Contactor main contact failure protection control device and method thereof

Abstract

The application discloses a kind of contactor main contact fault protection control device and method, it is related to electrical safety protection technical field.The device includes auxiliary contact signal processing module (RT), coil voltage detection module (CRT), logic and gate circuit and execution unit.RT module connects auxiliary normally open contact, and the first switch signal is output as after the closure signal is output after preset delay, and instantaneous output is disconnected signal;CRT module connects both ends of coil, and the second switch signal is output as disconnected state when coil is powered on, and it is output as closed state after preset delay after coil power failure;Logic and gate circuit is connected in series by the first switch signal and the second switch signal.When contactor occurs mechanical jam, coil power failure but auxiliary contact is still not disconnected, logic and gate circuit is turned on, and execution unit drives external electromagnetic release to cut off main circuit.The application does not need to detect high-voltage main circuit directly, and is indirectly protected by low-voltage logic, with high safety, low cost and strong anti-interference ability.

Description

Technical Field

[0001] This invention relates to electrical equipment safety protection technology, and more particularly to a contactor main contact fault protection control device and method. Background Technology

[0002] This seaport, serving as a crucial deep-water transshipment terminal for a certain company, undertakes extremely important iron ore allocation tasks. The port is equipped with comprehensive facilities, including two dedicated wharves for unloading and three dedicated wharves for loading. Regarding unloading equipment, five ship unloaders with a capacity of 2500 tons / hour are in operation. The electrical control systems of these machines, including hoisting, opening / closing, and internal transport mechanisms, all utilize the main contactor, a critical component.

[0003] When the main contactor is operating under high load, the contacts in the main contactor, also known as contacts, are the key components.

[0004] In industrial equipment that operates under frequent starts and long-term high loads, such as motors ≥20KW and those affected by high current, the main contactor, as the actuator, may experience mechanical failures due to aging and breakage of internal springs, jamming of mechanical parts, or intrusion of environmental contaminants such as mineral powder, dust, oil, or other foreign objects. This can result in the internal linkage failing to reset after the electromagnetic coil is normally de-energized, leaving the main contacts in a closed state, unable to disconnect or fully release. If the main circuit is not promptly cut off, the motor will continue to operate under high voltage while braking, potentially leading to serious accidents involving personnel and equipment safety.

[0005] Existing protection devices typically only detect coil current directly or rely on the temperature / insulation condition of the main contacts, lacking a logical judgment scheme for the specific fault state of "coil de-energization and failure of mechanical linkage and auxiliary contacts to release". More importantly, directly setting sensors in the main high-voltage circuit to detect the status of the main contacts not only requires extremely high insulation levels, resulting in high costs, but also poses an additional risk of introducing faults. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention provides a contactor main contact fault protection control device and method. It utilizes the physical characteristic that the "main contacts" and "auxiliary contacts" in industrial contactors are driven by the same linkage rod, completely eliminating the high-risk practice of setting detection sensors in the main circuit. By constructing a "logic AND gate" circuit through a low-voltage control circuit, it effectively identifies contactor jamming faults and quickly trips the main circuit, achieving high safety and low-cost protection.

[0007] On one hand, a contactor main contact fault protection control device includes: An auxiliary contact signal processing module, whose input terminal is connected to the auxiliary normally open contact of the contactor, is used to output the closed signal of the auxiliary contact as a first switch signal after a preset delay, and to output the open signal of the auxiliary contact as a first switch signal instantaneously. The coil voltage detection module has its input terminal connected to both ends of the electromagnetic coil of the contactor. It is used to output a second switch signal to the open state when the coil is energized, and to output a second switch signal to the closed state after a preset delay when the coil is de-energized. The logic AND gate circuit is composed of the first switch signal and the second switch signal connected in series; The execution unit is connected to the output terminal of the AND gate circuit. When the AND gate circuit is turned on, it drives the external electromagnetic trip unit to operate.

