Measurement and control system and control method for testing time parameters of thermal protector

Abstract

The present application relates to a measurement and control system and control method for testing the time parameters of a thermal protector. The measurement and control system for testing the time parameters of a thermal protector includes a power-on circuit for a thermal protector, a programmable controller, a current control circuit, a power supply circuit, and a touch screen. The power-on circuit for a thermal protector includes a transformer, a contactor, a rectifier bridge, an insulated gate bipolar transistor, a sampling resistor, and a current converter. The sampling signal of the current converter is converted into a DC voltage analog signal by a programmable controller. The current control circuit receives the DC voltage analog signal and superimposes the DC sampling signal, which is connected to the gate of the insulated gate bipolar transistor after amplification to control the conduction degree from the collector to the emitter of the insulated gate bipolar transistor. The input and output modules include a switch input module and a switch output module. The present application detects and dynamically adjusts the test current in real time to ensure the accuracy and stability of the test current; and controls the actuator to automatically classify and place according to the test results.

Description

Technical Field

[0001] The present application relates to a measurement and control system and a control method for testing time parameters of a thermal protector, which are mainly applicable to time parameter testing of a thermal protector. Background Art

[0002] Thermal protectors are used to protect motors. When overheating or overcurrent occurs during motor operation, the thermal protector automatically disconnects the power supply to prevent motor damage and further risks. The time parameters of the thermal protector mainly include the execution time of the thermal protector when the motor overcurrent (or overheating) occurs and the reset time of the thermal protector returning to the on state. These two parameters are very important and directly affect the protection reliability when the motor is abnormal and the starting state of the motor after the thermal protector is restored. Therefore, the time parameters of the thermal protector need to be accurately tested.

[0003] The test principle of thermal protector is shown in Figure 1 The thermal protector mainly includes a bimetallic strip 1, a heating wire 2, a reed 3, and a contact 4. The testing principle of the time parameter of the thermal protector is to connect the thermal protector to be tested to the test circuit. In the initial state, the terminal 2 RB-2 is electrically connected to the terminal 1 RB-1 through the heating wire 2, the reed 3, and the contact 4. The specified overload current is passed, and then the timer starts to record the protection action time. Under the action of the heat of the heating wire 2, the thermal protector causes the bimetallic strip 1 to jump suddenly and drive the reed 3, thereby disconnecting the contact 4 fixed on the reed 3. At this time, the terminal 1 RB-1 and the terminal 2 RB-2 are in a non-conducting state, and the protection action timing ends. After there is no current in the circuit, the timer starts to record the reset time. As the temperature drops, the bimetallic strip 1 jumps back, and the reed 3 resets to connect the contact 4 again. At this time, the terminal 1 RB-1 and the terminal 2 RB-2 are in a conducting state, and the reset timing ends.

[0004] The currently commonly used thermal protector time parameter test system has a low degree of automation, and the test current is adjusted by manual adjustment methods such as voltage regulators, rheostats or potentiometers. The test principle of the voltage regulator adjustment method is shown in Figure 2 The L and N terminals of the grid voltage are connected to the input terminal of the voltage regulator TB, and the output terminal of the voltage regulator TB is connected to the primary terminal of the transformer T. The secondary terminal of the transformer T outputs a safe low voltage. The secondary terminal T-1 passes through the test protector RB, the current limiting resistor RL, and the ammeter PA and returns to the other secondary terminal T-2 to form a test loop. The current size of the test loop is changed by adjusting the voltage output by the voltage regulator TB. The test principle using the variable resistor adjustment method is shown in Figure 3The L and N terminals of the grid voltage are connected to the primary of the transformer T. The secondary of the transformer T outputs a safe low voltage. The secondary terminal T-1 passes through the test protector RB, the variable resistor R, and the ammeter PA and then returns to the other secondary terminal T-2 to form a test loop. The current size of the test loop can be changed by adjusting the resistance value of the variable resistor R. The test principle using the potentiometer adjustment method is shown in Figure 4 , the L and N ends of the grid voltage are connected to the primary of transformer T, and the secondary of transformer T outputs a safe low voltage. The secondary end T-1 passes through the test protector RB, the current control circuit ICC, and the ammeter PA to return to the other end T-2 of the secondary to form a test loop. The current size of the test loop is changed by adjusting the resistance of the potentiometer RP to indirectly control the degree of conduction of the power module inside the current control circuit. The time parameter test method of the above three test circuits is to sense whether there is current in the test loop through the current transformer TA. When there is current in the loop, the counter S1 records the action time, and when there is no current in the loop, the counter S2 records the reset time. The common disadvantages of the above test circuits are: first, the current regulation uses mechanical adjustment devices, and there are problems with mechanical contact performance. The second is that the current sway caused by poor contact of the adjustment device and grid voltage fluctuations, the current deviation caused by the manual adjustment method, and the current drift caused by the difference in resistance between the cold and hot states of the heating wire in the thermal protector, because there is no real-time detection and control of the test current, the accuracy and stability of the current cannot be guaranteed, so that the tested time parameters have errors. The third is that the tester observes the action time and reset time recorded by counter S1 and counter S2, and manually determines whether the test result is qualified or a certain parameter is unqualified, and then classifies and places them. In summary, the above test methods use manual operations for current adjustment, test process judgment, and product classification and placement, which results in high workload and low work efficiency for operators, and also poses a major quality risk. Summary of the invention

