How we measure power draw and motor power
The biggest shortcoming of Arctic’s original P-series fans is the rumbling sound profile. The manufacturer realized this and decided to do something about it. Sensibly, by implementing a hoop to eliminate the critical vibrations that are the source of the annoying acoustic profile. The implementation turned out well, and already the P12 A-RGB shows how much quieter it is compared to the older P12 model. And the list of improvements doesn’t end there.
How we measure power draw…
Is it worth addressing the power draw 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 draw 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 draw tests, we will be interested in the power draw 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 draw 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 draw 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 draw, 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 draw. The more, the longer the life expectancy of the fan.
Over time and with wear, fan friction increases (through loss, hardening of the lubricant, dust contamination or abrasion of the bearings, etc.). However, a more powerful motor will overcome the deteriorating condition of the fan to some extent, albeit at a higher power draw, but somehow it will cope. However, if the difference between the motor power and the operating power draw of the new fan is small, it may no longer be able to exert sufficient force to turn the rotor 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 rotor in the middle. This is a higher load for the motor, with which the power draw naturally increases. But this is only up to a point, until the rotor stops. The power of the motor in our tests corresponds to the highest achieved power draw that we observed when the fan was being braked.
We use the Keysight U1231A high sample rate precision multimeters to analyse motor performance (as well as normal operating power draw). 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).
- Contents
- Arctic P12 PWM PST A-RGB in detail
- Overview of manufacturer specifications
- Basis of the methodology, the wind tunnel
- Mounting and vibration measurement
- Initial warm-up and speed recording
- Base 6 equal noise levels…
- ... and sound color (frequency characteristic)
- Static pressure measurement…
- … and airflow
- Everything changes with obstacles
- How we measure power draw and motor power
- Measuring the intensity (and power draw) of lighting
- Results: Speed
- Results: Airlow w/o obstacles
- Results: Airflow through a nylon filter
- Results: Airflow through a plastic filter
- Results: Airflow through a hexagonal grille
- Results: Airflow through a thinner radiator
- Results: Airflow through a thicker radiator
- Results: Static pressure w/o obstacles
- Results: Static pressure through a nylon filter
- Results: Static pressure through a plastic filter
- Results: Static pressure through a hexagonal grille
- Results: Static pressure through a thinner radiator
- Results: Static pressure through a thicker radiator
- Results: Static pressure, efficiency by orientation
- Reality vs. specifications
- Results: Frequency response of sound w/o obstacles
- Results: Frequency response of sound with a dust filter
- Results: Frequency response of sound with a hexagonal grille
- Results: Frequency response of sound with a radiator
- Results: Vibration, in total (3D vector length)
- Results: Vibration, X-axis
- Results: Vibration, Y-axis
- Results: Vibration, Z-axis
- Results: Power draw (and motor power)
- Results: Cooling performance per watt, airflow
- Results: Cooling performance per watt, static pressure
- Airflow per euro
- Static pressure per euro
- Results: Lighting – LED luminance and power draw
- Results: LED to motor power draw ratio
- Evaluation
This is a good study of the effect of rings. The blades are a bit shorter so there’s less airflow at the same noise level (despite higher static pressure), but it suppresses blade vibrations very effectively, improving the noise profile for fans using flexible blades.
I am thinking that the increased static pressure may be partially be due to the increased hub size. It was mentioned by Noctua that the inner parts of the blades have less efficiency, and may even allow air to flow back, so an increased hub size may actually contribute to better static pressure. I think the Gentle Typhoon-like fans all have very similar, large motor hub size because of this.
It’s also interesting to see that the official static pressure spec vs. the one you measured varies by so much between the P12 and the P12 ARGB. The official spec has the P12 having higher static pressure being higher than the ARGB version, yet it is opposite here.
The rotor looks pretty much identical to that of the P12 Max, the other minor difference is the ribs in the stator. Are there any differences apart from blade material and the bearing (aside from RGB?) Perhaps this is the budget fan to get if you want to avoid the dual ball bearing noise of the P12 Max, even if you do not want or need RGB.
Well, the best study would be with P14 rev. 1 vs. rev. 2, if the same motor is used across revisions and the only difference is really in the (non)presence of the hoop.
As for the comparison of the paper specifications of the P12 and P12 A-RGB, I really don’t see the technical reason why the static pressure of the P12 at the same speed should be higher by… what, 25%, when at a speed lower by 200 rpm it should be +19%? It makes sense to me the other way round. Of course, a higher static pressure is indirectly caused by the larger hub, if only because it leaves a smaller empty area between the blades. The smaller the fan format, the higher the static pressure per unit of airflow. With the P12 A-RGB, the hoop itself also increases the overall pressure (i.e. static pressure as well) to a certain extent, as I mentioned in the article.
Anyway, I don’t like to dwell on these things about official parameters. The last thing we want is to have unnecessary back-and-forth with some manufacturer about what they state in their materials. That’s not really the goal, but in this case it couldn’t be completely avoided in the text. Things must always be as clear as possible, that’s what we pride ourselves on. And for the Arctic P12 to have a higher static pressure at the same speed compared to the NF-A12x25, well… 🙂
Noctua has now reduced the hub size for 140mm LCP fans. From internal communication with their representative we know that it is mainly for better optimization of the Centrifugal Turbulator with the unconventional curvature of the blades. Due to the smaller hub, the part of the blades before the curve (i.e. the typical critical part where aerodynamic efficiency decreases) should catch more air streams.
Would be nice to have the P12 CO variants in there as well as an additional reference.
I got some P12 Max’s but was disappointed with the overall noise distribution so I returned them (they definitely moved a lot of air but they were considerably noisier across the entire rpm range compared to the P12 CO’s I had, and one was particularly noisy when placed on a radiator – maybe I got a bad early batch).
I have had regular P12’s before with that hum in the 1000-1100rpm range, but not had a CO variant with that hum before, though obviously limited sample size.
We will add the CO variants, but the closest will be P14 (P14 CO vs. P14), to give a little kick to the building of the 140 mm fan database. We have very few of these in comparison and maybe less than half a year left until the release of Noctua 140mm LCP fans. And of course we want to be adequately prepared for them, i.e. with a sufficiently large reference sample of other fans. But the P12 Max with ball bearings will be added to the tests.
I was able to find the exactly same enhancement from P14s. Unlike the original P14, P14 ARGB has very weak resonant noise at some RPM points and no RPM range that generates a tonal peak. Also the overall noise profile is much better than P14.
As you mentioned, I also think Arctic’s solution is very cost-efficient way to resolve the unintended vibration of impeller. Everyone knows that the better way is using LCP material, but then the price and difficulties of manufacturing becomes the main problem.
Although there are some small downsides of this solution(i.e. Increased a moment of inertia of a rotor and slightly smaller area of blades.), I hope the company apply a rotor frame to other models such as P12/P14 PWM PST.