What is a DC fan chassis? Description of motor, drive and speed regulation methods
The DC fan box drives the fan with a DC or electronically commutated power system. It does not simply replace the AC fan case with a motor, but the fan, motor and driver work together as a system. The driver receives power supply and control instructions, and the motor runs at the set speed. The final output still depends on the fan curve and air duct resistance. Aili Industry is discussingWhen designing a fan box plan, we will determine whether it is suitable to use a DC power solution based on the design air volume, external static pressure, operating period and control requirements, and confirm the matching relationship between the driver, control interface and box structure.
'DC' refers to the power solution
The DC fan case is not simply replacing the AC fan case with a motor. The fan, motor and driver need to be matched as a system: the driver receives power supply and control instructions, the motor runs at the set speed, and the final output still depends on the fan curve and air duct resistance. The actual product may use AC power input, and the driver will complete the motor control; the power supply method should be based on the specific electrical diagram.
There is a confusing concept that needs to be clarified first. EC motors are essentially DC motors, but their power supply methods are more flexible than traditional DC motors. Traditional DC motors require 12V, 24V or 310V DC power input, while EC motors have built-in rectification and control modules that can be directly connected to AC power and complete AC to DC conversion inside the motor. In other words, EC motors can achieve 'AC input and DC control'. The on-site power supply method is similar to that of ordinary AC fan cases, but the speed regulation capability comes from the DC side. This difference directly affects the electrical design of the project. If there is only AC power supply on site, the EC DC fan box does not require an additional DC power cabinet or rectifier device.
Why the project will consider the DC solution
When production shifts, the number of equipment turned on, or regional ventilation loads change frequently, the fan box can be operated according to demand through speed adjustment. Reducing unnecessary high air volume usually helps to reduce the input power of corresponding working conditions; the motor scheme itself should also compare efficiency under the same air volume and static pressure. You cannot promise a fixed power saving ratio just by relying on the word 'DC'. The actual energy saving depends on the load curve, system resistance characteristics and speed regulation strategy.
According to the fan law, power is proportional to the cube of rotational speed. The speed drops to 80% of the rated value, and the theoretical shaft power is about 51% of the rated value. This is the fundamental reason why speed regulation can save energy. If the system operates at full load for a long time, the energy saving space of the DC solution mainly comes from the improvement of motor efficiency; if there is an obvious part-load period, the benefits brought by speed regulation will increase significantly.
Confusing numbers in procurement documents
In the technical data of the DC fan case, the two numbers 'motor rated power' and 'machine input power' often appear at the same time, and they have different meanings. The rated power of the motor is used to define the continuous output capability of the motor itself under standard working conditions and is the upper limit of the motor's capability; the input power of the whole machine is the actual power consumption of the fan box under specific air volume, external static pressure and rotational speed, including the comprehensive results of motor loss, driver loss and fan aerodynamic efficiency.
For example: the rated power of the motor of a wind turbine chassis may be 1.5kW, but under certain common working conditions, the input power of the whole machine may be only 0.9kW because the motor is not running at the rated point. Conversely, if the system resistance is high and the fan operating point is far from the high efficiency area, the input power of the whole machine may be close to or even exceed expectations. Therefore, when comparing the energy consumption of DC and AC solutions, the supplier should be required to provide the input power data of the whole machine under the same air volume and external static pressure, and indicate the rotation speed, filter status and valve opening during the test. Comparing only the rated power of the motor cannot reflect the operating performance of the equipment in the actual system.
Write the control interface clearly
In addition to the design air volume and static pressure, the speed control signal, start and stop methods, fault feedback, minimum operating air volume and driver installation conditions should be confirmed when making an inquiry. Common speed control signals include analog, PWM and communication control. The terminal definitions of different drives may be different. Before on-site wiring, the electrical diagram and terminal description should be checked.
Analog signals are widely used in building automation and industrial control systems. The 0-10V voltage signal or 4-20mA current signal directly corresponds to the speed command, with simple wiring and good compatibility. The PWM signal transmits the speed command through the duty cycle of the square wave and does not rely on the voltage to control the speed. It is suitable for occasions where the speed command is issued by a PLC or microcontroller. Communication control is suitable for projects that require centralized monitoring or linkage of multiple devices. Through RS485 or Modbus protocol, the upper system can issue speed instructions and read operating status, fault alarms and actual speed feedback at the same time.
Ai Li industrialFan box products can be configured in terms of power and structure according to the project. If it involves local air supply at the clean equipment end, it is also necessary to distinguish whether it should be used insteadEquipment-side fan filter unit (EFU) . When the system end configurationWhen using HEPA/ULPA high-efficiency filters , the initial resistance of the filter and the resistance after use should be included in the calculation of the fan box operating point. When a large area of clean room ceiling air supply is required, you can compare at the same timeFFU fan filter unit ; it can be used when multiple devices are managed centrally.The FFU computer group control system realizes zone speed regulation and status monitoring. When final filtration and uniform air supply are required at the end of the air duct, you can also consider usingHigh-efficiency air supply outlet (HEPA BOX)。
Points to note when matching with filter equipment
When the DC fan box serves a clean or air-conditioning system, the resistance change of the filter will directly affect the fan operating point. If the filter resistance increases with dust accumulation, the speed adjustment strategy should be adjusted accordingly to ensure that the terminal air volume does not decrease due to the increase in resistance. The division of labor between power equipment and filtration equipment should be clear on the system flow chart to avoid confusing the functions of the fan box with FFU, EFU or high-efficiency air supply outlets.
If the project requires a higher level of particulate matter control, it can also be evaluatedWhether the ULPA ultra-high efficiency filter meets the process requirements. No matter which structure is adopted, the division of labor between power equipment and filtration equipment should be clear on the system flow diagram. Aili Industry isFor fan box products , the matching configuration of motors, fans, drivers and control interfaces can be discussed according to the project. The specific plan is subject to the confirmed electrical diagram and working condition parameters.
