Water pump external back pressure type dead head protection control method

Abstract

The application discloses a kind of water pump external back pressure type dead head protection control methods, by establishing rotational speed starting threshold, rotational speed corresponding power threshold table or current threshold table, and install abnormal dead head determination rotational speed threshold table, in operation Actual rotational speed and actual average power or actual average current are monitored;When rotational speed is higher than threshold and power or current is lower than corresponding value, it is determined that dead head state is and executes breakthrough control, and the output capacity of water pump is improved by increasing current command.If actual rotational speed in the process does not exceed installation abnormal dead head determination rotational speed threshold, it is determined that external back pressure type dead head, and breakthrough control is continued until stable operation is restored.This method can avoid unnecessary shutdown and improve operation continuity.

Description

Technical Field

[0001] This invention relates to a water pump dead head protection control method, specifically a water pump external back pressure dead head protection control method for monitoring, judging and actively controlling the external back pressure dead head state.

[0002] This invention mainly monitors the operating parameters of the water pump, such as speed, power, or current. After detecting a dead-end state, it executes dead-end breakthrough control to improve the water pump's output capacity, overcome external high back pressure, and enable the water pump to quickly resume normal operation. It is applicable to various water pump control systems that require continuous operation. Background Technology

[0003] When a water pump is operating, if the outlet flow rate is zero or extremely low, it is prone to entering a so-called "dead-head" state. In this state, the pump impeller continues to rotate but cannot effectively output fluid, causing energy to be converted into heat. This can easily lead to pump overheating, damage to seals, accelerated wear of the shaft or bearings, and even system failure. Traditional dead-head protection technologies for water pumps mainly include the following categories.

[0004] Low power or low current detection protection: This method directly executes shutdown or speed reduction protection when the motor input power or current falls below a fixed threshold. For example, some motor management relays (such as the Eaton Power Xpert C445 series) employ low power protection to detect load drops caused by dead starts, thus preventing pump damage. While this method can detect dead start conditions, it generally does not further classify the causes of dead starts and often directly handles all dead start situations with a single protection action (shutdown or power limiting), which can easily lead to unnecessary shutdowns or untimely protection.

[0005] Flow or pressure sensor protection: A flow switch, pressure sensor, or temperature sensor is installed at the pump outlet. Protection is triggered when no flow, abnormal pressure, or pump overheating is detected. This method requires additional hardware installation, increasing system cost and complexity. It also has limited sensitivity to small flow changes and struggles to distinguish different types of dead-end states in real time and accurately.

[0006] Mechanical bypass or recirculation lines: A minimum flow recirculation line or automatic bypass valve is installed at the pump outlet to ensure that a small amount of fluid continues to circulate even when the outlet is blocked, thus preventing overheating caused by prolonged dead-end operation. While this design can alleviate some dead-end problems, it cannot actively overcome high external back pressure and has limited protection against severe installation abnormalities (such as complete outlet closure or severe pipe blockage). It also increases the complexity of pipe design and maintenance costs.

[0007] Simple speed-power ratio judgment: Some MCU or inverter control systems rely solely on a simple comparison of speed and current / power, directly stopping or reducing speed when an anomaly is detected. This method lacks multi-stage judgment and dynamic adjustment mechanisms, making it prone to frequent actions due to misjudgment, or causing accelerated wear of mechanical components (shafts, impellers, seals, etc.) due to protection delays.

[0008] However, the aforementioned existing technologies generally have the following drawbacks: they cannot effectively distinguish the causes of dead ends (caused by excessive external back pressure, or by abnormal installation / severe obstruction of the flow path); they lack an active breakthrough and recovery mechanism for dead ends caused by external back pressure, which can easily lead to frequent shutdowns and affect system availability; the protection actions are too simple or passive, making it difficult to avoid damage while ensuring continuous operation; long-term dead end operation can still easily lead to severe wear of mechanical components such as shafts, bearings and impellers, affecting the overall reliability and service life of the system.

