How Does a VFD Control Water Pumps for Constant Pressure Water Supply?

Hello! This is Esme from KUVO.I’ve seen firsthand how technology can transform ordinary processes into efficient, almost magical systems. And nothing exemplifies this transformation more than the use of frequency converters in water pump operations.

A Variable Frequency Drive (VFD) achieves constant pressure water supply in a pump system through precise speed control of the pump motor. It begins by continuously monitoring the water pressure in the system using pressure sensors. This real-time pressure data is fed back to the VFD. Based on the pressure readings, the VFD adjusts the pump’s motor speed to either increase or decrease the flow rate. If the pressure is lower than the desired set point, the VFD increases the motor speed, leading to a higher pump output, and vice versa. This dynamic adjustment ensures that the water pressure remains constant, despite varying demand. By controlling the motor speed, the VFD also enhances energy efficiency, as the pump operates only at the speed necessary to maintain the set pressure, avoiding unnecessary energy consumption.

So, how exactly does this work? Let’s dive into the intricate dance of technology and necessity, where precision meets practicality, ensuring that water flows at the right pressure, whenever and wherever it’s needed.

What Role Does a Frequency Converter Play in Water Pump Management?

A frequency converter adjusts the frequency and voltage supplied to an electric motor, which is key in managing the operation of a water pump. This is critical because water demand varies throughout the day and across different settings. Imagine, for a moment, the chaos of a water system that couldn’t adapt to these changes.

The pressurization pump station in the water supply system generally adopts a multi-pump parallel water supply method. In the past, the number of pumps put into operation was controlled manually to keep the outlet pressure within an allowable range. This control method results in unstable water pressure, making it difficult to meet water usage requirements. Additionally, excessively high water pressure during light load conditions can lead to energy wastage.

How Does This Technology Ensure Constant Pressure?

The beauty of a VFD lies in its ability to provide what we call ‘constant pressure water supply’. This simply means that no matter how many people are using water at any given time, the pressure remains steady. It’s like ensuring every tap in a large building has the same strong flow, whether two or twenty are in use.

To achieve this,here are three methods:

Using the PI Controller Built into the Variable Frequency Drive

In modern pump systems, Variable Frequency Drives (VFDs) typically incorporate PI or PID controllers for closed-loop control of constant pressure water supply. This system works by feeding the water pressure feedback signal (such as the outlet water pressure measured by a pressure transmitter at the pump station) into the VFD.

This enables the VFD to adjust its output frequency in real-time, maintaining stable water pressure and minimizing pressure deviations. Additionally, a PLC (Programmable Logic Controller) primarily manages the number of pumps in operation based on the outlet pressure. It controls the start and stop of the VFD using digital signals, making coarse adjustments to the total water supply of the pump station.

Implementing Constant Pressure Automatic Control with PLC

In the implementation of a constant pressure automatic control system using a PLC (Programmable Logic Controller), the PLC serves as the core of the closed-loop controller. It requires an analog input module (such as an A/D converter) to receive pressure signals, and an analog output module (such as a D/A converter) to provide frequency setting signals to the Variable Frequency Drive (VFD). Although this configuration increases hardware investment, it effectively integrates analog closed-loop control with digital logic control.

Utilizing pressure feedback signals, the PLC can control the engagement and disengagement of mains-frequency pumps, and these signals can also be used for system monitoring and alarms.

Engaging and Disengaging the Water Pumps

In a multi-pump parallel water supply system, the PLC can flexibly choose any motor to operate in a variable frequency mode, while the other motors are driven by mains-frequency power. The system dynamically adjusts the number of mains-frequency operating pumps based on the actual water supply and the outlet water pressure of the pump station, allowing for coarse regulation of water supply volume and pressure.

When the water demand is less than the flow capacity of a single pump, a variable frequency pump will automatically adjust its speed to supply water. As water demand increases, the speed of the variable frequency pump automatically increases due to closed-loop control to maintain constant pressure. If the variable frequency pump reaches mains-frequency speed and the outlet pressure still does not meet the set value, the system will start a mains-frequency pump and gradually increase the number as needed.

Conversely, when water demand decreases, the frequency of the variable frequency pump automatically reduces. If the pipeline pressure remains above the set value after reducing to the set frequency, the mains-frequency pumps are sequentially disengaged until the pipeline pressure stabilizes at the set value.

What Are the Advantages of Using Frequency Converters for Constant Pressure Water Supply?

The introduction of frequency converters in water supply systems has brought about a sea change in how we manage water pressure. Here are some of the most notable benefits:

• Solving Low Water Pressure Issues: By using constant pressure frequency conversion water supply equipment, the water pressure throughout a building is maintained at a constant level. This is a significant advancement, especially in multi-story buildings where water pressure can be a persistent issue.
• Avoiding Water Pollution from Rooftop Tanks: Traditional water supply systems often rely on rooftop tanks, which can lead to water contamination. With frequency converters, this risk is mitigated, ensuring cleaner and safer water for users.
• Reducing Construction Costs and Increasing Space: The simplicity and efficiency of these systems mean that they occupy less space and are less complex to install, leading to reduced construction costs and more space for other uses.
• Energy Savings: Compared to conventional water supply equipment, systems with frequency converters can save over 30% in energy consumption. This is not just cost-effective but also aligns with global efforts towards energy conservation and sustainability.

What Are the Key Applications of Variable Frequency Constant Pressure Water Supply?

The variable frequency constant pressure water supply finds its application in various sectors, playing a crucial role in modern infrastructure:

• Residential Water Supply: High-rise buildings, residential complexes, and villas benefit significantly from this technology.
• Public Places: Hospitals, schools, sports complexes, golf courses, and airports are examples where this system is essential.
• Commercial Buildings: Hotels, office buildings, department stores, and large-scale sauna baths utilize this technology for efficient water management.
• Irrigation: Parks, playgrounds, orchards, and farms leverage this system for effective water distribution.
• Manufacturing Industry: Production manufacturing, washing units, food industry, and factories also rely on this technology for their water supply needs.

What Are the Operating Conditions for Variable Frequency Constant Pressure Water Supply in Pumps?

For the optimal functioning of these systems, certain conditions are necessary:

• Transmission Medium: The system is designed for cold, hot, clean, non-flammable, and non-explosive liquids without solid particles or fibers.
• Liquid Temperature: Standard models operate from -15°C to +70°C, and hot water models from +70°C to +120°C.
• Surrounding Environment: The ideal environment is free from water droplets, steam, floating dust, metal particles, and direct sunlight. Places with high temperatures or severe dust accumulation, corrosive, flammable gases, and liquids are unsuitable.
• Vibration-Free and Maintenance-Friendly Locations: The system should be installed in places without vibrations and where maintenance and inspections can be conducted easily.
• Environmental Temperature: The ideal operating temperature is up to +45°C with good ventilation.
• Connection and Configuration Control: Ensuring proper connections and configuration control is vital for the system’s efficient operation.

In conclusion, the adoption of frequency converters in water pump systems for constant pressure water supply represents a significant leap in technology. It not only solves practical problems but also contributes to energy efficiency and environmental sustainability. At KUVO VFD, we’re proud to be at the forefront of this revolution, continuously striving to bring innovative solutions to our clients worldwide.