Low-voltage motor protector restarting operation method

Abstract

The invention discloses a restart operation method for a low-voltage motor protector, which belongs to the technical field of electrical equipment and comprises the following steps of: clearing historical fault records of the low-voltage motor protector, resetting the state of a contactor and calibrating a sampling module; the method comprises the following steps: presetting a motor rated load current reference value, a voltage sag time threshold value, a power loss time upper limit, a batch restart delay gradient, a restart current limit value and fault retry times on the basis of the characteristics of field electrical equipment, and establishing a parameter synchronization link between the motor protection and the DCS system. Cable laying does not need to be purchased, the problem that the motor is disconnected due to transient faults is solved by optimizing a secondary circuit, setting parameters of a motor protection device and the like, and a motor protection device can automatically try to restart the motor after confirming that the faults are eliminated.

Description

Technical Field

[0001] This invention belongs to the field of electrical equipment technology, specifically referring to a restart operation method for a low-voltage motor protector. Background Technology

[0002] Motor protection devices are widely used in low-voltage systems, primarily to prevent motor damage due to overload, short circuit, undervoltage, or other electrical faults. They protect motors by monitoring parameters such as current and voltage in the circuit.

[0003] When a system malfunctions and a low-voltage ride-through occurs, the switch of a critical 400V low-voltage device trips, resulting in a loss of power supply. This poses a significant threat to the safe and stable operation of the unit. To address this, a restart operation method for the low-voltage motor protector is proposed. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a restart operation method 6CD5 for low-voltage motor protectors. This method abandons the traditional method of laying DC control cables and is flexibly applicable to AC-powered motor protectors. Through analysis of the working principle and power requirements of the motor protector, the secondary circuit is optimized and improved, and the parameters of the motor protector are adjusted to achieve the purpose of restarting the motor protector.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for restarting a low-voltage motor protector, comprising the following steps:

[0006] S1. System status initialization and restart parameter preset: Clear historical fault records of the low-voltage motor protector, reset the contactor status and calibrate the sampling module. Based on the characteristics of the field electrical equipment, preset the motor rated load current reference value, power drop time threshold, power failure time upper limit, batch restart delay gradient, restart current limit value and fault retry number. Establish parameter synchronization link between the motor protector and the DCS system, support remote parameter modification and automatic verification of rationality.

[0007] S2. Real-time monitoring of electrical parameters and stop command status: The motor sampling frequency at a preset time collects the motor operating current, the three-phase line voltage of the 400V system and the stop command signal. If the voltage drops below 240V and lasts for 0.1 seconds, a voltage abnormality mark is triggered. If a stop command mark is received, the stop command is valid. If the current signal is abnormal, a sampling fault alarm is triggered.

[0008] S3. Comprehensive judgment of restart allowable conditions: The sliding window algorithm is used to determine whether the motor running current is less than the preset restart current limit value for a preset time. If the stop command is valid and the voltage abnormality is caused by a momentary fault, a restart trigger signal is generated. Otherwise, the current state is maintained or the normal stop process is entered.

[0009] S4. Accurate identification of power dip and power failure duration: Calculate the duration of power dip and the total duration of power failure by voltage sampling timestamp, record the phase information at the moment of voltage recovery, and cancel the restart trigger signal when the power dip duration is >5 seconds or the total duration of power failure is >18 seconds.

[0010] S5. Control circuit logic optimization and restart preparation: Cancel the connection of R13 terminal through remote and local switches, and directly control the positive power supply of the control circuit through 1.5mm² copper core insulated wire. Monitor the auxiliary normally closed contact of the contactor to confirm complete disconnection. Connect a 1N4744 Zener diode in parallel in the control circuit to absorb peak voltage. After completion, enter the restart ready state.

[0011] S6. Batch delayed restart execution: The equipment is divided into preset batches according to the arrangement of cabinets or equipment priority. Before starting, the load rate of the power distribution section is monitored. Each batch starts sequentially according to the preset time interval. When the starting current exceeds the preset restart current limit, the starting voltage is adjusted through the PWM module. The preset time is continuously monitored to confirm that the contactor is engaged and the current is stable for successful startup.

[0012] S7. Restart Status Monitoring and Abnormal Handling: Monitor voltage, current and contactor status according to preset time. If an abnormality occurs during startup, perform a second restart with a maximum of 3 retries. After 3 failures, send a DCS alarm and cut off the power supply to the equipment. After all equipment has run for a preset time without any abnormalities, resume normal monitoring and record the restart process to the local SD card.

