Maximum bearing current testing system for thermal protector

Abstract

The utility model relates to a maximum bearing current testing system for a thermal protector, which is mainly used for testing the maximum bearing current of the thermal protector. The device comprises a programmable controller, a touch screen, an adjustable constant-current power supply, a current converter, a contactor, a current-limiting resistor and a test seat, and is structurally characterized in that the test seat is connected with the contactor, and the programmable controller comprises a central processing unit, an input interface, an output interface, an analog-to-digital conversion module, a digital-to-analog conversion module and a serial communication interface; the touch screen is connected with the serial communication interface, the adjustable constant current power supply is connected with the digital-to-analog conversion module, the current converter is connected with the analog-to-digital conversion module, and the contactor is respectively connected with the input interface and the output interface. The input interface, the output interface, the analog-to-digital conversion module, the digital-to-analog conversion module and the serial communication interface are all connected with the central processor.

Description

Technical Field

[0001] The utility model relates to a thermal protector maximum carrying current testing system, which is mainly used for testing the maximum carrying current of the thermal protector. Background Art

[0002] The so-called maximum carrying current test is to first pass the set initial current value Ic to the thermal protector, and continuously operate / reset according to the set number of cycles DT1. When the actual number of cycles DT8 reaches the set value, increase the step current value Ib, and continue to operate / reset according to the set number of cycles DT1 until it rises to a certain level, and the heating element in the thermal protector melts. The current at this time is the melting current value. The current value before this level is the maximum current value that the thermal protector can withstand for normal operation, that is, the maximum carrying current value. Figure 1 shown.

[0003] In the existing maximum load current test technology, the test system generally has the defect of low degree of automation. First, the current source used to energize the thermal protector has the problem of low control accuracy. In some simpler test systems, current regulation is achieved by manual adjustment devices such as voltage regulators, potentiometers, and resistors. When the current deviates from the set value, it needs to be adjusted manually. There are also some test systems that have been automated. Due to the use of open-loop adjustment methods or low control accuracy, there are disadvantages such as inability to control or slow control response speed when the current deviates from the set value. These disadvantages result in the current deviating from the set value and being unable to be quickly regulated when the power supply is unstable or the test load resistance and temperature characteristics change.

[0004] Secondly, existing test systems lack a high level of automation and specialization in test data processing. In some less automated systems, test data acquisition, analysis, comparison, and judgment are all performed manually. This low level of automation in data processing leads to large errors in test results and low test efficiency. For automated test systems, although the test data processing process is automated, it lacks consideration of the thermal protector's operating characteristics, requiring professional analysis to obtain test results. This specialization in data processing requires further improvement. Therefore, existing testing technologies suffer from poor test current accuracy and stability, low system test precision, large test data errors, and low test efficiency. Utility Model Content

[0005] The purpose of the utility model is to overcome the above-mentioned deficiencies in the prior art and to provide a maximum carrying current testing system for a thermal protector with a rational structural design.

[0006] The technical solution adopted by the utility model to solve the above-mentioned problem is: the maximum load current test system of the thermal protector includes a programmable controller, a touch screen, an adjustable constant current power supply, a current converter, a contactor, a current limiting resistor and a test socket. Its structural characteristics are: the touch screen, the adjustable constant current power supply, the current converter and the contactor are all connected to the programmable controller, the line connecting the adjustable constant current power supply and the contactor runs through the current converter, the two ends of the current limiting resistor are respectively connected to the adjustable constant current power supply and the contactor, and the test socket is connected to the contactor.

[0007] Furthermore, the programmable controller includes a central processing unit, an input interface, an output interface, an analog-to-digital conversion module, a digital-to-analog conversion module and a serial communication interface, the touch screen is connected to the serial communication interface, the adjustable constant current power supply is connected to the digital-to-analog conversion module, the current converter is connected to the analog-to-digital conversion module, the contactor is connected to the input interface and the output interface respectively, and the input interface, output interface, analog-to-digital conversion module, digital-to-analog conversion module and serial communication interface are all connected to the central processing unit.

