F. Operating Costs Sources of Loss No-Load Loss (Core Loss) •
Occurs when the transformer is energized but not supplying load No-load losses occur 24/7, even when the transformer isn’t supplying load Mostly constant regardless of load
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Full-Load Loss (Load Loss) • Occurs when the transformer is supplying rated current • Increases with load and temperature • Full-load losses scale with usage and temperature •
Utilities use their Load Factor (profile) data to calculate per day loss calculations
Why 65°C Matters •
Losses are temperature-corrected to 65°C for oil- filled units to reflect real-world operating conditions Higher temperature = higher resistance = more load loss Transformers with lower losses may cost more upfront but save thousands in energy costs. For example, reducing no-load loss by 100 W can save $3,000–$10,000 over the life of the transformer, depending on energy prices.
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Higher Efficiency = Lower Lifetime Cost •
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