[0009] In view of the fact that the existing technology cannot provide an effective active breakthrough mechanism for external back pressure dead head, the present invention provides a water pump external back pressure dead head protection control method. Through multi-dimensional monitoring and phased breakthrough control of speed and power or current, it can actively increase the output capacity to overcome the external back pressure after the external back pressure dead head is determined, so that the water pump can quickly resume normal operation and reduce unnecessary shutdowns. Summary of the Invention

[0010] In view of the above, the main objective of this invention is to provide a method for controlling the dead head protection of a water pump with external back pressure.

[0011] This invention provides a method for controlling the external back pressure type dead head protection of a water pump, comprising the following steps: pre-establishing a dead head protection start speed threshold, a power threshold table or current threshold table corresponding to the dead head detection speed, and a dead head judgment speed threshold table for installation abnormality; when the water pump is in operation, continuously monitoring the actual speed and actual average power or actual average current; when the actual speed is greater than the dead head protection start speed threshold and the actual average power is less than the power threshold corresponding to that speed, or the actual average current is less than the current threshold corresponding to that speed, the water pump is determined to have entered a dead head state; then, dead head breakthrough control is executed, increasing the current command to enhance the water pump's output capacity; during the breakthrough control process, if the actual speed does not exceed the preset dead head judgment speed threshold for installation abnormality, it is determined to be an external back pressure type dead head, and breakthrough control continues until the power or current reaches a stable range and normal operation resumes.

[0012] The power threshold table or current threshold table is pre-established or dynamically adjusted based on the power characteristics or current characteristics of the water pump at different speeds.

[0013] The current increase command is implemented in stages or gradually according to the degree of power or current deviation.

[0014] This also includes determining whether the breakthrough control was successful based on the upward trend or rate of change of power or current.

[0015] During the period of control failure, water pump temperature, vibration, or acoustic data are monitored simultaneously as auxiliary judgment criteria.

[0016] The dead-head protection start speed threshold, power threshold table or current threshold table, and the dead-head judgment speed threshold table for installation abnormality are dynamically set by the host computer or adaptively adjusted according to historical operating data.

[0017] The step of determining that the water pump has entered a dead-end state also includes a time accumulation condition, and the dead-end breakthrough control is only executed when the dead-end state continues for more than a preset time.

[0018] Once the breakthrough control is successful, the stable output is confirmed based on the pressure or flow-related derived data before the normal speed command is restored.

[0019] The method is executed by the MCU firmware and, combined with the state machine, initiates dead-head detection and overrun control only during operation.

[0020] It also includes: recording the speed, power or current, duration, current command change curve and breakthrough result of each dead-head breakthrough control event, for subsequent threshold optimization.

[0021] During the breakout control process, if the actual rotational speed exceeds the speed threshold for determining the abnormal dead head, the breakout control will stop and the system will switch to protection mode.

[0022] This invention uses a detection mechanism that combines speed and power or current as dual parameters, and a subsequent active dead-end breakthrough control, to accurately identify the dead-end state caused by excessive external back pressure, and actively increase the pump output capacity to overcome the external back pressure, rather than directly entering the protection shutdown.

[0023] Thus, the present invention can achieve at least the following effects: it can effectively overcome the dead head caused by external back pressure, enabling the water pump to quickly resume normal operation when faced with changes in external pressure, greatly reducing unnecessary shutdowns and improving the continuity of system operation; it avoids the problem of frequent shutdowns caused by misjudgment or overprotection in traditional protection methods; and it reduces the impact on the water pump mechanism by breaking through control in stages or gradually, while taking into account both protection and operational efficiency.

[0024] To enable those skilled in the art to understand the purpose, features and effects of the present invention, the present invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings. Attached Figure Description

[0025] Figure 1 This is a schematic flowchart of the external back pressure type dead head protection control method for water pumps according to the present invention.

[0026] Explanation of reference numerals in the attached drawings: S101~S111 - steps. Detailed Implementation

[0027] The above-mentioned objectives, processes, and functional characteristics of the present invention will be described with reference to the preferred embodiments shown in the accompanying drawings.

[0028] Please see Figure 1 The figure shows a flowchart of the water pump external back pressure type dead head protection control method of the present invention. As shown in the figure, the water pump external back pressure type dead head protection control method of the present invention is mainly executed by MCU firmware, and its specific implementation steps are as follows.

