An alternating current contactor contact on-line detector

Abstract

The present application relates to the technical field of AC contactor, in particular to an AC contactor contact on-line detector, comprising a signal generating circuit, a signal detecting circuit and a display circuit, the signal generating circuit comprises a constant current reference signal output module for providing a constant current square wave reference signal; the signal detecting circuit comprises an FM modulation module for superimposed modulation of the detection signal and the constant current square wave reference signal, and a PLL phase-locked loop demodulation module for separating and outputting the modulated detection signal as the constant current square wave reference signal, and the display circuit comprises a V / R display module for U / R conversion of the constant current square wave reference signal to obtain and display the current resistance value of the contact. The present application can quickly and accurately detect the contact condition of the contactor contact, greatly increasing the reliability and safety of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of AC contactor, in particular to an AC contactor contact on-line detector. BACKGROUND

[0002] The AC contactor is a kind of switch device controlled by voltage, which is suitable for remote and frequent on-off of AC / DC circuit system, and belongs to control class components, and is one of the most widely used low-voltage electrical appliances in power drive system, machine tool equipment control circuit and automatic control system. It is mainly used for on-off of power supply of executing components (such as motor, heater, etc.), and is widely used in industrial automatic control system.

[0003] The contactor works in a harsh environment, such as high temperature, corrosion, dust and damp place, which can easily cause poor contact of moving and static contacts, and cause a series of faults, such as open phase, poor contact of main contact, contact ablation, sound, light and heat, etc. Moreover, the contact condition may be randomly deteriorated and circulate, causing voltage fluctuation, equipment command confusion, false alarm, start-stop, etc., which can easily cause equipment damage, safety accidents and affect normal production. Since the structure of the contactor is closed and the fault is hidden, it is not easy to find during direct inspection, and the resistance range of the conventional multimeter cannot be measured under the running condition.

[0004] The existing solution is to measure the loop current and contact voltage drop, and to convert the contact resistance. When collecting the end resistance signal of the contact, two problems need to be solved, first, the front and rear circuit isolation, and second, the signal processing after signal collection. There are many mature circuit functions for isolation, but the signal processing circuit is various and has some disadvantages, for example, the most common operational amplifier + single-chip microcomputer small voltage sampling mode. Due to the complex power supply noise composition in the production environment, although a multi-stage anti-interference filter network, temperature drift compensation and other measures are adopted, the sampling signal processing effect is not ideal, and the display value deviates from the actual value. In addition, the contact voltage drop is different each time the contact is closed, the contact resistance is nonlinear and non-constant, and it changes dynamically. Especially in the case of rapid contact vibration of the contactor, the detection accuracy is lower, the value is distorted, and the display is unstable.

[0005] In addition, in the contact loop, due to the existence of various inductive loads and capacitive elements, the discharge caused by accidental bypass when the detection pen directly contacts the contact can damage the test equipment and endanger the operation safety, and the safety hazard cannot be ignored. SUMMARY

[0006] The purpose of the present application is to provide an AC contactor contact on-line detector, which can quickly and accurately detect the contact condition of the contactor contact, greatly increasing the reliability and safety of the system.

[0007] In order to achieve the above object, an alternating current contactor contact on-line detector is provided, comprising a signal generating circuit, a signal detecting circuit and a display circuit, the signal generating circuit comprising a constant current reference signal output module for providing a constant current square wave reference signal; the signal detecting circuit comprising an FM modulation module for superimposed modulation of a detection signal and the constant current square wave reference signal, and a PLL phase-locked loop demodulation module for separating and outputting the modulated detection signal as the constant current square wave reference signal, and the display circuit comprising a V / R display module for U / R conversion of the constant current square wave reference signal to obtain and display a current contact resistance value.

[0008] Further, the constant current reference signal output module comprises a constant current power supply unit and a square wave signal generation unit, the constant current power supply unit comprising an LM317 three-terminal adjustable voltage stabilizer IC1 and a resistor R1, the resistor R1 being connected between the 1 pin and the 2 pin of the LM317 three-terminal adjustable voltage stabilizer IC1, and the square wave signal generation unit being a square wave generator constructed by a 555 time base circuit IC2, the LM317 three-terminal adjustable voltage stabilizer IC1 being powered by the 555 time base circuit IC2.

