CN108957309B - Circuit and method for detecting contactor suction condition - Google Patents
Circuit and method for detecting contactor suction condition Download PDFInfo
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- CN108957309B CN108957309B CN201810977979.6A CN201810977979A CN108957309B CN 108957309 B CN108957309 B CN 108957309B CN 201810977979 A CN201810977979 A CN 201810977979A CN 108957309 B CN108957309 B CN 108957309B
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- 239000003990 capacitor Substances 0.000 description 13
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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Abstract
The invention relates to a circuit and a method for detecting the suction condition of a contactor, wherein the circuit comprises a voltage acquisition unit, a voltage processing unit and a hysteresis comparison unit, wherein the voltage acquisition unit is used for acquiring voltages at two ends of a buffer resistor connected with the contactor; the voltage processing unit is used for receiving the voltages at two ends of the buffer resistor input by the voltage acquisition unit, amplifying, limiting and level-lifting the voltages at two ends of the buffer resistor; and the hysteresis comparison unit is used for receiving the voltages at two ends of the buffer resistor processed by the voltage processing unit, comparing the voltages with the reference voltage, obtaining a comparison result and outputting a signal corresponding to the comparison result. The invention thoroughly solves the problem of false alarm of the auxiliary contact of the contactor caused by poor suction due to dust accumulation, has low cost, and can ensure high detection reliability by adopting a voltage detection mode.
Description
Technical Field
The invention relates to a soft start contactor detection circuit, in particular to a circuit and a method for detecting the attraction condition of a contactor.
Background
The contactor is an electric appliance which uses a coil to flow current to generate a magnetic field in industrial electricity so as to close a contact to control a load. The traditional mode for detecting whether the contactor is in attraction or not is to directly judge whether an auxiliary normally open contact of the contactor is in attraction or not and feed the signal back to a singlechip control chip for judgment. However, when the device is actually operated on site, dust is accumulated in the auxiliary contact after the contact is in a long time in a cabinet with poor dustproof condition, so that the auxiliary contact cannot be conducted after being attracted, an attracting signal cannot be detected by a singlechip control chip, and the problems of failure and faults of a soft starter connected with the contact are misreported.
Therefore, a new circuit is necessary to be designed, the problem of false alarm caused by poor suction due to dust accumulation of auxiliary contacts of the contactor is thoroughly solved, the cost is low, and the detection reliability is high.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a circuit and a method for detecting the suction condition of a contactor.
In order to achieve the above purpose, the present invention adopts the following technical scheme: the circuit for detecting the suction condition of the contactor comprises a voltage acquisition unit, a voltage processing unit and a hysteresis comparison unit, wherein the voltage acquisition unit is used for acquiring voltages at two ends of a buffer resistor connected with the contactor; the voltage processing unit is used for receiving the voltages at two ends of the buffer resistor input by the voltage acquisition unit, amplifying, limiting and level-lifting the voltages at two ends of the buffer resistor; and the hysteresis comparison unit is used for receiving the voltages at two ends of the buffer resistor processed by the voltage processing unit, comparing the voltages with the reference voltage, obtaining a comparison result and outputting a signal corresponding to the comparison result.
The further technical scheme is as follows: the voltage acquisition unit comprises a terminal J41.
The further technical scheme is as follows: the voltage processing unit comprises a differential amplification subunit, a limiting subunit, an inverting amplification subunit and a level lifting subunit which are sequentially connected, wherein the differential amplification subunit is connected with the voltage acquisition unit, and the level lifting subunit is connected with the hysteresis comparison unit.
The further technical scheme is as follows: the differential amplifying subunit comprises an amplifier U66, and feedback resistors R543 and R473 are connected between the inverting input end and the output end of the amplifier U66.
The further technical scheme is as follows: the limiting subunit comprises a current limiting resistor R596 connected with the output end of the amplifier U66, and a current limiting diode D101 with one end grounded is connected between the current limiting resistor R596 and the inverting amplifier subunit.
The further technical scheme is as follows: the inverting amplifying subunit comprises an amplifier U67, an inverting input end of the amplifier U67 is connected with the current limiting resistor R596, and an output end of the amplifier U67 is connected with the level lifting subunit.
