Pump Controller Using Motor Current Sensing
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Solution Overview
Problem
Existing pump control systems rely heavily on mechanical pressure switches and sensors, which suffer from non-linearity, repetitive behavior, and susceptibility to electromagnetic interference, leading to inconsistent pressure control.
Innovation Solution
A method and apparatus that use motor current as a sensing parameter to control pump operation at a constant pressure without direct pressure sensing, employing a table of voltage and current characteristics calibrated for each pump, and a PID controller to provide correction terms based on sensed current and voltage signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical pressure switches or sensors are used to control pump operation, then pressure control is achieved, but non-linearity, repetitive behavior, and electromagnetic interference cause inconsistent pressure control
Solution Approach 1:
The patent replaces mechanical pressure switches and direct pressure sensing systems with an electronic control system that uses motor current sensing and V-I characteristic tracking. This substitution eliminates the harmful effects of mechanical switches (arcing, scorching, non-repetitive behavior) and electromagnetic interference affecting pressure sensors, while achieving consistent pressure control through electrical parameter monitoring.
Solution Approach 2:
The patent introduces motor current as an intermediary parameter to indirectly sense pump operating conditions and outlet pressure. Instead of directly measuring pressure with susceptible sensors, the system monitors motor current which correlates with pump load and outlet pressure, using this intermediate electrical signal to trigger control actions and maintain consistent pressure without direct mechanical or electrical pressure sensing.
2Reliability
If pressure switches are used to shut off the pump, then pressure control is achieved, but arcing and scorching occur between contacts during repeated opening and closing
Solution Approach 1:
The patent replaces the mechanical pressure switch system with an electronic control system using motor current sensing. The control module monitors motor current to detect pump on/off conditions and triggers electronic switching instead of mechanical contact opening/closing, completely eliminating arcing and scorching between contacts while maintaining reliable pressure control.
Solution Approach 2:
The system uses the motor's own current characteristics to signal its operational state and control needs. By monitoring motor current, the system can determine when the pump should start or stop without external mechanical switches, allowing the motor's electrical parameters to serve the dual purpose of both driving the pump and controlling its operation.
3Measurement precision
If direct pressure sensing is used, then pressure control is achieved, but dependency on pressure switches and sensors increases leading to non-linear behavior
Solution Approach 1:
The patent substitutes direct pressure sensing devices with motor current sensing. The control module measures motor current to infer pump operating conditions and outlet pressure, eliminating the need for mechanical pressure switches and electrical pressure sensors. This reduces device complexity and removes the non-linear behavior associated with these sensing components while maintaining measurement capability through electrical parameter correlation.
Data Source
AI summary
The present invention provides a technique using current sensing to control the pressure at constant level without the direct sensing of the pressure. This technique will help to reduce dependency solely on switch or sensor and their non linearity and other associated problems such as the non-repetitive behavior, being affected by EMI etc. The technique includes using a pump controller featuring one or more modules configured to respond to one or more input signals containing information about current provided from a pump; and configured to provide one or more output signals containing information to control the pump to operate at a substantially constant pressure without the direct sensing of pump pressure. The one or more modules control the operation of the pump based at least partly on a table of characteristics related to voltage and current that is calibrated for each pump.