Sensorless Electronic Pressure Limiting for Electric Pumps
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Solution Overview
Problem
Mechanical high pressure bypass valves in fluid pumping systems are difficult to tune, prone to oscillation and wear, leading to pressure fluctuations, and are costly, necessitating oversized systems to manage varying back pressure and flow demands.
Innovation Solution
An electric pump pressure sensorless electronic pressure limiting and flow leveling system using a microprocessor-controlled variable speed motor with multi-mode control processes, including base current control, pressure limiting current control, and flow leveling current control, which utilizes low-cost transducer measurements to limit maximum pressure without a mechanical bypass valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical high pressure bypass valve is used to protect against over pressurization, then system safety is improved, but the valve is prone to oscillation and wear leading to pressure fluctuations and reduced reliability
Solution Approach 1:
The patent replaces the mechanical high pressure bypass valve with an electronic pressure limiting system that uses a microprocessor to monitor pump current and dynamically adjust motor speed. This substitution eliminates the mechanical components (ball bearing, spring, adjustable seat) that cause oscillation and wear, thereby removing the source of pressure fluctuations while maintaining overpressurization protection.
Solution Approach 2:
The system continuously monitors pump current as an indicator of back pressure and uses this feedback to dynamically adjust motor speed through the microprocessor. This closed-loop feedback mechanism prevents pressure from reaching dangerous levels in the first place, eliminating the need for mechanical relief valves and their associated oscillation problems.
2Reliability
If a mechanical high pressure bypass valve is used for pressure regulation, then over pressurization protection is achieved, but the valve is difficult to tune and requires frequent maintenance
Solution Approach 1:
The mechanical bypass valve requiring manual tuning of spring pressure and ball bearing positioning is replaced with an electronic system where the microprocessor automatically adjusts motor speed based on real-time current measurements. This eliminates the complex mechanical tuning process entirely, as the electronic control adapts automatically to system conditions.
Solution Approach 2:
The electronic pressure limiting system is self-regulating, using the microprocessor to continuously monitor pump current and automatically adjust motor speed without requiring manual intervention or tuning. The system adapts to changing conditions autonomously, eliminating the maintenance and tuning requirements of mechanical valves.
3Reliability
If the system is oversized to accommodate maximum back pressure and flow demand, then system safety and performance are ensured, but system cost increases significantly
Solution Approach 1:
The patent employs dynamic motor speed control that adjusts pump output in real-time based on actual system demand and back pressure conditions. This dynamic operation allows the use of a smaller, more cost-effective pump and associated components, as the system only provides maximum capacity when actually needed rather than continuously operating at oversized capacity.
Solution Approach 2:
The system changes the operating parameters (motor speed, pump flow rate) dynamically based on system conditions. This allows the pump system to operate efficiently across a range of conditions with appropriately sized components, rather than requiring oversized components to handle peak conditions continuously, thereby reducing overall system cost.
4Device complexity
If constant speed pumps are used to meet maximum flow demand, then system simplicity is maintained, but volumetric efficiency varies with back pressure causing flow inconsistency
Solution Approach 1:
The patent transitions from constant speed operation to dynamic variable speed control, where the microprocessor continuously adjusts motor speed based on pump current measurements. This dynamic adjustment compensates for volumetric efficiency variations caused by back pressure changes, maintaining consistent flow delivery without requiring complex mechanical valve systems.
Solution Approach 2:
The system uses pump current as a feedback signal to detect back pressure conditions and automatically adjusts motor speed to maintain desired flow characteristics. This electronic feedback loop provides flow consistency that cannot be achieved with simple constant speed pumps, while avoiding the complexity of mechanical flow control valves.
Data Source
AI summary
A pressure sensorless electronic pressure limiting and flow leveling system for an electric pump comprising a multi-mode control process for transferring fluid through a filter feeding a source consuming the fluid as the filter becomes clogged. The multi-mode control process comprising a closed loop current control mode, a pressure limiting control mode for controlling the speed of the motor as a function of a pre-calibrated profile correlating measured motor speed and voltage parameters to a predetermined value in the pre-calibrated profile utilized to set the speed of the motor driving the pump for pumping pressurized fluid through a clogging filter; and a flow leveling control mode correlating measured motor current to a predetermined value in a pre-calibrated profile utilized to set the speed of the motor driving the pump for pumping pressurized fluid as a function of clogging of the filter.