Blocking inductive load protection device and protection method

Abstract

The application provides a resistance and inductance load protection device and a protection method. The resistance and inductance load protection device comprises a power supply access module, an alternating current contactor connected to the output end of the power supply access module, a detection module connected to the alternating current contactor and comprising at least a current detection unit and a voltage detection unit, a resistance and inductance load module connected to the output end of the detection module and comprising a three-phase star-connected resistance unit and an inductance unit, a fan arranged in the heat dissipation area of the resistance and inductance load module, and a controller module electrically connected to the alternating current contactor, the detection module and the fan, configured to receive three-phase current signals and three-phase voltage signals and generate control instructions to control the on-off state of the alternating current contactor module and the start-stop or rotating speed of the fan. The application can identify abnormal working conditions and execute protection actions within milliseconds by real-time acquisition of three-phase current and voltage signals by the detection module and the built-in logic judgment criteria of the controller module, thereby avoiding the expansion of faults.

Description

Technical Field

[0001] This application relates to the field of inverter load protection technology, and in particular to an inductive load protection device and protection method. Background Technology

[0002] As the core equipment for speed control of AC motors, frequency converters are widely used in many fields such as industrial automation, rail transportation, wind power generation, and electric vehicles. During the research and development, production, and factory inspection of frequency converters, load capacity testing is a crucial step in verifying product performance and reliability. The test load needs to simulate the electrical characteristics of an actual motor, including resistive losses (heat generation) and inductive reactive power (magnetic field energy storage), to assess the frequency converter's current control accuracy, overload capacity, heat dissipation design, and the effectiveness of its protection logic.

[0003] Currently, the most commonly used inverter load testing equipment in the industry is the resistive-inductive load bank (RL Load Bank). Its typical structure is: a three-phase star connection, with each phase consisting of a high-power non-inductive resistor and a core reactor connected in series; the resistor units use stainless steel strips or cast iron resistor sheets, and the inductor units use air-core or core reactors; the cooling method is forced air cooling, typically using one or more axial fans to ventilate and dissipate heat from the resistors and reactors. This type of load bank has a simple structure, low cost, and can basically meet the requirements of inverter steady-state temperature rise and overload testing.

[0004] However, existing resistive-inductive load devices have obvious limitations: existing load boxes only serve as passive energy-consuming components and do not have the ability to sense their own operating status; key parameters such as the operating temperature of the resistor unit, current amplitude, and operating status of the cooling fan are not monitored online; when the cooling fan fails due to mechanical jamming, motor burnout, or power outage, the operator cannot know it in time; under continuous current flow, the resistor unit will rapidly heat up to several hundred degrees within minutes, far exceeding the tolerance limit of the insulation material, which can easily cause serious safety accidents such as cable insulation carbonization, resistance wire melting, or even equipment fire. Summary of the Invention

[0005] The purpose of this application is to provide a resistive-inductive load protection device and method to solve the technical problem that existing resistive-inductive load devices only act as passive energy-consuming components and do not have the ability to sense their own operating status, which leads to safety hazards.

[0006] To achieve the above and other related objectives, a first aspect of this application provides a resistive-inductive load protection device. The resistive-inductive load protection device includes: a power input module connected to the output terminal of a frequency converter to connect to a three-phase AC power supply;

[0007] An AC contactor, whose input terminal is connected to the output terminal of the power access module, is configured to controllably connect or disconnect the main circuit;

[0008] The detection module, connected between the AC contactor and the resistive-inductive load module, includes at least a current detection unit and a voltage detection unit, and is configured to detect three-phase current signals and three-phase voltage signals in real time.

[0009] The resistive-inductive load module, whose input is connected to the output of the AC contactor, includes a three-phase star-connected resistor unit and an inductor unit, and is configured to simulate motor-type load characteristics.

