Start-up and shut-down voltage
This chapter should be read with caution and attention as long as the fans are not purely analog, i.e. DC-controlled with 3-pin connector. The PWM control electronics almost always stand in the way of clean voltage regulation and it is also therefore not advisable to regulate PWM fans via voltage. Nevertheless, we also performed this measurement for all models, regardless of whether they are DC or PWM fans, because even strange results say a lot about the control electronics and the use as a DC-controlled fan.
First, however, we check the maximum speed at 100% PWM to be on the safe side and compare it with the data sheet. The fan manages the specified data and is only slightly below it after the 24-hour run-in. Of course, there is usually also a smaller series spread in play, so that already fits quite neatly.
In today’s DC test, we see that the fan only starts up with voltages from about 3.2 volts. The cutoff voltage is 2.8 volts, whereby the stated 400 rpm hardly differ from the measured 413 rpm. The fan is thus also conditionally suitable for real DC control, since you can regulate it down quite far enough.
The PWM-controlled start-up speed is at least 189 rpm, and the PWM-controlled fan stop is below that. Nevertheless, we only measured the fan from 400 rpm (analogous to the DC control) because the values for airflow and static pressure below 400 rpm already slide into the area of measurement errors and hardly plausibly measurable results.
Start-up and shut-down behavior
The following measurement curves once again illustrate the very different behavior. Let’s look at DC control first. Here, the fan requires a starting speed of 445 rpm, and a standstill already occurs below 413 rpm. This is still quite usable as a control range and also makes these fans interesting as pure DC fans.
With the PWM protocol, we can also see very well the progression up to the minimum speed, which then leads to the desired standstill and the slight switch-on pulse (boot).
Power consumption
This value of open operation as a case fan is pleasantly low, especially at low speeds, but completely contradicts the data sheet, which shows much higher values. However, you should also consider that 4 fans together would consume a bit over 11 watts at full load. As such, common DC control of all the installed fans in a system via a single 1-A header would be possible if there were four or fewer.
However, power consumption is not the same as power consumption, because it fluctuates quite a bit between radiator operation and free installation as case fan! This graph is also new and should help in assessing the system load, because the power consumption increases to 2.8 watts and is thus miles below the data sheet’s values of almost 4.5 watts.
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