[0013] Preferably, in step S1, the preset parameters based on the characteristics of the on-site electrical equipment specifically include: calculating the FLC baseline value according to the rated power of the motor, such as 18A for a 10kW motor; setting the upper limit of the power outage time to 18 seconds according to the rated capacity of the distribution section; prioritizing according to the importance of the equipment process and matching corresponding batch delay gradients, with a critical load interval of 5 seconds, an important load interval of 8 seconds, and a general load interval of 10 seconds; the parameter synchronization link uses TCP / IP or RS485 communication protocol. When parameters are remotely modified, the built-in verification module of the device limits the parameter range. If the verification fails, it sends a "parameter out of range" alarm to the DCS system and maintains the original parameter operation.

[0014] Preferably, step S1 further includes a communication link initialization detection: upon startup, the device sends a heartbeat packet to the DCS system. If no response is received from the DCS system for three consecutive times or there is no data exchange on the RS485 bus, a communication interruption is determined, and the local storage mode is immediately activated to temporarily store the monitoring data and operation instructions to the local SD card. After communication is restored, the temporarily stored data is automatically synchronized to the DCS system to avoid data loss. At the same time, emergency parameters for communication interruption are preset to ensure that the device can still restart according to the emergency logic when communication is interrupted, thus ensuring the operation of critical equipment.

[0015] Preferably, in step S2, the motor operating current is acquired through a 0.5-level precision current transformer built into the motor control unit. The current signal is converted into a digital signal by a 16-bit AD converter. The 400V system three-phase line voltage monitoring uses a star-connected voltage sensor to simultaneously acquire the voltages of phases AB, BC, and CA. When any phase voltage is ≤240V and lasts for 0.1 seconds, the motor control unit immediately triggers a voltage anomaly marker and records the voltage drop start time stamp. The stop command signal acquisition adopts a dual redundancy design. The local signal acquisition uses the normally open passive contact of the local operation box, and the remote signal acquisition uses the DC24VDO signal output by the DCS system. The two signals are determined by OR logic. If either signal is valid, the stop command is marked as valid, and the command source is uploaded to the DCS through the communication link.

[0016] Preferably, in step S3, the specific execution logic of the sliding window algorithm is as follows: extract current sampling values ​​every 0.05 seconds to form a sliding window containing 6 sampling points. If all sampling values ​​in the window are less than the preset current limit value, the current condition is determined to be met. The determination that the voltage abnormality is caused by a transient fault also includes: Ma Bao queries the status of the upper-level circuit breaker of the distribution section through the communication link and reads the internal fault record. If the upper-level circuit breaker trips or has a permanent fault code, it is determined to be a non-transient fault, the restart process is immediately terminated, and the fault type is recorded in the historical database.

[0017] Preferably, in step S4, the calculation logic for the duration of the power slump is as follows: the difference between the timestamp of the first frame of sampling data satisfying voltage ≤ 240V and the timestamp of the first frame of sampling data satisfying voltage ≥ 360V is the duration of the power slump. If the difference is within the range of 0.5 seconds to 5 seconds, it is marked as a short-term power slump; otherwise, it is marked as a long-term power slump. The calculation logic for the total power loss duration is as follows: the difference between the timestamp of the contactor's auxiliary normally closed contact changing from open to closed and the timestamp of the voltage recovering to ≥ 360V and the timetamp when the motor protector receives the signal for the contactor to prepare to engage is the total power loss duration. The phase information recording is achieved through the phase detection chip built into the motor protector, which detects the phase angle of the grid voltage and stores the phase value at the moment of voltage recovery. When restarting, the motor protector adjusts the start signal output time according to the phase value to control the phase difference between the motor stator voltage phase and the rotor induced electromotive force within ±10°, thereby reducing the impact of the restart current.

[0018] Preferably, in step S5, the positive power supply of the control circuit is selected as DC220V or AC220V according to the site configuration. Before connecting the wires, an insulation test is required. After connection, the voltage between terminal R13 and the negative terminal of the power supply is measured with a multimeter to confirm that the voltage value is consistent with the rated value of the power supply, ensuring that the circuit power supply is normal. The confirmation logic for the complete disconnection of the contactor is as follows: the contactor auxiliary normally closed contact signal is collected by the power supply. If the contact signal is closed and lasts for 0.2 seconds, the contactor is determined to be completely disconnected. If the contact signal is open or the continuous closing time is <0.2 seconds, the contactor disconnection abnormal alarm is triggered, and the contactor mechanical structure or contact is prompted to be repaired through the DCS. The 1N4744 Zener diode is connected to the control circuit in reverse parallel. A current-limiting resistor is connected in parallel across the diode to ensure that the reverse breakdown current is stable within the range of 5-10mA, avoiding overcurrent damage to the diode.