[0008] The auxiliary contact signal processing module includes: An RC charging circuit includes a capacitor, and the input terminal of the RC charging circuit is connected to a DC power supply through an auxiliary normally open contact of a contactor. A Zener diode is connected in parallel across the capacitor to clamp the initial voltage of the capacitor to a preset value. The comparator chip is an NE555 timer chip. Its second and sixth pins are connected to the positive terminal of the capacitor, and its third pin is the signal output terminal. The output terminal of the comparator chip flips when the voltage of the capacitor exceeds the reference value. The relay, whose control terminal is connected to the output terminal of the comparator chip and driven by the output terminal of the comparator chip, is used to output the first switching signal.

[0009] The preset delay of the closing signal is the contactor activation anti-maloperation delay, and the duration of the preset delay is set to 3 to 5 seconds.

[0010] The coil voltage detection module includes: The rectifier and voltage regulator unit converts the AC voltage of the contactor's electromagnetic coil into a DC operating voltage; The microcontroller has at least one energy storage capacitor connected in parallel to its power supply terminal; A magnetic latching relay has an engaging coil and a releasing coil; When the electromagnetic coil is energized, the microcontroller controls the coil to be energized, causing the magnetic latching relay contacts to close and outputting the second switch signal to be in the off state. After the electromagnetic coil loses power, the microcontroller is powered by the energy storage capacitor and releases the coil according to a preset delay, causing the magnetic latching relay contacts to release and output the second switch signal to restore the closed state.

[0011] The coil voltage detection module also includes a delay adjustment potentiometer, which is connected to the microcontroller and used to adjust the preset delay.

[0012] The first control terminal of the microcontroller is connected to the first driving transistor, and the output terminal of the first driving transistor is connected to the pull-in coil of the magnetic latching relay; the second control terminal of the microcontroller is connected to the second driving transistor, and the output terminal of the second driving transistor is connected to the release coil of the magnetic latching relay.

[0013] After the electromagnetic coil of contactor KM is de-energized, the coil voltage detection module outputs the second switch signal as closed after a delay of 500 milliseconds to 1.5 seconds.

[0014] The execution unit includes a fault trip relay, the coil of which is connected in parallel with a fault control indicator light between the output of the logic AND gate circuit and zero potential.

[0015] The logic AND gate circuit includes a normally open contact of the first switch signal and a normally closed contact of the second switch signal connected in series.

[0016] On the other hand, a fault protection control method for a contactor main contact fault protection control device includes the following steps: S1. Detect the on / off state of the auxiliary contacts of the contactor, output the closed signal as the first switch signal after a preset delay, and output the open signal instantaneously; S2. Detect the presence or absence of voltage in the contactor's electromagnetic coil. If the electromagnetic coil is energized, output the second switch signal in an open state; if the electromagnetic coil is de-energized, output the closed state after a preset delay. S3. Connect the first switch signal and the second switch signal in series to form a logic AND gate; S4. When the aforementioned AND gate is activated, it drives the external electromagnetic trip unit to disconnect the main circuit.

[0017] The contactor main contact fault protection control device and method of the present invention have the following advantages: 1. This invention does not require any series detection sensors to be set in the main circuit of high voltage (AC220V and above). It cleverly utilizes the mechanical characteristics of the physical linkage between the auxiliary contacts and the main contacts, and indirectly obtains the true physical state of the main contacts through the logic combination of low voltage circuits.

[0018] 2. By using the dual confirmation of "coil de-energization + auxiliary contact not released" and two precise delay processes, the malfunctions caused by electrical jitter during normal start-stop of the contactor are completely isolated.

[0019] 3. The low-voltage logic control circuit is completely electrically isolated from the high-voltage main circuit, which greatly improves system reliability, significantly reduces manufacturing costs, and provides an extremely high level of safety protection. Attached Figure Description

[0020] Figure 1 This is a circuit schematic diagram of the auxiliary contact signal processing module (RT) of the present invention.

[0021] Figure 2 This is a circuit diagram of the coil voltage detection module (CRT) of the present invention.

[0022] Figure 3 This is a control diagram of the logic gate circuits and execution units of the present invention.