[0005] The technical problem solved by the present application is to overcome the above-mentioned deficiencies in the prior art and to provide a measurement and control system and a control method for testing the time parameters of a thermal protector with a simple structure, small error and high degree of automation.

[0006] The technical solution adopted by the present application to solve the above technical problems includes: a measurement and control system for testing the time parameters of a thermal protector, including a thermal protector power-on circuit, characterized in that a programmable controller, a current control circuit, a power supply circuit, a touch screen, The power supply circuit is connected to both ends of the grid voltage and provides power to the programmable controller, the current control circuit, and the touch screen. The three output ends of the power supply circuit are respectively a positive power supply end, a zero potential end, and a negative power supply end. The programmable controller includes a central processing unit, an analog-to-digital conversion module, a digital-to-analog conversion module, and an input-output module. The central processing unit, the analog-to-digital conversion module, the digital-to-analog conversion module, the input-output module, and the touch screen are all connected. The thermal protector power-on circuit includes a transformer, a contactor, a rectifier bridge, an insulated gate bipolar transistor, a sampling resistor 1, and a current converter. The primary ends of the transformer are respectively connected to the two ends of the grid voltage. The secondary ends of the transformer output a test voltage that does not exceed the safety voltage. One end of the test voltage is connected to the other end of the test voltage through one contact of the contactor, the thermal protector, another contact of the contactor, one arm of the rectifier bridge, the collector and emitter of the insulated gate bipolar transistor, the sampling resistor 1, the other arm of the rectifier bridge, and the current converter to form a test loop. The test loop is divided into an AC test loop and a DC test loop. The AC test loop current flows in both directions alternately in the positive and negative half cycles of the power supply (test voltage), and the DC test loop current flows unidirectionally. The positive end of the rectifier bridge is connected to the collector of the insulated gate bipolar transistor, the emitter of the insulated gate bipolar transistor is connected to the negative end of the rectifier bridge and the zero potential end of the power supply circuit through a sampling resistor 1, the current converter is connected to the input end of the analog-to-digital conversion module of the programmable controller, the output end of the digital-to-analog conversion module is connected to the input end of the current control circuit, the central processing unit calculates and converts the signal obtained by the analog-to-digital conversion module into a DC voltage analog signal and transmits it to the current control circuit through the digital-to-analog conversion module, the current control circuit receives the DC voltage analog signal transmitted by the digital-to-analog conversion module and superimposes the DC sampling signal taken from one end of the sampling resistor 1, and connects it to the gate of the insulated gate bipolar transistor after amplification, controls the conduction degree from the collector to the emitter of the insulated gate bipolar transistor, thereby adjusting the size of the AC test loop current, the input and output module includes a switch input module and a switch output module, the switch input module is used for switch input related to the control timing, and the switch output module is used to output a switch control signal to indicate the test state and / or control the test action, and the special case is to control the actuator of the prior art to classify the measured thermal protectors and send them to the corresponding positions.

[0007] The current control circuit is composed of an operational amplifier, a transistor, a resistor 2, a resistor 3, a resistor 4, a resistor 5, a resistor 6, and a resistor 7. One end of the resistor 2 is connected to the positive end of the digital-to-analog conversion module, the zero potential end of the power supply circuit, the other end of the sampling resistor 1, and the negative end of the rectifier bridge. The positive input end of the operational amplifier is connected to the other end of the resistor 2; the reverse input end of the operational amplifier is respectively connected to one end of the resistor 3, the resistor 4, and the resistor 5, the other end of the resistor 3 is connected to the negative end of the digital-to-analog conversion module, the other end of the resistor 4 is respectively connected to the emitter of the insulated gate bipolar transistor and one end of the sampling resistor 1, the other end of the resistor 5 is connected to the output end of the operational amplifier and one end of the resistor 6, the other end of the resistor 6 is connected to the base of the transistor, the collector of the transistor is connected to one end of the resistor 7, the other end of the resistor 7 is connected to the positive power supply end, and the emitter of the transistor is connected to the gate of the insulated gate bipolar transistor. The operational amplifier, resistor 2, resistor 3, resistor 4 and resistor 5 form a first-stage signal amplification circuit; the triode, resistor 6 and resistor 7 form a second-stage signal amplification circuit. The input end of the first-stage signal amplification circuit receives the DC voltage analog signal output by the digital-to-analog conversion module and the DC sampling signal taken from one end of the sampling resistor 1 through resistor 4. The DC voltage analog signal and the DC sampling signal are superimposed and amplified by the first-stage signal amplification circuit and then output from the output end of the operational amplifier to the input end of the second-stage signal amplification circuit for second-stage signal amplification. After two-stage signal amplification, the conduction degree from the collector to the emitter of the insulated gate bipolar transistor is controlled to achieve the purpose of controlling the current of the test main loop.