[0008] Furthermore, the V1 and V2 terminals of the adjustable constant current power supply are respectively connected to the L and N terminals of the AC power supply, the V3 terminal of the adjustable constant current power supply is connected to the 3 terminal of the contactor, and the connected wire passes through the induction hole of the current converter, the V4 terminal of the adjustable constant current power supply is connected to one end of the current limiting resistor, and the U+ and U- terminals of the adjustable constant current power supply are respectively connected to the + and - terminals of the digital-to-analog conversion module.

[0009] Furthermore, the U+ terminal and U- terminal of the current converter are connected to the + terminal and the - terminal of the analog-to-digital conversion module respectively.

[0010] Furthermore, the 2nd and 6th ends of the contactor are connected to one end of the test socket, the 4th and 8th ends of the contactor are connected to the other end of the test socket, the 5th end of the contactor is connected to the V-end of the DC power supply, the 1st end of the contactor is connected to the other end of the current limiting resistor, the 7th end of the contactor is connected to the X1 end of the input interface, the B end of the drive coil of the contactor is connected to the Y1 end of the output interface, and the A end of the drive coil of the contactor is connected to the V+ end of the DC power supply.

[0011] Furthermore, the com terminal of the input interface is connected to the V+ terminal of the DC power supply, and the - terminal of the output interface is connected to the V- terminal of the DC power supply.

[0012] Furthermore, the test socket is used to connect the thermal protector to be tested.

[0013] Compared with existing technologies, the present invention has the following advantages: The thermal protector maximum load current test system utilizes software and hardware automatic measurement and control technologies such as programmability, touch screen control and display, and current closed-loop adjustment. During the power-on process of the test, real-time current detection, closed-loop control, and dynamic adjustment are achieved. This has the advantages of fast control response speed and rapid adjustment to dynamic fluctuations in the loop current, ensuring the accuracy and stability of the power-on current, improving the test system's test accuracy and the correctness of the test data. The test system automates the acquisition, calculation, processing, comparison, and judgment of test data. Based on the test data and the operating characteristics of the thermal protector, the touch screen displays test results that meet the thermal protector's performance requirements and fault alarm signals, effectively improving the automation and specialization of the test system. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the maximum carrying current test of an embodiment of the present utility model.

[0015] Figure 2 It is a schematic diagram of a maximum carrying current testing system for a thermal protector according to an embodiment of the present utility model.

[0016] Figure 3 It is a schematic diagram of the maximum carrying current test principle of the thermal protector in an embodiment of the present utility model.

[0017] Figure 4 It is a schematic diagram of parameter setting of an embodiment of the present utility model.

[0018] Figure 5 It is a schematic diagram of the test interface of an embodiment of the present utility model.

[0019] Figure 6 It is a schematic diagram of the three-dimensional structure of the thermal protector of an embodiment of the utility model.

[0020] Figure 7 This is a schematic diagram of an explosion of the thermal protector according to an embodiment of the present invention (when the heating element is a spiral heating element).

[0021] Figure 8 This is a schematic diagram of the three-dimensional structure of the base when the heating element is a spiral heating element in an embodiment of the present utility model.

[0022] Figure 9 This is a schematic diagram of an explosion of the thermal protector according to an embodiment of the present invention (when the heating element is a planar heating element).

[0023] Figure 10 This is a schematic diagram of the three-dimensional structure of the base when the heating element is a planar heating element according to an embodiment of the present invention.

[0024] Figure 11It is a structural diagram of a thermal protector base in the prior art.

[0025] In the figure: programmable controller PLC, touch screen MT, adjustable constant current power supply IT, current converter BI, contactor J, current limiting resistor RL, test socket QD,

[0026] Central processing unit CPU, input interface IN, output interface OUT, analog-to-digital conversion module AD, digital-to-analog conversion module DA, serial communication interface RS232,

[0027] Pin 01, cover 02, dynamic reed 03, bimetallic strip 04, static pin 1 05, static pin 2 06, heating element 07, static pin 3 08, base 09,

[0028] Loading chamber 09-1, limiting platform 09-2, energy gathering platform 09-3. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and through examples. The following examples are provided to explain the present invention, but the present invention is not limited to the following examples.

