PWM noise WC32

[Efried]

Hello,
 
I'm experiencing extreme fan operation when changing PWM duty cycle. The frequency is 25,000 Hz  or 25 Hz that does not matter, but I don't know whether the indicated Hz should read kHz.
May be increasing  duty cycle step by step would be necessary?
 
thanks

 

[CAI_Support]

The GUI title stated the frequency is HZ, that is integer number. not real number with decimal point. Please make sure the number entered in in integer format.
Please let us know what the exact steps you take and the problem you experienced.   We had measured PWM output with digital scope and did not see noise.
If you provided detailed information, we will take a look closely with your setup number.  Thanks.

 

[Efried]

The GUI title stated the frequency is HZ, that is integer number. not real number with decimal point. Please make sure the number entered in in integer format.
Please let us know what the exact steps you take and the problem you experienced.   We had measured PWM output with digital scope and did not see noise.
If you provided detailed information, we will take a look closely with your setup number.  Thanks.

Thanks for the swift answer. Not the WC32, but the fan makes noise running to full speed for a moment, after changing duty cycle. It's an application problem. May be fans require ramps. Or the transition from one to another duty cycle has a short period having 100 % duty cycle, even if you switch from 0 % to 40 %. But may be its a fan induced problem.
What bothers me is that the PWM  control works either way, using 25 Hz or kHz.

 

[CAI_Support]

What kind of PWM power module do you have?  From WC32, PWM duty cycle change is instant. 0% is a special case, during 0%, PWM is shut down for that one, the output pin can be float.  Please try from 1 to 40 to see if that problem still exist?

 

[rossw]

What bothers me is that the PWM  control works either way, using 25 Hz or kHz.

 
As long as the frequency is high enough that the fan doesn't have time to really respond to it, 25Hz or 25KHz makes no difference.
The fan is working on the "average voltage".... and 50% PWM will give the same AVERAGE voltage output regardless if the frequency is 25Hz or 25KHz.

 

[Efried]

Thanks for the replies. Also for pneumatic reasons my second fan spins now at 16 %, swapping PWM level with the first. Below, the fan controller is upset and tweets. 

 

[CAI_Support]

Could you please be more detail on what you described?  Thanks.

 

[Efried]

Could you please be more detail on what you described?  Thanks.

1- there ar two fans alternating, one could idle at a time
2- it is not possible to set the duty cycle at 10% because the fan controller is not in specified mode
3. the problem was solved by counterrotation of the idling fan, whih gives also higher air pressurer

 

[CAI_Support]

I see, your fan PWM power module does not like the load when duty cycle is below certain number.