Question

Calculate the instantaneous value at 60°, average value and RMS value of an alternating current whose peak value is 20 A.

Answer 1

Given data:

I_m = 20 A Q = 60°

i) Instantaneous value of current

i = I_m sin θ

= 20 × Sin 60°

= 20 × `sqrt3/2`

= 10 × `sqrt3`

= 10 × 1.732

i = 17.32 A

ii) Average value

I_av = 0.637 I_m

I_av = 0.637 × 20

= 6.37 × 2

I_av = 12.74 A

iii) I_rms = 0.707 I_m

= 0.707 × 20

= 7.07 × 2

I_rms = 14.14 A