# RC network values

9 posts / 0 new

Offline

Joined: Sep 16, 2020

Replies: 3
RC network values
September 16, 2020 - 1:23pm

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.

Offline

Joined: Nov 21, 2019

Replies: 35

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.

Offline

Joined: Sep 16, 2020

Replies: 3

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?

Offline

Joined: Feb 12, 2018

Replies: 318

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?

Offline

Joined: Sep 16, 2020

Replies: 3

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.

Offline

Joined: Feb 27, 2020

Replies: 17

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.

Offline

Joined: Feb 12, 2018

Replies: 318

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

Offline

Joined: Sep 16, 2020

Replies: 3

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?

Offline

Joined: Feb 12, 2018

Replies: 318

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