Pump Frequency Converter Soft Start Using Pressure Feedback
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Solution Overview
Problem
Pump systems face challenges in controlling rotation speed during startup when pipes are empty or incompletely filled, leading to pressure peaks that can stress mechanical components and require costly and time-consuming experiments to determine suitable control parameters for different piping systems.
Innovation Solution
The rate of change of rotation speed is made dependent on the rate of change of measured liquid pressure, with adjustments made to ensure the rate of change is a descending function, reducing the risk of pressure peaks and allowing for universal control parameter values across different piping systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the pump runs at maximum speed during startup when pipes are empty, then the startup time is reduced, but pressure peaks occur when pipes get full of liquid
Solution Approach 1:
The control system dynamically adjusts the pump's rotation speed based on real-time pressure feedback. During startup, the system transitions from a static maximum speed operation to a dynamic speed control mode where the rotation speed is continuously modified according to the measured pressure, allowing the system to adapt to changing pipe fill conditions and avoid pressure peaks while maintaining reasonable startup time
Solution Approach 2:
A pressure sensor provides real-time feedback about the liquid pressure in the pipes to the control unit. This feedback mechanism allows the control system to detect when pressure is increasing and respond by reducing the pump's rotation speed, thereby preventing pressure peaks. The feedback loop creates a closed-control system that continuously monitors and adjusts operation to maintain safe pressure levels
2Object-affected harmful factors
If a maximum rate of change of rotation speed is limited, then pressure peaks are avoided, but the startup process becomes slow and requires system-specific parameter tuning
Solution Approach 1:
Instead of using a fixed, pre-determined maximum rate of change that requires system-specific tuning, the invention employs real-time pressure feedback to dynamically determine the appropriate rate of change of rotation speed. The control unit continuously monitors pressure and adjusts the rotation speed accordingly, eliminating the need for manual parameter optimization while maintaining both safety and efficiency
Solution Approach 2:
The control system is self-adjusting and does not require external tuning or experimentation for different piping systems. The pressure sensor and control unit work together to automatically determine the optimal rotation speed profile for any given system configuration, making the system universally applicable without requiring commissioning experiments or theoretical studies
3Reliability
If PI-control is used to regulate rotation speed according to pressure difference, then pressure control is achieved, but the system requires extensive experimentation to determine suitable control parameters for different piping systems
Solution Approach 1:
The control system automatically adapts to different piping systems without requiring manual parameter tuning. By using real-time pressure feedback and a control strategy that responds dynamically to actual system conditions, the system eliminates the need for extensive experimentation and parameter optimization that would otherwise be required for PI-control implementation
Solution Approach 2:
Instead of relying on fixed PI-controller parameters that require system-specific tuning, the invention changes the control approach to dynamically adjust the rotation speed based on the actual rate of change of pressure. This parameter-free approach allows the system to automatically adapt to different piping configurations without requiring complex parameter optimization
Data Source
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AI summary
The invention relates to a method and arrangement for soft start up of a pump system that comprises a pump (401) for generating a liquid flow, an electrical drive (402, 403, 404) disposed to actuate the pump, and a pressure sensor (408) disposed to measure a liquid pressure at a flow output of the pump. The objectives of the invention are achieved with a solution in which a rate of change of rotation speed of the pump during a start up phase is made to be dependent on a rate of change of measured liquid pressure in such a way that the rate of change of the rotation speed is a descending function of the rate of change of the measured liquid pressure.