[0008] The technical solution adopted by the present application to solve the above technical problems also includes: a control method of the measurement and control system for testing the time parameters of the thermal protector, which is characterized by comprising the following steps:

[0009] S1: Set the test AC current (set current data), action time lower limit, action time upper limit, reset time lower limit, reset time upper limit required by the technical indicators of the thermal protector to be tested on the touch screen. These setting data are saved in the programmable controller through the data line;

[0010] S2. The central processor converts the set current data into corresponding current control data (compared with the real-time current conversion data input by the analog-to-digital conversion module) and saves it in the programmable controller, and the programmable controller simultaneously receives the real-time current conversion data input by the AC sampling circuit;

[0011] S3. Start the test, the central processing unit compares the current control data with the real-time current conversion data and controls the digital-to-analog conversion module to output a DC voltage analog signal, the DC voltage analog signal is superimposed on the DC sampling signal taken from one end of the sampling resistor and connected to the current control circuit, and after amplification, it is output to the gate of the insulated gate bipolar transistor, controls the collector to emitter conduction of the insulated gate bipolar transistor and adjusts the real-time current conversion data, so as to realize the use of the current control circuit to quickly increase the real-time current of the AC test loop to the set current data and stabilize it near the set current data;

[0012] S4. After the thermal protector of the AC test circuit is powered on and the real-time current conversion data reaches the on-set value, the central processor determines that the thermal protector is in a stable on state, and the internal timer starts to record the on time. When the thermal protector is disconnected under the action of the AC current, the central processor determines that the thermal protector is in a disconnected state by identifying that the real-time current conversion data is lower than the disconnection set value. The on timer ends and the off timer starts at the same time. The time from the thermal protector being on to being off recorded by the timer is the action time; as the temperature drops, the thermal protector is turned on again, the off timer ends, and the time from the thermal protector being off to being on recorded by the timer is the reset time, and a test cycle ends; the central processor compares the test time data with the set time range parameters for judgment and processing. If the test If the measured action time is less than the set action time lower limit, it is an action time exceeding the lower limit unqualified item; if the measured action time is greater than the set action time upper limit, it is an action time exceeding the upper limit unqualified item; if the measured action time is between the set action time lower limit and the set action time upper limit, it is an action time qualified item; the measured reset time data is compared with the set reset time upper and lower limit data; if the measured reset time is less than the set reset time lower limit, it is an reset time exceeding the lower limit unqualified item; if the measured reset time is greater than the set reset time upper limit, it is an reset time exceeding the upper limit unqualified item; if the measured reset time is between the set reset time lower limit and the set reset time upper limit, it is a reset time qualified item;

[0013] S5: According to the test results, the switch output module of the programmable controller outputs the corresponding control signal to control the actuator to automatically classify and place.

[0014] Compared with the prior art, the present application has the following advantages and effects: the thermal protector measurement and control system applies software and hardware automatic control technologies such as programmable control, touch screen, and constant current control, and performs real-time detection and dynamic adjustment of the test current to ensure the accuracy and stability of the test current; the test parameters are automatically compared and judged, and the actuator is controlled to be automatically classified and placed according to the output test result signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the time parameter test principle of the thermal protector.

[0016] Figure 2 It is a circuit diagram of a voltage regulator used in the prior art.

[0017] Figure 3 It is a circuit diagram of a prior art using a variable resistor.

[0018] Figure 4 It is a circuit diagram of a potentiometer used in the prior art.

[0019] Figure 5 Schematic diagram of a circuit according to an embodiment of the present application.

[0020] Figure 6 yes Figure 5 The diagram shows the current direction of the positive half cycle of the AC circuit of the thermal protector energized circuit.

[0021] Figure 7 yes Figure 5 The schematic diagram of the negative half-cycle current direction of the AC circuit of the thermal protector energized circuit is shown. DETAILED DESCRIPTION

[0022] The present application will be further described in detail below in conjunction with the accompanying drawings and through examples. The following examples are intended to explain the present application but the present application is not limited to the following examples.

[0023] See also Figure 5 to Figure 7 The embodiment of the present application includes a thermal protector power-on circuit (including a current converter IT and a sampling resistor R1), a programmable controller PLC, a current control circuit, a power supply circuit 5, and a touch screen 6.