[0030] Example

[0031] See also Figures 1 to 10 As shown, it should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they have no substantial technical significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, if there are references to terms such as "upper", "lower", "left", "right", "middle" and "one" in this specification, they are only for the convenience of description and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be considered as the scope of the implementation of the present invention without substantially changing the technical content.

[0032] The thermal protector maximum load current test system in this embodiment includes a programmable controller PLC, a touch screen MT, an adjustable constant current power supply IT, a current transformer BI, a contactor J, a current limiting resistor RL and a test socket QD. The touch screen MT, the adjustable constant current power supply IT, the current transformer BI and the contactor J are all connected to the programmable controller PLC. The line connecting the adjustable constant current power supply IT and the contactor J runs through the current transformer BI. The two ends of the current limiting resistor RL are respectively connected to the adjustable constant current power supply IT and the contactor J. The test socket QD is connected to the contactor J. The test socket QD is used to connect the thermal protector to be tested.

[0033] The programmable controller PLC in this embodiment includes a central processing unit CPU, an input interface IN, an output interface OUT, an analog-to-digital conversion module AD, a digital-to-analog conversion module DA and a serial communication interface RS232. The touch screen MT is connected to the serial communication interface RS232, the adjustable constant current power supply IT is connected to the digital-to-analog conversion module DA, the current converter BI is connected to the analog-to-digital conversion module AD, the contactor J is connected to the input interface IN and the output interface OUT respectively, and the input interface IN, the output interface OUT, the analog-to-digital conversion module AD, the digital-to-analog conversion module DA and the serial communication interface RS232 are all connected to the central processing unit CPU.

[0034] In this embodiment, the V1 and V2 terminals of the adjustable constant current power supply IT are connected to the L and N terminals of the AC power supply respectively, the V3 terminal of the adjustable constant current power supply IT is connected to the 3 terminal of the contactor J, and the wire connected thereto passes through the sensing hole of the current converter BI, the V4 terminal of the adjustable constant current power supply IT is connected to one end of the current limiting resistor RL, the U+ and U- terminals of the adjustable constant current power supply IT are connected to the + and - terminals of the digital-to-analog conversion module DA respectively; the U+ and U- terminals of the current converter BI are connected to the + and - terminals of the analog-to-digital conversion module AD respectively; the 2 and 6 terminals of the contactor J are connected to the test One end of the socket QD is connected, the 4th and 8th ends of the contactor J are connected to the other end of the test socket QD, the 5th end of the contactor J is connected to the V- end of the DC power supply, the 1st end of the contactor J is connected to the other end of the current limiting resistor RL, the 7th end of the contactor J is connected to the X1 end of the input interface IN, the B end of the drive coil of the contactor J is connected to the Y1 end of the output interface OUT, and the A end of the drive coil of the contactor J is connected to the V+ end of the DC power supply; the com end of the input interface IN is connected to the V+ end of the DC power supply, and the - end of the output interface OUT is connected to the V- end of the DC power supply.

[0035] In this embodiment, the input interface IN receives external switching signals, the analog-to-digital conversion module AD receives external analog signals and converts them into digital signals, and the serial communication interface RS232 receives parameter setting data or switching execution signals generated by the touch screen MT. These digital signals are all input to the central processing unit CPU, which performs data calculations, timing, comparisons, and other processing on the input digital signals. Based on the processing results, the output interface OUT outputs switching signals for corresponding switching control. The digital-to-analog conversion module DA converts the digital control signals into analog control signals for corresponding analog control. The processed data and signals are then transmitted to the touch screen MT via the serial communication interface RS232 for display.

[0036] The touch screen MT in this embodiment can generate setting parameters for comparison and judgment, switch signals for starting and stopping the test system, and display real-time data and result data of the programmable controller PLC during the test through the editing of the touch screen software. These data and signals can be bidirectionally transmitted with the central processing unit CPU via the serial communication interface RS232.

[0037] The function of the adjustable constant current power supply IT in this embodiment is to provide the test system with an automatically adjustable constant current source, the current of which depends on the size of the analog control signal. The analog control signal comes from the digital-to-analog conversion module DA, that is, the test loop current can be automatically adjusted through the programmable controller PLC.