The further technical scheme is as follows: the level lifting subunit comprises level lifting operational amplifiers U68 and U69, wherein an inverting input end of the level lifting operational amplifier U68 and an inverting input end of the level lifting operational amplifier U69 are respectively connected with an output end of the amplifier U67, an output end of the level lifting operational amplifier U68 is connected with an inverting input end of the level lifting operational amplifier U68, an inverting input end of the level lifting operational amplifier U68 is connected with an output end of the level lifting operational amplifier U69, and an output end of the level lifting operational amplifier U69 is connected with the hysteresis comparison unit.
The further technical scheme is as follows: the hysteresis comparison unit comprises hysteresis comparators U71 and U72, wherein an inverting input end of the hysteresis comparator U71 is connected with an output end of the level-lifting operational amplifier U69, a non-inverting input end of the hysteresis comparator U72 is connected with an output end of the level-lifting operational amplifier U69, and an output end of the hysteresis comparator U71 is connected with an output end of the hysteresis comparator U72.
The further technical scheme is as follows: the model numbers of the hysteresis comparators U71 and U72 are LM2903DMR2 respectively.
The invention also provides a method for detecting the suction condition of the contactor, which comprises the following steps:
the voltage acquisition unit acquires voltages at two ends of a buffer resistor connected with the contactor;
the voltage processing unit receives the voltages at two ends of the buffer resistor input by the voltage acquisition unit, amplifies the voltages at two ends of the buffer resistor, limits the amplitude and improves the level;
and the hysteresis comparison unit receives the voltages at two ends of the buffer resistor processed by the voltage processing unit, compares the voltages with a reference voltage, acquires a comparison result, outputs a signal corresponding to the comparison result, and detects the suction condition of the contactor according to the output signal.
Compared with the prior art, the invention has the beneficial effects that: according to the invention, through setting the voltage at two ends of the buffer resistor which is connected with the contactor in parallel, the collected voltage is input to the hysteresis comparison unit after differential amplification, amplitude limiting treatment, reverse amplification and level lifting treatment, the collected voltage at two ends is compared with the set reference voltage, and whether the contactor is sucked or not is judged according to a comparison result, so that the problem that the auxiliary contact of the contactor is mistakenly reported due to poor suction caused by dust accumulation is thoroughly solved, the cost is very low, and the detection reliability is high by adopting a voltage detection mode.
The invention is further described below with reference to the drawings and specific embodiments.
Drawings
FIG. 1 is a schematic diagram of a controllable rectifier bridge using contactors according to an embodiment of the present invention;
FIG. 2 is a schematic block diagram of a circuit for detecting contactor pull-in provided in accordance with an embodiment of the present invention;
FIG. 3 is a schematic diagram of a circuit for detecting contactor pull-in according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a differential amplifying subunit (including a terminal J41) according to an embodiment of the present invention;
fig. 5 is a schematic circuit diagram of a clipping subunit according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of an inverting amplifier subunit according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a level-boosting subunit according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of a hysteresis comparison unit according to an embodiment of the present invention;
FIG. 9 is a waveform diagram of a comparison value of a hysteresis comparator U72 according to an embodiment of the present invention;
fig. 10 is a schematic waveform diagram of a voltage across a snubber resistor according to an embodiment of the present invention.
Detailed Description
In order to more fully understand the technical content of the present invention, the following technical solutions of the present invention will be further described and illustrated with reference to specific embodiments, but are not limited thereto.
It should be understood that the terms "comprises" and "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be further understood that the term "and/or" as used in this specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.
As shown in the specific embodiments of fig. 1 to 10, the circuit for detecting the engaging condition of the contactor provided in this embodiment can be applied in the process of judging the engaging condition of the contactor connected to the soft starter, so as to thoroughly solve the problem that the auxiliary contact of the contactor is misreported due to poor engaging caused by dust accumulation, and has low cost and high detection reliability.