[0029] Step S101 is system initialization and parameter setting. It is mainly used to establish various thresholds and tables required for subsequent detection and control. Specific implementation methods include: pre-setting the dead-end protection start-up speed threshold based on the pump characteristic curve; establishing a power threshold table or current threshold table corresponding to the dead-end detection speed (which can be set in segments according to different speed ranges); setting a dead-end judgment speed threshold table for installation abnormalities to distinguish dead-end types later; and setting parameters such as the gradual rules for overrun control, the staged increase range, the maximum current command upper limit, and the time accumulation condition. These parameters can be dynamically set by the host computer through the communication interface, or adaptively adjusted by the MCU based on historical operating data.

[0030] Step S102 is the confirmation of the operating status. It mainly uses the state machine to determine whether the water pump is currently in the "operating state". Only when the state machine confirms that the pump is in the operating state will the subsequent dead-end detection process be started; otherwise, the state machine will continue to determine whether the pump is currently in the "operating state".

[0031] Step S103 involves continuously monitoring the actual operating parameters of the water pump. During this time, the MCU will continuously acquire and calculate the following monitoring data: actual rotational speed; actual average power or actual average current; and, if necessary, temperature, vibration, or acoustic data as supplementary information.

[0032] Step S104 involves the detection and determination of a dead-end state. The water pump is determined to have entered a dead-end state if the following conditions are met simultaneously and persist for a preset time: the actual pump speed is greater than the dead-end protection start-up speed threshold, and the actual average power is less than the power threshold corresponding to that speed, or the actual average current is less than the current threshold corresponding to that speed. This determination can be further combined with time accumulation conditions (e.g., persisting for more than a preset number of seconds) to improve accuracy. The subsequent dead-end breakout control process is only initiated when the water pump is determined to be in a dead-end state; otherwise, the actual operating parameters of the water pump are continuously monitored.

[0033] Step S105 is to execute dead-end breakout control. After entering the dead-end state, dead-end breakout control is executed immediately. Specific implementation methods include: increasing the current command in stages (e.g., increasing it by 10% first, observing the power or current change, and then continuing to increase it); gradually increasing the current command until the power or current reaches the preset target value; and simultaneously monitoring the rate of change and upward trend of power or current as the basis for adjusting the current command.

[0034] Steps S106 and S107 respectively monitor the rotational speed and distinguish the type during the breakthrough process. While increasing the current command, the actual rotational speed is continuously monitored: if the actual rotational speed does not exceed the speed threshold for judging the abnormal installation dead head, it is judged as an external back pressure dead head, and the breakthrough control continues; if the rotational speed abnormally exceeds the speed threshold for judging the abnormal installation dead head, the subsequent process of switching to protection mode can be initiated (depending on system requirements), and at this time, the process directly proceeds to step S111.

[0035] Steps S108 and S109 are respectively for determining successful breakthrough and restoring normal operation. The determination of successful breakthrough control may specifically include: the power or current upward trend meeting preset conditions; the power, current, or speed reaching a stable range and maintaining it for a period of time; and pressure or flow data obtained through derived calculations showing that a stable output has been established, i.e., the power or current has reached a stable range. After confirming successful breakthrough, the normal speed command is gradually or directly restored, bringing the water pump back to normal operation mode.

[0036] Step S110 is event recording. This invention records the rotational speed, power or current, duration, current command change curve, and final breakthrough result for each dead-end breakthrough event, in order to facilitate subsequent threshold optimization or fault analysis.

[0037] This implementation method can effectively solve the problem of dead head caused by external back pressure by actively breaking through control, thereby reducing unnecessary downtime while maintaining the continuity of system operation.