[0038] The current converter BI in this embodiment plays the role of loop current detection. The detected real-time current analog signal is input into the analog-to-digital conversion module AD, converted into a real-time current digital signal, and then processed accordingly by the central processing unit CPU. In addition to playing the role of current detection, the current converter BI also constitutes a current closed-loop adjustment link with the adjustable constant current power supply IT and the programmable controller PLC. When the real-time current detected by the current converter BI is greater than or less than a certain range of the set current, the programmable controller PLC processes it to reduce or increase the analog control signal output to the adjustable constant current power supply IT, so that the real-time current is as close to the set current as possible. The above-mentioned current closed-loop adjustment link reduces the test current error and improves the test current accuracy.

[0039] The function of the contactor J in this embodiment is to control the contactor J to be attracted / released by the programmable controller PLC according to the test requirements, to control the connection / disconnection of the thermal protector and the constant current circuit by closing / releasing the normally open contact, and to control the disconnection / connection of the thermal protector and the on-off detection circuit by opening / closing the normally closed contact.

[0040] For example: when contactor J is energized, the normally open contact closes and the normally closed contact opens. One end of the thermal protector is connected to the V3 end of the adjustable constant current power supply IT through the closed contact 3-4 end, and the other end of the thermal protector is connected to the other end of the current limiting resistor RL through the closed contact 1-2 end. At this time, the thermal protector is connected to the constant current power supply circuit; since the normally closed contact 5-6 end and the normally closed contact 7-8 end are opened, the thermal protector is disconnected from the on-off detection circuit; when contactor J is released, the normally open contact opens and the normally closed contact closes. One end of the thermal protector is connected to the V- end of the DC power supply through the closed contact 5-6 end, and the other end of the thermal protector is connected to the X1 end of the input interface IN through the closed contact 7-8 end. At this time, the thermal protector is connected to the on-off detection circuit. Since the normally open contact 1-2 end and the normally open contact 3-4 end are opened, the thermal protector is disconnected from the constant current power supply circuit.

[0041] The current-limiting resistor RL in this embodiment serves to limit the current in the power-on loop, thereby preventing the current in the power-on loop from exceeding a limit value when the adjustable constant-current power supply IT loses control, thereby preventing the test system and the test product from being damaged.

[0042] The two test terminals of the test socket QD in this embodiment are connected to the switching contacts through the contactor J. When the thermal protector to be tested is inserted into the test socket QD, the test socket QD serves as a connection between the thermal protector and the test system.

[0043] The test method of the thermal protector maximum carrying current test system in this embodiment is as follows:

[0044] S1. Turn on the test system and insert the thermal protector to be tested into the test socket QD.

[0045] S2, in Figure 4 In the parameter setting interface of the touch screen MT shown, the initial current value Ic, step current value Ib, number of cycles DTI, action time upper limit DT2, action time lower limit DT3, reset time upper limit DT4, and reset time lower limit DT5 are set according to test requirements.

[0046] S3, in Figure 4 In the test interface of the touch screen MT shown in the figure, press the "Start" button, and the test start signal generated by the touch screen MT is transmitted to the central processing unit CPU through the serial communication interface RS232. After receiving the signal, the central processing unit CPU starts to execute the test program. First, the output interface OUT turns on the Y1 terminal to output the control signal. The control loop formed by the V+ terminal of the DC power supply → the drive coil A and B terminals of the contactor J → the Y1 terminal of the output interface OUT → the V- terminal of the DC power supply energizes the drive coil of the contactor J, and the contactor J is attracted, so that the normally closed contacts 5-6 and the normally closed contacts 7-8 of the contactor J are released, the thermal protector is disconnected from the on-off detection circuit, and the normally open contacts 1-2 and the normally open contacts 3-4 of the contactor J are closed. At this time, the constant current current circuit of the thermal protector is formed by the V3 terminal of the adjustable constant current power supply IT → the contact 3-4 terminals of the contactor J → the thermal protector → the contact 2-1 terminal of the contactor J → the current limiting resistor RL → the V4 terminal of the adjustable constant current power supply IT.

