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I am using a rectifier, and 4500uF capacitor to reduce the ripple. After connecting to the power source (60Hz, 120V), I was able to turn on the fan. The issue occurs when I turn the switch on to power the other load. Below is the schematic. After turning the switch on to power the processor, the fan would start slowing down. I have noticed that the ripple does increase after adding another load. I have tried adding multiple capacitor on the output of the rectifier, and it would only increase the delay in fan slowing down. I am positive that the rectifier can output more than 20Amps. Both the load added takes in less that 11Amps.

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Is there anything I can add to this circuit to help reduce the effect on the fan when the switch has been turned on to power the processor?

Sam Shurp
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    Is the 160V to 24V converter voltage regulated? If not, it sounds like you have increased voltage drop in the rectifiers and/or wiring with increasing load, and that is lowering the voltage to the fan. – crj11 Sep 21 '20 at 02:50
  • It's perfectly normal and expected that ripple increases under a heavier load. In fact, a proper design will plan on that fact and arrange for the capacitor sizing (in a simple design like this one) such that the ripple is at or below some desired maximum. But you must also realize that the drop across the diodes also increases with increased current. And finally that the diodes only conduct for a short period, so their peak current is usually very much more than the average current needed. – jonk Sep 21 '20 at 02:51
  • @crj11, once the switch is turned on to power the processor, the ripple increases but the issue is that no matter how many capacitor I add, it will only delay the unavoidable; the fan will slow down later. 160V TO 24V is regulated. The minimum voltage that converter takes is 100V. The ripple goes below 100V. – Sam Shurp Sep 21 '20 at 02:58
  • Check the fan voltage. Is it a steady 24v? or does it decrease when you power on the second load? If that's not it, then maybe the ripple is not being rejected by the regulator, in that case try a different reg. – Drew Sep 21 '20 at 03:03
  • @jonk I have looked at the datasheet of the rectifier, the max output is 40Amps and the load, in total, takes 11Amps. The other idea is to separately use two rectifier; each powering single load. How is that idea? – Sam Shurp Sep 21 '20 at 03:03
  • It is a steady 24V until the other load is powered. I have looked at the output of the rectifier, and the voltage ripple goes below 100V. The 160V to 24V converter takes in minimum of 100V; therefore, I think converter is turning on and off due to the ripple. The output of the converter goes from 24V to 8.8V; kinda like a square wave when the switch is turned on to power the other load. – Sam Shurp Sep 21 '20 at 03:07
  • What is the spec for the 160V to 24V convertor? In particular what is it's minimum input voltage for operation? – mhaselup Sep 21 '20 at 03:47
  • @mhaselup, the minimum voltage for the converter to operate is 100V. – Sam Shurp Sep 21 '20 at 03:54
  • The 4500uF isn't maintaining >=100V that your convertor requires. You could try significantly increasing the capacitance or pick an alternative DC/DC convertor with a lower input threshold which can still handle the peak. Can you connect to a smaller load (say 5A) to verify the issue? – mhaselup Sep 21 '20 at 04:13
  • Add small value capacitors (100uF 200V, 10uF 200V and 100nF 200V) in parallel to the 1500uF capacitors to filter the ripples. – Paul Ghobril Sep 21 '20 at 04:54
  • I added more capacitor to make the ripple stable enough. I guess that solves my issue. – Sam Shurp Sep 22 '20 at 23:03

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