[0023] Figure 4 This is a flowchart of the contactor main contact fault protection control process of the present invention. Detailed Implementation

[0024] The following is a further description of a contactor main contact fault protection control device according to the present invention.

[0025] The contactor main contact fault protection control device of the present invention includes: an auxiliary contact signal processing module, a coil voltage detection module, a logic AND gate circuit, and an execution unit.

[0026] For detailed circuit structure of the auxiliary contact signal processing module RT, please refer to [link / reference]. Figure 1 As shown. This module is built based on the NE555 timer chip.

[0027] The contactor auxiliary contact KM sends the contactor's engagement and disengagement signals to RT. DC 24V power supply B1 provides 24V power to the line. The normally open auxiliary contact KM provides the contactor's engagement / disengagement status signal. Resistor R1, potentiometer W1, and capacitor C3 form an RC time constant loop to set the signal hysteresis time constant. Resistor R1 prevents potentiometer W1 from directly charging capacitor C3 when adjusted to its minimum value. Zener diode VR regulates the voltage to 12V, clamping the time constant potential to a minimum of 12V. Capacitor C1 provides isolation and interference suppression. Capacitor C2 maintains power supply momentarily after power failure (≤200ms). LED D1 and resistor R2 form a grounding loop for power indication and a 555 timer.

[0028] The core power supply connection for the chip is as follows: Pin 8 (VCC) of the NE555 chip is directly connected to the output terminal of the auxiliary normally open contact KM of the contactor, and is connected to a 24V DC power supply through the auxiliary normally open contact KM; Pin 1 (GND) is connected to the system 0V ground line in series with LED D1 and resistor R2, and LED D1 is used to indicate the power supply status of the module. Pin 4 (reset terminal) of the NE555 is shorted to pin 8 and connected to the 24V power supply terminal to ensure that the chip is always in a non-reset working state.

[0029] The time-constant RC charging network: Pins 2 (trigger) and 6 (threshold) of the NE555 are shorted and connected to the positive terminal of the first capacitor C3. The negative terminal of the first capacitor C3 is connected in series with a Zener diode VR (12V regulator) to 0V ground; simultaneously, the negative terminal of the first capacitor C3 is directly connected to pin 8 (VCC) of the NE555. This topology stabilizes the initial potential of the negative terminal of the first capacitor C3 at a potential difference of (24V-12V), i.e., 12V. A first resistor R1 and a first adjustable potentiometer W1 are connected in series between the 24V power supply terminal and the positive terminal of the first capacitor C3, forming a charging and discharging circuit for the first capacitor C3.

[0030] Output and Drive Network: Pin 5 (control voltage) of the NE555 is connected to 0V ground via the second anti-interference capacitor C1 (100pF), while pin 7 (discharge) remains floating. Pin 3 (output) of the NE555 is connected to the base of the PNP driver transistor Q1 (2N5401) via the current-limiting resistor R3. The emitter of the driver transistor Q1 is connected to a 24V power supply, and its collector is connected in series with the coil of the intermediate control relay KA1 and then to 0V ground. A freewheeling diode D3 is connected in reverse parallel across the coil of the intermediate control relay KA1 to absorb the reverse induced electromotive force when the coil of the intermediate control relay KA1 is de-energized.

[0031] The working principle is as follows: When the contactor is functioning normally, the 24V power supply is instantly supplied to the entire circuit via the contactor's auxiliary contact KM upon engagement. Capacitor C2 (small capacitance, 1uF) is quickly charged to its potential via diode D1 and resistor R2. The 24V power supply is then connected to ground via pin 8 (according to the internal block diagram of the 555 chip, three 5KΩ equivalent resistors are built between pin 8 and pin 1), diode D1, and resistor R2. LED D1 illuminates, indicating normal power supply. This provides a reference potential of (24-0.7)*11 / 16=16V for the comparator.