[0047] S4. The analog signal output by the digital-to-analog conversion module DA controls the adjustable constant current power supply IT to adjust the power-on current to the set initial current value Ic. The current converter BI detects the loop current in real time. The generated analog signal is converted into a digital signal by the analog-to-digital conversion module AD and then transmitted to the central processing unit CPU. If there is no real-time current signal input, it is determined that the thermal protector is not conducting or no thermal protector is connected. The test is completed and the alarm indicator light on the touch screen MT test interface lights up.

[0048] S5. After the central processing unit CPU confirms that there is current in the constant current power circuit, the internal timer starts to record the power-on time of the thermal protector. During the power-on process, the current converter BI, the adjustable constant current power supply IT, and the programmable controller PLC form a current closed-loop adjustment link to compare the power-on circuit current and the set current in real time. When the deviation is large, it is adjusted to ensure the accuracy of the test current; during the power-on timing process, the real-time recorded action time test value DT6 is compared with the set action time upper limit value DT2. When DT6>DT2 and the thermal protector is not disconnected, it is judged that the action time exceeds the upper limit, the test ends, and the alarm indicator light on the touch screen MT test interface lights up.

[0049] S6. Under the action of constant current, the heating element inside the thermal protector begins to heat up. When the heat accumulates to a certain level, the bimetallic strip jumps and disconnects the contacts, and the constant current circuit is disconnected. The central processing unit CPU detects through the current converter BI that there is no current in the power circuit, confirming that the thermal protector is disconnected, and the power-on timing ends. At this time, the recorded power-on timing value is the action time test value DT6 of the thermal protector. The action time test value DT6 is compared with the set action time lower limit value DT3. When DT6 < DT3, it is judged that the action time exceeds the lower limit, the test ends, and the alarm indicator light on the touch screen MT test interface lights up.

[0050] S7. If DT2>DT6>DT3, the action time is determined to be qualified and the test continues. Then the test system starts the disconnection timing of the thermal protector, and the output interface OUT closes the Y1 terminal output control signal, so that the drive coil of the contactor J loses power, the contactor J is released, and the normally open contacts 1-2 and 3-4 of the contactor J are released. The thermal protector is disconnected from the constant current circuit; the normally closed contacts 5-6 and 7-8 of the contactor J are closed, and the thermal protector is connected to the on-off detection circuit. The circuit is composed of the V+ terminal of the DC power supply → the com terminal of the input interface IN → The X1 terminal of the input interface IN → the normally closed contact 7-8 terminal of the contactor J → the thermal protector → the normally closed contact 6-5 terminal of the contactor J → the V- terminal of the DC power supply forms an on-off detection circuit. Since the thermal protector is in the off state at this time, there is no input signal at the X1 terminal of the input interface IN. During the off timing process, the reset time test value DT7 recorded in real time is compared with the set reset time upper limit value DT4. When DT7>DT4 and the thermal protector is not reset and connected, it is determined that the reset time exceeds the upper limit, the test ends, and the alarm indicator light on the MT test interface of the touch screen lights up.

[0051] S8. As the internal heating element of the thermal protector cools down, the internal temperature drops. When the temperature drops to a certain level, the bimetallic strip resets and the contacts are connected. The X1 end of the input interface IN detects the input signal, and the central processing unit CPU ends the disconnection timing. At this time, the recorded reset time test value DT7 is the reset time. The reset time test value DT7 is compared with the set reset time lower limit value DT5. When DT7 < DT5, it is judged that the reset time exceeds the lower limit, the test ends, and the alarm indicator light on the touch screen MT test interface lights up.

[0052] S9. If DT4>DT7>DT5, it is determined that the reset time is qualified. Thus, one action / reset test cycle of the thermal protector is completed, and the real-time value of the test cycle number DT8 is increased by 1.

[0053] S10. Compare the actual cycle number real-time value DT8 with the cycle number DT1. If DT8 < DT1 and the thermal protector does not have a test failure (heating wire blown) alarm, proceed to the next action / reset test cycle.

[0054] S11. If DT8 ≥ DT1, it means that the real-time value DT8 of the number of action / reset test cycles for the current level has reached the number of cycles DT1. The programmable controller PLC controls the adjustable constant current power supply IT to increase the test current by a step current, and the test system continues the action / reset cycle test under the current level.