[0010] A fan, located in the heat dissipation area of ​​the resistive-inductive load module, is configured for forced ventilation cooling;

[0011] The controller module is electrically connected to the AC contactor, the detection module, and the fan, and is configured to receive the three-phase current signal and the three-phase voltage signal, and generate control commands based at least on the three-phase current signal and / or the three-phase voltage signal. The control commands are used to control the on / off state of the AC contactor module and the start / stop or speed of the fan.

[0012] In some embodiments of the first aspect of this application, the current detection unit in the detection module includes a Hall closed-loop current sensor, and the voltage detection unit is a resistive voltage divider voltage sensor or a Hall voltage sensor; the detection module and the controller module transmit analog signals through a shielded cable.

[0013] In some embodiments of the first aspect of this application, in the resistive-inductive load module, the resistor unit of each phase is connected in series with the inductor unit, one end of the three series branches is respectively connected to the three-phase output terminal of the detection module, and the other ends of the three series branches are connected together to form a neutral point.

[0014] In some embodiments of the first aspect of this application, the resistor unit is an adjustable resistor or a fixed resistor, and the inductor unit is an adjustable reactor or a fixed reactor; both the resistor unit and the inductor unit are installed in the same heat dissipation duct.

[0015] In some embodiments of the first aspect of this application, the fan further includes a temperature sensor mounted on the surface of the resistive load module, the output signal of the temperature sensor being connected to the controller module.

[0016] In some embodiments of the first aspect of this application, the control module generates a fan adjustment control command based on the output signal of the temperature sensor to adjust the fan speed and control its start / stop.

[0017] In some embodiments of the first aspect of this application, the AC contactor integrates auxiliary contacts, the status signals of which are fed back to the controller module for monitoring the actual engagement / disengagement state of the AC contactor.

[0018] To achieve the above and other related objectives, a second aspect of this application provides a method for protecting resistive-inductive loads, applied to the aforementioned resistive-inductive load protection device. The method includes: performing a power-on self-test on the controller module and reading the initial states of the fan and the resistive-inductive load module;

[0019] The controller sends a closing command to the AC contactor, causing the auxiliary contacts of the AC contactor to close, so that the three-phase AC power output from the frequency converter is delivered to the resistive-inductive load module via the detection module;

[0020] The detection module acquires three-phase current signals and three-phase voltage signals in real time, and transmits the three-phase current signals and the three-phase voltage signals to the controller module.

[0021] The controller module generates control commands based on the three-phase current signals and / or the three-phase voltage signals;

[0022] According to the control command, adjust the fan speed or start / stop status, and / or control the engagement / disengagement of the AC contactor.

[0023] In some embodiments of the second aspect of this application, the controller module generates control commands based on the three-phase current signals and / or the three-phase voltage signals, including:

[0024] The three-phase current signals are compared with a preset overload current threshold, and the three-phase voltage signals are compared with a preset overload voltage threshold, respectively.

[0025] When the three-phase current signal exceeds the preset overload current threshold or the three-phase voltage signal exceeds the preset overload voltage threshold, the controller module immediately outputs a disconnect command to the AC contactor and simultaneously outputs a fault alarm signal.

[0026] In some embodiments of the second aspect of this application, the protection method further includes:

[0027] The temperature sensor attached to the resistive load module transmits the real-time detected temperature signal to the controller module.

[0028] The controller module generates fan speed control commands or start / stop commands based on the comparison result between the temperature signal and a preset temperature threshold.

[0029] As described above, the resistive-inductive load protection device and protection method of this application have the following beneficial effects:

[0030] First, this application uses a detection module to collect three-phase current and voltage signals in real time, and the controller module has built-in logic judgment criteria, which can identify abnormal operating conditions and execute protection actions within milliseconds to prevent the fault from escalating.