[0019] Preferably, in step S6, the batching by panel arrangement specifically involves: numbering the low-voltage distribution panels from left to right as 1-10; classifying the motors in panels 1-3 as the first batch, panels 4-6 as the second batch, and panels 7-10 as the third batch; equipment within the same batch starts simultaneously, and different batches are executed at preset intervals; the load rate monitoring of the distribution section is achieved by collecting the total incoming current of the distribution section using a data acquisition device, combined with the rated total current of the distribution section (e.g., a 200kVA distribution section with a rated current of 288.7A), and calculating the load rate as (actual total current / rated total current) × 100%. If the load rate is >80%, the current batch start interval will be extended to 1.5 times the original interval. If the load rate is >90%, the restart process will be immediately paused, and an alarm for excessive load in the power distribution section will be sent to the DCS. After the DCS system adjusts the load to ≤80%, the batch start will be triggered again. The specific process of the PWM module adjusting the start voltage is as follows: in the initial stage of start-up, the output voltage is 70% of the rated voltage, which is increased by 10% every 0.5 seconds until it reaches 100% of the rated voltage. During this period, the current is monitored in real time. If the current exceeds 120% FLC, the voltage increase will be paused, and the current voltage will be maintained until the current drops below the threshold.

[0020] Preferably, step S6 further includes a motor pre-lubrication detection step before the batch restart execution: For motors requiring pre-lubrication, Mabo collects the lubricating oil pump operating status signal through the DI terminal. If the lubricating oil pump is not started or the oil supply pressure is <0.2MPa, the start-up process of the batch containing the motor is suspended, and a pre-lubrication insufficiency alarm is sent to the DCS. After the DCS starts the lubricating oil pump and the pressure reaches the standard, the motor is included in the current batch start-up. If the lubricating oil pump fails to start, the motor is marked as a faulty device, and the restart of other devices is skipped to avoid affecting the overall batch start-up efficiency due to the failure of a single device.

[0021] Preferably, in step S7, the types of startup exceptions and corresponding restart strategies include:

[0022] Sudden current surge: This is determined to be a startup overload. The PWM voltage rise time is extended to 5 seconds, the voltage rise rate is reduced, and a second restart is performed after 3 seconds.

[0023] Sudden drop in current: If the problem is determined to be poor contact in the power supply circuit or motor stall, the machine will first output a contactor trip signal, then perform a second restart, and at the same time send a current abnormality warning to the DCS.

[0024] Contactor stuck: This is determined to be a mechanical fault in the contactor. The circuit breaker outputs a strong tripping signal. If the contacts still do not break, it will not retry and will directly send a contactor stuck alarm to the DCS.

[0025] The restart process records the following information: restart trigger time, power slump duration, total power outage duration, restart time of each batch, peak startup current of each device, number of anomalies and their handling results. The data is stored on the local SD card of the device. The DCS system can query historical data for the past year through the communication link and supports export in Excel format.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. This invention addresses the drawback of low-voltage power distribution section fault statistics, where, due to the lack of DC power supply, when a system fault causes the 400V ride-through voltage to drop to below 60%, some important load switch contactors return to de-energized status and cannot be restarted.

[0028] 2. This invention solves the problem of motor disconnection due to momentary faults by optimizing the secondary circuit and setting the parameters of the motor protection device, without the need to purchase and lay cables when there is no DC system introduced into the field equipment. The motor protection device can automatically attempt to restart the motor after confirming that the fault has been eliminated.

[0029] 3. This invention improves the system's flexibility and adaptability by adjusting the restart strategy according to different electrical equipment application scenarios, such as setting different restart delay times or deciding whether to restart based on specific environmental conditions, while reducing unnecessary downtime and maintenance needs. Attached Figure Description

[0030] Figure 1 This is a flowchart of the motor protection device operation control method for restarting a low-voltage motor according to the present invention.

[0031] Figure 2 This is a structural schematic diagram of the delayed start-up timing diagram of a low-voltage motor protector restart operation method according to the present invention;

[0032] Figure 3This is a comparative schematic diagram of the optimized control loop structure for the restart operation method of a low-voltage motor protector according to the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example

[0035] Please see Figure 1-3 As shown, the present invention provides a technical solution comprising the following steps:

[0036] S1. System status initialization and restart parameter preset: Clear historical fault records of the low-voltage motor protector, reset the contactor status and calibrate the sampling module. Based on the characteristics of the field electrical equipment, preset the motor rated load current reference value, power drop time threshold, power failure time upper limit, batch restart delay gradient, restart current limit value and fault retry number. Establish parameter synchronization link between the motor protector and the DCS system, support remote parameter modification and automatic verification of rationality.

