RC network values

Pdsbrg's picture

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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.

marry roser's picture

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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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Pdsbrg's picture

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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?

Sourav Gupta's picture

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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?

Pdsbrg's picture

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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.

Olivia Williams's picture

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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.

Sourav Gupta's picture

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

Pdsbrg's picture

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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?

Sourav Gupta's picture

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