[0032] Because of the clamping of the Zener diode VR (12V regulator), the potential between pin 8 of the chip and the negative terminal of the first capacitor C3 is always clamped at 12V. The positive terminal of capacitor C3 is connected to pins 2 and 6 of the chip, which are the positive input terminals of the comparator. (Since the potential across the capacitor cannot change instantaneously, the positive terminal of the comparator is 12V at the moment of power-on. Then, the 24V power supply starts to charge the first capacitor C3 through resistor R1 and potentiometer W1. The potential at the positive terminal of the comparator gradually increases from 12V over time. (The rate of increase is changed by the values ​​of resistor R1, potentiometer W1, and first capacitor C3. Resistor R1 and first capacitor C3 are fixed values, so adjusting W1 can change the RC time constant). When the positive terminal potential of the comparator rises to a level greater than 16V, the comparator outputs a signal to the RS flip-flop, and pin 3 outputs a low potential. After current limiting by resistor R3, LED D2 lights up (indicator signal output), transistor 2N5401 conducts, and 24V flows through the emitter and collector to relay KA and ground. Relay KA activates and outputs a signal, thereby realizing the hysteresis processing of the contactor's contact closing signal before sending it to the logic AND gate circuit.

[0033] When the contactor is in normal operation, the auxiliary contact KM of the contactor opens instantly upon release, causing the entire circuit to lose power momentarily. The potential of capacitor C3 is maintained for 200ms to prevent malfunction. Then, relay KA releases, directly outputting the contactor's release signal to the logic control circuit.

[0034] In summary: When the contactor's auxiliary contact KM closes, the contactor's energizing signal is delayed by RT before being sent to the AND gate circuit. When the contactor's auxiliary contact KM opens, the signal is directly sent to the AND gate circuit via RT.

[0035] For detailed circuit structure of the coil voltage detection module CRT, please refer to [link / reference]. Figure 2 As shown.

[0036] Among them, the oxide film anti-interference resistor RY is used to absorb surge pulses from the power grid momentarily, protecting the power supply. Resistors R1, R2, R3, and R9 are used for isolation, voltage reduction, and current limiting. Magnetic latching relays HC and HB are the two coils of KA2; HC is engaged, and HB is released. Transistor Q1 controls the HC engagement terminal of the KA2 magnetic latching relay, with its base connected to pin 7 of the microcontroller (such as an MCU). Transistor Q2 controls the HC release terminal of the KA2 magnetic latching relay, with its base connected to pin 6 of the microcontroller. Resistors R4 and R5 are the base bias resistors for Q1 and Q2. Resistor R8 and potentiometer W1 are connected to pins 5 and 9 of the microcontroller, controlling the potential circuit during power-off. The LED is used for power indication. Diodes D1-D4 are used for bridge rectification. Diodes D5, D8, and D9 are used for current reverse phase isolation. Diodes D6 and D7 are used for surge absorption. Zener diode VR1 regulates 24V, providing power to the circuit. Zener diode VR2: Stabilizes 5V, powering the microcontroller. Microcontroller: Can be a high-performance, ultra-low-power MC32P7031. Capacitors C1, C6, C9, and C10: Used for pulse interference suppression. Capacitor C2: Used for power supply filtering, with a value of 1uF, discharging completely upon power failure. Third holding capacitor C3: 100uF, providing power to HB after power failure. Capacitors C4 and C5: Pins 1 and 4 of the microcontroller are internally connected by bidirectional diodes; after power failure, 470uF and 100uF of charge respectively power the microcontroller. Capacitors C7, C8, and XATL: Microcontroller operating crystal oscillator circuit.

[0037] Its main connection structure is as follows: Isolation step-down and rectification-regulation network: The A1 and A2 terminals of the contactor coil are connected to AC220V, which is then connected to a bridge rectifier circuit composed of diodes D1-D4 via the first current-limiting step-down resistor R1 (1MΩ). The rectified output is regulated to ground by the second isolation current-limiting resistor R2 (2.2KΩ) and the first Zener diode VR1 (12V), forming an internal DC24V operating power supply. This DC24V is further regulated by the third current-limiting step-down resistor R9 (20KΩ), the isolation diode D9, and the second Zener diode VR2 (5V) to form a DC5V voltage, which is connected to pin 1 (VDD) of the microcontroller.