[0009] Further, the square wave generator further comprises a capacitor C1, a capacitor C2 and a resistor R2, the 2 pin of the 555 time base circuit IC2 being connected with the capacitor C2 between the negative terminal, the 5 pin being connected with the capacitor C1 between the negative terminal, the 4 pin and the 8 pin being connected to the 3 pin of the LM317 three-terminal adjustable voltage stabilizer IC1, the 2 pin and the 3 pin being connected with the resistor R2 between them, the capacitor C2 being a timing capacitor, and the resistor R2 being a timing resistor.

[0010] Further, a filter unit for improving filtering effect is provided between the 3 pin of the 555 time base circuit IC2 and the FM modulation module, the filter unit comprising a resistor R3, a capacitor C3, a polarity capacitor C4 and a polarity capacitor C5, the resistor R3 being connected in series with the combination of the capacitor C3, the polarity capacitor C4 and the polarity capacitor C5, the polarity capacitor C4 and the polarity capacitor C5 being connected in reverse series, and the capacitor C3 being connected in parallel with the polarity capacitor C4 and the polarity capacitor C5 in series.

[0011] Further, the FM modulation module comprises a voltage transformer TV1, a capacitor C8 and a capacitor C9, the P1 end of the primary winding of the voltage transformer TV1 being connected to the square wave generator, and the P2 end of the primary winding being grounded; the S2 end of the secondary winding of the voltage transformer TV1 being connected to the capacitor C8, the other end of the capacitor C8 being a detection point a, the S1 end of the secondary winding of the voltage transformer TV1 being connected to the capacitor C9, the other end of the capacitor C9 being a detection point b, and the detection point a and the detection point b being connected to the contactor contact.

[0012] Further, the FM modulation module is connected with an isolated coupling network, the isolated coupling network comprises a capacitor C10, a capacitor C11 and a voltage transformer TV2, one end of the capacitor C10 is connected with the capacitor C8, and the other end is connected with a P1 end of a primary winding of the voltage transformer TV2; one end of the capacitor C11 is connected with the capacitor C9, and the other end is connected with a P2 end of the primary winding of the voltage transformer TV2.

[0013] Further, the PLL phase-locked loop demodulation module is a demodulator constructed by an LM567 tone decoding chip IC3; a S2 end of a secondary winding of the voltage transformer TV2 is connected to a 3 pin of the LM567 tone decoding chip IC3, and a S1 end of the secondary winding is grounded.

[0014] Further, the S2 end and the S1 end of the secondary winding of the voltage transformer TV2 are connected in parallel with a capacitor C12, a diode D1 and a diode D2, and the diode D1 and the diode D2 are reversely arranged.

[0015] Further, an inductor L and an optical coupler OC are connected between a 8 pin of the LM567 tone decoding chip IC3 and a 3 pin of an LM317 three-terminal adjustable voltage regulator IC1, and the optical coupler OC is connected to a V / R terminal, and the power supply on-off of the V / R terminal is controlled.

[0016] Further, the V / R terminal is a digital voltmeter, a capacitor C17 and a resistor R5 are connected in series between a 2 pin of the LM317 three-terminal adjustable voltage regulator IC1 and a negative electrode, one end of the resistor R5 is grounded, the resistor R5 is connected in parallel with a resistor R6 and a capacitor C18, one end of the capacitor C18 is grounded, and the V / R terminal is connected in parallel with the capacitor C18.

[0017] Principle and advantages:

[0018] 1. The LM317 three-terminal adjustable voltage regulator IC1 and R1 constitute a constant current output LM317 circuit, supply power to the 555 time base circuit IC2, and k can generate a 10mA / 1KHz (square wave) alternating constant current output source. After the detection lines a and b contact the contactor contact resistance Rx, the detection lines a and b inject a constant alternating current to the two ends of the contactor contact, so that the square wave reference signal passes through the voltage transformer TV1, the capacitors C8 and C9, and is modulated with the contact voltage drop signal at the a and b points to generate an alternating voltage signal, and the carrier wave modulation is completed. Then, the alternating voltage signal is coupled to the next stage PLL phase-locked loop decoding circuit through the capacitors C10 and C11 and the voltage transformer TV2, is amplified through the subsequent PLL phase-locked loop demodulation, is detected by the synchronous phase shift ADC, and is accurately displayed by the LCD. The scheme accurately detects the contact resistance by comparing the voltage drop of the measured contact. Moreover, the greater the constant current flowing through the measured resistance Rx, the easier to accurately measure small resistance.