[0037] S2. Real-time monitoring of electrical parameters and stop command status: The motor sampling frequency at a preset time collects the motor operating current, the three-phase line voltage of the 400V system and the stop command signal. If the voltage drops below 240V and lasts for 0.1 seconds, a voltage abnormality mark is triggered. If a stop command mark is received, the stop command is valid. If the current signal is abnormal, a sampling fault alarm is triggered.

[0038] S3. Comprehensive judgment of restart allowable conditions: The sliding window algorithm is used to determine whether the motor running current is less than the preset restart current limit value for a preset time. If the stop command is valid and the voltage abnormality is caused by a momentary fault, a restart trigger signal is generated. Otherwise, the current state is maintained or the normal stop process is entered.

[0039] S4. Accurate identification of power dip and power failure duration: Calculate the duration of power dip and the total duration of power failure by voltage sampling timestamp, record the phase information at the moment of voltage recovery, and cancel the restart trigger signal when the power dip duration is >5 seconds or the total duration of power failure is >18 seconds.

[0040] S5. Control circuit logic optimization and restart preparation: Cancel the connection of R13 terminal through remote and local switches, and directly control the positive power supply of the control circuit through 1.5mm² copper core insulated wire. Monitor the auxiliary normally closed contact of the contactor to confirm complete disconnection. Connect a 1N4744 Zener diode in parallel in the control circuit to absorb peak voltage. After completion, enter the restart ready state.

[0041] S6. Batch delayed restart execution: The equipment is divided into preset batches according to the arrangement of cabinets or equipment priority. Before starting, the load rate of the power distribution section is monitored. Each batch starts sequentially according to the preset time interval. When the starting current exceeds the preset restart current limit, the starting voltage is adjusted through the PWM module. The preset time is continuously monitored to confirm that the contactor is engaged and the current is stable for successful startup.

[0042] S7. Restart Status Monitoring and Abnormal Handling: Monitor voltage, current and contactor status according to preset time. If an abnormality occurs during startup, perform a second restart with a maximum of 3 retries. After 3 failures, send a DCS alarm and cut off the power supply to the equipment. After all equipment has run for a preset time without any abnormalities, resume normal monitoring and record the restart process to the local SD card.

[0043] In this embodiment, S1, the preset parameters based on the characteristics of the on-site electrical equipment, specifically includes: calculating the FLC baseline value according to the rated power of the motor, such as 18A for a 10kW motor; setting the upper limit of the power outage time to 18 seconds according to the rated capacity of the distribution section; prioritizing according to the importance of the equipment process and matching corresponding batch delay gradients, with a critical load interval of 5 seconds, an important load interval of 8 seconds, and a general load interval of 10 seconds; the parameter synchronization link uses TCP / IP or RS485 communication protocol. When parameters are remotely modified, the built-in verification module of the device limits the parameter range. If the verification fails, it sends a "parameter out of range" alarm to the DCS system and maintains the original parameter operation.

[0044] In this embodiment, S1 further includes the initialization detection of the communication link of the device: when the device starts, it sends a heartbeat packet to the DCS system. If it does not receive a response from the DCS for three consecutive times or there is no data interaction on the RS485 bus, it is determined that the communication is interrupted. The local storage mode is immediately started to temporarily store the monitoring data and operation instructions to the local SD card. After the communication is restored, the temporarily stored data is automatically synchronized to the DCS system to avoid data loss. At the same time, the communication interruption emergency parameters are preset to ensure that the device can still be restarted according to the emergency logic when the communication is interrupted, so as to protect the operation of critical equipment.

[0045] In this embodiment, in step S2, the motor operating current acquisition is achieved through a 0.5-level precision current transformer built into the motor control unit. The current signal is converted into a digital signal by a 16-bit AD converter. The 400V system three-phase line voltage monitoring uses a star-connected voltage sensor to simultaneously acquire the voltages of phases AB, BC, and CA. When any phase voltage is ≤240V and lasts for 0.1 seconds, the motor control unit immediately triggers a voltage anomaly marker and records the voltage drop start time stamp. The stop command signal acquisition adopts a dual redundancy design. The local signal acquisition is performed by the normally open passive contact of the local operation box, and the remote signal acquisition is performed by the DC24VDO signal output by the DCS system. The two signals are determined by OR logic. If either signal is valid, the stop command is marked as valid, and the command source is uploaded to the DCS through the communication link.

[0046] In this embodiment, the specific execution logic of the sliding window algorithm in S3 is as follows: extract the current sampling value once every 0.05 seconds to form a sliding window containing 6 sampling points. If all the sampling values ​​in the window are less than the preset current limit value, the current condition is determined to be met. The determination that the voltage abnormality is caused by a transient fault also includes: Ma Bao queries the status of the upper-level circuit breaker of the distribution section through the communication link and reads the internal fault record. If the upper-level circuit breaker trips or there is a permanent fault code, it is determined to be a non-transient fault, the restart process is immediately terminated, and the fault type is recorded in the historical database.

