Anti-sticking method and system of electric hoist contactor based on current detection and logic control

Abstract

The application discloses a current detection and logic control based anti-sticking method and system for electric hoist contactors, and belongs to the field of electric control of hoisting machinery. The method comprises the following steps: monitoring operation instructions; controlling contactor drive signals according to the instructions; collecting at least two main circuit currents of a motor and calculating effective values; and judging sticking faults logically. In case A, if the current is still greater than a threshold value after a delay after both contactors are disconnected, it is determined that there is sticking. In case B, if there is current in the lowering circuit when only the upward contactor is attracted, or if there is current in the upward circuit when only the downward contactor is attracted, it is determined that the corresponding contactor is stuck. When sticking is determined, the total power supply is immediately cut off, an audible and visual alarm is sounded, and the system is locked to manual reset. The system comprises a main controller and instruction input, contactor drive, current detection, total power supply cut-off, and alarm units. The application does not rely on auxiliary contacts, accurately judges the actual state of the contactor in real time, and effectively prevents safety accidents.

Description

Technical Field

[0001] This invention relates to the field of electrical control technology for lifting machinery, and in particular to a method and system for preventing the contactor of an electric hoist from sticking together based on current detection and logic control. Background Technology

[0002] As a type of light and small lifting equipment, the lifting action of an electric hoist is usually achieved by a pair of AC contactors (i.e., forward contactor and reverse contactor) controlling the forward and reverse rotation of the motor.

[0003] In practical applications, especially under conditions of frequent inching operation, load start-stop, or load fluctuation, the main contacts of AC contactors are prone to generating strong electric arcs when interrupting large currents. The high temperature of the arc can cause the contact material to melt and stick together, a phenomenon known as "contactor sticking." To address potential contactor-related faults, existing technologies generally employ a combination of mechanical and electrical interlocking to prevent phase-to-phase short circuits caused by the simultaneous engagement of both forward and reverse contactors. Furthermore, some technical solutions indirectly determine the contactor's operating status by collecting data on the status of its auxiliary contacts.

[0004] However, existing technologies still have the following drawbacks: (1) Mechanical interlocking and electrical interlocking can only prevent two contactors from accidentally engaging at the same time, but cannot effectively detect and protect against the fault of main contact sticking of a single contactor.

[0005] (2) The detection scheme based on auxiliary contacts has a fundamental limitation: the on / off state of the auxiliary contacts can only reflect whether the contactor coil is energized or not, and cannot truly characterize the actual physical state of the main contacts. When the main contacts remain closed after the coil is de-energized due to sticking, the auxiliary contacts will still open normally, leading to misjudgment by the control system and failure to identify the sticking fault. Once the main contacts stick, the motor is very likely to continue running after the operator issues a stop command, causing serious safety accidents such as "hook slippage" or "uncontrolled ascent", or even short circuit of the main circuit due to the accidental engagement of another contactor, burning out electrical components and seriously threatening the safety of equipment and personnel.

[0006] Therefore, there is an urgent need for a method that can directly and effectively detect and prevent contactor sticking, and take immediate safety measures when sticking occurs. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method and system for preventing contactor sticking of electric hoists based on current detection and logic control. This method does not rely on the auxiliary contacts of the contactor, but rather collects the working current of the main circuit of the motor in real time to accurately determine whether the actual on / off state of the contactor is consistent with the drive command, and immediately executes safety locking and alarm when a sticking fault is detected, thereby effectively preventing safety accidents caused by contactor sticking.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for preventing the contactor of an electric hoist from sticking together based on current detection and logic control includes the following steps: Command status monitoring: Real-time monitoring of operation commands from the electric hoist control handle or remote control, including up commands, down commands and stop commands; Contactor drive control: According to the operation command, the control drive circuit sends an engaging or disengaging drive signal to the coil of the rising or falling contactor; Current signal acquisition and processing: The operating current signal is acquired by current sensors installed in at least two phases of the main circuit of the motor, and the effective value of the current is calculated; The logic for judging adhesion faults includes: Scenario A: After the control system sends a disconnect drive signal to both the rising contactor and the falling contactor, it continuously monitors the motor current. If the effective value of the current detected after the set delay time is still greater than the preset threshold current, it is determined that a contactor has stuck. Scenario B: When the control system only sends a pull-in drive signal to the rising contactor, if the effective value of the current detected in the circuit where the falling contactor is located is greater than the preset threshold current, it is determined that the falling contactor has stuck. When the control system only sends a pull-in drive signal to the falling contactor, if the effective value of the current detected in the circuit where the rising contactor is located is greater than the preset threshold current, it is determined that the rising contactor has stuck. Safety response measures: When either situation A or situation B is determined by the adhesion fault logic, immediately cut off the main power supply to the electric hoist, issue an audible and visual alarm signal, and lock the control system in the fault state until it is manually reset.

