Alain G wrote:jointbk
How long has it been?
Do you have pictures, a diagram, the exact model of the fan?
Please, if you can come back with this info.
The thank you box
Should try to contact him via his email address!
Already, roughly, that's what brings the 4eme pin (DRIVE):
It is connected to a transistor that is there to limit the average current in the windings of the stator, so the magnetic field, so the speed.
How is he doing?
It acts as a switch, quickly switching from the on state to the open state, to a frequency and a duty cycle dictated by the signal coming from the CM.
I'm not going to retrain a course on inductors but you should know that the higher the duty cycle is higher the current will be large. For a cyclic ratio of 100% (always passing), it is as if we were not modulating anything (like a 3 pins).
But you will tell me: yes but the PWM was already used, with speedfan for example.
Yes, but what we modulated was the total power of the circuit (+ V), and not the windings alone, ie all the electronics (and yes, it's a brushless motor in PC fans), and it apprecie means that we switch its power supply like that, so we limited the frequency to about 30 Hz, otherwise we risk to grill everything (short circuit at decoupling condo for example).
But at 30Hz, the problem is that we generate vibrations in the engine, totally audible and function of the meca.
In addition we lost the reading of the speed of rotation (see here)
With this 4eme pin, there is no longer this limitation, the electronics are always fed continuously. So, we switch to 25Khz, inaudible.
Why not more? It is necessary that the current can reach the desired average value, in fact, the higher the frequency, the more the current will be stable (little variation) but the longer it will take time to establish itself.
In the end, we obtain a speed of rotation proportional to the duty cycle of the input signal with a wider range than for "conventional" PWM.
The rheobus that will manage these fans will be much smaller than the current ones, all the electronic part of power having more place to be.
It should also cost much less ... in theory Evil or Very Mad
I will add that there is only in the computer environment where we still see the MLI (Pulse Width Modulation, PWM in English) low frequency at the fan level, it was time for us to evolve a little Wink
Capt_Maloche wrote:hmm ...
no video
pas de photo
Capt_Maloche wrote:Our friend Quartz is there, I have retained this small tools that will allow them to visualize the lines of fields: http://www.dailymotion.com/naca4412/vid ... _apcm_tech
I thought about nlc or Eleph
TagorThank you for your reminder links
on the diagram you publish, the motor has 4 windings
while PC motors to 4 pins are not designed in the same way (see the diagrams published on my post)
Already, we should start by giving the right model of engine, type, nbr windings, operation.
Capt_Maloche wrote:Because this a 12V battery type telecom can power a small PC fan for weeks ... so how long do they work?
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