[0019] 2. In the scheme, a, b modulation points before and after use voltage transformer TV, capacitor to form an isolation coupling network, to realize the accurate separation of power frequency signal and detection signal, and to ensure the electrical safety isolation of front and rear stages, increase the reliability and safety of the system. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The circuit principle diagram of the AC contactor contact on-line detector according to an embodiment of the application. DETAILED DESCRIPTION

[0021] The following will be further described in detail through specific embodiments:

[0022] Embodiment

[0023] The AC contactor contact on-line detector basically as shown in the accompanying drawings, comprising a signal generating circuit, a signal detecting circuit and a display circuit. Figure 1 The signal generating circuit comprises a constant current reference signal output module for providing a constant current square wave reference signal; the signal detecting circuit comprises an FM modulation module for superimposed modulation of the detection signal and the constant current square wave reference signal, and a PLL phase-locked loop demodulation module for separating and outputting the modulated detection signal as the constant current square wave reference signal; and the display circuit comprises a V / R display module for converting the constant current square wave reference signal through U / R to obtain and display the current resistance value of the contact.

[0024] The constant current reference signal output module comprises a constant current power supply unit and a square wave signal generation unit, the constant current power supply unit comprises an LM317 three-terminal adjustable voltage stabilizer IC1 and a resistor R1, the resistor R1 is connected between the 1 pin and the 2 pin of the LM317 three-terminal adjustable voltage stabilizer IC1, and the square wave signal generation unit is a square wave generator constructed by a 555 time base circuit IC2, and the LM317 three-terminal adjustable voltage stabilizer IC1 supplies power for the 555 time base circuit IC2.

[0025] The square wave generator further comprises a capacitor C1, a capacitor C2 and a resistor R2, the 2 pin of the 555 time base circuit IC2 is connected with the negative electrode through the capacitor C2, the 5 pin is connected with the negative electrode through the capacitor C1, the 4 pin and the 8 pin are connected to the 3 pin of the LM317 three-terminal adjustable voltage stabilizer IC1, the 2 pin and the 3 pin are connected through the resistor R2, the capacitor C2 is a timing capacitor, and the resistor R2 is a timing resistor.

[0026] The 3-pin of the 555 time base circuit IC2 is provided with a filter unit for improving filter effect between the FM modulation module, the filter unit comprises resistance R3, capacitor C3, polarity capacitor C4 and polarity capacitor C5, the resistance R3 is combined in series with the capacitor C3, polarity capacitor C4 and polarity capacitor C5, the polarity capacitor C4 and the polarity capacitor C5 are reversely connected in series, and the capacitor C3 is connected in parallel with the polarity capacitor C4 and the polarity capacitor C5 in series.

[0027] The constant-current square wave reference signal is superimposed and modulated with the contact voltage drop signal at points a and b through the voltage transformer TV1, the capacitor C8 and the capacitor C9. The constant alternating current is injected to the contactor contact through the detection lines A and B, and the contact resistance is accurately detected by comparing the voltage drop of the measured contact a and b.

[0028] The FM modulation module comprises the voltage transformer TV1, the capacitor C8 and the capacitor C9, the P1 end of the primary winding of the voltage transformer TV1 is connected with the square wave generator, and the P2 end of the primary winding is grounded; the S2 end of the secondary winding of the voltage transformer TV1 is connected with the capacitor C8, the other end of the capacitor C8 is the detection point a, the S1 end of the secondary winding is connected with the capacitor C9, the other end of the capacitor C9 is the detection point b, and the detection point a and the detection point b are connected to the contactor contact.

[0029] The FM modulation module is connected with an isolation coupling network, and the isolation coupling network comprises the capacitor C10, the capacitor C11 and the voltage transformer TV2, one end of the capacitor C10 is connected with the capacitor C8, and the other end is connected with the P1 end of the primary winding of the voltage transformer TV2; one end of the capacitor C11 is connected with the capacitor C9, and the other end is connected with the P2 end of the primary winding of the voltage transformer TV2.

[0030] The voltage transformers TV1 and TV2 are both 1:1 current type precision voltage transformers, DL-PT202H1, small in size and good in linearity. Since the primary and secondary windings exchange energy through a magnetic field without physical hard connection, the isolation withstand voltage is greater than or equal to 4KV, and the safety of the measuring equipment and the operator is ensured.