[0031] Secondly, this application achieves real-time direct measurement of the actual temperature of the heating element by integrating an isolated temperature sensor mounted on the surface of the resistor unit into the resistive load module, rather than relying on indirect estimation based on current. When the fan fails, the air duct is blocked, or the system is overloaded, the controller module can dynamically execute protection strategies based on the measured temperature signal. This protection strategy fundamentally solves the major safety hazard of traditional load boxes continuing to operate after a fan failure until the resistor burns out or catches fire. Attached Figure Description

[0032] Figure 1 The diagram shown is a structural schematic of the resistive-inductive load protection device described in the embodiments of this application.

[0033] Figure 2 The diagram shown is a schematic diagram of the circuit structure of the resistive-inductive load protection device described in the embodiments of this application.

[0034] Figure 3 The diagram shown is a flowchart illustrating the resistive-inductive load protection method described in an embodiment of this application.

[0035] Figure 4 The diagram shown is a schematic representation of the process by which the controller module generates control commands, as described in an embodiment of this application.

[0036] Figure 5 The diagram shows a flowchart illustrating the process of controlling the fan speed or start / stop status based on temperature signals, as described in an embodiment of this application.

[0037] Figure 6 The diagram shown is a flowchart illustrating a resistive-inductive load protection method according to another embodiment of this application.

[0038] Label Explanation

[0039] 100 Inductive load protection device 101 Power input module 102 AC contactor 103 Detection module 104 Inductive load module 1041 Current detection unit 1042 Voltage detection unit 105 fan 106 Controller module S301~S305 step S401~S502 step S501~S502 step S601~S606 step Detailed Implementation

[0040] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0041] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. Therefore, the drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0042] This application provides a resistive-inductive load protection device and method. The detection module collects three-phase current and voltage signals in real time, and the controller module has built-in logic judgment criteria, which can identify abnormal operating conditions and execute protection actions within milliseconds to prevent the fault from escalating. By integrating an isolated temperature sensor mounted on the surface of the resistor unit into the resistive-inductive load module, the real-time direct measurement of the actual temperature of the heating element is realized. The controller module can dynamically execute protection strategies based on the measured temperature signal, which solves the technical problem that the resistive-inductive load device only acts as a passive energy-consuming element and does not have the ability to sense its own operating status, thus causing safety hazards.

[0043] The principles and implementation methods of the resistive-inductive load protection device and protection method of this application will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can understand the resistive-inductive load protection device and protection method of this embodiment without creative effort.

[0044] To facilitate understanding of the embodiments of this application, the appendix will be consulted first. Figure 2 Detailed explanation, such as Figure 1 As shown, the inductive load protection device 100 includes: a current input module, an AC contactor 102, a detection module 103, an inductive load module 104, a fan 105, and a controller module 106.

[0045] The power access module 101 is connected to the output terminal of the frequency converter to access a three-phase AC power supply.

[0046] The input terminal of the AC contactor 102 is connected to the output terminal of the power access module 101 and is configured to controllably connect or disconnect the main circuit.

[0047] The detection module 103 is connected to the AC contactor 102 and includes at least a current detection unit 1041 and a voltage detection unit 1042, and is configured to detect three-phase current signals and three-phase voltage signals in real time.

[0048] The input terminal of the resistive-inductive load module 104 is connected to the output terminal of the detection module 103, and includes a three-phase star-connected resistor unit and an inductor unit, which are configured to simulate the characteristics of a motor-type load.

[0049] Fan 105 is located in the heat dissipation area of ​​resistive load module 104 and is configured for forced ventilation cooling;

[0050] The controller module 106 is electrically connected to the AC contactor 102, the detection module 103 and the fan 105 respectively. It is configured to receive three-phase current signals and three-phase voltage signals, and generate control commands based on at least the three-phase current signals and / or three-phase voltage signals. The control commands are used to control the on / off state of the AC contactor 102 module and the start or speed of the fan 105.

[0051] In some implementations, the current detection unit 1041 in the detection module 103 is a Hall closed-loop current sensor, and the voltage detection unit 1042 is a resistive voltage divider voltage sensor or a Hall voltage sensor; the detection module 103 and the controller module 106 transmit analog signals through a shielded cable.