Referring to fig. 1, the controllable rectifier bridge rectifies three-phase ac input R, S, T into dc in a rectification working state, inverts bus electric energy into ac in an inversion working state and feeds back the ac to a power grid, the power-on buffer link comprises a three-phase ac contactor and two current limiting resistors R1 and R2, after the frequency converter is powered on, the contactor is disconnected, charging current flowing through the rectifier bridge and the capacitor is limited by the current limiting resistors R1 and R2, when voltages at two ends of the electrolytic capacitors C4, C5, C6 and C7 reach normal working voltages, the contactor is controlled to be attracted, and the current limiting resistors R1 and R2 are short-circuited by the contactor connected with the current limiting resistors in parallel. As shown in fig. 1, two ends of the contactor are connected in parallel with buffer resistors (such as R8 and R9 in fig. 1), when the contactor is not sucked, current flows through the buffer resistors, and two ends of the buffer resistor are correspondingly provided with voltages; after the contactor is sucked, the buffer resistor is short-circuited, and the voltage at two ends of the buffer resistor is close to zero, so that the voltage at two ends of the buffer resistor can be detected to judge whether the contactor is sucked or not, the problem that the auxiliary contact of the contactor is misreported due to poor suction caused by dust accumulation is thoroughly solved, the cost is very low, and the detection reliability is high.
Referring to fig. 2 and 3, the circuit for detecting the pull-in condition of the contactor includes a voltage acquisition unit 1, a voltage processing unit 2 and a hysteresis comparison unit 3, wherein the voltage acquisition unit 1 is used for acquiring voltages at two ends of a buffer resistor connected with the contactor; the voltage processing unit 2 is used for receiving the voltages at two ends of the buffer resistor input by the voltage acquisition unit 1, amplifying and limiting the voltages at two ends of the buffer resistor and carrying out level lifting processing; and the hysteresis comparison unit 3 is used for receiving the voltages at two ends of the buffer resistor processed by the voltage processing unit 2, comparing the voltages with the reference voltage, obtaining a comparison result and outputting a signal corresponding to the comparison result.
Specifically, in this embodiment, the circuit is used to detect voltages at two ends of the buffer resistor to determine whether the contactor of the short-circuit power-on buffer resistor is closed, and the voltages at two ends of the buffer resistor detected by the voltage acquisition unit 1 are amplified, limited and level-lifted by the voltage processing unit 2 and then sent to the hysteresis comparison unit 3; when the voltage at two ends of the buffer resistor is smaller than 20V (other set reference voltage values can be adopted), the contactor is considered to be closed, and the hysteresis comparison unit 3 outputs high level; when the voltage at two ends of the buffer resistor is larger than 20V (other set reference voltage values can be adopted), the contactor is considered to be disconnected, the hysteresis comparison unit 3 outputs pulse signals, the actuation condition of the contactor is judged according to the difference of the signals output by the hysteresis comparison unit 3, the signals output by the hysteresis comparison unit 3 are input to the main control chip, the main control chip is timely informed of the actuation condition of the contactor, and the problems that false alarm of failure and faults occur in a soft starter connected with the contactor are avoided.
In this embodiment, the voltage acquisition unit 1 includes a terminal J41, however, in other embodiments, the voltage acquisition unit 1 may be an acquisition unit of other voltage.
In an embodiment, as shown in fig. 2, the voltage processing unit 2 includes a differential amplifying subunit 21, a clipping subunit 22, an inverting amplifying subunit 23, and a level raising subunit 24, which are sequentially connected, where the differential amplifying subunit 21 is connected to the voltage collecting unit 1, and the level raising subunit 24 is connected to the hysteresis comparing unit 3. After the collected voltage is amplified, limited and level-lifted, the comparison of the later hysteresis comparison unit 3 can be more accurate.
In one embodiment, as shown in fig. 4, the differential amplifying subunit 21 includes an amplifier U66, and feedback resistors R543, R473 are connected between the inverting input terminal and the output terminal of the amplifier U66.
In addition, compensation resistors R478, R479, R474, R477 are connected between the non-inverting input terminal of the amplifier U66 and the terminal J41 to reduce or eliminate oscillation; compensation resistors R480, R481, R475 and R476 are connected between the inverting input terminal of the amplifier U66 and the terminal J41 to reduce or eliminate oscillation; in addition, a filter capacitor C365 is further disposed between the inverting input terminal of the amplifier U66 and the non-inverting input terminal of the amplifier U66, so as to filter the voltages at two ends of the collected buffer resistor.
