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Given the maximum efficiency of a transformer of a 500 kVA, 3300/500V, 50 Hz single-phase transformer is 97% and occurs at 3/4 of full-load, unity power factor. If the impedance is 10%, the regulation at full-load, power factor 0.8 lagging will be _____ % .
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- 8.25%
- 17.52%
- 7.52%
- 10.52%
Correct Option: C
| η = 0.97 = | 500 × | × 1 | ||
| 4 | ||||
| 500 × | + Pcore + Pcu × | |||
| 4 | 16 | |||
| ⇒ Pcore + Pcu × | = 11.60 | |
| 16 |
⇒ Pcu = 10.31 kW (at full-load)
| ∴ re (p.u.) = | = | = 0.02062 | ||
| kVArated | 500 |
xe (p.u.) = √Ze² - re²
= √0.1² - (0.02062)² = 0.0978
∴ Regulation = re cos θ + xe sin θ
= 0.02062 × 0.8 + 0.0978 × 0.6 = 7.52%
