Introduce: How does the magnetic suspension blower control the air output of the fan?

The core of controlling the air output of magnetic suspension blower is the combination of frequency conversion speed regulation+inlet guide vane/valve+reflux venting, and the high-speed frequency conversion of magnetic suspension bearing is given priority to realize accurate and efficient air adjustment.

The following is clear from three aspects: principle, control mode and system logic:

First, the core principle: the relationship between air volume and speed.

Magnetic suspension blower is a centrifugal blower, which follows the basic law of centrifugal blower:

air quantity

Q∝n

(rotational speed)

wind pressure

P∝n

2

power

N∝n

three

Simply put: the higher the speed, the greater the air volume; Magnetic bearing supports ultra-high speed and stable operation at 20000-50000 rpm, without mechanical friction, and has a very wide speed regulation range (usually 20%–100% rated speed), which is the basis for its accurate air volume control.

Second, three mainstream air volume control methods (by priority)

1. Variable frequency speed regulation (most commonly used and most efficient)

Control logic: according to the feedback of outlet pressure/flow, PLC adjusts the output frequency of frequency converter of magnetic suspension motor and directly changes the speed.

Advantages: the energy saving is the strongest (the power decreases obviously when the air volume is low), the adjustment accuracy is high (1% fs), the response is fast (in seconds), and there is no extra pressure loss.

Applicability: More than 80% working conditions, especially scenes that need continuous and stable air volume (such as sewage aeration and chemical transportation).

2. Inlet guide vane adjustment (auxiliary/large flow fine adjustment)

Control logic: Install adjustable guide vanes at the inlet of the fan, and change the guide vane angle (0–90) through the servo motor to change the intake direction and resistance, thus adjusting the air volume.

Advantages: wider speed regulation range (down to 10% rated air volume), slightly better efficiency than pure frequency conversion at high load, and quick air intake cut-off (anti-surge).

Disadvantages: there is extra pressure loss at low air volume, and the energy saving is not as good as pure frequency conversion.

Application: Large flow, high pressure ratio, or scenes that need rapid anti-surge, often used in conjunction with frequency conversion.

3. Outlet reflux/vent valve (safety cover+extreme working condition)

Control logic: install a backflow valve (bypass) or a vent valve in the outlet pipeline. When the required air volume of the system is less than the minimum stable air volume (anti-surge lower limit) of the fan, open the valve to allow part of the gas to backflow to the inlet or directly vent, so as to ensure that the fan runs in a safe interval.

Advantages: prevent surge (low air volume of centrifugal fan is easy to cause airflow oscillation and damage equipment) and protect the stable operation of the fan.

Disadvantages: Waste of energy (power is wasted by the backflow/venting gas).

Application: safety protection under low load, start/stop and sudden change of working conditions, not for normal regulation.

Three, complete control system logic (automatic closed loop)

The air volume control of a typical magnetic levitation blower is a closed-loop system of PLC+sensor+actuator, and the process is as follows:

Target setting: Set the target air volume (m³/min) or outlet pressure (kPa) on the touch screen/central control.

Real-time detection: the sensor collects signals such as outlet flow, pressure, speed, temperature and vibration, and feeds them back to PLC.

Operation adjustment: PLC compares "set value" and "feedback value" and calculates by PID algorithm:

Normal working condition: adjust the frequency of inverter first → change the speed → control the air volume.

Low air volume approaches the surge line: first turn down the inlet guide vane and open the reflux valve if necessary.

Excessive high air volume: reduce the speed or open the inlet guide vane.

Execution action: frequency converter, inlet guide vane servo motor and return valve act according to PLC instructions to correct the air volume in real time until it is stable at the target value.

Four, the key features (compared with the traditional fan)

Wide adjustment range: 20%–100% of the rated air volume (as low as 10% with guide vanes), and the traditional roots blower can only be adjusted "on/off" or in a small range.

Remarkable energy saving: at low air volume, the power ≈ rotational speed decreases, saving 30%–50% energy compared with traditional fans.

High precision and fast response: PID closed-loop control, air volume fluctuation * * 1%, response time < 5 seconds * *.

No mechanical loss: the magnetic suspension bearing has no contact and friction, and it does not need to replace the bearing for a long time, so the maintenance is simple.

V. Examples of common application scenarios

Aeration of sewage treatment: automatically adjust the air volume according to the concentration of dissolved oxygen (DO), with high DO decreasing the speed and decreasing the wind, and low DO increasing the speed and increasing the wind.

Chemical gas transportation: according to the closed-loop control of pressure/flow of the reaction kettle, the stable gas supply is ensured.

Cement/electric power desulfurization: adjust the air volume according to the SO concentration of flue gas to match the desulfurization demand.

Summary: Magnetic levitation blower takes frequency conversion speed regulation as the core, inlet guide vanes as the auxiliary, backflow venting as the safety bottom, and realizes wide-range, high-precision and high-efficiency air output adjustment through automatic closed-loop control system, which is the first choice for modern industrial energy-saving air supply.