[0024] The thermal protector power-on circuit includes a transformer T, a contactor KM, a rectifier bridge D, the collector C to the emitter E of the insulated gate bipolar transistor IGBT, a sampling resistor R1, and a current converter IT. The two ends of the primary of the transformer T are respectively connected to the L end and the N end of the grid voltage, and the two ends of the secondary of the transformer T output a test voltage that does not exceed the safety voltage (36V) to provide a test power supply for the thermal protector RB to be tested. One end of the test voltage, i.e., the T-1 end of the secondary of the transformer T → the 1-3 end of one contact of the contactor KM → the thermal protector RB → the 4-2 end of the other contact of the contactor KM → one arm of the rectifier bridge D → the collector C to the emitter E of the insulated gate bipolar transistor IGBT → the sampling resistor R1 → the other arm of the rectifier bridge D → the current converter IT → the other end of the test voltage, i.e., the T-2 end of the secondary of the transformer T, forms a test loop. The magnitude of the loop current can be adjusted by controlling the degree of conduction from the collector C to the emitter E of the insulated gate bipolar transistor IGBT; the test loop is divided into an AC test loop. Test circuit and DC test circuit, the thermal protector RB to be tested is connected to the AC test circuit, its terminal 1 RB-1 is connected to the 3rd terminal of one contact of the contactor KM, the 1st terminal of one contact of the contactor KM is connected to one end of the test voltage, the terminal 2 RB-2 is connected to the 4th terminal of another contact of the contactor KM, the 2nd terminal of the other contact of the contactor KM is connected to an AC input terminal AC1 of the rectifier bridge D, and the other AC input terminal AC2 of the rectifier bridge D is connected to the other end of the test voltage. The current in the above AC test circuit flows alternately in the positive and negative half cycles of the power supply. The current direction in the positive half cycle is shown in Figure 6 , the negative half cycle current direction is Figure 7 The current of the DC test loop flows in one direction, and its connection method is that the + end (positive end) of the rectifier bridge D is connected to the collector C of the insulated gate bipolar transistor IBGT, the emitter E of the insulated gate bipolar transistor IGBT is connected to one end of the sampling resistor R1, and the other end of the sampling resistor R1 is connected to the - end (negative end) of the rectifier bridge D and connected to the GND end of the power supply circuit 5.

[0025] The present application samples the current when the test loop is powered on in real time, and provides sampling signals for real-time current display, current regulation and constant current control. In order to ensure accurate control of the test current, the present application is designed with AC sampling and DC sampling drawn from one end of the sampling resistor R1. As described below, the AC sampling uses a current transformer IT, and the AC test loop wire passes through the current transformer on the current transformer IT. The signal sensed by the current transformer is processed by the internal conversion of the current transformer IT, and a DC voltage analog signal proportional to the AC test loop current is output at the V+ and V- ends, which are connected to the input end of the analog-to-digital conversion module AD inside the programmable controller PLC, and its V+ end is connected to the + end of the analog-to-digital conversion module AD of the programmable controller PLC, and the V- end is connected to the - end of the analog-to-digital conversion module AD. The DC sampling is taken from the sampling resistor R1 connected in series in the DC test loop. When the DC current flows through the sampling resistor R1, a DC sampling voltage proportional to the current will be formed at both ends of the sampling resistor R1. The DC sampling voltage is introduced into the reverse input terminal IN- of the operational amplifier IC as a DC sampling signal after passing through the resistor R4, playing an auxiliary constant current role.

[0026] The function of the programmable controller PLC is to output data and control signals after performing logical operations on the input data and signals according to the software design requirements. The programmable controller PLC includes a central processing unit CPU, an analog-to-digital conversion module AD, a digital-to-analog conversion module DA and an input-output module. The central processing unit CPU generates processing results after performing logical operations on the input data; the two input ends of the analog-to-digital conversion module AD are respectively connected to the two ends (V+ and V- ends) of the DC voltage analog signal output by the current converter IT, and its function is to convert the DC voltage analog signal converted and output by the current converter IT into a digital signal; the + end of the digital-to-analog conversion module DA output is connected to one end of the resistor R2 and the GND end of the power supply circuit 5, and the other end of the resistor R2 is connected to the positive input end IN+ of the operational amplifier IC, and the - end of the digital-to-analog conversion module DA output is connected to the reverse input end IN- of the operational amplifier IC through the resistor R3 in the current control circuit, and its function is to convert the digital signal generated after the logical operation of the central processing unit CPU into a DC voltage analog signal; the input-output module includes a switch input module IN and a switch output module OUT, and the switch input module IN is connected to various switch input signals, such as the test start / stop signal (The test start and stop test in the embodiment of the present application can adopt automatic mode or manual mode. The automatic mode requires the installation of a position sensor at the thermal protector test position, and the manual mode requires the setting of a start-stop button on the touch screen 6; when the automatic mode is adopted, when the thermal protector to be tested is placed in the test position, the position sensor installed at the test position detects a thermal protector in place signal, that is, a thermal protector in place signal is sent to the central processing unit, and the central processing unit automatically starts the test process; when the manual mode is adopted, the operator needs to press the start-stop button after placing the thermal protector in the test position, and the central processing unit will control the start-stop button of this embodiment to start the test process until the test is completed or the start-stop button is pressed again during the test process, and the central processing unit stops the test process), the action position signal of the actuator, etc.; the switch output module OUT outputs various switch control signals, such as the test result switch signal, the action control signal of the actuator, etc.

