The impeller is oriented so that, in the installed position, nothing visually obstructs the view. This refers to the stator struts, which can otherwise “spoil” the appearance. But this is not just about looks—it is about combining them with the efficient geometry of the proven five-blade design with a stabilizing ring (familiar from the P12 A-RGB). It is not exactly the same design, though, if only because what used to be behind the impeller is now in front of it.
How we measure power consumption…
Is it worth addressing the power consumption of fans? If you have seven of them in your computer (three on the radiator of the cooler and four for system cooling in the case) and they are also backlit, the power consumption starts at tens of watts. This makes it worth dealing with.
All fans are powered by Gophert CPS-3205 II laboratory power supply. It is passive and virtually noiseless, so it does not distort our noise level measurements. However, for the PWM fans, a Noctua NA-FC1 controller is connected through which the fans are regulated. We also have a shunt between the power supply and the Noctua controller. On it, we read the voltage drop, from which we then calculate the current. However, the voltage on the power supply is set so that 12 V goes to the Noctua NA-FC1. We then also set the exact 12 V to measure the maximum power of the 3-pin linear power supply fans.
In the power consumption tests, we will be interested in the power consumption in fixed noise level modes in addition to the maximum power consumption at 12 V or 100% PWM. That is, at those settings at which we also measure other parameters. Finally, in the graphs you will also find the power consumption corresponding to the start-up and minimum speeds. The difference between these two settings is that at start-up speed you need to overcome the frictional forces, so the power consumption is always higher than at minimum speed. At these, the fan is already running and just reduces power to just before a level where it stops.
These start-up and minimum power consumption data are a substitute for the start-up and minimum voltage information. You often encounter this when reading about fans, but with PWM fans there is no point in dealing with it. And although it is possible to power a PWM fan linearly, it will always perform better with PWM control—lower starting and minimum speeds. Therefore, it would be unfair to compare these parameters for all fans using linear control. That way, fans with PWM would be disadvantaged and the results distorted.
…and motor power
In addition to power consumption, it is important to consider one more parameter that is related to the power supply—the power of the motor. This is usually listed on the back on a label and is often mistaken for power draw. However, the voltage and current indication here is usually not about power draw, but about the power of the motor. The latter must always be well above the operating power consumption. The higher it is, the longer the life expectancy of the fan.
Over time and with wear, fan friction increases (through loss or hardening of the lubricant, dust contamination or abrasion of the bearings, etc.). However, a more powerful motor will overcome the deteriorating conditions of the fan to some extent, albeit at a higher power consumption, but somehow it will cope. However, if the difference between the motor power and the operating power consumption of a new fan is small, it may no longer be able to exert sufficient force to turn the impeller under increased friction due to adverse circumstances.
To test the power of the motor, we set the fan to full power (12 V/100 % PWM) and increase the mechanical resistance by braking the impeller in the middle. This is a higher load for the motor, with which the power consumption naturally increases. But this is only up to a point, until the impeller stops. The power of the motor in our tests corresponds to the highest achieved power consumption that we observed when the fan was being braked.
We use the Keysight U1231A high sample rate precision multimeters to analyse motor power (as well as normal operating power consumption). In addition, the individual samples are recorded in a spreadsheet, from which we then graph the maximum. The final value is the average of three measurements (three maximums).
Hmm, the 100th fan in the database—counting 140 mm models as well. On Thursday, we’ll do a kind of recap or summary, where all fans tested so far will appear together in the charts. 🙂
After reading the methodology section I’m still uncertain about when the tests were performed with the obstacles infront or behind the fan. Could you please clarify that?
Scenario by scenario, it varies. The radiators (both thinner and thicker ones) are behind the fans, as they are more commonly used in practice, while the dust filters (both nylon and plastic) are in front of them, i.e. in front of the impeller. That also makes more sense.
There is also a hexagonal grille in front of the fan, on the intake side, although in PC cases (for example, on the exhaust) it is often located behind it. We chose this placement because having it behind the impeller doesn’t change the acoustic profile very much, whereas with the opposite orientation, the difference can sometimes be quite significant, especially when it comes to tonal peaks. 🙂
Thanks for the clarification!
Your setup is what I was hoping for, for the reasons you already stated yourself. And just to make sure I’m not misunderstanding a fine detail: Whether **reverse blade fan or regular fan**, your dust filter test setup (both nylon an plastic) will always reflect typical real world usage, i.e. air will be “pulled” through the filter instead of being “pushed” through it. Right? Thanks in advance!
Yes, the dust filters are always on the intake side of the fans. 🙂
For the most accurate comparison possible, reverse fans are also positioned in the same relationship to the anemometer (in pull). That’s a more complicated discussion, but this is always the case regardless of the fan. If we did it the opposite way, in push, the area where we measure the wind/air speed—which is subsequently used to calculate the airflow in cubic units—would be too turbulent, and the results would therefore be distorted. 🙂