[0038] Residual voltage maintenance and energy storage (delay) network: A first energy storage capacitor C4 (470uF) and a second energy storage capacitor C5 (100uF) are connected in parallel between pin 4 (power maintenance pin) of the microcontroller and 0V ground. The positive terminal of the second energy storage capacitor C5 is also connected to the DC24V power supply terminal through a fourth resistor R6; at the same time, DC24V is connected to the positive terminal of the first energy storage capacitor C4 through a reverse isolation diode D8. When the external main power supply AC220V fails and pin 1 of the microcontroller loses 5V power, the first energy storage capacitor C4 and the second energy storage capacitor C5 discharge in parallel, continuing to provide power for the microcontroller to operate continuously through pin 4 for more than 60 seconds.

[0039] The magnetic latching relay drive network is as follows: Pin 7 of the microcontroller is connected to the base of NPN driver transistor Q1. The collector of transistor Q1 is connected in series with the magnetic latching relay's pull-in coil HC and then to DC 24V. Pin 6 of the microcontroller is connected to the base of NPN driver transistor Q2. The collector of Q2 is connected in series with the magnetic latching relay's release coil HB and then to 24V. The power input terminal of the release coil HB is connected to the positive terminal of the third holding capacitor C3 via a reverse isolation diode D6. The negative terminal of the third holding capacitor C3 is grounded.

[0040] Its working principle is as follows: Depend on Figure 2 It can be seen that when the contactor coils A1 and A2 are energized (AC220V), the AC220V voltage is reduced to AC35V after being stepped down and isolated by resistor R1 (1MΩ). A bridge rectifier composed of diodes D1-D4Z, current-limiting isolation by resistor R2, and voltage regulation by Zener diode VR1 (24V) constitute a DC24V power supply. The 24V flows to ground through the reverse diode D6 and the third sustaining capacitor C3, charging the third sustaining capacitor C3 (100uF) to 23.3V (24V - D6 junction voltage 0.7V = 23.3V). Another 24V flows to ground through the reverse diode D8 and capacitor C4, charging capacitor C4 (470uF) to 23.3V (24V - D8 junction voltage 0.7V = 23.3V). Another path is through resistor R6 and capacitor C5 to ground, slowly charging capacitor C5 (100uF) to about 23.3V to pin 4 of the integrated circuit microcontroller, providing the microcontroller with operating power (when pin 1 of the microcontroller is de-energized).

[0041] The 24V power supply is isolated and current-limited by resistor R9, reverse-isolated by diode D9, and regulated to ground by Zener diode VR2 (5V), forming a 5V power supply applied to pin 1 of the microcontroller to provide operating power to the microcontroller.

[0042] When the microcontroller is powered on, its internal program runs. Pin 7 outputs a low potential, and the 24V current is limited by resistor R3, illuminating the LED and indicating that the power supply and circuit are operating normally. Pin 6 outputs a high potential, turning on transistor Q1. The 24V current flows through KA2's HC, Q1's collector and emitter to ground, energizing the magnetic latching relay HC. The contacts of KA2 close and are magnetically held in place. The CRT sends the contactor's closing signal to the AND gate circuit.

[0043] When the contactor coil is de-energized and released, the power indicator LED turns off, the magnetic latching relay HC is de-energized, and the magnetic latching relay KA2 contacts remain closed. The charge of capacitors C4 and C5 continues to maintain the normal operation of the microcontroller through pin 4 (≥60S). After receiving the de-energization information from pin 1, the microcontroller begins a delay operation. The duration of this delay is determined by the duration circuit of the first adjustable potentiometer W1 and resistor R1 on pins 5 and 9 (changing the value of potentiometer W1 changes the duration by 100ms-6s). After the delay ends, pin 6 of the microcontroller outputs a high potential, transistor Q2 conducts, diode D6 reverse-isolates, and the charge of the third capacitor C3 (potential 23.3V) flows through the magnetic latching relay HB, the collector and emitter of transistor Q2 to ground, energizing the magnetic latching relay HB. The contacts of the magnetic latching relay KA2 then release (i.e., the second switch signal is output in the "closed" state). The release delay of the KA2 contacts is precisely set to 500 milliseconds to 1.5 seconds. The CRT sends the contactor's release signal to the AND gate circuit.

