Cybenetic fan tests: A detailed explanation of a new label for the industry

Fans are ubiquitous in electronics and provide cooling for heat-sensitive components. They are often overlooked as they do their job reliably over long periods of time until they finally fail. In this article, we take a detailed look at how fans are rated and classified according to their performance.

Fan operation and bearing types

The most important components of a fan are its bearing and the shaft to which the fan blade is attached. The bearing is a stationary cylinder in which the shaft rotates. To ensure high reliability and low noise levels, friction between the shaft and bearing must be minimized. In most cases, oil is used as a lubricant. However, there are also other methods (e.g. Teflon-coated surfaces).

If the oil is not properly sealed in the bearing, its quantity will decrease over time, resulting in increased friction. This slows down fan rotation, increases noise and can eventually lead to fan failure.

The most common bearing types in PC cooling fans are:

• Plainbearings: Least reliable
• Rifle bearings: Improved reliability compared to plain bearings
• Double ball bearings (DBB): High temperature resistance, typically bearing noise at low speeds
• Fluid dynamic bearings (FDB) and hydrodynamic bearings (HDB): Even more reliable than DBB bearings, no bearing noise at low speeds
• Magnetic bearings: High temperature resistance, no bearing noise at low speeds, expensive

Test equipment

The main instrument for fan measurements is the LW-9266 Fan PQ Performance Measurement Apparatus [1]. This sophisticated scientific instrument is manufactured in Taiwan by Long Win.

Technical specifications of the LW-9266:

• Manufacturer: Long Win Science & Technology Corporation
• Air flow rate: 2.4 – 250 CFM
• Air flow rate accuracy: <3.5% INFS
• Repeatability accuracy: < 2%
• Static pressure: 0-20mmAq (100mmAq with the high pressure throttling device)
• Dimensions: 0.7 (W) x 2.2 (L) x 1.6 (H) m
• Power supply: 220VAC, 5A, single phase, 50/60Hz
• Based on standards: ISO 5801-2007, AMCA 210-0, ASHRAE 51-2007, IEC 61591-2005, GB/T 1236-200

In addition to the Long Win machine you use:

• Noise test environment: Semi-anechoic room with < 6 dB(A) noise level
• Conditions: 25 (±2) degrees Celsius, 40-50% humidity
• Sound analyzer: Bruel & Kjaer 2270-S G4
• Microphone: Bruel & Kjaer type 4955-A
• Microphone calibrator: Bruel & Kjaer Type 4231
• Data logger: Picoscope TC-08 [2]

Fan power: P-Q curve

Every fan, whether DC or AC powered, has a characteristic curve called P-Q. This curve shows the correlation between the fan’s airflow and its static pressure.

• Airflow: The total amount of air the fan pushes or generates per unit of time. Measured in cubic feet per minute (CFM).
• Static pressure: The wind pressure of the fan in a completely closed duct. Measured in pascals (Pa), inches of water (inH2O) or millimeters of water (mmAq).

Standardized noise tests

Testing fans at full speed only shows a small part of their performance, as in most cases they are not operated at full speed. At full speed, the noise development is extremely high and the service life is severely impaired.

Therefore, the fan speed is typically regulated according to the thermal loads. It is therefore important to test each fan under the same conditions.

Source: Cybenetics