[0009] A further improvement of the technical solution of the present invention is that the delay time set in scenario A is 100ms to 500ms.

[0010] A further improvement of the technical solution of the present invention is that the preset threshold current is 1.5 times the no-load current of the motor.

[0011] A further improvement of the technical solution of the present invention is that the current sensor is a Hall current sensor, which is installed in the U-phase and W-phase circuits of the motor respectively.

[0012] A further improvement of the technical solution of the present invention is that, in the safety response measures, the method of cutting off the main power supply of the electric hoist is to control the main contactor to disconnect or trigger the shunt trip circuit breaker to trip.

[0013] A further improvement of the technical solution of the present invention is that the audible and visual alarm signal includes an indicator light flashing alarm and a buzzer sound alarm.

[0014] A further improvement of the technical solution of the present invention is that: after the control system is locked in a fault state, it can only be unlocked after maintenance personnel troubleshoot the fault and perform a manual reset operation.

[0015] An anti-sticking system for electric hoist contactors based on current detection and logic control includes: The instruction input unit is used to receive operation instructions from the control handle or remote control, including up instructions, down instructions and stop instructions; The main controller is electrically connected to the instruction input unit, contactor drive unit, current detection unit, main power cut-off unit and alarm unit, respectively, and is used to execute the electric hoist contactor anti-sticking method based on current detection and logic control. The contactor drive unit has its input terminal connected to the main controller and its output terminal connected to the coil of the rising contactor and the coil of the falling contactor, respectively, and is used to drive the coil of the rising contactor or the falling contactor to engage or disengage according to the control command of the main controller. The current detection unit includes at least two current sensors installed in the main circuit of the motor and their signal conditioning circuits, which are used to collect the operating current signal of the motor in real time and transmit it to the main controller. The main power cut-off unit is connected in series in the main power supply circuit of the electric hoist and is used to disconnect the main power supply after receiving the cut-off command from the main controller. An alarm unit is used to issue an audible and visual alarm signal after receiving an alarm command from the main controller.

[0016] A further improvement of the technical solution of the present invention is that the main controller is a programmable logic controller, a microcontroller, a microcontroller, or a digital signal processor.

[0017] A further improvement to the technical solution of this invention lies in: The instruction input unit is a control handle, a button, and / or a remote control receiver; The contactor drive unit is an intermediate relay and / or a solid-state relay circuit. The main power disconnection unit is a main contactor and / or a shunt trip circuit breaker. The alarm unit includes indicator lights and / or a buzzer.

[0018] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows: 1. This invention directly reflects the physical on / off state of the contactor's main contacts by real-time detection of the motor's main circuit current, avoiding the unreliability issues caused by relying on auxiliary contact detection. Since the main circuit current accurately reflects the actual conduction status of the contactor, the accuracy of detecting sticking faults is significantly improved, effectively eliminating safety hazards caused by inconsistencies between the auxiliary and main contact states.

[0019] 2. This invention not only enables timely disconnection of the main power supply through continuous current monitoring after a single contactor becomes stuck, preventing operator error from causing danger, but also detects the potential risk of a phase-to-phase short circuit caused by one contactor sticking while another is engaged, proactively triggering protection before the short circuit fault actually occurs. This bidirectional detection mechanism achieves a leap from passive response to proactive early warning, significantly improving the safety of equipment operation.

[0020] 3. This invention fully utilizes the existing current detection function in existing electric hoist control systems. It only requires adding a low-cost standard current sensor to the main circuit of the motor, without any modification to the contactor itself. Compared to replacing the anti-sticking contactor or adding complex detection devices, this invention has lower hardware costs, is easier to implement, and is readily adaptable to existing equipment.

[0021] 4. This invention does not rely on a specific model of contactor or motor and can be widely applied to various types of electric hoists, overhead cranes, and other lifting equipment where the forward and reverse rotation of the motor is controlled by an AC contactor. Its logical judgment rules are independent of the specific implementation of the control system, making it suitable for control systems based on numberable logic controllers, as well as those based on microcontrollers, microcontrollers, or digital signal processors, exhibiting good versatility and portability.