[0055] S12. If a test failure occurs within the set number of cycles in the action / reset cycle of a certain current, the test system stops testing. The current in this gear is the melting current of the thermal protector, and the previous current is the carrying current.

[0056] S13. During the test, if the "Stop" button is pressed on the test interface of the touch screen MT, the test system stops the test and the test ends.

[0057] Among them, the model of the adjustable constant current power supply IT is ANJ11.

[0058] Among them, the model of the current converter BI is WBI415S91.

[0059] Among them, the model of contactor J is LC1D32M7C.

[0060] Among them, the model of the programmable controller PLC is FPXC40R; the central processing unit CPU is the control chip inside the programmable controller PLC; the input interface IN, the output interface OUT, and the serial communication interface RS232 are interfaces on the programmable controller PLC; the analog-to-digital conversion module AD is a plug-in on the programmable controller PLC, model AD2; the digital-to-analog conversion module DA is a plug-in on the programmable controller PLC, model DA2.

[0061] Among them, the model of the touch screen MT is MT6070iH.

[0062] Among them, the model of the current limiting resistor RL is RXG-01.

[0063] The above test system and test method are used to test the maximum carrying current of the heating element 07 in the following thermal protector.

[0064] The thermal protector in this embodiment includes a pin 01, a cover plate 02, a movable reed 03, a bimetallic strip 04, a stationary pin 1 05, a stationary pin 2 06, a heating element 07, a stationary pin 3 08 and a base 09. The two ends of the heating element 07 are respectively welded to the stationary pin 1 05 and the stationary pin 2 06. One end of the movable reed 03 is electrically connected to the stationary pin 1 05, and the other end of the movable reed 03 cooperates with the stationary pin 3 08. The pin 01 is electrically connected to the stationary pin 3 08.

[0065] In this embodiment, the plug pin 01 is arranged on the cover 02, and the movable spring 03, bimetallic strip 04, static pin 1 05, static pin 2 06, heating element 07, and static pin 3 08 are all arranged in the cavity formed by the cover 02 and the base 09. The heating element 07, bimetallic strip 04 and movable spring 03 are arranged in sequence from bottom to top. The contact of the movable spring 03 and the contact of the static pin 3 08 constitute an energized circuit that is electrically connected under normal circumstances and disconnected under abnormal circumstances.

[0066] The base 09 in this embodiment is provided with a loading cavity 09-1 for installing the heating element 07. The loading cavity 09-1 is provided with a concave circular structure. The bottom of the loading cavity 09-1 is provided with a limiting platform 09-2 for placing the heating element 07. The heating element 07 is a spiral heating element or a flat heating element.

[0067] When the heating element 07 is a spiral heating element, and the limiting platform 09-2 is provided with a plurality of semicircular protrusion structures, when the spiral heating element is loaded into the loading cavity 09-1 provided with a plurality of semicircular protrusion structures, the heat energy generated when the spiral heating element is energized and heated is no longer absorbed by the energy collecting platform 09-3 in the loading cavity 09-1, but directly radiates the heat energy to the upper bimetallic strip 04, which also accelerates the accumulation of heat energy of the bimetallic strip 04, and reaches the set temperature value suddenly (such as Figure 6 、 7 -8).

[0068] When the heating element 07 is a planar heating element and the limiting platform 09-2 is provided with two strip-shaped protrusion structures, when the planar heating element is loaded into the loading cavity 09-1 provided with the two strip-shaped protrusion structures, the heat energy generated when the planar heating element is energized and heated is no longer absorbed by the energy collecting platform 09-3 in the loading cavity 09-1, but is directly radiated to the bimetallic strip 04 above, which also accelerates the accumulation of heat energy of the bimetallic strip 04 and reaches the set temperature value suddenly (such as Figure 6 、 9 -10).

[0069] The thermal protector is connected to the compressor via the compressor's three-core terminal. Simply insert pin 01 into the compressor's three-core terminal; at the same time, the connecting plug of static pin 2 06 serves as the power connection. After the starter is inserted into the compressor's three-core terminal and electrically connected, it can be put into normal use. When the grid voltage is too high or too low, or a refrigeration system failure occurs, the bimetallic strip 04 is deformed by heat, pushing the contact of the movable reed 03 away from the contact of static pin 3 08, and the thermal protector is activated, thereby cutting off the above-mentioned protective circuit and protecting the compressor motor.