[0027] The touch screen 6 realizes the setting of the test main circuit current value, the setting of the upper and lower limit ranges of each time test item of the thermal protector through software editing, and the display of real-time test current data and test time data; the touch screen 6 realizes bidirectional data transmission between the programmable controller PLC through the data line.

[0028] The current control circuit is composed of an operational amplifier IC, a transistor Q, (gate G to emitter E of an insulated gate bipolar transistor IGBT), resistor R2, resistor R3, resistor R4, resistor R5, resistor R6, and resistor R7. The operational amplifier IC and resistor R2, resistor R3, resistor R4, and resistor R5 form a first-stage signal amplification circuit; the transistor Q, resistor R6, and resistor R7 form a second-stage signal amplification circuit. The input end of the first-stage signal amplification circuit receives the DC voltage analog signal related to the current regulation control converted and output by the digital-to-analog conversion module DA and the DC sampling signal taken from one end of the sampling resistor R1 introduced through the resistor R4. The two signals are superimposed (in essence, the DC voltage analog signal is subtracted from the DC sampling signal) and then amplified by the first-stage signal and output from the output end OUT of the operational amplifier IC to the input end of the second-stage signal amplification circuit for second-stage signal amplification. After the two-stage signal amplification, the conduction degree from the collector C to the emitter E of the insulated gate bipolar transistor IGBT is controlled to achieve the purpose of controlling the current of the test main loop. The circuit connection mode of the current control circuit is as follows: one end of the resistor R2 is connected to the + end of the digital-to-analog conversion module DA, the GND end of the power supply circuit 5, the other end of the sampling resistor R1, and the - end of the rectifier bridge D; the positive input terminal IN+ of the operational amplifier IC is connected to the other end of the resistor R2; the reverse input terminal IN- of the operational amplifier IC is respectively connected to one end of the resistor R3, the resistor R4, and the resistor R5; the other end of the resistor R3 is connected to the - end of the digital-to-analog conversion module DA; the other end of the resistor R4 is respectively connected to the emitter E of the insulated gate bipolar transistor IGBT and one end of the sampling resistor R1; the other end of the resistor R5 is connected to the output terminal OUT of the operational amplifier IC and one end of the resistor R6; the other end of the resistor R6 is connected to the base b of the transistor T; the collector c of the transistor Q is connected to one end of the resistor R7; the other end of the resistor R7 is connected to the positive power supply terminal Vcc; and the emitter e of the transistor Q is connected to the gate G of the insulated gate bipolar transistor IGBT.

[0029] The power supply circuit 5 provides power required for normal operation of each circuit, and the three output terminals are respectively a positive power terminal Vcc, a zero potential terminal GND, and a negative power terminal Vee.

[0030] Working principle of this embodiment

[0031] The test process of this embodiment is as follows: this embodiment provides an alternating current to the thermal protector RB to be tested, and determines whether the thermal protector RB is in the on state or the off state by detecting whether the current transformer IT has an alternating current. In the process of detecting the current state of the test main circuit, this embodiment continuously compares the detected real-time current conversion data with the current control data. If the real-time current conversion data is greater than the current control data, the real-time current of the test main circuit is reduced through the programmable controller PLC and the current control circuit; if the real-time current conversion data is less than the current control data, the real-time current of the test main circuit is increased through the programmable controller PLC and the current control circuit, and the dynamic control of the adjustment process is adjusted to keep the test AC current always within a certain accuracy range. During the test process, this embodiment records the time when the test main circuit has a current state, which is the action time of the thermal protector RB to be tested, and records the time when the test main circuit has no current state, which is the reset time of the thermal protector RB. The measured action time is compared with the action time upper and lower limit data (normal range) set in this embodiment. If the measured action time is less than the set action time lower limit, it is an action time exceeding the lower limit unqualified item. If the measured action time is greater than the set action time upper limit, it is an action time exceeding the upper limit unqualified item. If the measured action time is between the set action time lower limit and the set action time upper limit, it is an action time qualified item. The measured reset time is compared with the reset time upper and lower limit data set in this embodiment. If the measured reset time is less than the set reset time lower limit, it is an reset time exceeding the lower limit unqualified item. If the measured reset time is greater than the set reset time upper limit, it is an reset time exceeding the upper limit unqualified item. If the measured reset time is between the set reset time lower limit and the set reset time upper limit, it is a reset time qualified item. According to the test results, the present embodiment outputs the corresponding control signal to control the actuator to automatically classify and place, and can also display or alarm on the touch screen 6 or the alarm device to indicate an unqualified situation.

