Pump Sleep Mode Control Using Pressure-Based Demand Detection
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Solution Overview
Problem
Existing pumping systems continue to operate at low speeds during zero-demand conditions, leading to heat generation, wear, and unnecessary electricity consumption, and rely on expensive and susceptible flow meters for demand detection.
Innovation Solution
A method and system that uses a pressure sensor to control the motor frequency, entering a sleep mode when demand is zero or low, and waking up in response to pressure changes, utilizing a controller to manage the motor's frequency based on pressure thresholds and timers to maintain system pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pump operates continuously at low speed during zero-demand conditions, then the system maintains readiness to respond to demand, but heat generation, wear, and electricity consumption increase
Solution Approach 1:
The system dynamically transitions the pump between two operational states: active mode (maintaining system pressure) and sleep mode (stopped). The controller monitors system pressure and automatically starts the pump when pressure drops below a threshold and stops it when pressure reaches the target, creating a dynamic on-demand operation pattern that eliminates continuous low-speed operation and its associated energy waste
Solution Approach 2:
The system uses its own operational state (system pressure level) to control itself. The pressure sensor monitors the pressure generated by the pump's own operation, and the controller uses this feedback to automatically start or stop the pump without external intervention, making the system self-regulating and eliminating the need for continuous operation
2Reliability
If a flow meter is used to detect zero-demand condition, then demand detection is possible, but system cost increases and susceptibility to damage from contaminants increases
Solution Approach 1:
The system uses system pressure as an intermediary indicator to infer demand conditions. Instead of directly measuring flow (which requires a flow meter in the water path), the pressure sensor measures system pressure, which indirectly indicates whether water is being consumed. When pressure remains stable at the target level, it indicates zero demand; when pressure drops, it indicates active consumption. This intermediary approach keeps the sensing system isolated from water contaminants
Solution Approach 2:
The patent replaces the mechanical flow meter (which has moving parts and direct contact with water) with a pressure-based detection system using a pressure sensor and controller. This substitution eliminates the mechanical flow meter's vulnerability to contaminant damage while maintaining the ability to detect demand conditions through pressure changes
Data Source
AI summary
A method of controlling a motor in a liquid system is provided, comprising: controlling an operating frequency of the motor to cause a pump to maintain an actual pressure of liquid in the liquid system at or near a first pressure; determining whether a first timer has elapsed during the controlling step; responding to a determination that the first timer has elapsed by initiating a sleep mode determination, comprising: ramping the operating frequency to a low frequency; determining whether the actual pressure remains above a second pressure which is less than the first pressure for a second timer; and responding to the actual pressure remaining above the second pressure for the second timer by causing the motor to enter a sleep mode.