Question:
An electrical device draws 2kW power from AC mains (voltage 223V (rms) = 50,000 V). The current differs (lags) in phase by φ (tan φ = -3/4) as compared to voltage. Find
(i) R,
(ii) XC – XL, and
(iii) IM. Another device has twice the values for R, XC and XL. How are the answers affected?
Solution:
Impedance = Z = 25 ohms
635 = 25R2/16
(a) Resistance = R = √25 × 16 = √400 = 20 ohms
(b) Xc – Xl = -3R/4 = -15 ohms
(c) Main current = Im = 12.6 A
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