FFU fan filter unit is a necessary equipment for clean room projects.It is also an indispensable air supply filter unit for dust free clean room. It is also required for ultra-clean work benches and clean booth.
With the development of the economy and the improvement of people's living standards, people have higher and higher requirements for product quality. FFU determines product quality based on production technology and production environment, which forces manufacturers to pursue better production technology.
The fields that use FFU fan filter units, especially electronics, pharmaceuticals, food, bioengineering, medical, and laboratories, have strict requirements for the production environment. It integrates technology, construction, decoration, water supply and drainage, air purification, HVAC and air conditioning, automatic control and other various technologies. The main technical indicators to measure the quality of the production environment in these industries include temperature, humidity, cleanliness, air volume, indoor positive pressure, etc.
Therefore, reasonable control of various technical indicators of the production environment to meet the requirements of special production processes has become one of the current research hotspots in clean room engineering. As early as the 1960s, the world's first laminar flow clean room was developed. Applications of FFU have begun to appear since its establishment.
1. Current status of FFU control method
At present, FFU generally uses single-phase multi-speed AC motors, single-phase multi-speed EC motors. There are roughly 2 power supply voltages for FFU fan filter unit motor: 110V and 220V.
Its control methods are mainly divided into the following categories:
(1). Multi-speed switch control
(2). Stepless speed adjustment control
(3). Computer control
(4). Remote control
The following is a simple analysis and comparison of the above four control methods:
2. FFU multi-speed switch control
The multi-speed switch control system only includes a speed control switch and a power switch that come with the FFU. Since the control components are provided by the FFU and are distributed in various locations on the ceiling of the clean room, the staff must adjust the FFU through the shift switch on site, which is extremely inconvenient to control. Moreover, the adjustable range of the wind speed of the FFU is limited to a few levels. In order to overcome the inconvenient factors of FFU control operation, through the design of electrical circuits, all multi-speed switches of FFU were centralized and placed in a cabinet on the ground to achieve centralized operation. However, no matter from the appearance Or there are limitations in functionality. The advantages of using the multi-speed switch control method are simple control and low cost, but there are many shortcomings: such as high energy consumption, inability to adjust speed smoothly, no feedback signal, and inability to achieve flexible group control, etc.
3. Stepless speed adjustment control
Compared with the multi-speed switch control method, the stepless speed adjustment control has an additional stepless speed regulator, which makes FFU fan speed continuously adjustable, but it also sacrifices the motor efficiency, making its energy consumption higher than the multi-speed switch control method.
- Computer control
The computer control method generally uses a EC motor. Compared with the previous two methods, the computer control method has the following advanced functions:
(1). Using distributed control mode, centralized monitoring and control of FFU can be easily realized.
(2). Single unit, multiple units and partition control of FFU can be easily realized.
(3). The intelligent control system has energy-saving functions.
(4). Optional remote control can be used for monitoring and control.
(5). The control system has a reserved communication interface that can communicate with the host computer or network to achieve remote communication and management functions. The outstanding advantages of controlling EC motors are: easy control and wide speed range. But this control method also has some fatal flaws:
(6). Since FFU motors are not allowed to have brushes in clean room, all FFU motors use brushless EC motors, and the commutation problem is solved by electronic commutators. The short life of electronic commutators makes the entire control system service life greatly reduced.
(7). The entire system is expensive.
(8). The later maintenance cost is high.
5. Remote control method
As a supplement to the computer control method, the remote control method can be used to control each FFU, which complements the computer control method.
To sum up: the first two control methods have high energy consumption and are inconvenient to control; the latter two control methods have short lifespan and high cost. Is there a control method that can achieve low energy consumption, convenient control, guaranteed service life, and low cost? Yes, that is the computer control method using AC motor.
Compared with EC motors, AC motors have a series of advantages such as simple structure, small size, convenient manufacturing, reliable operation, and low price. Since they do not have commutation problems, their service life is far longer than that of EC motors. For a long time, due to its poor speed regulation performance, the speed regulation method has been occupied by EC speed regulation method. However, with the emergence and development of new power electronic devices and large-scale integrated circuits, as well as the continuous emergence and application of new control theories, AC control methods have gradually developed and will eventually replace EC speed control systems.
In FFU AC control method, it is mainly divided into two control methods: voltage regulation control method and frequency conversion control method. The so-called voltage regulation control method is to adjust the speed of the motor by directly changing the voltage of the motor stator. The disadvantages of the voltage regulation method are: low efficiency during speed regulation, severe motor heating at low speeds, and narrow speed regulation range. However, the disadvantages of the voltage regulation method are not very obvious for FFU fan load, and there are some advantages under current situation:
(1). The speed regulation scheme is mature and the speed regulation system is stable, which can ensure trouble-free continuous operation for a long time.
(2). Easy to operate and low cost of the control system.
(3). Since the load of the FFU fan is very light, the motor heat is not very serious at low speed.
(4). The voltage regulation method is particularly suitable for the fan load. Since FFU fan duty curve is a unique damping curve, the speed regulation range can be very wide. Therefore, in the future, the voltage regulation method will also be a major speed regulation method.
Post time: Dec-18-2023