[0032] Specific implementation process:

[0033] 1. Set the test AC current (set current data), action time lower limit, action time upper limit, reset time lower limit, reset time upper limit required by the technical indicators of the thermal protector RB to be tested on the touch screen 6. These setting data are transmitted to the programmable controller PLC through the data line.

[0034] 2. The central processing unit CPU converts the set current data into corresponding current control data (compared with the real-time current conversion data input by the analog-to-digital conversion module AD) according to the software design requirements and saves it in the programmable controller PLC. The programmable controller PLC also receives the real-time current conversion data input by the AC sampling circuit and converted by the analog-to-digital conversion module AD.

[0035] 3. Click the start / stop button on the touch screen 6 (or the automatic mode thermal protector is installed in place), the programmable controller PLC output module controls the two contacts of the contactor KM to close, and the thermal protector to be tested is connected to the AC test circuit. The test starts. Because there is no current in the test circuit at the beginning, the real-time current conversion data is very small, far less than the current control data. The central processing unit CPU compares the current control data with the real-time current conversion data and controls the digital-to-analog conversion module DA to output a large DC voltage analog signal. The signal is reversely connected to the input end of the operational amplifier IC through resistors R2 and R3 and superimposed through resistors The DC sampling signal introduced by R4 from one end of the sampling resistor 1 is amplified by the first stage amplifier circuit composed of the operational amplifier IC, the resistor 2 R2, the resistor 3 R3, the resistor 4 R4, and the resistor 5 R5, and then the amplified signal is output at the output end OUT of the operational amplifier IC. The first stage amplifier circuit is a reverse proportional amplifier circuit, and the output signal is in reverse proportion to the input signal. The amplification factor depends on the ratio of the resistor 5 R5 to the resistor 3 R3 and the resistor 4 R4. The specific calculation formula is UOUT=-R5(UDA / R3+UR1 / R4). As a special case, the resistance of R3 is 4.7KΩ, the resistance of R4 is 1.8KΩ, and the resistance of R5 is 5.1MΩ. The signal output by the first stage amplifier circuit is amplified by the second stage amplifier circuit composed of the transistor Q, the resistor 6 R6, and the resistor 7 R7. The signal after two-stage amplification is output by the emitter e of the transistor Q and connected to the gate G of the insulated gate bipolar transistor IGBT, controlling the collector C to the emitter E of the insulated gate bipolar transistor IGBT to conduct, and the test loop generates current. As the current of the test loop increases, the sampled real-time current data also increases. After comparison and processing by the central processing unit CPU, the DC analog voltage output by the control digital-to-analog conversion module DA slows down, and the controlled test loop current also slows down. When the real-time current of the test loop reaches the set current data (the corresponding real-time current conversion data reaches the current control data), the DC analog voltage output by the digital-to-analog conversion module DA tends to be stable, and the control voltage connected to the gate G of the insulated gate bipolar transistor IGBT after amplification by the two-stage amplifier circuit also tends to be stable, so that the conduction degree from the collector C to the emitter E is maintained in this state, and the test loop current also remains stable at this time. After the test loop is powered on, this embodiment dynamically detects the fluctuation of the real-time current through the current sampling circuit. When the current fluctuates, the conduction degree from the collector C to the emitter E of the insulated gate bipolar transistor IGBT is feedback-controlled after the comparison and processing of the real-time current data and the set current data, so as to ensure the stability and accuracy of the current and achieve the effect of constant current. The two-way current constant control process is introduced below.The first route is the sampling circuit at the end of the AC test loop. When the real-time current is greater than the set current data, the sampling voltage output by the current converter IT rises. The programmable controller PLC compares the current control data with the real-time current conversion data and controls the DC analog voltage output by the digital-to-analog conversion module DA to decrease. After amplification by the two-stage amplifier circuit, the control voltage input to the gate G of the insulated gate bipolar transistor IGBT decreases, thereby reducing the conduction degree from the collector C to the emitter E, and the real-time current of the test loop decreases. Conversely, when the real-time current is less than the set current data, the DC analog voltage output by the digital-to-analog conversion module DA increases accordingly, thereby increasing the conduction degree from the collector C to the emitter E of the insulated gate bipolar transistor IGBT, and the real-time current of the test loop increases. The second is a DC test loop sampling circuit, whose DC sampling voltage is the voltage across the sampling resistor R1 connected in series in the DC test loop. The DC sampling voltage is superimposed on the DC voltage analog signal output by the digital-to-analog conversion module DA through the resistor R4 and then connected to the reverse input terminal IN- of the operational amplifier IC. The DC sampling signal is connected in the forward direction, while the DC voltage analog signal output by the digital-to-analog conversion module DA is connected in the reverse direction, so the two signals are subtracted inputs. Since the DC sampling signal is much smaller than the DC voltage analog signal output by the digital-to-analog conversion module DA, it can only play the role of auxiliary constant current. The specific constant current control process is as follows: when the current in the DC test loop increases, the DC sampling voltage increases, the voltage value of the input after subtracting the two signals decreases, and the control voltage input to the gate G of the insulated gate bipolar transistor IGBT after amplification by the two-stage amplifier circuit decreases, thereby reducing the degree of conduction from the collector C to the emitter E, and the real-time current of the test loop decreases; conversely, when the real-time current in the DC test loop decreases, the DC sampling voltage decreases, and correspondingly increases the degree of conduction from the collector C to the emitter E of the insulated gate bipolar transistor IGBT, and the real-time current of the test loop increases.

