Transformer Terms & Frequently Asked Questions
Efficiency of a Transformer
Transformers are among the most efficient electrical apparatus commercially manufactured. Most transformers of sizes form 1 KVA through 1000 KVA will have a full-load efficiency of from 95% to 98.5%. The items, which lower the efficiency of a transformer, are losses, which appear in the iron and those which appear in the windings. The iron losses are explained in the above question. The losses in the windings are due to the resistance of the wire. When current flows through a wire, losses appear in the form of heat just the same as when an ordinary electric hot plate is turned on. The wire used in quality transformers is generally made of copper. Aluminum is sometimes used in low quality transformers where life expectancy is not important or transformers which only have a constant load. These metals are among the best commercial metals for conducting electricity. They offer the least amount of resistance. Therefore, little energy is lost in the form of heat through the windings. These losses run on the order of 1% to 2% of the full-load rating. They vary inversely as the square of the load.