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What is Inside Our Fan Engineering?

With the advance of modern technology, it may not be a surprise to observe that there is an apparent trend of packing more performance into a smaller footprint in all products across the industries. At the same time, this has a side effect of increasing power density within the products, and led to an increasing demand for fan cooling capacity and efficiency. There is a constant pressure of delivering fans with higher performance and efficiency to ensure the components run at their most optimum and provide undisturbed operation. With more than 300 highly skilled engineers in multiple disciplines, AVC is perfectly positioned to meet this challenge.

1. Motor – powerful drive for less

Motor converts electric energy into kinetic energy. In compact fan application, in particular in the electronics cooling industry, DC brushless motor has become the mainstream choice of power drive. Unlike the traditional motor, brushless motor does not have contact brush which means this form of motor design is maintenance free and has virtually no wear and tear. Moreover, it has the additional advantages of high efficiency, low noise and ease of control. DC brushless motor is typically mounted inside the impeller, so it is largely isolated from the potential hazardous working environment and yields no external protrusion which makes overall fan size compact.

2. Aerodynamics – elegance at work

Aerodynamic design has a direct impact on fan performance in terms of f low volume and pressure delivery. It is so subtle that any small aerodynamic design detail change could have a significant influence on the fan output.

At AVC, fan aerodynamics is designed, tested and optimized using a combination of analytical, computational and empirical approaches. In-house developed analytical design software is first used to produce a basic aerodynamic design, before it is further optimized by using Computational Fluid Dynamics (CFD) analyses and experiments.

Commercial CFD packages are available to carry out computer simulations at standalone fan as well as system level. CFD offers a cost effective way to calculate the flow field inside and around the fan. It is particular useful when used to evaluate interactions between components and its effect in a thermal system.

3. Acoustics – quietness by scientific excellence

Depends on the fan speed, the main contributor to fan noise can be either aerodynamic related or motor/electronics related. Typical sources of the aerodynamic noise include turbulence from impeller and interactions between rotating and static components.

Motor or electronics related noise is commonly found at low fan speed, and it is of particular significance in the consumer electronics market. In order to produce an acoustically optimized fan, inter-disciplinary expertises as well as appropriate facility are essential to analyze and optimize acoustics in a scientific way.

Fan acoustic measurements are taken in a specialized semi-anechoic chamber, where the roof and walls are covered with sound absorbing material. AVC in-house test facility has background noise level sufficiently low enough to measure any quiet devices of interest. Traditionally, sound pressure is the parameter used by fan industry to compare fan “noise”. However, sound pressure gives little information about how human ears truly react to sound and this parameter has become increasingly inadequate for the thermal management market.

The extensive facility at AVC provides much more information than just sound pressure measurement. Firstly, the binaural recording using dummy head and the subsequent advanced analysis are capable to provide more insight about the sound quality. Secondly, the multiple microphones arranged in hemispherical array are used to measure sound power from a device. These acoustic data forms the valuable resources when optimizing fan acoustics.

4. Electronics – intelligent and sophisticated

For DC brushless motor, the current in the motor winding coil change direction constantly according to the relative position of the stator and rotor. Fan electronics is the brain that determines the relative position aforementioned and controls the current switching time accordingly, so it plays a crucial role in keeping the motor running. Fan electronics also provides a number of other advanced functions such as fan speed control, outputting fan speed information and fail-safe designs such as over-current protection.

For certain applications, fans are required to have a specific level of electro-magnetic capability (EMC) to guarantee fan operation as well as not affecting other components in user systems. This is an application specific problem, and our engineers are fully equipped and experienced to work with our customers for EMC optimized solutions.

5. Bearing Systems – dependable workhorse

There are two major types of bearing system used in AVC fan products: ball bearing and advanced hydraulic bearing.

5-1. Ball Bearing

Ball bearings are normally installed in pair and spring loaded in the axial direction. Ball bearing is the traditional choice for high performance fans that require long life expectancy. Metallic balls are sandwiched between two races with side plates in place to prevent lubricant leakage and protect it from the environment.

5-2. Advanced Hydraulic Bearing

AVC proprietary Advanced Hydraulic Bearing (AHB) consists of a polished steel shaft, a sintered bearing and fluid lubricant. There is no contact between shaft and bearing, and the bearing load is carried solely by a film of fluid lubricant. AHB is suitable for fans that operate at lower speed. Compare to ball bearing, AHB runs quieter, costs less and is less sensitive to shock and vibration.

6. Fan Construction – stand up against the extremes

Most of AVC fans are made from glass-fiber reinforced plastic. The plastic used has fire retardant added and is UL 94V-0 approved. Plastic is light, cost effective, and suitable for mass production. Moreover, plastic parts can be easily made into complicated 3D shapes, which is useful for parts such as impeller to produce the best aerodynamic performance. The housing of larger fans may be made from Aluminum, and for the very large radial fans (310+cm), the impellers are also made from aluminum.

7. Product Compliance – safety in mind

All AVC fans are designed to meet product compliances from a number of international organizations such as UL, CSA, CE, TUV, VDE and CCC. Users are reminded to ensure fans are well installed and operated in accordance with the appropriate safety codes.

8. Life and Reliability – robust design

The quality and reliability of AVC fan products are tested by carrying out a series of tests such as high/low temperature running, thermal/mechanical shock, thermal cycling and vibration. Facilities for further testing such as water and corrosion resistance are available at requested.

Fan life expectancy is evaluated using zero failure Weibull test strategy together with accelerated testing technique. This approach was chosen to obtain life expectancy with sufficient confidence in a sensible time-frame that is acceptable to both the fan vendor and end users.

During the endurance test, fans run continuously at an elevated temperature, sometimes higher than their recommended operating range, to accelerate the aging effect under controlled conditions. Statistical method is then used to evaluate the life expectancy. A fan is classified as failure if any one of its key performance parameters, for example fan speed and sound pressure, is out of specification.

9. Rapid Prototyping – shortened development time

AVC is well aware that fast turn around time is critical to the success of our client development programs. Our R&D team has in-house facility and workshop to produce prototypes quickly for customers. This helps to resolve problems early in the development stage and, more importantly, reduces the number of iterations and development time.

10. Manufacturing – mass production at your fingertips

AVC is proud to have the manufacturing capability that can produce millions of fans a month. Apart from supplying fans with the highest performance, quality and efficiency, AVC is also a keen participant in the “Green” initiative, striving for products that have the minimum impact on the environment.

All AVC fan products conform to the European directive on the restriction of the use of hazardous substances in electrical and electronic equipments (RoHS). In addition, 100% Halogen free products are also available at request.