[0031] The PLL phase-locked loop demodulation module is a demodulator constructed by the LM567 tone decoding chip IC3; the S2 end of the secondary winding of the voltage transformer TV2 is connected to the 3-pin of the LM567 tone decoding chip IC3, and the S1 end of the secondary winding is grounded.

[0032] The capacitor C12, the diode D1 and the diode D2 are connected in parallel between the S2 end and the S1 end of the secondary winding of the voltage transformer TV2, and the diode D1 and the diode D2 are reversely arranged. Interference signals can be filtered, and the detection accuracy is improved.

[0033] The LM567 tone decoding chip IC3 adopts a conventional connection mode, the 1-pin thereof is connected with a polar capacitor C14 and grounded, the 2-pin thereof is connected with a capacitor C16 and grounded, the 3-pin thereof is an input connected with a capacitor C13, the 4-pin thereof is connected with the 3-pin of the LM317 three-terminal adjustable voltage regulator IC1, the variable resistor Rp and the resistor R4 are connected in series between the 5-pin and the 6-pin thereof, the 6-pin thereof is connected with a capacitor C15 and grounded, the 7-pin thereof is directly grounded, and the 8-pin thereof is connected with a resistor R7.

[0034] The tone decoding chip LM567 has excellent performance, is immune to error signals, has stable center frequency, precise and reliable passband limitation and noise suppression, can effectively filter out interference stray false signals, and ensures accurate and undistorted detection results. The internal current control oscillator generates an oscillation signal of a certain frequency and phase, which is sent to the phase detector together with the mixed signal input at the 3-pin for comparison. When the input signal amplitude is ≥25 mV and the frequency falls within the 1000 Hz passband, the phase-locked loop locks the signal, simultaneously controls the internal triode to be powered on, and outputs a low level at the output end. The 2-pin is the phase-locked loop phase detector output, i.e. the demodulation voltage signal after frequency / voltage conversion, and the amplitude size is proportional to the resistance value of the contactor contact to be measured. The 3-pin input signal component is integrated by superimposing the 1000 Hz square wave reference signal, the 50 Hz power frequency signal, and the line stray interference signal.

[0035] The resistor R7 connected to the 8-pin of the LM567 tone decoding chip IC3 is connected with the inductor L and the optocoupler OC between the 3-pin of the LM317 three-terminal adjustable voltage regulator IC1, and the optocoupler OC is connected to the V / R terminal to control the power supply on / off of the V / R terminal display. When the LM567 tone decoding chip IC3 receives a signal, the 8-pin high level becomes low level, a saturated transistor resistor switch providing ground is turned on, and the optocoupler OC is turned on, and the V / R display unit is powered on and works.

[0036] The V / R terminal is a digital voltmeter, the capacitor C17 and the resistor R5 are connected in series between the 2-pin of the LM317 three-terminal adjustable voltage regulator IC1 and the negative electrode, one end of the resistor R5 is grounded, the resistor R6 and the capacitor C18 are connected in parallel with the resistor R5, one end of the capacitor C18 is grounded, and the V / R terminal is connected in parallel with the capacitor C18.

[0037] The scheme directly adopts the digital 200 mV meter through V / R display. The voltage drop between the contact points a and b is subjected to A / D conversion, and the voltage drop established on the sampling resistor R5 is the equivalent resistance value of the contact points. When the contactor contact voltage drop to be measured is introduced into the detector, the points a and b have no positive and negative distinction, and there is no need to worry about the positive and negative during use, and the operation is more simple and convenient.

[0038] The above-mentioned are only embodiments of the present application, and the common knowledge of the specific structure and characteristics in the scheme is not described too much, the ordinary skilled in the art knows all the ordinary technical knowledge in the field of the present application before the application date or the priority date, can know all the prior art in the field, and has the ability to apply the conventional experimental means before the date, the ordinary skilled in the art can improve and implement the present scheme under the inspiration given by the present application, and some typical known structure or known method should not become the obstacle for the ordinary skilled in the art to implement the present application. It should be pointed out that for those skilled in the art, without departing from the structure of the present application, a number of modifications and improvements can be made, which should also be considered as the protection scope of the present application, which will not affect the effect and practicality of the patent. The protection scope of the present application should be subject to the content of its claims, and the specific implementation mode and the like in the specification can be used to explain the content of the claims.