[0047] In this embodiment, the calculation logic for the duration of the power slump in S4 is as follows: the difference between the timestamp of the first frame of sampling data satisfying voltage ≤240V and the timestamp of the first frame of sampling data satisfying voltage ≥360V is the duration of the power slump. If the difference is within the range of 0.5 seconds to 5 seconds, it is marked as a short-term power slump; otherwise, it is marked as a long-term power slump. The calculation logic for the total power loss duration is as follows: the difference between the timestamp of the contactor's auxiliary normally closed contact changing from open to closed and the timestamp of the voltage recovering to ≥360V and the timetamp when the motor protector receives the signal for the contactor to prepare to engage is the total power loss duration. The phase information recording is achieved through the phase detection chip built into the motor protector, which detects the phase angle of the grid voltage and stores the phase value at the moment of voltage recovery. When restarting, the motor protector adjusts the start signal output time according to the phase value to control the phase difference between the motor stator voltage phase and the rotor induced electromotive force within ±10°, thereby reducing the impact of the restart current.

[0048] In this embodiment, in step S5, the positive power supply of the control circuit is selected as DC220V or AC220V according to the site configuration. Before connecting the wires, an insulation test is required. After connection, the voltage between terminal R13 and the negative terminal of the power supply is measured with a multimeter to confirm that the voltage value is consistent with the rated value of the power supply, ensuring that the circuit power supply is normal. The confirmation logic for the complete disconnection of the contactor is as follows: the contactor auxiliary normally closed contact signal is collected by the power supply. If the contact signal is closed and lasts for 0.2 seconds, the contactor is determined to be completely disconnected. If the contact signal is open or the continuous closing time is <0.2 seconds, the contactor disconnection abnormal alarm is triggered, and the DCS prompts for maintenance of the contactor mechanical structure or contacts. The 1N4744 Zener diode is connected to the control circuit in reverse parallel. A current-limiting resistor is connected in parallel across the diode to ensure that the reverse breakdown current is stable within the range of 5-10mA, avoiding overcurrent damage to the diode.

[0049] In this embodiment, S6, the batching by cabinet arrangement, specifically involves numbering the low-voltage distribution cabinets from left to right as 1-10. The motors in cabinets 1-3 are grouped into the first batch, cabinets 4-6 into the second batch, and cabinets 7-10 into the third batch. Equipment within the same batch starts simultaneously, and different batches are executed at preset intervals. The load rate monitoring of the distribution section uses a data acquisition device to collect the total incoming current of the distribution section, combined with the rated total current of the distribution section. For example, if the rated current of a 200kVA distribution section is 288.7A, the load rate is calculated as: (actual total current / rated total current) × 100%. If the load rate is >80%, the current batch start interval will be extended to 1.5 times the original interval. If the load rate is >90%, the restart process will be immediately suspended, and an alarm for excessive load in the power distribution section will be sent to the DCS. After the DCS system adjusts the load to ≤80%, the batch start will be triggered again. The specific process of the PWM module adjusting the start voltage is as follows: in the initial stage of start-up, the output voltage is 70% of the rated voltage, and it is increased by 10% every 0.5 seconds until it reaches 100% of the rated voltage. During this period, the current is monitored in real time. If the current exceeds 120% FLC, the voltage increase will be suspended, and the current voltage will be maintained until the current drops below the threshold.

[0050] In this embodiment, step S6, before the batch restart execution, also includes a motor pre-lubrication detection step: For motors requiring pre-lubrication, Ma Bao collects the lubricating oil pump operating status signal through the DI terminal. If the lubricating oil pump is not started or the oil supply pressure is <0.2MPa, the start-up process of the batch containing the motor is suspended, and a pre-lubrication insufficiency alarm is sent to the DCS. After the DCS starts the lubricating oil pump and the pressure reaches the standard, the motor is included in the current batch start-up. If the lubricating oil pump fails to start, the motor is marked as a faulty device, and the restart of other devices is skipped to avoid affecting the overall batch start-up efficiency due to the failure of a single device.

[0051] In this embodiment, step S7, the type of startup exception and the corresponding restart strategy, includes:

[0052] Sudden current surge: This is determined to be a startup overload. The PWM voltage rise time is extended to 5 seconds, the voltage rise rate is reduced, and a second restart is performed after 3 seconds.

[0053] Sudden drop in current: If the problem is determined to be poor contact in the power supply circuit or motor stall, the machine will first output a contactor trip signal, then perform a second restart, and at the same time send a current abnormality warning to the DCS.

