- #26

- 196

- 0

L=0.0524j

I=17.89*(0.45+0.89j)/(0.0524j-286.4j)=-0.0625*(0.45+j0.89)/j=0.0625j*0.45+j*j*0.89*0.0625=0.028j-0.056

- Thread starter builder_user
- Start date

- #26

- 196

- 0

L=0.0524j

I=17.89*(0.45+0.89j)/(0.0524j-286.4j)=-0.0625*(0.45+j0.89)/j=0.0625j*0.45+j*j*0.89*0.0625=0.028j-0.056

- #27

gneill

Mentor

- 20,880

- 2,840

- #28

- 196

- 0

I forgot that angle is -64 not 64.

- #29

- 196

- 0

Why?|I| = |56.1 + 27.4| = 62.5 mA

- #30

gneill

Mentor

- 20,880

- 2,840

(I think when I originally calculated it I was keeping more decimal places, so the ".4" crept up to ".5" on rounding)

- #31

- 196

- 0

I see.Thanks

I've found

Uc(t)=7.7328-16.0384j

Ul(t)=0.0014+0.003j

Ur(t)=0.224+0.108j

e(t)=7.9554-15.92746j

Are the result correct? 'cause I'm not sure...

I've found

Uc(t)=7.7328-16.0384j

Ul(t)=0.0014+0.003j

Ur(t)=0.224+0.108j

e(t)=7.9554-15.92746j

Are the result correct? 'cause I'm not sure...

Last edited:

- #32

gneill

Mentor

- 20,880

- 2,840

To summarize, you are given a series RLC circuit and an expression for the voltage waveform that exists across the inductor and capacitor combination. The inductor is L = 3mH, the resistor is R = 4 Ω, and the capacitor is C = 200μF. The order of the components seems to change depending upon what voltages are to be calculated.

The current across the series connected LC pair is given to us as:

Ulc = 17.89V*sin(1000(degrees/s)*t - 64 degrees)

You are looking to find the values for the voltage supply e(t), and the voltages across the individual components as well as several (shuffled) component pairs, and the reactive and complex power used by the circuit. Does that about sum it up?

- #33

- 196

- 0

yes.

I've found P

p=e(t)*I*=e(t)*0.027j=0.43+0.216j

P-reactive - - - - - - 0.216 var?

P-active - - - - - - - - - - 0.43 W?

I've found P

p=e(t)*I*=e(t)*0.027j=0.43+0.216j

P-reactive - - - - - - 0.216 var?

P-active - - - - - - - - - - 0.43 W?

Last edited:

- #34

gneill

Mentor

- 20,880

- 2,840

For:

ω = 1000 deg/sec; φ = -64° ; B = 17.89V; Ulc(t) = B*sin(ωt + φ)

R = 4Ω ; L = 3mH ; C = 200μF

ZL = 52.36 mΩ {milli Ohms}

ZC = -286.48Ω

ZLC = -286.48Ω {ZL + ZC}

Z = 4 - 286.48Ω {Total impedance of series RLC}

Ulc = B(cos(φ) + jsin(φ)) = 7.842 - j16.079 V ; |Ulc| = 17.89V ; Angle: -64°

I = Ulc/ZLC = 0.056 + j0.027 A ; |I| = 62.46 mA ; Angle: 26°

e = I*Z = 8.067 - j15.97 V; |e| = 17.89 V ; Angle: -63.2°

Ul = I*ZL = -1.434 + j2.939 mV ; |Il| = 3.27 mV ; Angle: 116°

Uc = I*ZC = 7.844 - j16.082 V; |Uc| = 17.89 V ; Angle: -64°

Ur = I*R = 0.225 + j0.11 V ; |Ur| = 250 mV ; Angle: 26°

P = e * conjugate(I) = 0.0156 - j1.117 W ;

|P| = 1.12 VA {Apparent power}

Re(P) = 0.0156 W = ; 15.6 mW {Real power dissipated}

Im(P) = -1.12 VAR {Reactive power -- negative means it's "capacitive" looking - current is leading voltage}

- #35

- 196

- 0

I think your results are correct so I'll use them.

I can't get this resultP = e * conjugate(I) = 0.0156 - j1.117 W ;

- #36

gneill

Mentor

- 20,880

- 2,840

You should check your math to see if you can't arrive at the same results; it's important to be able to work these sorts of problems before things get even more complicated! Besides, you never know, I might have mucked up somewhere!Some of your results are similar to mine but some of them are completely different.

I think your results are correct so I'll use them.

You may need to hang on to more decimal places in your intermediate results.P = e * conjugate(I) = 0.0156 - j1.117 W ;

I can't get this result

e = 8.0670 - j15.9699 V

I = 0.0561 + j0.0274 A

e*conj(I) = (8.0670 - j15.9699)*(0.05614 - j0.02738) W

= [8.0670 x 0.05614 - (-15.9699 x -0.02738)] + j[-15.9699 x 0.05614 + 8.0670 x -0.02738]

= [0.4529 - 0.4373] + j[-0.2209 + -0.8966]

= 0.0156 - j1.117

- #37

- 196

- 0

I've already checked it. The core of the problem was accuracy.

- Last Post

- Replies
- 15

- Views
- 2K

- Last Post

- Replies
- 1

- Views
- 3K

- Last Post

- Replies
- 4

- Views
- 1K

- Last Post

- Replies
- 1

- Views
- 2K

- Last Post

- Replies
- 2

- Views
- 1K

- Last Post

- Replies
- 3

- Views
- 3K

- Last Post

- Replies
- 1

- Views
- 2K

- Last Post

- Replies
- 8

- Views
- 1K

- Last Post

- Replies
- 6

- Views
- 2K

- Last Post

- Replies
- 7

- Views
- 3K