[0052] In some implementations, in the resistive-inductive load module 104, the resistor unit and the inductor unit of each phase are connected in series, one end of the three series branches are respectively connected to the three-phase output terminals of the detection module 103, and the other ends of the three series branches are connected together to form a neutral point.

[0053] In some implementations, the resistor unit is an adjustable resistor or a fixed resistor, and the inductor unit is an adjustable reactor or a fixed reactor; both the resistor unit and the inductor unit are installed in the same heat dissipation duct.

[0054] In some implementations, the fan 105 also includes a temperature sensor mounted on the surface of the resistive load module 104, and the output signal of the temperature sensor is connected to the controller module 106.

[0055] Optionally, the power supply for fan 105 is independent of the main circuit and is drawn from the auxiliary power supply circuit.

[0056] In some implementations, the control module generates fan 105 adjustment control commands based on the output temperature signal of the temperature sensor, so as to adjust the speed and start / stop the fan 105.

[0057] In some implementations, the AC contactor 102 integrates auxiliary contacts, and the status signal of the auxiliary contacts is fed back to the controller module 106 to monitor the actual engagement / disengagement status of the AC contactor 102.

[0058] like Figure 2 The diagram shown is a schematic diagram of the circuit structure of the resistive-inductive load protection device according to an embodiment of this application.

[0059] In this embodiment, the input terminal of the AC contactor is connected to the three-phase AC power supply of the frequency converter, and the output terminal is connected to the input terminal of a Hall closed-loop current sensor. The output terminal of each Hall closed-loop current sensor is connected to a resistor and an inductor connected in series. The three series branches of the resistor and inductor are connected together to form a neutral point.

[0060] In this embodiment, the control board is provided with a current detection circuit and a voltage detection circuit. The current detection circuit receives the primary-side high current output from the Hall closed-loop current sensor and linearly converts it into a secondary-side weak current signal, then converts it into a three-phase current signal that can be transmitted to the control board. The voltage detection circuit reduces the detected primary-side high voltage signal to a secondary-side low voltage signal through isolation or non-isolation, then converts it into a three-phase voltage signal that can be transmitted to the control board. A temperature sensor is also mounted on the surface of the resistor. Figure 2 (Not shown in the image).

[0061] The control board is also equipped with an AC contactor control circuit and a fan control circuit. The AC contactor control circuit is used to control the on / off state of the AC contactor based on control commands, and the fan control circuit is used to adjust the fan speed and control the start / stop of the fan based on control commands.

[0062] This application also provides a resistive-inductive load protection method, which is applied to the resistive-inductive load protection device in the above embodiments.

[0063] like Figure 3 The diagram shown is a schematic flowchart of an embodiment of the resistive-inductive load protection method of this application. It includes the following steps S301 to S305.

[0064] Step S301: Power on the controller module for self-test and read the initial status of the fan and inductive load modules.

[0065] In step S302, the controller sends a closing command to the AC contactor, causing the auxiliary contacts of the AC contactor to close, so that the three-phase AC power output by the frequency converter is delivered to the inductive load module through the detection module.

[0066] In step S303, the detection module acquires the three-phase current signal and the three-phase voltage signal in real time and transmits them to the controller module.

[0067] In step S304, the controller module generates control commands based on the three-phase current signals and / or three-phase voltage signals.

[0068] Step S305: According to the control command, adjust the fan speed or start / stop status, and / or control the engagement / disengagement of the AC contactor.

[0069] In some implementations, the controller module generates control commands based on the three-phase current signal and / or three-phase voltage signal, including comparing the three-phase current signal with a preset overload current threshold and the three-phase voltage signal with a preset overload voltage threshold, respectively. When the three-phase current signal exceeds the preset overload current threshold or the three-phase voltage signal exceeds the preset overload voltage threshold, the controller module immediately outputs a disconnect command to the AC contactor and outputs a fault alarm signal at the same time.

