Stuck on an assignment for college

[LotusBiscuit]

The question is:
If the supply voltage is 100v ac with a period of 20ms, and the supply current (Is) taken by the coil is 6A, calculate the frequency of the supply, overall impedance, Inductive reactance and the inductance of the coil.

I've worked out the frequency to be 50Hz and in order to get the Inductive reactance I need to work out the inductance of the coil.

f = 1/t
1/20ms

1/20x10^-3 = 50hz
Z = v/I
Z= 100/6
Z =17.6

Xl = sqroot z^2 - r^2
17.66^2 - 100 = 13.24

2pifl
L =xl ÷ 2pif
13.24 ÷ 2 x pi x 50=
0.04H

Just want to double check any help??

 

[LotusBiscuit]

Yes they are; the resistance can be calculated from the previous part of the question - exactly how I suggested previously.

You calculate the dc resistance from that portion of the question, the impedance Z from the ac part giving Z and R, therefore you can calculate pf and phase angle


You really need to look at the whole question - just selecting one aspect will not give the whole answer

Ok so,

So the resistance that i got from the DC part of the question is 100v / 10A = 10ohms

Therefore the powerfactor would be R/Z = 10/ (100/6) = 10/16.7 = 0.59....

And for the phase angle I am unsure about the equation, I've googled it and got; Angle = tan^-1(Xl-Xc/R) just want to double check that before I write it down

Thank you

 

[Julie.]

Ok so,

So the resistance that i got from the DC part of the question is 100v / 10A = 10ohms

Therefore the powerfactor would be R/Z = 10/ (100/6) = 10/16.7 = 0.59....

And for the phase angle I am unsure about the equation, I've googled it and got; Angle = tan^-1(Xl-Xc/R) just want to double check that before I write it down

Thank you

If you do R/Z, you could just use cos^-1 (arc-cos) of the pf - R/Z is the pf

Or if you do X/Z you could use sin^-1 (arc-sin) of X/Z

Or if you do X/R you use tan^-1 (arc-tan) of X/R

Do a search for an online tutorial about power triangle on ac circuits, or impedance triangle on ac circuits, try a few until it clicks with you

 

[Copperfield]

'Hey, I'm actually doing the same assignment atm and im stuck on a few of these questions i.e question 2f, 2g, 2h, 2i and 5, 8 and 9 lol. My teacher isn't helping me out at all with them. Would you be able to shed some light on them for me please?

Thanks!

 

[Lister1987]

'Hey, I'm actually doing the same assignment atm and im stuck on a few of these questions i.e question 2f, 2g, 2h, 2i and 5, 8 and 9 lol. My teacher isn't helping me out at all with them. Would you be able to shed some light on them for me please?

Thanks!

Work thr calculations in order and you should be fine.

Remember you'll like get marks for each part;

Circuit Diagram - Draw thr Circuit out and label it.

Formula to be used

Formula with values substituted in

Power Triangle

Impedance Triangle

Phasor Diagram

That way even of your end result is wrong, the assessor can see how you got there and award marks for the correct steps

 

[Lister1987]

https://youtube.com/playlist?list=PL7eNzIRgKe07BOqPH7MrrKy89M3o4wU-2

This playlist should help.

 

[MohamedMohamed]

The question is:
If the supply voltage is 100v ac with a period of 20ms, and the supply current (Is) taken by the coil is 6A, calculate the frequency of the supply, overall impedance, Inductive reactance and the inductance of the coil.

I've worked out the frequency to be 50Hz and in order to get the Inductive reactance I need to work out the inductance of the coil.

f = 1/t
1/20ms

1/20x10^-3 = 50hz
Z = v/I
Z= 100/6
Z =17.6

Xl = sqroot z^2 - r^2
17.66^2 - 100 = 13.24

2pifl
L =xl ÷ 2pif
13.24 ÷ 2 x pi x 50=
0.04H

Just want to double check any help??

Xl = sqroot z^2 - r^2
17.66^2 - 100 = 13.24 can you explain this part please
thanks