[0054] Contactor stuck: This is determined to be a mechanical fault in the contactor. The circuit breaker outputs a strong tripping signal. If the contacts still do not break, it will not retry and will directly send a contactor stuck alarm to the DCS.

[0055] The restart process records the following information: restart trigger time, power slump duration, total power outage duration, restart time of each batch, peak startup current of each device, number of anomalies and their handling results. The data is stored on the local SD card of the device. The DCS system can query historical data for the past year through the communication link and supports export in Excel format.

[0056] Figure 1 To determine if a restart has occurred: if no stop command is received and the current is less than 5% of the load current, a restart is deemed permissible. If the electrical equipment successfully restarts within the power dip period, it will continue to operate. If it fails to restart, a command will be issued to enter the stop state.

[0057] Figure 2 The restart timing sequence diagram is as follows: Based on the power dip time, power failure time, and restart time, and according to the characteristics of the on-site equipment, the actual parameters are set. In order to avoid the voltage drop caused by the simultaneous start-up of equipment that has lost power, the restart time is set sequentially according to the arrangement of the cabinets to ensure reliable self-starting after a momentary AC power failure.

[0058] Figure 3 To optimize the control loop: In order to prevent the switch position from affecting the success rate of self-starting, and to ensure that the self-starting process can be completed regardless of whether the switch is in a local or remote position, the loop is optimized by eliminating the connection of the R13 terminal through the remote position and instead connecting it directly to the positive power supply. This ensures that the load switch subjected to an impact can achieve the self-starting function under any operating condition.

[0059] The method of this invention has been put into use and is flexibly applicable to AC-powered generator sets. The method is simple, easy for maintenance personnel to operate, and can maximize safety and economy. It will be applied to the same type of retrofitting of other units in the future.

[0060] Working Principle: First, clear historical faults of the motor current transformer (MDT), reset the contactor, and calibrate the sampling module to eliminate early interference. Then, based on motor power, distribution section capacity, and equipment priority, preset parameters such as FLC reference value, power outage limit, and batch delay are used to adapt to the on-site working conditions. Simultaneously, a parameter synchronization link with the DCS is established, supporting remote modification and automatic verification. Local storage and emergency parameters are enabled when communication is interrupted. The MDT uses a 0.5-class current transformer and a 16-bit AD converter to collect motor current, and a star-type voltage sensor measures three-phase voltage. A voltage ≤240V for 0.1 seconds is marked as abnormal. Dual redundancy is used to collect local and remote stop commands or to logically determine their validity. An abnormal current signal triggers an alarm. A sliding window algorithm is used to determine if the current is continuously less than the preset value, combined with the motor temperature to correct the threshold. If no stop command is confirmed, and the voltage abnormality is determined to be an instantaneous fault by checking the status of the upstream circuit breaker and reading the fault record, a restart signal is generated only if all three conditions are met; otherwise, the circuit breaker is blocked. Invalid start-up protects equipment; calculates power dip duration based on voltage sampling timestamp and power failure duration based on contactor status timestamp, cancels restart if timeout occurs; simultaneously records voltage recovery phase, matches motor rotor phase during startup to reduce restart current surge, eliminates connection of R13 terminal via remote or local switch, directly controls circuit positive power supply to adapt to all operating conditions; monitors contactor contacts for 0.2 seconds of continuous closure to confirm disconnection; uses parallel Zener diodes to absorb spikes, and shielded grounding of conductors to resist interference, enters restart ready state after completion; prioritizes cabinets or equipment in batches, starts within the same batch and delays between batches by 5-10 seconds; calculates distribution section load rate before startup, extends interval if over 80%, pauses if over 90%; soft-starts PWM module for voltage adjustment when current exceeds limit, pre-lubricated motor must meet standard first; monitors voltage, current, and contactor status at preset times, retrying in stages if abnormal, alarms and cuts off power after 3 failures; records the entire restart process to SD card, resumes regular monitoring after 30 minutes without abnormalities.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their likenesses.