[0036] 4. After the thermal protector RB of the AC test circuit is powered on and the real-time current conversion data reaches the set value for connection (which can be pre-set in the test program according to the actual situation), the CPU inside the programmable controller PLC determines that the thermal protector RB is in a stable connected state through the real-time current conversion data, and the internal timer starts to record the connection time. When the thermal protector RB is under the action of the AC current, its internal bimetal 1 operates to disconnect the contact 4. The CPU determines that the thermal protector RB is in a disconnected state by identifying that the current converter IT has no signal (the real-time current conversion data is lower than the disconnection set value). The connection timing ends and the disconnection timing starts at the same time. The time recorded by the timer from the connection to the disconnection of the thermal protector RB is the action time. As the temperature drops, the bimetal 1 resets, causing the contact to connect again, and the disconnection timing ends. The time recorded by the timer from the disconnection to the connection of the thermal protector RB is the reset time. At this point, a test cycle ends. The central processing unit CPU compares and judges the test time data with the set time range parameters. If the measured action time is less than the set action time lower limit, it is an action time exceeding the lower limit and is unqualified. If the measured action time is greater than the set action time upper limit, it is an action time exceeding the upper limit and is unqualified. If the measured action time is between the set action time lower limit and the set action time upper limit, it is an action time qualified item. The measured reset time data is compared with the set reset time upper and lower limit data. If the measured reset time is less than the set reset time lower limit, it is an reset time exceeding the lower limit and is unqualified. If the measured reset time is greater than the set reset time upper limit, it is an reset time exceeding the upper limit and is unqualified. If the measured reset time is between the set reset time lower limit and the set reset time upper limit, it is a reset time qualified item.

[0037] 5. According to the test results, the switch output module OUT of the programmable controller PLC outputs the corresponding control signal to control the actuator to automatically classify and place.

[0038] Any simple deformation or combination of the technical features and technical solutions of this application should be considered to fall within the protection scope of this application.

Claims

1. A measurement and control system for testing the time parameters of a thermal protector, comprising a thermal protector power-on circuit, characterized in that A programmable controller, a current control circuit, a power supply circuit, and a touch screen are also provided. The power supply circuit is connected to both ends of the grid voltage and provides power to the programmable controller, the current control circuit, and the touch screen. The three output ends of the power supply circuit are respectively a positive power supply end, a zero potential end, and a negative power supply end. The programmable controller includes a central processing unit, an analog-to-digital conversion module, a digital-to-analog conversion module, and an input-output module. The central processing unit, the analog-to-digital conversion module, the digital-to-analog conversion module, the input-output module, and the touch screen are all connected. The thermal protector power-on circuit includes a transformer, a contactor, a rectifier bridge, an insulated gate bipolar transistor, a sampling resistor 1, and a current converter. The two ends of the primary of the transformer are respectively connected to the two ends of the grid voltage. The two ends of the secondary of the transformer output a test voltage that does not exceed the safety voltage. One end of the test voltage is connected to the other end of the test voltage through one contact of the contactor, the thermal protector, another contact of the contactor, one arm of the rectifier bridge, the collector and emitter of the insulated gate bipolar transistor, the sampling resistor 1, the other arm of the rectifier bridge, and the current converter to form a test loop. The rectifier bridge The positive end is connected to the collector of the insulated gate bipolar transistor, the emitter of the insulated gate bipolar transistor is connected to the negative end of the rectifier bridge and the zero potential end of the power supply circuit through the sampling resistor 1, the current converter is connected to the input end of the analog-to-digital conversion module of the programmable controller, the output end of the digital-to-analog conversion module is connected to the input end of the current control circuit, the central processing unit calculates and converts the signal obtained by the analog-to-digital conversion module into a DC voltage analog signal and transmits it to the current control circuit through the digital-to-analog conversion module, the current control circuit receives the DC voltage analog signal transmitted by the digital-to-analog conversion module and superimposes the DC sampling signal taken from one end of the sampling resistor 1, and connects it to the gate of the insulated gate bipolar transistor after amplification, controls the conduction degree from the collector to the emitter of the insulated gate bipolar transistor, the input and output module includes a switch quantity input module and a switch quantity output module, the switch quantity input module is used for switch quantity input, and the switch quantity output module is used for switch quantity output, and the control actuator classifies the measured thermal protectors and sends them to the corresponding positions.