[0044] In summary: When the contactor's auxiliary coil is energized, the contactor's activation signal is sent directly to the AND logic circuit via the CRT. When the contactor coil is de-energized, the signal is sent to the AND logic circuit after the CRT has been running for a certain period of time.

[0045] For detailed circuit connections between the aforementioned AND gates and the execution unit, please refer to [link / reference needed]. Figure 3 As shown.

[0046] The positive terminal of an external 24V DC power supply is connected in series with the main switch (Q1), fuse (FUSE), and reset switch to form the main control node (03). Two parallel branches are drawn from the main control node (03): the first branch is a fault detection branch, which is composed of the normally open contact of the auxiliary contact signal processing module (RT) and the normally closed contact of the coil voltage detection module (CRT) connected in series; the second branch is a self-locking branch, which is composed of the self-locking normally open contact of the trip execution relay (KA). The tail ends of the first and second branches converge at the confluence node (04). The confluence node (04) is connected to the positive terminal of the trip execution relay (KA) coil, and the negative terminal of the relay KA coil is connected to the 0V ground wire; at the same time, a fault control indicator light is connected in parallel across the two ends of the relay KA coil.

[0047] When the contactor is normally de-energized, the auxiliary contact KM immediately opens, and the RT contact opens instantaneously, blocking the first branch. Simultaneously, after detecting coil de-energization, the CRT module waits 500 milliseconds to 1.5 seconds for a preset delay before its internal normally closed contact reopens. Therefore, during normal contactor shutdown, RT and CRT cannot conduct simultaneously, and KA will not malfunction. When a contactor experiences a jamming / welding fault, although the coil is de-energized, the auxiliary contact KM fails to open due to mechanical jamming, causing RT to remain closed and conducting. At this time, CRT reopens after a 500ms-1.5s delay. The first branch (RT and CRT) then conducts simultaneously, energizing the KA coil. After KA closes, the self-locking normally open contact in the second branch closes synchronously, forming a bypass self-locking mechanism, maintaining KA's continuous engagement. At this time, the normally open contacts (08, 09) of KA close, driving the electromagnetic trip unit of the external main switch. After troubleshooting, the reset switch must be pressed manually to cut off the power and release the self-locking before the circuit can return to standby mode.

[0048] Please refer to the workflow of the contactor main contact fault protection control of this invention. Figure 4 As shown: Normal startup: Coil is energized -> CRT switches KA2 to the open state; simultaneously KM closes -> RT delays for 3-5 seconds before KA1 engages. The AND gate circuit has no output because KA2 is open, and the device starts normally.

[0049] Normal shutdown: Coil de-energized -> CRT delays 500ms-1.5s before KA2 closes; simultaneously KM opens -> RT momentarily opens KA1. The AND gate circuit has no output due to KA1 opening, and the equipment shuts down normally.

[0050] Abnormal jamming (fault protection): Coil de-energization -> CRT delays 500ms-1.5s before KA2 closes; however, due to mechanical jamming, KM remains closed, and RT keeps KA1 engaged. At this time, KA1 and KA2 conduct simultaneously, the AND gate closes, the execution relay KA is immediately energized, the control indicator light illuminates, and in a very short time, the external electromagnetic trip unit is driven to cut off the main power supply, thus achieving protection.