[0022] 5. The logical judgment rules of this invention are simple and clear, requiring only a comparison between the effective value of the current and a preset threshold, without the need for complex algorithm calculations, and have strong anti-interference capabilities. Furthermore, the acquisition and processing of the current signal are completed within milliseconds, and the fault judgment delay is much shorter than the time that equipment malfunction could cause a safety accident, enabling immediate safety response after a fault occurs and minimizing the risk of an accident. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a flowchart of an anti-sticking method for electric hoist contactors based on current detection and logic control provided in an embodiment of the present invention. Detailed Implementation

[0024] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments: like Figure 1 As shown, a method for preventing the contactor of an electric hoist from sticking together based on current detection and logic control includes the following steps: Command status monitoring: Real-time monitoring of operation commands from the electric hoist control handle or remote control, including up commands, down commands and stop commands; Contactor drive control: According to the operation command, the control drive circuit sends a drive signal to the coil of the rising contactor (KM1) or the falling contactor (KM2) to activate or deactivate. Current signal acquisition and processing: The operating current signal is acquired by current sensors installed in at least two phases of the main circuit of the motor, and the effective value of the current is calculated; The logic for judging adhesion faults includes: Scenario A: The drive signal is "disconnected" (stopped). After the control system sends a disconnect drive signal to both the rising contactor and the falling contactor, it continuously monitors the motor current. If the effective value of the current detected after the set delay time is still greater than the preset threshold current, it is determined that a contactor has stuck. Scenario B: Unexpected power-on when the drive signal is "engaged" (running state) When the control system sends a pull-in drive signal only to the rising contactor (theoretically there should be no current in the falling contactor circuit, and the system monitors the circuit current of both the rising and falling contactors at the same time), if the effective value of the current detected in the circuit where the falling contactor is located is greater than the preset threshold current, it is determined that the falling contactor has stuck (a dangerous phase-to-phase short circuit potential path has occurred, and the system should immediately trigger the fault). When the control system sends a pull-in drive signal only to the lowering contactor, if the effective value of the current detected in the circuit where the upper contactor is located is greater than the preset threshold current, it is determined that the upper contactor has stuck. Safety response measures: When the logic judgment of any adhesion fault in either Situation A or Situation B is valid, immediately cut off the main power supply of the electric hoist, issue an audible and visual alarm signal (indicating "contactor adhesion fault"), and lock the control system in the fault state until maintenance personnel troubleshoot the fault and manually reset it.

[0026] Furthermore, the delay time set in scenario A is 100ms to 500ms, which is used to avoid the contactor interrupting the arc time.

[0027] Furthermore, the preset threshold current is approximately 1.5 times the no-load current of the motor.

[0028] Furthermore, the current sensors are Hall current sensors, which are installed in the U-phase and W-phase circuits of the motor, respectively.

[0029] Furthermore, in the safety response measures, the main power supply to the electric hoist is cut off by controlling the main contactor to disconnect or triggering the shunt trip circuit breaker to trip.

[0030] Furthermore, the audible and visual alarm signals include flashing indicator lights and audible buzzers.

[0031] Furthermore, once the control system is locked in a fault state, it can only be unlocked after maintenance personnel troubleshoot the fault and perform a manual reset operation.

[0032] An anti-sticking system for electric hoist contactors based on current detection and logic control includes: The instruction input unit is used to receive operation instructions from the control handle or remote control, including up instructions, down instructions and stop instructions; The main controller is electrically connected to the instruction input unit, contactor drive unit, current detection unit, main power cut-off unit and alarm unit respectively, and is used for the above-mentioned anti-sticking method of electric hoist contactor based on current detection and logic control. The contactor drive unit has its input terminal connected to the main controller and its output terminal connected to the coil of the rising contactor and the coil of the falling contactor, respectively. It is used to drive the coil of the rising contactor or the falling contactor to engage or disengage according to the control command of the main controller. The current detection unit includes at least two current sensors installed in the main circuit of the motor and their signal conditioning circuit, which are used to collect the operating current signal of the motor in real time and transmit it to the main controller. The main power cut-off unit is connected in series in the main power supply circuit of the electric hoist and is used to disconnect the main power supply after receiving the cut-off command from the main controller. The alarm unit is used to issue audible and visual alarm signals after receiving an alarm command from the main controller.

[0033] Furthermore, the main controller can be a programmable logic controller, a microcontroller, a microcontroller, or a digital signal processor.