2. According to claim 1, the measurement and control system for testing the time parameters of the thermal protector is characterized by: The current control circuit is composed of an operational amplifier, a transistor, a resistor 2, a resistor 3, a resistor 4, a resistor 5, a resistor 6, and a resistor 7. One end of the resistor 2 is connected to the positive end of the digital-to-analog conversion module, the zero potential end of the power supply circuit, the other end of the sampling resistor 1, and the negative end of the rectifier bridge. The positive input end of the operational amplifier is connected to the other end of the resistor 2; the reverse input end of the operational amplifier is respectively connected to one end of the resistor 3, the resistor 4, and the resistor 5; the other end of the resistor 3 is connected to the negative end of the digital-to-analog conversion module; the other end of the resistor 4 is respectively connected to the emitter of the insulated gate bipolar transistor and one end of the sampling resistor 1; the other end of the resistor 5 is connected to the output end of the operational amplifier and one end of the resistor 6; the other end of the resistor 6 is connected to the base of the transistor; the collector of the transistor is connected to one end of the resistor 7; and the The other end of resistor seven is connected to the positive power supply end, the emitter of the transistor is connected to the gate of the insulated gate bipolar transistor, the operational amplifier, resistor two, resistor three, resistor four, and resistor five form a first-stage signal amplification circuit; the transistor, resistor six, and resistor seven form a second-stage signal amplification circuit, the input end of the first-stage signal amplification circuit receives the DC voltage analog signal output by the digital-to-analog conversion module and the DC sampling signal taken from one end of the sampling resistor one through resistor four, the DC voltage analog signal and the DC sampling signal are superimposed and then output from the output end of the operational amplifier to the input end of the second-stage signal amplification circuit after passing through the first-stage signal amplification circuit for second-stage signal amplification, and after two-stage signal amplification, the conduction degree from the collector to the emitter of the insulated gate bipolar transistor is controlled.

3. A control method for the measurement and control system for testing the time parameters of the thermal protector according to claim 1 or 2, characterized in that The following steps are involved: S1: Set the current data, action time lower limit, action time upper limit, reset time lower limit, reset time upper limit required by the technical indicators of the thermal protector to be tested on the touch screen and save them in the programmable controller; S2. The central processor converts the set current data into the corresponding current control data and saves it in the programmable controller, and the programmable controller simultaneously receives the real-time current conversion data input by the AC sampling circuit; S3. Start the test, the central processing unit compares the current control data with the real-time current conversion data and controls the digital-to-analog conversion module to output a DC voltage analog signal, the DC voltage analog signal is superimposed on the DC sampling signal taken from one end of the sampling resistor, and connected to the current control circuit, and after amplification, it is output to the gate of the insulated gate bipolar transistor, controls the collector to emitter conduction of the insulated gate bipolar transistor and adjusts the real-time current conversion data; S4. After the thermal protector of the AC test circuit is powered on and the real-time current conversion data reaches the on-set value, the central processor determines that the thermal protector is in a stable on state, and the internal timer starts to record the on time. When the thermal protector is disconnected under the action of the AC current, the central processor determines that the thermal protector is in a disconnected state by identifying that the real-time current conversion data is lower than the disconnection set value. The on timer ends and the off timer starts at the same time. The time from the thermal protector being on to being off recorded by the timer is the action time; as the temperature drops, the thermal protector is turned on again, the off timer ends, and the time from the thermal protector being off to being on recorded by the timer is the reset time, and a test cycle ends; the central processor compares the test time data with the set time range parameters for judgment and processing. If the test If the measured action time is less than the set action time lower limit, it is an action time exceeding the lower limit unqualified item; if the measured action time is greater than the set action time upper limit, it is an action time exceeding the upper limit unqualified item; if the measured action time is between the set action time lower limit and the set action time upper limit, it is an action time qualified item; the measured reset time data is compared with the set reset time upper and lower limit data; if the measured reset time is less than the set reset time lower limit, it is an reset time exceeding the lower limit unqualified item; if the measured reset time is greater than the set reset time upper limit, it is an reset time exceeding the upper limit unqualified item; if the measured reset time is between the set reset time lower limit and the set reset time upper limit, it is a reset time qualified item; S5: According to the test results, the switch output module of the programmable controller controls the actuator to automatically classify and place.

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