Claims

1. An AC contactor contact on-line detector characterized by: The signal generating circuit, the signal detecting circuit and the display circuit, the signal generating circuit includes the constant current reference signal output module for providing 10mA / 1kHz constant current square wave reference signal which is constructed by LM317 three-terminal adjustable voltage regulator and 555 time base circuit; the signal detecting circuit includes the FM modulation module which superimposes and modulates the detection signal and the constant current square wave reference signal through the voltage transformer TV1 and the capacitors C8, C9, the PLL phase-locked loop demodulation module which separates and outputs the modulated detection signal as the constant current square wave reference signal through the voltage transformer TV2 isolation and then through the LM567 tone decoding chip, the voltage transformer TV2 secondary winding is connected with the diodes D1, D2 which are reversely arranged in parallel; the display circuit includes the V / R display module which directly converts the constant current square wave reference signal through U / R and controls the power supply on-off through the optical coupling OC, the V / R display module displays the current resistance value of the contact in real time.

2. An AC contactor contact on-line detector according to claim 1, characterized in that: The resistor R1 is connected between the pins 1 and 2 of the LM317 three-terminal adjustable voltage regulator IC1, and the LM317 three-terminal adjustable voltage regulator IC1 supplies power for the 555 time base circuit IC2.

3. An AC contactor contact on-line detector according to claim 2, characterized in that: The capacitor C2 is connected between the pin 2 and the negative terminal of the 555 time base circuit IC2, the capacitor C1 is connected between the pin 5 and the negative terminal, the pins 4 and 8 are connected to the pin 3 of the LM317 three-terminal adjustable voltage regulator IC1, the resistor R2 is connected between the pins 2 and 3, the capacitor C2 is a timing capacitor, and the resistor R2 is a timing resistor.

4. An AC contactor contact on-line detector according to claim 3, characterized in that: The filter unit which improves the filtering effect is arranged between the pin 3 of the 555 time base circuit IC2 and the FM modulation module, the filter unit includes the resistor R3, the capacitor C3, the polarity capacitor C4 and the polarity capacitor C5, the resistor R3 is connected in series with the capacitor C3, the polarity capacitor C4 and the polarity capacitor C5, the polarity capacitor C4 and the polarity capacitor C5 are reversely connected in series, and the capacitor C3 is connected in parallel with the polarity capacitor C4 and the polarity capacitor C5.

5. An AC contactor contact on-line detector according to claim 2, characterized in that: The square wave generator is connected to the P1 end of the primary winding of the voltage transformer TV1, and the P2 end of the primary winding is grounded; the capacitor C8 is connected to the S2 end of the secondary winding of the voltage transformer TV1, the other end of the capacitor C8 is the detection point a, the capacitor C9 is connected to the S1 end of the secondary winding of the voltage transformer TV1, the other end of the capacitor C9 is the detection point b, and the detection point a and the detection point b are connected to the contactor contact.

6. An AC contactor contact on-line detector according to claim 5, characterized in that: The FM modulation module is connected with the isolation coupling network, the isolation coupling network includes the capacitor C10, the capacitor C11 and the voltage transformer TV2, one end of the capacitor C10 is connected to the capacitor C8, and the other end is connected to the P1 end of the primary winding of the voltage transformer TV2; one end of the capacitor C11 is connected to the capacitor C9, and the other end is connected to the P2 end of the primary winding of the voltage transformer TV2.

7. An AC contactor contact on-line detector according to claim 6, characterized in that: The S2 end of the secondary winding of the voltage transformer TV2 is connected to the pin 3 of the LM567 tone decoding chip IC3, and the S1 end of the secondary winding is grounded.

8. An AC contactor contact on-line detector according to claim 7, characterized in that: The 8-pin of the LM567 tone decoding chip IC3 is connected with the 3-pin of the LM317 three-terminal adjustable voltage regulator IC1, and an inductor L and an optical coupler OC are arranged between them, and the optical coupler OC is connected to the V / R terminal, and the power supply on-off of the V / R terminal is controlled.

9. An AC contactor contact on-line detector according to claim 8, characterized in that: The V / R terminal is a digital voltmeter, and a capacitor C17 and a resistor R5 are connected in series between the 2-pin of the LM317 three-terminal adjustable voltage regulator IC1 and the negative electrode, one end of the resistor R5 is grounded, the resistor R5 is connected in parallel with a resistor R6 and a capacitor C18, one end of the capacitor C18 is grounded, and the V / R terminal is connected in parallel with the capacitor C18.

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