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Frequently Asked Questions

This section is for informational purposes only and should not be used as a design tool or to generate technical specifications. For further details, please contact CTI and discuss with a representative for clarification. Search for terms or questions by entering words or phrases in the text box and clicking Search, by selecting a category from the drop-down list and clicking Show. Then simply click on the linked term or question below.

Question: Efficiency of a Transformer

Answer: 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.

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