[0062] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A restart operation method for a low-voltage motor protector, characterized in that, Includes the following steps: S1. System status initialization and restart parameter preset: Clear historical fault records of the low-voltage motor protector, reset the contactor status and calibrate the sampling module. Based on the characteristics of the field electrical equipment, preset the motor rated load current reference value, power drop time threshold, power failure time upper limit, batch restart delay gradient, restart current limit value and fault retry number, and establish a parameter synchronization link between the motor protector and the DCS system. S2. Real-time monitoring of electrical parameters and stop command status: The motor sampling frequency at a preset time collects the motor operating current, the three-phase line voltage of the 400V system and the stop command signal. If the voltage drops below 240V and continues for a preset time, a voltage abnormality mark is triggered. If a stop command mark is received, the stop command is valid. If the current signal is abnormal, a sampling fault alarm is triggered. S3. Comprehensive judgment of restart allowable conditions: The sliding window algorithm is used to determine whether the motor running current is less than the preset restart current limit value for a preset time. If the stop command is valid and the voltage abnormality is caused by a momentary fault, a restart trigger signal is generated. Otherwise, the current state is maintained or the normal stop process is entered. S4. Accurate identification of power dip and power loss duration: Calculate the duration of power dip and the total duration of power loss through voltage sampling timestamps, and record the phase information at the moment of voltage recovery; S5. Control circuit logic optimization and restart preparation: Cancel the connection of R13 terminal through remote and local switches, and directly control the positive power supply of the control circuit through 1.5mm² copper core insulated wire. Monitor the auxiliary normally closed contact of the contactor to confirm complete disconnection. Connect a 1N4744 Zener diode in parallel in the control circuit to absorb peak voltage. After completion, enter the restart ready state. S6. Batch delayed restart execution: The equipment is divided into preset batches according to the arrangement of cabinets or equipment priority. Before starting, the load rate of the power distribution section is monitored. Each batch starts sequentially according to the preset time interval. When the starting current exceeds the preset restart current limit, the starting voltage is adjusted through the PWM module. The preset time is continuously monitored to confirm that the contactor is engaged and the current is stable for successful startup. S7. Restart Status Monitoring and Abnormal Handling: Monitor voltage, current and contactor status according to preset time. If an abnormality occurs during startup, perform a second restart with a maximum of 3 retries. After 3 failures, send a DCS alarm and cut off the power supply to the equipment. After all equipment has run for a preset time without any abnormalities, resume normal monitoring and record the restart process to the local SD card.

2. The restart operation method for a low-voltage motor protector according to claim 1, characterized in that: S1, the preset parameters based on the characteristics of the on-site electrical equipment specifically includes: calculating the FLC reference value according to the rated power of the motor, setting the upper limit of the power outage time to 18 seconds according to the rated capacity of the power distribution section, dividing the priority according to the importance of the equipment process, and matching the corresponding batch delay gradient. The parameter synchronization link is through a communication protocol. When the parameters are remotely modified, the built-in verification module of the device limits the parameter range. When the verification fails, it sends a "parameter out of range" alarm to the DCS system and maintains the original parameter operation.

3. The restart operation method for a low-voltage motor protector according to claim 1, characterized in that: S1 also includes the initialization detection of the communication link of the Mabao: when the Mabao sends a heartbeat packet to the DCS system, if it does not receive a response from the DCS bus for 3 consecutive times and there is no data interaction, it is determined that the communication is interrupted and the local storage mode is immediately started to temporarily store the monitoring data and operation instructions to the local SD card. After the communication is restored, the temporarily stored data is automatically synchronized to the DCS system to avoid data loss.

4. The restart operation method for a low-voltage motor protector according to claim 1, characterized in that: In S2, the motor operating current is acquired through a 0.5-level precision current transformer built into the motor control unit. The current signal is converted into a digital signal by a 16-bit AD converter. The 400V system three-phase line voltage monitoring uses a star-connected voltage sensor to simultaneously acquire the voltages of phases AB, BC, and CA. When any phase voltage is ≤240V for 0.1 seconds, the motor control unit immediately triggers a voltage anomaly marker and records the voltage drop start time stamp. The stop command signal acquisition adopts a dual redundancy design. The local signal acquisition is performed by the normally open passive contact of the local operation box, and the remote signal acquisition is performed by the DC24VDO signal output by the DCS system. The two signals are determined by OR logic. If either signal is valid, the stop command is marked as valid, and the command source is uploaded to the DCS through the communication link.

5. The restart operation method for a low-voltage motor protector according to claim 1, characterized in that: The specific execution logic of the sliding window algorithm in S3 is as follows: extract the current sampling value once every 0.05 seconds to form a sliding window containing 6 sampling points. If all the sampling values ​​in the window are less than the preset current limit value, the current condition is determined to be met. The determination that the voltage abnormality is caused by a transient fault also includes: Ma Bao queries the status of the upper-level circuit breaker of the distribution section through the communication link and reads the internal fault record. If the upper-level circuit breaker trips or there is a permanent fault code, it is determined to be a non-transient fault, the restart process is immediately terminated, and the fault type is recorded in the historical database.

