Clean room FFU Shanghai Sujing

With the development of the economy and the improvement of people's living standards, people's requirements for product quality are getting higher and higher. The production technology and production environment determine the quality of the product, which forces manufacturers to pursue better production technology and higher production environment. Especially in the fields of electronics, pharmaceuticals, food, bioengineering, medical, laboratory, etc., it has strict requirements on the production environment. It integrates technology, construction, decoration, water supply and drainage, air purification, HVAC, air conditioning, automatic control and so on. Technology. The main technical indicators to measure the quality of the production environment in these industries are temperature, humidity, cleanliness, air volume, and indoor positive pressure. Therefore, reasonable control of various technical indicators of the production environment to meet the requirements of special production processes has become one of the research hotspots of clean engineering. As a purification equipment, FFU is widely used in various clean engineering projects. FFU's full name is Fan Filter Unit "fan filter unit", which is a clean device that connects the fan and filter together and can provide power by itself. As early as the 1960s, the world's first laminar clean room The establishment of the FFU has begun to appear.

2. Current status of FFU control methods

At present, FFU generally adopts single-phase multi-speed AC motor, three-phase multi-speed AC motor and DC motor. The supply voltage of the motor is roughly 110V, 220V, 270V, 380V. The control methods are mainly divided into the following types:

◆ Multi-speed switch control

◆ Continuous speed adjustment control

◆ Computer control

◆ Remote control

The following is a simple analysis and comparison of the above four control methods:

2.1 multi-speed switch control

The multi-speed switch control system only includes one speed switch and one power switch that are included in the FFU. Since the control elements are self-contained by the FFU and distributed in various positions in the ceiling of the clean room, the staff must adjust the FFU through the shift switch at the site, which is extremely inconvenient to control, and the wind speed of the FFU can be adjusted in a limited range, limited to several files. . We have done a project. In order to overcome the inconvenient factors of FFU control operation, through the design of the electric circuit, all the FFU multi-speed switches are collected and placed in a cabinet on the ground to achieve centralized operation, but no matter from the appearance There are still functional limitations. The advantages of using multiple-speed switch control methods are simple control and low cost, but there are many defects: for example, high energy consumption, smooth speed regulation, no feedback signal, and inability to achieve flexible group control.

2.2 continuous speed adjustment control

Compared with the multi-speed switch control mode, the continuous speed adjustment control has a continuous speed regulator, which makes the FFU fan speed continuously adjustable, but at the same time sacrifices the motor efficiency, making its energy consumption higher than the multi-speed switch control mode. .

2.3 computer control

The computer control method generally adopts a DC motor. Compared with the previous two methods, the computer control mode has the following advanced functions:

◆ Adopting distributed control mode, it can easily realize centralized monitoring and control of FFU.

◆ It is convenient to realize single, multiple and partition control of FFU.

◆ Intelligent control system has energy saving function.

◆ Optional remote control for monitoring and control.

◆ The control system reserves communication interface, which can communicate with the host computer or network to realize remote communication and management functions.

The outstanding advantages of controlling DC motors are: easy control and wide speed range. But this control method also has some fatal flaws:

◆ Since the clean factory does not allow the FFU motor to have a brush, the FFU motor uses a brushless DC motor, the commutation problem is solved by the electronic phase changer, and the short life of the electronic phase changer makes the whole control system use. Life expectancy is also greatly reduced.

◆ The entire system is expensive.

◆ High maintenance costs in the later period.

2.4 remote control mode

The remote control mode is a supplement to the computer control mode. Each FFU can be controlled by the remote control, which is complementary to the computer control mode. In summary, the first two control methods have high energy consumption and inconvenient control; the latter two control methods have short life and high cost. Is there a control method that can achieve low energy consumption, convenient control, and can guarantee the service life and low cost? Yes, that is, the computer control method using AC motor. Compared with DC motors, AC motors have a series of advantages such as simple structure, small size, convenient manufacturing, operation, and low price. Because they do not have commutation problems, their service life far exceeds that of DC motors. For a long time, due to its poor speed regulation performance, the speed regulation mode has been occupied by the DC speed regulation mode. However, with the emergence and development of new power electronic devices and large-scale integrated circuits, as well as the emergence and application of new control theories, the AC control method has gradually developed and will eventually replace the DC speed control system.

In the FFU AC control mode, it is mainly divided into two control modes: voltage regulation control mode and frequency conversion control mode. The so-called voltage regulation method is to adjust the motor speed by directly changing the magnitude of the motor stator voltage. The disadvantages of the voltage regulation method are: the efficiency at the time of speed regulation is low, and at low speed, the motor has a serious heat generation and a narrow speed regulation range. However, the pressure regulation method is not obvious for the FFU fan load, and there are some advantages in the current situation:

◆ The speed control scheme is mature, the speed control system is stable, and it can guarantee continuous operation without failure for a long time.

◆ Easy to operate, low cost of control system.

◆ Because the FFU fan load is very light, at low speed, the motor heat is not very serious.

◆ The pressure regulation mode is especially suitable for the fan load. Since the FFU fan is responsible for the unique damping curve, the speed adjustment range can be made very wide.