- Asked 3/22
- 2075 Asoj · 4 marks
- 2072 Kartik · 4 marks
- 2082 Chaitra (new course) · 3 marks
Power versus distribution transformer
Short answer
Power transformers have high ratings, run near full load, maximize efficiency at full load, allow higher iron loss, use forced cooling. Distribution transformers have lower ratings, are energized continuously, maximize all‑day efficiency near 50–70% load, keep iron loss low, and use natural cooling with low reactance for better regulation.
What are the differences between power transformer and distribution transformer from design aspect?
A power transformer is used in generating stations and transmission substations to step voltages up or down at high power, and runs near full load most of the time. A distribution transformer feeds consumers at the final voltage (for example 11 kV/400 V) and its load varies widely through the day.
| Design aspect | Power transformer | Distribution transformer |
|---|---|---|
| Rating and voltage | Large kVA (above ~500 kVA), high voltage | Small kVA (up to ~500 kVA), 11 or 33 kV/400 V |
| Loading pattern | Nearly full load, switched in/out with load | Varies; energised 24 h even at light load |
| Max efficiency | Designed for max efficiency near full load | Designed for max efficiency at about 50–70% load |
| Iron vs copper loss | Iron loss can be higher, copper loss low at full load | Iron loss kept low (low , good steel); higher copper loss allowed |
| Efficiency criterion | Ordinary (power) efficiency | All-day (energy) efficiency |
| constant (3-ph core) | 0.6–0.7 | about 0.45 |
| Regulation | Not critical (tap changers used); higher reactance allowed to limit fault current | Low leakage reactance for good regulation |
| Cooling | Forced oil/air (ONAF, OFAF) | Natural oil cooling (ONAN) |
So a distribution transformer is designed with smaller iron loss and better regulation, while a power transformer is designed for high full-load efficiency and to withstand large fault levels.
✓ Answer checked by Claude Sonnet 5.5
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