6. The restart operation method for a low-voltage motor protector according to claim 1, characterized in that: In S4, the calculation logic for the duration of the power slump is as follows: from the timestamp of the first frame of sampling data that satisfies a voltage ≤ 240V to the timestamp of the first frame of sampling data that satisfies a voltage ≥ 360V, the difference between the two is the duration of the power slump. If the difference is within the range of 0.5 seconds to 5 seconds, it is marked as a short-term power slump; otherwise, it is marked as a long-term power slump. The calculation logic for the total power loss duration is as follows: from the timestamp of the contactor's auxiliary normally closed contact changing from open to closed to the timestamp of the voltage recovering to ≥ 360V and the contactor receiving a signal to prepare to engage, the difference between the two is the total power loss duration. The phase information recording is achieved through the phase detection chip built into the MAB (Motor Power Supply), which detects the phase angle of the grid voltage and stores the phase value at the moment of voltage recovery. When restarting, the MAB adjusts the timing of the start signal output based on the phase value, so that the phase difference between the stator voltage phase and the rotor induced electromotive force is controlled within ±10°, thereby reducing the impact of the restart current.

7. The restart operation method for a low-voltage motor protector according to claim 1, characterized in that: In S5, the positive power supply of the control circuit needs to undergo an insulation test before the wires are connected, depending on the site configuration. After connection, the voltage between terminal R13 and the negative terminal of the power supply is measured with a multimeter. The confirmation logic for the complete disconnection of the contactor is as follows: the contactor auxiliary normally closed contact signal is collected by the power supply. If the contact signal is closed and lasts for 0.2 seconds, the contactor is determined to be completely disconnected. If the contact signal is open or the continuous closing time is <0.2 seconds, the contactor disconnection abnormal alarm is triggered, and the DCS prompts for maintenance of the contactor mechanical structure or contacts. The 1N4744 Zener diode is connected to the control circuit in reverse parallel mode, and a current-limiting resistor is connected in parallel across the diode to ensure that the reverse breakdown current is stable within the range of 5-10mA.

8. The restart operation method for a low-voltage motor protector according to claim 1, characterized in that: S6, the batching by cabinet arrangement, specifically involves numbering the low-voltage distribution cabinets from left to right as 1-10. The motors in cabinets 1-3 are grouped into the first batch, cabinets 4-6 into the second batch, and cabinets 7-10 into the third batch. Equipment within the same batch starts simultaneously, and different batches are executed at preset intervals. The load rate monitoring of the distribution section involves collecting the total incoming current of the distribution section using a data acquisition system, combined with the rated total current of the distribution section. For example, a 200kVA distribution section with a rated current of 288.7A is calculated using the formula: Load Rate = (Actual Total Current / Rated Total Current) × 100%. If the load rate is low... If the load rate is >80%, the start interval of the current batch will be extended to 1.5 times the original interval. If the load rate is >90%, the restart process will be immediately suspended, and an alarm for excessive load in the power distribution section will be sent to the DCS. After the DCS system adjusts the load to ≤80%, the batch start will be triggered again. The specific process of the PWM module adjusting the start voltage is as follows: in the initial stage of start-up, the output voltage is 70% of the rated voltage, which is increased by 10% every 0.5 seconds until it reaches 100% of the rated voltage. During this period, the current is monitored in real time. If the current exceeds 120% FLC, the voltage increase will be suspended, and the current voltage will be maintained until the current drops below the threshold.

9. The restart operation method for a low-voltage motor protector according to claim 8, characterized in that: Before the batch restart execution, S6 also includes a motor pre-lubrication detection step: For motors that require pre-lubrication, Ma Bao collects the lubricating oil pump operating status signal through the DI terminal. If the lubricating oil pump is not started or the oil supply pressure is <0.2MPa, the start-up process of the batch containing the motor is suspended, and a pre-lubrication insufficiency alarm is sent to the DCS. After the DCS starts the lubricating oil pump and the pressure reaches the standard, the motor is included in the current batch for start-up. If the lubricating oil pump fails to start, the motor is marked as a faulty device, and the restart of other devices is skipped.

10. The restart operation method for a low-voltage motor protector according to claim 1, characterized in that: The types of startup exceptions and corresponding restart strategies mentioned in S7 include: Sudden current surge: This is determined to be a startup overload. The PWM voltage rise time is extended to 5 seconds, the voltage rise rate is reduced, and a second restart is performed after 3 seconds. Sudden drop in current: If the problem is determined to be poor contact in the power supply circuit or motor stall, the machine will first output a contactor trip signal, then perform a second restart, and at the same time send a current abnormality warning to the DCS. Contactor stuck: This is determined to be a mechanical fault in the contactor. The circuit breaker outputs a strong tripping signal. If the contacts still do not break, it will not retry and will directly send a contactor stuck alarm to the DCS. The restart process records the following information: restart trigger time, power slump duration, total power outage duration, restart time of each batch, peak startup current of each device, number of anomalies and their handling results. The data is stored on the local SD card of the device. The DCS system can query historical data for the past year through the communication link and supports export in Excel format.

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