Diodes D93 and D92 are connected to the non-inverting input terminal of the amplifier U66 and the inverting input terminal of the amplifier U66, respectively, and the diodes D93 and D92 are applied to the input terminal of the amplifier U66 as protection devices to prevent the amplifier U66 from being damaged due to electrostatic discharge and input voltage exceeding the maximum input voltage range of the amplifier U66.
Furthermore, the non-inverting input terminal of the amplifier U66 is further connected to a first-order low-pass filter to suppress noise of the amplifier U66, and the first-order low-pass filter includes a filter capacitor C356 and filter resistors R472 and R542.
A compensation resistor R464 is further connected between the output end of the amplifier U66 and the clipping subunit 22, and performs in-loop compensation on the amplifier U66, so as to increase the capacity of the amplifier U66 with capacitive load.
The inverting input terminal of the amplifier U66 is also connected to filter capacitors C353 and C357 to suppress the noise of the amplifier U66.
In the present embodiment, the parameters of the amplifier U66 are
In one embodiment, as shown in fig. 5, the limiting subunit 22 includes a current limiting resistor R596 connected to the output terminal of the amplifier U66, and a current limiting diode D101 with one end grounded is connected between the current limiting resistor R596 and the inverting amplifier subunit 23.
Specifically, the compensation resistor R464 is connected between the output end of the amplifier U66 and the current limiting resistor R596, and the current limiting resistor R596 and the current limiting diode D101 form a limiting circuit, and the output signal is equal to the input signal only when the voltage amplitude of the input signal is smaller than the dead zone voltage of the current limiting diode D101. In this embodiment, the current limiting diode D101 is of the type MMBD7000LT1, and the device data is checked, and the dead zone voltage of the current limiting diode D101 is about 0.49V at 25 ℃.
In one embodiment, as shown in fig. 6, the inverting amplifying subunit 23 includes an amplifier U67, an inverting input terminal of the amplifier U67 is connected to the current limiting resistor R596, and an output terminal of the amplifier U67 is connected to the level raising subunit 24.
Specifically, a resistor R353 is connected between the current limiting resistor R596 and the inverting input terminal of the amplifier U67, the inverting input terminal of the amplifier U67 is further connected with a filter capacitor C398 with one grounded end, a feedback resistor R595 and a capacitor C396 are connected between the inverting input terminal of the amplifier U67 and the output terminal of the amplifier U67, and the non-inverting input terminal of the amplifier U67 is connected with a resistor R592 with one grounded end.
In the present embodiment, the parameters of the amplifier U67 areIf the amplitude limit of the front stage is-0.7V to +0.7V, the amplified amplitude limit is +4.767V to-4.767V.
Referring to fig. 7, the level-lifting subunit 24 includes level-lifting op-amps U68 and U69, wherein an inverting input terminal of the level-lifting op-amp U68 and an inverting input terminal of the level-lifting op-amp U69 are respectively connected with an output terminal of the amplifier U67, an output terminal of the level-lifting op-amp U68 is connected with an inverting input terminal of the level-lifting op-amp U68, an inverting input terminal of the level-lifting op-amp U68 is connected with an output terminal of the level-lifting op-amp U69, and an output terminal of the level-lifting op-amp U69 is connected with the hysteresis comparing unit 3.
The level-boosting op-amp U68 provides a 5V level-boosting circuit to compare positive and negative half waves of the detected voltage, specifically, to convert +4.767V to-4.767V of positive and negative voltage changes into a range of 0.223 to 9.767V.
Let the buffer resistor collect voltage as U i The output voltage after the level-boosting circuit is U o The correspondence is:
U O ＝-(A 1 ×A 2 ×U i -5)＝5-0.0681U i (-70V≤U i ≤+70V)；
U O ＝0.223V(U i ≥+70V)；
U O ＝9.767V(U i ≤-70V)。
specifically, the non-inverting input end of the level-raising operational amplifier U68 is connected with resistors R536 and R539; the inverting input end of the level-lifting operational amplifier U68 is connected with resistors R545 and R544; compensation resistors R548 and R546 and a filter capacitor C385 are connected between the inverting input terminal of the level-raising op-amp U69 and the amplifier U67.