[0070] It should be noted that the test process and principle of the maximum carrying current of only one thermal protector are described here. Multiple thermal protectors can be tested by switching contactors, and the test principles are the same.

[0071] In addition, it should be noted that the shapes and names of the parts and components of the specific embodiments described in this specification may be different, and the above content described in this specification is merely an example of the structure of the utility model. Any equivalent changes or simple changes made based on the structure, features and principles described in the concept of the utility model patent are included in the scope of protection of the utility model patent. Technicians in the technical field of the utility model can make various modifications or supplements to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the utility model or exceed the scope defined by the claims, they should fall within the scope of protection of the utility model.

Claims

1. A thermal protector maximum carrying current test system, including a programmable controller (PLC), a touch screen (MT), an adjustable constant current power supply (IT), a current transformer (BI), a contactor (J), a current limiting resistor (RL) and a test socket (QD), characterized by: The touch screen (MT), adjustable constant current power supply (IT), current converter (BI) and contactor (J) are all connected to a programmable controller (PLC); the line connecting the adjustable constant current power supply (IT) and the contactor (J) runs through the current converter (BI); the two ends of the current limiting resistor (RL) are respectively connected to the adjustable constant current power supply (IT) and the contactor (J); and the test socket (QD) is connected to the contactor (J).

2. The thermal protector maximum carrying current testing system according to claim 1, characterized in that: The programmable controller (PLC) includes a central processing unit (CPU), an input interface (IN), an output interface (OUT), an analog-to-digital conversion module (AD), a digital-to-analog conversion module (DA) and a serial communication interface (RS232); the touch screen (MT) is connected to the serial communication interface (RS232); the adjustable constant current power supply (IT) is connected to the digital-to-analog conversion module (DA); the current converter (BI) is connected to the analog-to-digital conversion module (AD); the contactor (J) is connected to the input interface (IN) and the output interface (OUT) respectively; the input interface (IN), the output interface (OUT), the analog-to-digital conversion module (AD), the digital-to-analog conversion module (DA) and the serial communication interface (RS232) are all connected to the central processing unit (CPU).

3. The thermal protector maximum carrying current testing system according to claim 2, characterized in that: The V1 and V2 terminals of the adjustable constant current power supply (IT) are respectively connected to the L and N terminals of the AC power supply, the V3 terminal of the adjustable constant current power supply (IT) is connected to the 3 terminal of the contactor (J), and the connected wire passes through the induction hole of the current converter (BI), the V4 terminal of the adjustable constant current power supply (IT) is connected to one end of the current limiting resistor (RL), and the U+ and U- terminals of the adjustable constant current power supply (IT) are respectively connected to the + and - terminals of the digital-to-analog conversion module (DA).

4. The thermal protector maximum carrying current testing system according to claim 2, characterized in that: The U+ terminal and the U- terminal of the current converter (BI) are connected to the + terminal and the - terminal of the analog-to-digital conversion module (AD) respectively.

5. The thermal protector maximum carrying current testing system according to claim 2, characterized in that: Ends 2 and 6 of the contactor (J) are connected to one end of the test socket (QD), ends 4 and 8 of the contactor (J) are connected to the other end of the test socket (QD), end 5 of the contactor (J) is connected to the V-end of the DC power supply, end 1 of the contactor (J) is connected to the other end of the current limiting resistor (RL), end 7 of the contactor (J) is connected to the X1 end of the input interface (IN), end B of the drive coil of the contactor (J) is connected to the Y1 end of the output interface (OUT), and end A of the drive coil of the contactor (J) is connected to the V+ end of the DC power supply.

6. The thermal protector maximum carrying current testing system according to claim 2, characterized in that: The com terminal of the input interface (IN) is connected to the V+ terminal of the DC power supply, and the - terminal of the output interface (OUT) is connected to the V- terminal of the DC power supply.

7. The thermal protector maximum carrying current testing system according to claim 1, characterized in that: The test socket (QD) is used to connect the thermal protector to be tested.

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