The variable frequency air pump is adjusted according to the frequency of the working load

The variable frequency air pump ADAPTS to the working load by adjusting the frequency. Its core lies in using a frequency converter to change the motor speed, thereby precisely controlling the output flow and pressure. The following are the specific adjustment methods and analyses:

First, the principle of variable frequency regulation

The relationship between rotational speed and frequency: The formula for the rotational speed of an asynchronous motor is n=60f(1 - s)/p, where n is the rotational speed, f is the power supply frequency, s is the slip rate, and p is the number of magnetic pole pairs. The frequency converter regulates the rotational speed by changing the power supply frequency f, thereby controlling the flow and pressure of the air pump.

The relationship between flow rate and rotational speed: The flow rate of an air pump is directly proportional to its rotational speed, and the pressure is directly proportional to the square of the rotational speed. Therefore, by adjusting the frequency to change the rotational speed, the flow rate can be linearly adjusted and the pressure can be nonlinearly adjusted.

Second, adjust the method according to the frequency of the load

PID control

Principle: By comparing the deviation between the set flow value (target flow) and the actual flow value, the output frequency of the frequency converter is adjusted to control the rotational speed of the pump. The proportion (P) term is used to respond to deviations quickly, the integral (I) term is used to eliminate steady-state errors, and the differential (D) term is used to predict the trend of deviation changes.

Setup steps:

Enable the PID control function in the frequency converter, set the parameter values corresponding to the target flow rate, and convert them into signal values that the frequency converter can recognize.

Configure the feedback signal, connect the output signal of the flow sensor to the feedback signal input port of the frequency converter, and set the type and range of the feedback signal.

Set the parameters of proportional gain (P), integral time (I) and differential time (D), and adjust these parameters according to the response of flow regulation to achieve the best control effect.

DCS system control

Principle: The DCS system collects signals from flow sensors and calculates the frequency that the frequency converter should output based on the pre-written control strategy. Then, it sends the control signal to the frequency converter to maintain a stable flow.

Implementation method: Configure the input signal channel of the flow sensor in the DCS system, write the control logic using the control algorithm function of the DCS, and send the calculated frequency adjustment signal of the frequency converter to the frequency converter.

Combined control of flow transmitters and frequency converters

Principle: The flow transmitter converts the flow signal into an electrical signal. The DCS or other controller monitors this signal and sends signals to the frequency converter to increase or decrease the frequency based on the upper and lower limit set values of the flow.

Implementation method: Calibrate in accordance with the instructions of the flow transmitter to ensure the accuracy of the linear relationship between the flow and the output signal. Set the upper and lower limit alarm values of the flow rate in the controller; Configure the connection between the output signal and the frequency converter, and achieve it through methods such as relay output or analog output.

Third, precautions during the adjustment process

Load change monitoring: Load changes can affect the frequency of the air pump frequency converter. It is necessary to monitor the load changes in real time and adjust the frequency promptly to ensure the performance of the air pump.

Parameter setting and optimization

V/F ratio: It needs to be adjusted according to the load characteristics to avoid difficulties in starting due to an overly large ratio.

Acceleration time: If the acceleration time is too short, it may trigger an overcurrent alarm. A reasonable value should be set according to the load inertia.

Maximum/minimum frequency: The upper and lower limits should be set according to the capacity of the equipment to avoid equipment damage or performance degradation caused by improper frequency setting.

Hardware and power supply stability

Power supply voltage: Voltage stabilizers and other equipment should be used to ensure voltage stability and avoid the impact of frequency fluctuations on the air pump.

Hardware fault troubleshooting: When the frequency adjustment is abnormal, it is necessary to check the status of hardware such as the transformer and the mainboard measurement components, and promptly eliminate the fault.