In an embodiment, as shown in fig. 8, the hysteresis comparing unit 3 includes hysteresis comparators U71 and U72, where an inverting input terminal of the hysteresis comparator U71 is connected to an output terminal of the level-raising op-amp U69, a non-inverting input terminal of the hysteresis comparator U72 is connected to an output terminal of the level-raising op-amp U69, and an output terminal of the hysteresis comparator U71 is connected to an output terminal of the hysteresis comparator U72.
In this embodiment, the types of the hysteresis comparators U71 and U72 are LM2903DMR2, respectively.
In addition, a resistor R502 is connected between the inverting input terminal of the hysteresis comparator U71 and the output terminal of the level-boosting operational amplifier U69, the non-inverting input terminal of the hysteresis comparator U71 is connected with the output terminal of the hysteresis comparator U71 through a resistor R603, and in addition, the non-inverting input terminal of the hysteresis comparator U71 is also connected with resistors R604, R600 and a capacitor C348 to suppress noise of the hysteresis comparator U71.
The output end of the hysteresis comparator U71 is connected with a compensation resistor R449 and a filter capacitor C386, so as to filter and compensate the output signal.
Further, a resistor R559 is connected between the non-inverting input terminal of the hysteresis comparator U72 and the output terminal of the level-boosting operational amplifier U69, the non-inverting input terminal of the hysteresis comparator U72 is connected to the output terminal of the hysteresis comparator U72 through a resistor R601, and the inverting input terminal of the hysteresis comparator U72 is further connected to resistors R598, R602 and a capacitor C347 to suppress noise of the hysteresis comparator U72.
The output end of the hysteresis comparator U72 is connected with a resistor R566, and a compensation resistor R597 and a filter capacitor C413 are connected between the output ends of the hysteresis comparator U72 to filter and compensate the output signal.
In addition, one end of the compensation resistor R597 is further connected to a chip U69 for inverting the hysteresis comparator U72. The output end of the chip U69 is also connected with a compensation resistor R618 and a filter capacitor C419 to filter and compensate the output signal.
In this embodiment, the circuit design considers contactor actuation when the absolute value of the voltage peak across the sense buffer resistor is less than 20V. From U O ＝-(A 1 ×A 2 ×U i -5)＝5-0.0681U i (-70V≤U i Less than or equal to +70V),
when U is i When=20v, U o = 3.638V; when U is o When the U is positioned between 0V and 3.638V i >20V, contactor suction; otherwise, the contactor is opened.
When U is i When= -20V, U o = 6.362V, when U o >6.362V, U i <-20V, contactor actuation; otherwise, the contactor is opened.
The negative half-wave of the voltage at the two ends of the buffer resistor adopts a hysteresis comparator U71 with inverting input, and the parameters of the hysteresis comparator U71 are as follows:
the positive half-wave of the voltage at the two ends of the buffer resistor adopts a hysteresis comparator U72 with in-phase input. Wherein, the reference voltage of the inverting terminal is:
the output of the hysteresis comparator U72 is flipped when the hysteresis comparator U72 has a non-inverting input voltage greater than or less than 3.47.
When the hysteresis comparator U72 outputs a low level,obtaining U H2 ＝3.93V；
When the hysteresis comparator U72 outputs a high level,obtaining U L2 ＝3.31V。
From U O ＝-(A 1 ×A 2 ×U i -5)＝5-0.0681U i (-70V≤U i And less than or equal to +70V) can obtain the actual comparison voltage values of the two ends of the corresponding buffer resistor as shown in the following table 1:
TABLE 1 actual comparison of voltage values across snubber resistors
Buffer resistor positive half-wave voltage: u's' H2 ＝15.7V，U' L2 =24.8v, i.e. when the positive half-wave of the buffer resistor voltage is less than 15.7V, a level rising edge jump occurs, and the recovery level is 24.8V.
Buffer resistor negative half-wave voltage: u's' H1 ＝-24.7V，U' L1 -19.7V. Namely, when the negative half-wave of the buffer resistor voltage is smaller than minus 24.7V, the level falling edge jumps,the recovery level is-19.7V.