[0070] like Figure 4 The diagram shown is a flowchart illustrating the generation of control commands by the controller module according to an embodiment of this application. It includes the following steps S401 to S402.

[0071] Step S401: Compare the three-phase current signals with the preset overload current threshold and the three-phase voltage signals with the preset overload voltage threshold, respectively.

[0072] In step S402, when the three-phase current signal exceeds the preset overload current threshold or the three-phase voltage signal exceeds the preset overload voltage threshold, the controller module immediately outputs a disconnect command to the AC contactor and simultaneously outputs a fault alarm signal.

[0073] In this embodiment, when any one of the three-phase current signal and the three-phase voltage signal exceeds the corresponding threshold, the controller module will immediately generate and output a disconnect command to release the contacts of the AC contactor, disconnect the AC contactor, and stop the load output.

[0074] In some implementations, the resistive load protection method further includes: a temperature sensor attached to the resistive-inductive load module transmits the temperature signal detected in real time to the controller module; the controller module generates a fan speed control command or start / stop command based on the comparison result between the temperature signal and a preset temperature threshold.

[0075] like Figure 5 The diagram shown is a schematic flowchart illustrating the control of fan speed or start / stop status based on temperature signals according to an embodiment of this application. It includes the following steps S501 to S502.

[0076] In step S501, the temperature sensor attached to the resistive load module transmits the real-time detected temperature signal to the controller module.

[0077] Step S502: The controller module generates a fan speed control command or start / stop command based on the comparison result between the temperature signal and the preset temperature threshold.

[0078] In some implementations, when the temperature signal is less than a first temperature threshold, a first fan speed control command is generated to adjust the fan speed to a low setting. When the temperature signal is greater than the first temperature threshold but less than a second temperature threshold, a second fan speed control command is generated to adjust the fan speed to a medium setting. When the temperature signal is greater than the second temperature threshold but less than a third temperature threshold, a third fan speed control command is generated to adjust the fan speed to a high setting. When the temperature signal is greater than the third temperature threshold, a disconnect command is generated to release the contacts of the AC contactor, disconnect the AC contactor, stop the load output, and turn off the fan.

[0079] Figure 6 The diagram shows a flow chart of a resistive-inductive load protection method according to another embodiment of this application. It includes the following steps S601 to S605.

[0080] Step S601: Power on the controller module.

[0081] In step S602, the controller module detects the three-phase current signal, three-phase voltage signal, and temperature signal in real time.

[0082] In step S603, determine whether the three-phase current signal, three-phase voltage signal, and temperature signal exceed the standard. If any one of the three-phase current signal, three-phase voltage signal, or temperature signal exceeds the standard, the controller module outputs a disconnect command and executes step S606. If none of the three-phase current signal, three-phase voltage signal, or temperature signal exceeds the standard, the controller module outputs a close command and executes step S604.

[0083] Step S604: Close the AC contactor to allow the load to output normally.

[0084] Step S605: Adjust the fan speed based on the real-time temperature signal.

[0085] Step S606: Disconnect the AC contactor and stop the load output.

[0086] In this embodiment, it is determined whether the three-phase current signal, three-phase voltage signal and temperature signal exceed the standard, including: determining whether the three-phase current signal exceeds the preset overload current threshold, determining whether the three-phase voltage signal exceeds the preset overload voltage threshold, and determining whether the temperature signal exceeds the preset temperature threshold.

[0087] Among them, the preset overload current threshold, preset overload voltage threshold, and preset temperature threshold are not unique fixed values ​​and can be adjusted according to the actual use scenario.

