RC network values

Submitted by Pdsbrg on

I'm trying to figure out the value (and wattage) for c and r in this circuit (with or without the inductor) connected to a 15 Amp 110v outlet.  It's like a high pass filter but not looking for any cutoff frequency or voltage drop, just the 90° phase shift.

marry roser

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 Thus, the transient response or a series RC circuit is equivalent to 5 time constants. ... This transient response time T, is measured in terms of τ = R x C, in seconds, where R is the value of the resistor in ohms and C is the value of the capacitor in Farads.

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  Joined November 21, 2019      36
Thursday at 02:40 PM

I'm not sure I understand, so would a 90° transient shift be T=90, then just figure out the values that sum to that?

  Joined September 16, 2020      4
Wednesday at 01:07 PM

Then used this calculator (https://www.digikey.ca/en/resources/conversion-calculators/conversion-calculator-time-constant) to find the time constant that equals 90 degrees, with a 1M resistor and 90uF capacitor, is that correct values to use? Do you know what wattage resistor I should use? I tried ohm's law, but it says I need a 1650 W, is that right?

  Joined September 16, 2020      4
Wednesday at 01:07 PM

It is extremely difficult to get 90 degree phase shift in rela scenario. What is your planning? Are you making this circuit in real? What is your planning?

  Joined February 12, 2018      696
Monday at 02:11 PM

Yes I want to make this for real, I replied another comment that didn't show up here yet (I think it said awaiting moderator approval), but I calculated 1M for the resistor and 90uF for the capacitor on a webite that showed that would give the time delay for 90 degree shift I believe, I'm not sure if that is right.

  Joined September 16, 2020      4
Wednesday at 01:07 PM

Thus, the transient response or a series RC circuit is equivalent to 5 time constants.This transient response time T, is measured in terms of τ = R x C, in seconds, where R is the value of the resistor in ohms and C is the value of the capacitor in Farads.

  Joined February 27, 2020      55
Thursday at 11:08 AM

That will be inefficient. What is your load? Motors? Induction one? Or what?

  Joined February 12, 2018      696
Monday at 02:11 PM

Thank you for the reply. The load is just the 0.00271H inductor (31.5ohms).

I think I miscalculated before, I figured it to be 4.7k resistor and 90uF capacitor, to make a delay of 4.2ms (0.0042s). I calculated the delay for a 90° shift using this website: sengpielaudio(.)com/calculator-timedelayphase(.)htm (sorry just remove the brackets, I don't think posting links is allowed on this forum), then I used this calculator: digikey(.)ca/en/resources/conversion-calculators/conversion-calculator-time-constant,  to find c and r to equal the 4.2ms delay. 

So this is not right?

  Joined September 16, 2020      4
Wednesday at 01:07 PM

You can use it, but it is good to simulate this in any simulation software.

  Joined February 12, 2018      696
Monday at 02:11 PM