Servomotor Pump Controller for Wide Turndown and GFCI Compatibility
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Solution Overview
Problem
Industrial pumps, particularly positive displacement pumps, face limitations in achieving high turndown ratios and precise operational control, especially when using variable frequency drives that fail at low frequencies and lack compatibility with ground-fault circuit interrupters, constraining their operating range and safety.
Innovation Solution
A pump controller assembly utilizing a servomotor with a bracket, enclosure, and a human machine interface, which includes a controller configured to control the servomotor via pulse signals and receive commands, enabling a turndown ratio of 128,000:1 and precise flow rate accuracy of 0.001%, eliminating the need for variable frequency drives and allowing GFCI compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If variable frequency drives are used to control motor speed, then operational control is improved, but the system cannot operate at low frequencies below 4 Hz and loses GFCI compatibility
Solution Approach 1:
The patent replaces the variable frequency drive (electronic control system) with a servomotor that uses pulse-width modulation (PWM) control. This substitution enables the motor to operate effectively at very low frequencies (down to 0.001 Hz) while maintaining precise control, thereby expanding the operating range and restoring GFCI compatibility.
Solution Approach 2:
The patent changes the control parameter from frequency modulation (4-120 Hz range) to pulse-width modulation with variable pulse widths. This parameter change allows the servomotor to achieve precise speed control across an extended frequency range starting from 0.001 Hz, overcoming the limitations of traditional variable frequency drives.
2Adaptability or versatility
If gearboxes are used to convert motor operational range, then pump operational range is improved, but the overall operating range is constrained and output pressure is limited
Solution Approach 1:
The patent employs a dynamically controllable servomotor with variable speed capability across an extremely wide range (128,000:1 turndown ratio). This dynamic control allows the motor to adapt its speed to match different pump requirements without needing fixed gearboxes, thereby maintaining both wide operating range and high output pressure capability simultaneously.
Solution Approach 2:
The patent changes the motor control approach from fixed-ratio mechanical transmission to variable-speed electronic control. By adjusting the PWM frequency and pulse width dynamically, the system can achieve any desired pump speed while maintaining optimal torque and pressure output, eliminating the trade-off between operating range and pressure.
3Ease of operation
If traditional variable frequency drives are used, then motor control is achieved, but leakage current to ground prevents GFCI circuit breaker operation
Solution Approach 1:
The patent replaces the variable frequency drive with a servomotor control system that does not generate leakage current to ground. The PWM-based control method eliminates the harmful leakage current effect, allowing the system to operate safely with GFCI circuit breakers while maintaining precise motor control capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a wide operating range, precise control, and enhanced safety by achieving a turndown ratio of 128,000:1 and 0.001% accuracy, surpassing conventional systems and enabling safer operation with GFCI compatibility.
Implementation Method 1
a controller configured to control the servomotor via a plurality of pulse signals
Implementation Method 2
a servomotor having a bracket; an enclosure assembly having a housing coupled to the bracket and communicatively coupled to the servomotor
Data Source
AI summary
Embodiments provided herein relate to a pump controller assembly for a positive displacement pump, the pump controller assembly including a servomotor, an enclosure assembly having a housing and communicatively coupled to the servomotor, the enclosure assembly including a controller, a power supply, a terminal block, and a plurality of field connectors, and a human machine interface positioned above the servomotor in a vertical direction, the human machine interface communicatively coupled to the enclosure assembly, the human machine interface including a housing and a display touch-screen interface positioned at least partially within the housing, wherein the controller is configured to control the servomotor via a plurality of pulse signals, and the controller is configured to receive commands from the human machine interface.