and exemplary rather than restrictive. Since the present application can be embodied in various forms without departing from the spirit or essence of the present application, it should be understood that the above-described embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all changes and modifications that fall within the scope of the claims or their equivalents are intended to be covered by the appended claims.

Claims

1. A method for predicting a short circuit of a sampling resistor of an inverter, characterized in that: include: Conducting between the input end of the frequency converter and the input end of the load, and conducting between the output end of the load and the input end of the sampling resistor; Applying a voltage to the input end of the frequency converter and the output end of the sampling resistor to apply a first pulse voltage to the sampling resistor; The controller in the frequency converter obtains the voltage on the sampling resistor within a time period corresponding to the pulse width of the first pulse voltage, and compares the voltage on the sampling resistor with a preset voltage; If the voltage on the sampling resistor reaches or exceeds the preset voltage, it is determined that the sampling resistor is not short-circuited; If the voltage on the sampling resistor is lower than a preset voltage, conducting the input end of the inverter and the input end of the sampling resistor; Applying a second pulse voltage less than or equal to a preset pulse width to the sampling resistor; In a time period corresponding to the pulse width of the second pulse voltage, obtaining the voltage on the sampling resistor and comparing it with a preset voltage; If the voltage on the sampling resistor reaches or exceeds a preset voltage, it is determined that the sampling resistor is not short-circuited and the load is open-circuited; If the voltage on the sampling resistor is lower than a preset voltage, it is determined that the sampling resistor is short-circuited.

2. The inverter sampling resistor short circuit prediction method according to claim 1, characterized in that: If the voltage on the sampling resistor is lower than the preset voltage, determining that the sampling resistor is short-circuited includes: Repeating applying a second pulse voltage less than or equal to the preset pulse width to the sampling resistor for a preset number of times, obtaining a voltage on the sampling resistor each time the second pulse voltage is applied and comparing the voltage with the preset voltage; If the ratio of the number of times the voltage on the sampling resistor is lower than the preset voltage to the preset number of times reaches or exceeds a predetermined value, it is determined that the sampling resistor is short-circuited.

3. The inverter sampling resistor short circuit prediction method according to claim 1, characterized in that: The pulse width of the first pulse voltage is less than a preset pulse width; and after the controller in the inverter obtains the voltage on the sampling resistor and compares it with the preset voltage within a time period corresponding to the preset pulse width, the method further includes: If the voltage on the sampling resistor is lower than the preset voltage, a third pulse voltage is applied to the sampling resistor; the pulse width of the third pulse voltage is greater than the pulse width of the first pulse voltage and less than or equal to the preset pulse width; The controller in the frequency converter obtains the voltage on the sampling resistor and compares it with a preset voltage within a time period corresponding to the pulse width of the third pulse voltage; If the voltage on the sampling resistor reaches or exceeds the preset voltage, it is determined that the sampling resistor is not short-circuited.

4. The method for predicting a short circuit of a sampling resistor of a frequency converter according to claim 3, wherein: If the voltage on the sampling resistor is lower than the preset voltage, a third pulse voltage is applied to the sampling resistor; the pulse width of the third pulse voltage is greater than the pulse width of the first pulse voltage and less than or equal to the preset pulse width; There is a preset time interval between the start of the third pulse voltage and the end of the first pulse voltage.

5. The method for predicting a short circuit of a sampling resistor of a frequency converter according to claim 1, wherein: The preset pulse width is less than or equal to 2 microseconds.

6. A frequency converter for driving a load, characterized in that: include: Sampling resistor; Controller, which performs: Conducting between the input end of the frequency converter and the input end of the load, and conducting between the output end of the load and the input end of the sampling resistor; Applying a voltage to the input end of the frequency converter and the output end of the sampling resistor to apply a first pulse voltage to the sampling resistor; obtaining a voltage on the sampling resistor within a time period corresponding to a pulse width of the first pulse voltage, and comparing the voltage on the sampling resistor with a preset voltage; If the voltage on the sampling resistor reaches or exceeds the preset voltage, it is determined that the sampling resistor is not short-circuited; If the voltage on the sampling resistor is lower than the preset voltage, conducting the input end of the inverter and the input end of the sampling resistor; Applying a second pulse voltage less than or equal to a preset pulse width to the sampling resistor; In a time period corresponding to the pulse width of the second pulse voltage, obtaining the voltage on the sampling resistor and comparing it with a preset voltage; If the voltage on the sampling resistor reaches or exceeds the preset voltage, it is determined that the sampling resistor is not short-circuited and the load is open-circuited; If the voltage on the sampling resistor is lower than the preset voltage, it is determined that the sampling resistor is short-circuited.

7. A refrigerator, characterized in that: The invention comprises a compressor and the inverter according to claim 6, wherein the inverter is used to drive the compressor to operate.

8. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

Images