[0088] In this embodiment, adjusting the fan speed based on the real-time temperature signal includes: when the temperature signal is less than a first temperature threshold T1, generating a first speed control command for the fan to adjust the fan speed to a low setting; when the temperature signal is greater than the first temperature threshold T1 and less than a second temperature threshold T2, generating a second speed control command for the fan to adjust the fan speed to a medium setting; when the temperature signal is greater than the second temperature threshold T2 and less than a third temperature threshold T3, generating a third speed control command for the fan to adjust the fan speed to a high setting; and when the temperature signal is greater than the third temperature threshold T3, generating a disconnect command to release the contacts of the AC contactor, disconnect the AC contactor, stop the load output, and turn off the fan.

[0089] The third temperature threshold T3 can be freely set from the preset temperature threshold, and can be different values ​​or the same value.

[0090] The protection scope of the resistive-inductive load protection method of this application is not limited to the execution order of the steps listed in this embodiment. Any solution implemented by adding, deleting, or replacing steps in the prior art based on the principle of this application is included within the protection scope of this application.

[0091] Since the specific implementation of this embodiment corresponds to the aforementioned method embodiment, the same details will not be repeated here, and those skilled in the art should also understand this. Figure 1 The division of the modules in the embodiments is only a logical functional division. In actual implementation, they can be fully or partially integrated into one or more physical entities. These modules can be fully implemented in software through processing element calls, fully implemented in hardware, or some modules can be implemented in software through processing element calls and some modules can be implemented in hardware.

[0092] It should be noted that the above division of modules is merely a logical functional division. In actual implementation, they can be fully or partially integrated into a single physical entity, or they can be physically separated. Furthermore, these modules can be implemented entirely in software via processing element calls; they can be fully implemented in hardware; or some modules can be implemented by processing element calls to software, while others are implemented in hardware. For example, module x can be a separate processing element, or it can be integrated into a chip in the aforementioned device. Alternatively, it can be stored as program code in the memory of the aforementioned device, and its function can be called and executed by a processing element of the device. The implementation of other modules is similar. Moreover, these modules can be fully or partially integrated together, or they can be implemented independently. The processing element here can be an integrated circuit with signal processing capabilities. In the implementation process, the steps of the above method or the various modules can be completed through integrated logic circuits in the hardware of the processor element or through software instructions.

[0093] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, or methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of modules / units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or units may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the shown or discussed mutual couplings or direct couplings or communication connections may be through some interfaces, or indirect couplings or communication connections between devices, modules, or units, and may be electrical, mechanical, or other forms. Modules / units described as separate components may or may not be physically separate. Components shown as modules / units may or may not be physical modules, i.e., they may be located in one place or distributed across multiple network units. Some or all of the modules / units can be selected to achieve the purpose of the embodiments of this application according to actual needs. For example, the functional modules / units in the various embodiments of this application may be integrated into one processing module, or each module / unit may exist physically separately, or two or more modules / units may be integrated into one module / unit.

[0094] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0095] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0096] The descriptions of the processes or structures corresponding to the above figures each have their own emphasis. For parts of a process or structure that are not described in detail, please refer to the relevant descriptions of other processes or structures.

[0097] In summary, this application provides a resistive-inductive load protection device and method. This application uses a detection module to collect three-phase current and voltage signals in real time, and a controller module with built-in logic judgment criteria can identify abnormal operating conditions and execute protection actions within milliseconds, preventing the escalation of faults. By integrating an isolated temperature sensor mounted on the surface of the resistor unit into the resistive-inductive load module, real-time direct measurement of the actual temperature of the heating element is achieved, rather than indirect estimation based on current. When the fan fails, the air duct is blocked, or overload occurs, the controller module can dynamically execute protection strategies based on the measured temperature signal. This protection strategy fundamentally solves the major safety hazard of traditional load boxes continuing to operate after fan failure until the resistor burns out or catches fire. Therefore, this application effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0098] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A resistive-inductive load protection device, characterized in that, The protective device includes: The power input module is connected to the output terminal of the frequency converter to access a three-phase AC power supply. An AC contactor, whose input terminal is connected to the output terminal of the power access module, is configured to controllably connect or disconnect the main circuit; The detection module, connected to the AC contactor, includes at least a current detection unit and a voltage detection unit, and is configured to detect three-phase current signals and three-phase voltage signals in real time. The resistive-inductive load module, whose input terminal is connected to the output terminal of the detection module, includes a three-phase star-connected resistor unit and an inductor unit, and is configured to simulate motor-like load characteristics. A fan, located in the heat dissipation area of ​​the resistive-inductive load module, is configured for forced ventilation cooling; The controller module is electrically connected to the AC contactor, the detection module, and the fan, and is configured to receive the three-phase current signal and the three-phase voltage signal, and generate control commands based at least on the three-phase current signal and / or the three-phase voltage signal. The control commands are used to control the on / off state of the AC contactor module and the start / stop or speed of the fan.