[0034] Furthermore, the command input unit is a control handle, a button, and / or a remote control receiver; The contactor drive unit is an intermediate relay and / or solid-state relay circuit; The main power disconnection unit consists of a main contactor and / or a shunt trip circuit breaker. The alarm unit includes indicator lights and / or a buzzer.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preventing contactor sticking in an electric hoist based on current detection and logic control, characterized in that: Includes the following steps: Command status monitoring: Real-time monitoring of operation commands from the electric hoist control handle or remote control, including up commands, down commands and stop commands; Contactor drive control: According to the operation command, the control drive circuit sends an engaging or disengaging drive signal to the coil of the rising or falling contactor; Current signal acquisition and processing: The operating current signal is acquired by current sensors installed in at least two phases of the main circuit of the motor, and the effective value of the current is calculated; The logic for judging adhesion faults includes: Scenario A: After the control system sends a disconnect drive signal to both the rising contactor and the falling contactor, it continuously monitors the motor current. If the effective value of the current detected after the set delay time is still greater than the preset threshold current, it is determined that a contactor has stuck. Scenario B: When the control system only sends a pull-in drive signal to the rising contactor, if the effective value of the current detected in the circuit where the falling contactor is located is greater than the preset threshold current, it is determined that the falling contactor has stuck. When the control system only sends a pull-in drive signal to the falling contactor, if the effective value of the current detected in the circuit where the rising contactor is located is greater than the preset threshold current, it is determined that the rising contactor has stuck. Safety response measures: When either situation A or situation B is determined by the adhesion fault logic, immediately cut off the main power supply to the electric hoist, issue an audible and visual alarm signal, and lock the control system in the fault state until it is manually reset.

2. The method for preventing contactor sticking of an electric hoist based on current detection and logic control according to claim 1, characterized in that: The delay time set in scenario A is 100ms to 500ms.

3. The method for preventing contactor sticking of an electric hoist based on current detection and logic control according to claim 1, characterized in that: The preset threshold current is 1.5 times the no-load current of the motor.

4. The method for preventing contactor sticking of an electric hoist based on current detection and logic control according to claim 1, characterized in that: The current sensors are Hall effect current sensors, which are installed in the U-phase and W-phase circuits of the motor, respectively.

5. The method for preventing contactor sticking of an electric hoist based on current detection and logic control according to claim 1, characterized in that: In the aforementioned safety response measures, the method of cutting off the main power supply to the electric hoist is to control the main contactor to disconnect or trigger the shunt trip circuit breaker to trip.

6. The method for preventing contactor sticking of an electric hoist based on current detection and logic control according to claim 1, characterized in that: The audible and visual alarm signals include flashing indicator lights and audible buzzers.

7. The method for preventing contactor sticking of an electric hoist based on current detection and logic control according to claim 1, characterized in that: Once the control system is locked in a fault state, it can only be unlocked after maintenance personnel troubleshoot the fault and perform a manual reset operation.

8. A current detection and logic control-based anti-sticking system for electric hoist contactors used to perform the method according to any one of claims 1-7, characterized in that, include: The instruction input unit is used to receive operation instructions from the control handle or remote control, including up instructions, down instructions and stop instructions; The main controller is electrically connected to the instruction input unit, the contactor drive unit, the current detection unit, the main power cut-off unit, and the alarm unit, respectively, and is used to execute the electric hoist contactor anti-sticking method based on current detection and logic control as described in any one of claims 1-7. The contactor drive unit has its input terminal connected to the main controller and its output terminal connected to the coil of the rising contactor and the coil of the falling contactor, respectively, and is used to drive the coil of the rising contactor or the falling contactor to engage or disengage according to the control command of the main controller. The current detection unit includes at least two current sensors installed in the main circuit of the motor and their signal conditioning circuits, which are used to collect the operating current signal of the motor in real time and transmit it to the main controller. The main power cut-off unit is connected in series in the main power supply circuit of the electric hoist and is used to disconnect the main power supply after receiving the cut-off command from the main controller. An alarm unit is used to issue an audible and visual alarm signal after receiving an alarm command from the main controller.

9. The anti-sticking system for electric hoist contactors based on current detection and logic control according to claim 8, characterized in that: The main controller is a programmable logic controller, a microcontroller, a microcontroller, or a digital signal processor.

10. The anti-sticking system for electric hoist contactors based on current detection and logic control according to claim 8, characterized in that: The instruction input unit is a control handle, a button, and / or a remote control receiver; The contactor drive unit is an intermediate relay and / or a solid-state relay circuit. The main power disconnection unit is a main contactor and / or a shunt trip circuit breaker. The alarm unit includes indicator lights and / or a buzzer.

Images