Run Dry Protection – induction motor pumps
Run Dry Protection: At Parts-Ring, we are developing a pool, irrigation, and borehole run-dry protection system for integration with our Solar Battery Runtime Saving circuit (SBRS). The core of our approach is a non-invasive phase shift detection circuit, which leverages the characteristic current lag in induction motors to detect cavitation events. Cavitation, often resulting from insufficient water flow, can cause severe internal damage to pumps due to inadequate cooling. In extreme cases, this leads to pump seizure, with the motor only shutting down when the stator’s thermal cut-out is triggered. Our current design is optimised for single-phase pumps, which are widely used and represent a significant investment for property owners. To illustrate the importance of this technology, consider a scenario where a homeowner leaves their pool pump running during a vacation without monitoring the water levels. If the water dips too low, the pump could run dry, leading to costly repairs. Therefore, our system aims to provide peace of mind and protect investments.
Importance of Run Dry Protection
Cavitation is most likely to occur when pumps are left unattended, such as during holidays when pool pumps may be left in recirculation mode. Low water levels or obstructions in the suction line can exacerbate this risk. We recommend the use of a pressure relief or regulator valve, especially when employing automatic pool cleaners, to prevent the pump from running dry. For example, installing a regulator valve can help maintain a consistent water flow, ensuring optimal operation of the pump and preventing damage.
Our technical review found that most existing solutions are analogue circuits, particularly prevalent in India, with limited digital alternatives for single-phase applications. While there is a patent for a digital controller for polyphase motors, we found no suitable digital solutions for single-phase pumps. This gap in the market highlights the need for innovative solutions like ours.
The typical analogue circuit configuration involves a voltage sensor (using a 240V to 12V transformer) and a current sensor (such as a coil loop or current transformer placed over the live or neutral conductor). The outputs are generally configured as zero-voltage switches, which then feed either a logic gate (e.g., XOR) or the A1 and A2 inputs of a microcontroller such as an Arduino Nano. The microcontroller calculates the phase shift between voltage and current, which is indicative of pump load conditions and can be used to detect cavitation or dry-run scenarios. We plan to provide further technical details and performance data once our prototype has been constructed and tested. This data will be crucial for demonstrating the effectiveness of our solution and its advantages over existing systems.
During our research, we identified a local manufacturer, Rhomberg, which produces the MP-820 (for single-phase pumps) and MP-830 (for three-phase pumps). Despite attempts to establish contact, we have not received a response. For international customers interested in acquiring such protection devices, please contact us at ad***@********ng.com. We will share updates on our SBRS-integrated solution in a forthcoming article. We also encourage readers to share their experiences and feedback, as community input is invaluable for refining our product.
Further Reading:
United States Patent Application Publication Pub. No.: US 2007/0017284 A1
by Vinodkumar Sadasivam
also, patents by the above.
A Review of Pump Cavitation Fault Detection Methods Based on Different Signals
by Xiaohui Liu, Jiegang Mou, Xin Xu, Zhi Qiu and Buyu Dong
Hackaday contributor Luc Brun – Monitor the phase shift between current and voltage to stop a pump when there is not enough water.
For those interested in understanding more about the technical aspects of pump operation and maintenance, we recommend resources that delve deeper into induction motors and their applications. Books and online courses focusing on electrical engineering can provide foundational knowledge that complements our innovative solutions.