Wherein U is TH Referring to the voltage at the inverting input of hysteretic comparator U72.
U H1 、U L1 、U H2 、U L2 The comparison value of the hysteresis comparator U72 is shown in fig. 9, and the voltages across the corresponding snubber resistors are shown in fig. 10.
When the contactor is in an off state, the hysteresis comparison unit 3 outputs a pulse signal, and when the contactor is in an on state, the hysteresis comparison unit 3 outputs a high-level signal, so that the main control chip can judge whether the contactor is in an on state according to different signals output by the hysteresis comparison unit 3, the problem that the auxiliary contact of the contactor is misreported due to poor on state caused by dust accumulation is thoroughly solved, the cost is very low, and the detection reliability is high due to the adoption of voltage detection.
The circuit for detecting the suction condition of the contactor is characterized in that the collected voltages are subjected to differential amplification, amplitude limiting treatment, reverse amplification and level lifting treatment by setting the voltages at two ends of the buffer resistor connected with the contactor in parallel, then the collected voltages are input into the hysteresis comparison unit 3, the collected voltages at two ends are compared with the set reference voltage, and whether the contactor is sucked or not is judged according to a comparison result, so that the problem that the auxiliary contact of the contactor is misreported due to poor suction caused by dust accumulation is thoroughly solved, the cost is very low, and the detection reliability is high by adopting a voltage detection mode.
In one embodiment, there is also provided a method for detecting contactor pull-in, comprising:
the voltage acquisition unit 1 acquires voltages at two ends of a buffer resistor connected with a contactor;
the voltage processing unit 2 receives the voltages at two ends of the buffer resistor input by the voltage acquisition unit 1, and amplifies, limits and level-raises the voltages at two ends of the buffer resistor;
the hysteresis comparison unit 3 receives the voltages at two ends of the buffer resistor processed by the voltage processing unit 2, compares the voltages with a reference voltage, obtains a comparison result, outputs a signal corresponding to the comparison result, and detects the contactor suction condition according to the output signal.
The foregoing examples are provided to further illustrate the technical contents of the present invention for the convenience of the reader, but are not intended to limit the embodiments of the present invention thereto, and any technical extension or re-creation according to the present invention is protected by the present invention. The protection scope of the invention is subject to the claims.
Claims (10)
1. A method for detecting a contactor pull-in condition, comprising:
the voltage acquisition unit acquires voltages at two ends of a buffer resistor connected with the contactor;
the voltage processing unit receives the voltages at two ends of the buffer resistor input by the voltage acquisition unit, amplifies the voltages at two ends of the buffer resistor, limits the amplitude and improves the level;
the hysteresis comparison unit receives the voltages at two ends of the buffer resistor processed by the voltage processing unit, compares the voltages with a reference voltage, obtains a comparison result, outputs a signal corresponding to the comparison result, and detects the suction condition of the contactor according to the output signal;
the negative half-wave of the voltage at the two ends of the buffer resistor adopts a hysteresis comparator U71 with inverting input, and the parameters of the hysteresis comparator U71 are as follows:the positive half-wave of the voltage at the two ends of the buffer resistor adopts a hysteresis comparator U72 with in-phase input; />The noninverting input end of the hysteresis comparator U71 is also connected with resistors R604 and R600; the output end of the hysteresis comparator U71 is also connected with a resistor R512; the non-inverting input end of the hysteresis comparator U71 is connected with the output end of the hysteresis comparator U71 through a resistor R603; the inverting input terminal of the hysteresis comparator U72 is also connected with resistors R598 and R602.