2. The resistive-inductive load protection device according to claim 1, characterized in that, The current detection unit in the detection module includes a Hall closed-loop current sensor, and the voltage detection unit is a resistive voltage divider type voltage sensor or a Hall voltage sensor; the detection module and the controller module transmit analog signals through a shielded cable.

3. The resistive-inductive load protection device according to claim 1, characterized in that, In the resistive-inductive load module, the resistor unit of each phase is connected in series with the inductor unit, one end of the three series branches is respectively connected to the three-phase output terminal of the detection module, and the other ends of the three series branches are connected together to form a neutral point.

4. The resistive-inductive load protection device according to claim 3, characterized in that, The resistor unit is an adjustable resistor or a fixed resistor, and the inductor unit is an adjustable reactor or a fixed reactor; both the resistor unit and the inductor unit are installed in the same heat dissipation duct.

5. The resistive-inductive load protection device according to claim 1, characterized in that, The fan also includes a temperature sensor mounted on the surface of the resistive load module, and the output signal of the temperature sensor is connected to the controller module.

6. The resistive-inductive load protection device according to claim 5, characterized in that, The control module generates fan adjustment control commands based on the output signal of the temperature sensor to adjust the fan speed and control its start / stop.

7. The resistive-inductive load protection device according to claim 1, characterized in that, The AC contactor integrates auxiliary contacts, and the status signal of the auxiliary contacts is fed back to the controller module to monitor the actual engagement / disengagement status of the AC contactor.

8. A method for protecting an inductive load, applied to the inductive load protection device according to any one of claims 1 to 7, characterized in that, The protection method includes: The controller module performs a power-on self-test and reads the initial status of the fan and resistive-inductive load modules. The controller sends a closing command to the AC contactor, causing the auxiliary contacts of the AC contactor to close, so that the three-phase AC power output from the frequency converter is delivered to the resistive-inductive load module via the detection module; The detection module acquires three-phase current signals and three-phase voltage signals in real time, and transmits the three-phase current signals and the three-phase voltage signals to the controller module. The controller module generates control commands based on the three-phase current signals and / or the three-phase voltage signals; According to the control command, adjust the fan speed or start / stop status, and / or control the engagement / disengagement of the AC contactor.

9. The resistive-inductive load protection method according to claim 8, characterized in that, The controller module generates control commands based on the three-phase current signals and / or the three-phase voltage signals, including: The three-phase current signals are compared with a preset overload current threshold, and the three-phase voltage signals are compared with a preset overload voltage threshold, respectively. When the three-phase current signal exceeds the preset overload current threshold or the three-phase voltage signal exceeds the preset overload voltage threshold, the controller module immediately outputs a disconnect command to the AC contactor and simultaneously outputs a fault alarm signal.

10. The resistive-inductive load protection method according to claim 8, characterized in that, The protection method further includes: The temperature sensor attached to the resistive load module transmits the real-time detected temperature signal to the controller module. The controller module generates fan speed control commands or start / stop commands based on the comparison result between the temperature signal and a preset temperature threshold.

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