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In industrial production and daily applications, equipment such as pumps must operate continuously to ensure a stable water supply or other processes. However, dry-run conditions—where equipment operates without a medium—can lead to seal damage. Therefore, implementing dry-run protection is essential. With VFDs, the following three methods are commonly used to achieve this:
Inlet Pressure Sensor Monitoring
Installing a pressure sensor at the inlet of the equipment enables real-time monitoring of pipeline pressure. If the inlet pressure falls below a preset safety threshold, it usually indicates a lack of water, prompting the VFD to receive the sensor signal and trigger the protection mechanism to automatically shut down the equipment. This method is suitable for scenarios requiring precise pressure control, such as large-scale water supply systems or industrial processes with strict pressure requirements.
Float Switch Control
A float switch is a simple and reliable liquid level detection device that can be installed in reservoirs, sumps, or other liquid containers. When the liquid level drops below the preset minimum safety line, the float switch triggers and sends a signal to the VFD to stop the equipment. This method is cost-effective, easy to install and maintain, and is suitable for small to medium-sized water supply systems or scenarios with significant water level fluctuations.
Low-Current Protection
VFDs have built-in current monitoring functions that allow real-time detection of motor operating current. When the equipment runs in a dry-run state, the motor load decreases, causing the operating current to drop significantly below the normal working range. By setting a lower current limit, the VFD stops the equipment immediately when the current falls below the threshold. This method requires no additional hardware and is suitable for budget-sensitive projects or applications where operating conditions vary.
Conclusion:
These three dry-run protection methods each have distinct advantages. Inlet pressure sensor monitoring is ideal for conditions requiring precise control; float switches are simple to use and effective for scenarios with noticeable liquid level changes; and low-current protection offers a cost-effective solution without additional hardware. Users should select the appropriate protection method based on specific application needs and budget considerations to ensure safe operation, extend equipment lifespan, and reduce overall operational risks and maintenance costs.