I. Overview
As people's living standards improve, their requirements for the quality of domestic water are also increasing. Variable frequency constant pressure water supply is gaining more and more recognition in the water supply industry due to its advantages such as environmental protection, energy saving and high water quality. The variable frequency constant pressure water supply system can maintain a constant pressure 24 hours a day and automatically start and stop the standby pump according to the pressure change to adjust the water supply and avoid the water hammer phenomenon in traditional water supply, which greatly improves the utilization rate and energy saving ratio of the equipment.
II. Composition and Working Principle of a One-to-One Constant Pressure Water Supply System
A single-unit constant pressure water supply system mainly consists of a pump unit, a remote pressure gauge, and a frequency converter. The pressure sensor converts the measured pressure signal into an electrical signal. In a variable frequency water supply system, the pressure sensor is typically voltage-type or current-type. The pump unit integrates the motor and pump, controlling the water flow and pressure by adjusting the motor's speed; it is the actuator of the constant pressure water supply system. The variable frequency constant pressure water supply system uses a single pressure sensor (feedback of 4~20mA or 0-10V) to detect the pressure in the pipe network. The pressure sensor sends the signal to the frequency converter's PID loop. After processing, the PID loop sends out a signal to increase or decrease the water flow, controlling the motor speed.
Water pump unit
III. Functions of a One-to-One Constant Pressure Water Supply System
The functions of a single-unit constant pressure water supply system include:
1. Maintain constant pressure 24 hours a day and automatically start the backup pump (sleep function) according to the pressure signal, steplessly adjust the pressure, and ensure good water supply quality;
2. Smooth start-up reduces the starting impact of the motor and water pump, increases the service life of the motor and water pump, and avoids the water hammer phenomenon in traditional water supply.
3. The variable frequency constant pressure water supply system should have complete protection functions and reliable operation, including undervoltage, overcurrent, overload, overheat, phase loss, and short circuit protection.
IV. Application of AC300 in One-to-One Constant Pressure Water Supply
To achieve constant pressure water supply, the PID function of the AC300 frequency converter can be used. Customers can set the pressure value (pressure percentage) and select the feedback signal source as needed. When using the sleep function, sleep-related parameters need to be set. The wiring for the resistive voltage-type pressure sensor is as follows:
Recommended parameters for a resistive voltage-type pressure sensor with sleep function are as follows:
Sleep parameter description:
1. F11.30 Sleep Frequency: If the output frequency is lower than the sleep frequency, it enters hibernation via F11.31.
2. F11.31 Sleep delay can be set by the customer.
3. F11.32 Wake-up Deviation: When the PID setpoint - wake-up deviation > PID feedback, sleep mode will be stopped, and the system will start after F11.33.
4. The wake-up delay of F11.33 can be set by the customer.
V. Summary
The AC300 general-purpose frequency converter, when used in a single-split constant pressure water supply system, offers a more optimized PID control algorithm and faster response compared to the AC70 frequency converter. Its more user-friendly sleep function is particularly noteworthy, with simpler parameter adjustments and easier implementation. It is also more reliable.