2. The circuit for detecting the attraction condition of the contactor is characterized by being suitable for the method for detecting the attraction condition of the contactor according to claim 1, and comprises a voltage acquisition unit, a voltage processing unit and a hysteresis comparison unit, wherein the voltage acquisition unit is used for acquiring voltages at two ends of a buffer resistor connected with the contactor; the voltage processing unit is used for receiving the voltages at two ends of the buffer resistor input by the voltage acquisition unit, amplifying, limiting and level-lifting the voltages at two ends of the buffer resistor; the hysteresis comparison unit is used for receiving the voltages at two ends of the buffer resistor processed by the voltage processing unit, comparing the voltages with a reference voltage, obtaining a comparison result and outputting a signal corresponding to the comparison result;
the circuit is used for detecting the voltages at the two ends of the buffer resistor to judge whether the contactor of the short-circuit power-on buffer resistor is closed or not, and the voltages at the two ends of the buffer resistor detected by the voltage acquisition unit are amplified and limited by the voltage processing unit and are subjected to level lifting processing and then are sent to the hysteresis comparison unit; when the voltage at two ends of the buffer resistor is smaller than the set reference voltage value, the contactor is considered to be closed, and the hysteresis comparison unit outputs high level; when the voltage at two ends of the buffer resistor is larger than the set reference voltage value, the contactor is considered to be disconnected, the hysteresis comparison unit outputs pulse signals, the actuation condition of the contactor is judged according to different signals output by the hysteresis comparison unit, the signals output by the hysteresis comparison unit are input to the main control chip, and the main control chip is timely informed of the actuation condition of the contactor.
3. The circuit for detecting a contactor actuation according to claim 2, wherein the voltage acquisition unit comprises a terminal J41.
4. A circuit for detecting a contactor pull-in condition according to claim 2 or 3, wherein the voltage processing unit comprises a differential amplifying subunit, a limiting subunit, an inverting amplifying subunit and a level lifting subunit which are sequentially connected, the differential amplifying subunit is connected with the voltage acquisition unit, and the level lifting subunit is connected with the hysteresis comparing unit.
5. The circuit for detecting a contactor pull-in according to claim 4, wherein the differential amplifying subunit comprises an amplifier U66, and feedback resistors R543, R473 are connected between an inverting input terminal and an output terminal of the amplifier U66.
6. The circuit for detecting a contactor pull-in according to claim 5, wherein the limiting subunit comprises a current limiting resistor R596 connected to the output of the amplifier U66, and a current limiting diode D101 having a grounded end is connected between the current limiting resistor R596 and the inverting amplifier subunit.
7. The circuit for detecting a contactor actuation according to claim 6, wherein said inverting amplifying subunit comprises an amplifier U67, an inverting input of said amplifier U67 is connected to said current limiting resistor R596, and an output of said amplifier U67 is connected to said level boosting subunit.
8. The circuit for detecting a contactor pull-in condition according to claim 7, wherein the level-up subunit comprises level-up op-amps U68, U69, wherein an inverting input of the level-up op-amp U68 and an inverting input of the level-up op-amp U69 are respectively connected to an output of the amplifier U67, and an output of the level-up op-amp U68 is connected to an inverting input of the level-up op-amp U68, an inverting input of the level-up op-amp U68 is connected to an output of the level-up op-amp U69, and an output of the level-up op-amp U69 is connected to the hysteresis comparison unit.
9. The circuit for detecting a contactor pull-in condition according to claim 8, wherein the hysteresis comparison unit comprises hysteresis comparators U71, U72, wherein an inverting input terminal of the hysteresis comparator U71 is connected to an output terminal of the level-boosting op-amp U69, a non-inverting input terminal of the hysteresis comparator U72 is connected to an output terminal of the level-boosting op-amp U69, and an output terminal of the hysteresis comparator U71 is connected to an output terminal of the hysteresis comparator U72.
10. The circuit for detecting contactor actuation according to claim 9, wherein the hysteresis comparators U71, U72 are each of the LM2903DMR2 type.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810977979.6A CN108957309B (en) | 2018-08-27 | 2018-08-27 | Circuit and method for detecting contactor suction condition |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810977979.6A CN108957309B (en) | 2018-08-27 | 2018-08-27 | Circuit and method for detecting contactor suction condition |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN108957309A CN108957309A (en) | 2018-12-07 |
| CN108957309B true CN108957309B (en) | 2023-12-29 |
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| CN113970357B (en) * | 2021-11-30 | 2023-06-23 | 河南职业技术学院 | Power switch cabinet detection circuit based on Internet of things |
| CN117075003A (en) * | 2023-10-19 | 2023-11-17 | 青岛锐捷智能仪器有限公司 | Four-terminal test line contact detection method and system |
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