[0051] However, those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Any changes or modifications to the above embodiments that are within the essential spirit of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A contactor main contact fault protection control device, characterized in that, include: An auxiliary contact signal processing module, whose input terminal is connected to the auxiliary normally open contact of the contactor, is used to output the closed signal of the auxiliary contact as a first switch signal after a preset delay, and to output the open signal of the auxiliary contact as a first switch signal instantaneously. The coil voltage detection module has its input terminal connected to both ends of the electromagnetic coil of the contactor. It is used to output a second switch signal to the open state when the coil is energized, and to output a second switch signal to the closed state after a preset delay when the coil is de-energized. The logic AND gate circuit is composed of the first switch signal and the second switch signal connected in series; The execution unit is connected to the output terminal of the AND gate circuit. When the AND gate circuit is turned on, it drives the external electromagnetic trip unit to operate.

2. The contactor main contact fault protection control device as described in claim 1, characterized in that: The auxiliary contact signal processing module includes: An RC charging circuit includes a capacitor, and the input terminal of the RC charging circuit is connected to a DC power supply through an auxiliary normally open contact of a contactor. A Zener diode is connected in parallel across the capacitor to clamp the initial voltage of the capacitor to a preset value. The comparator chip is an NE555 timer chip. Its second and sixth pins are connected to the positive terminal of the capacitor, and its third pin is the signal output terminal. The output terminal of the comparator chip flips when the voltage of the capacitor exceeds the reference value. The relay, whose control terminal is connected to the output terminal of the comparator chip and driven by the output terminal of the comparator chip, is used to output the first switching signal.

3. The contactor main contact fault protection control device as described in claim 1, characterized in that: The preset delay of the closing signal is the contactor activation anti-maloperation delay, and the duration of the preset delay is set to 3 to 5 seconds.

4. The contactor main contact fault protection control device as described in claim 1, characterized in that: The coil voltage detection module includes: The rectifier and voltage regulator unit converts the AC voltage of the contactor's electromagnetic coil into a DC operating voltage; The microcontroller has at least one energy storage capacitor connected in parallel to its power supply terminal; A magnetic latching relay has an engaging coil and a releasing coil; When the electromagnetic coil is energized, the microcontroller controls the coil to be energized, causing the magnetic latching relay contacts to close and outputting the second switch signal to be in the off state. After the electromagnetic coil loses power, the microcontroller is powered by the energy storage capacitor and releases the coil according to a preset delay, causing the magnetic latching relay contacts to release and output the second switch signal to restore the closed state.

5. The contactor main contact fault protection control device as described in claim 4, characterized in that: The coil voltage detection module also includes a delay adjustment potentiometer, which is connected to the microcontroller and used to adjust the preset delay.

6. The contactor main contact fault protection control device as described in claim 4, characterized in that: The first control terminal of the microcontroller is connected to the first driving transistor, and the output terminal of the first driving transistor is connected to the pull-in coil of the magnetic latching relay; the second control terminal of the microcontroller is connected to the second driving transistor, and the output terminal of the second driving transistor is connected to the release coil of the magnetic latching relay.

7. The contactor main contact fault protection control device as described in claim 1, characterized in that: After the electromagnetic coil of contactor KM is de-energized, the coil voltage detection module outputs the second switch signal as closed after a delay of 500 milliseconds to 1.5 seconds.

8. The contactor main contact fault protection control device as described in claim 1, characterized in that: The execution unit includes a fault trip relay, the coil of which is connected in parallel with a fault control indicator light between the output of the logic AND gate circuit and zero potential.

9. The contactor main contact fault protection control device as described in claim 1, characterized in that: The logic AND gate circuit includes a normally open contact of the first switch signal and a normally closed contact of the second switch signal connected in series.

10. The fault protection control method of the protection control device according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Detect the on / off state of the auxiliary contacts of the contactor, output the closed signal as the first switch signal after a preset delay, and output the open signal instantaneously; S2. Detect the presence or absence of voltage in the contactor's electromagnetic coil. If the electromagnetic coil is energized, output the second switch signal in an open state; if the electromagnetic coil is de-energized, output the closed state after a preset delay. S3. Connect the first switch signal and the second switch signal in series to form a logic AND gate; S4. When the aforementioned AND gate is on, it drives the external electromagnetic trip unit to disconnect the main circuit.

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