[0038] In summary, the technical effects achieved by this invention through dual parameter detection of speed and power or current, dead-end breakout control, speed anomaly differentiation, and multiple auxiliary judgment mechanisms are as follows: It can accurately detect external back pressure type dead-end states and proactively enhance the pump's output capacity (output capacity may include output power, output pressure, or fluid output capacity) by gradually increasing the current command in stages, effectively overcoming high external back pressure, enabling the pump to quickly restore stable output and normal operation, significantly reducing unnecessary downtime and improving system continuity; during the breakout control process, by real-time monitoring of whether the actual speed exceeds the speed threshold for judging abnormal installation type dead-ends, it can accurately distinguish between external back pressure type and abnormal installation type dead-ends, avoiding misjudgment; it supports dynamic adjustment of dead-end protection start-up speed threshold, power threshold table, current threshold table, and breakout control. The parameters can be set by the host computer or adaptively optimized based on historical data, improving the adaptability and accuracy of detection and control. Combining multi-dimensional auxiliary judgments such as power or current change rate, upward trend, time accumulation conditions, temperature, vibration, or acoustic data effectively reduces the false alarm rate and improves the reliability of overshoot control. After successful overshoot control, the normal speed command can be restored only after confirming a stable state based on pressure or flow-related derived data, avoiding excessive impact or secondary anomalies. Each dead-end event is fully recorded (including speed, power or current, duration, overshoot process, and result), facilitating subsequent system optimization, fault analysis, and preventative maintenance. The overall solution is implemented by MCU firmware combined with a state machine, initiating detection and control only during operation, meeting the requirements of actual water pump control systems and exhibiting high feasibility and good compatibility. Therefore, this invention not only effectively solves the external back pressure type dead-end problem but also maintains high system availability while considering mechanism protection and control flexibility.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention; any equivalent changes or modifications made without departing from the spirit disclosed in the present invention should be included within the scope of the appended claims.

Claims

1. A method for controlling dead-head protection of a water pump with external back pressure, characterized in that, Includes the following steps: Pre-establish the dead head protection start speed threshold, the power threshold table or current threshold table corresponding to the dead head detection speed, and the speed threshold table for determining abnormal dead head installation. When the water pump is running, continuously monitor the actual speed, as well as the actual average power or actual average current. When the actual rotational speed is greater than the dead-head protection start-up speed threshold, and the actual average power is less than the power threshold corresponding to that speed, or the actual average current is less than the current threshold corresponding to that speed, the water pump is determined to enter a dead-head state. Execute dead-end breakout control to increase current command to enhance pump output capacity; as well as During the breakthrough control process, if the actual speed does not exceed the preset threshold for judging the abnormal installation dead head, it is judged as an external back pressure dead head, and breakthrough control continues until the power or current reaches a stable range and then normal operation is restored.

2. The method as described in claim 1, characterized in that, The power threshold table or current threshold table is pre-established or dynamically adjusted based on the power characteristics or current characteristics of the water pump at different speeds.

3. The method as described in claim 1, characterized in that, The current increase command is implemented in stages or gradually according to the degree of power or current deviation.

4. The method as described in claim 1, characterized in that, It also includes: determining whether the breakthrough control was successful based on the upward trend or rate of change of power or current.

5. The method as described in claim 1, characterized in that, During the period of control failure, water pump temperature, vibration, or acoustic data are monitored simultaneously as auxiliary judgment criteria.

6. The method as described in claim 1, characterized in that, The dead-head protection start speed threshold, power threshold table or current threshold table, and the dead-head judgment speed threshold table for installation abnormality are dynamically set by the host computer or adaptively adjusted based on historical operating data.

7. The method as described in claim 1, characterized in that, The step of determining that the water pump has entered a dead head state also includes a time accumulation condition, and the dead head breakthrough control is only executed if the dead head state continues for more than a preset time.

8. The method as described in claim 1, characterized in that, After successfully breaking through the control, confirm stable output based on pressure or flow-related data, and then resume normal speed command.

9. The method as described in claim 1, characterized in that, The method is executed by the MCU firmware, and the state machine is used to initiate dead head detection and overrun control only when the system is in operation.

10. The method as described in claim 1, characterized in that, It also includes: recording the speed, power or current, duration, current command change curve and breakthrough result of each dead-head breakthrough control event, for subsequent threshold optimization.

11. The method as described in claim 1, characterized in that, If the actual rotational speed exceeds the speed threshold for determining the abnormal dead head during the breakthrough control process, the breakthrough control will stop and the system will switch to protection mode.

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