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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: How does Impedance apply to Transformers?

Answer: Impedance is the resistance found in all circuits where alternating current is used. Electrically, impedance is made up of three components- DC resistance, inductance and capacitance. The inductance and capacitance can be added directly when converted to like units. One is positive and the other negative. The result of the quantity is then added vectorally to the resistance. (Vectoral addition is done the same way that sides are added to a triangle when trying to obtain the hypotenuse.) The impedance of most ordinary transformers runs between 3% and 6%. Very low impedance transformers tend to give better regulation. If the secondary of the transformer should be accidentally short-circuited and the impedance of the transformer is low, there would be a very high current flow on both the primary and secondary windings. This may cause mechanical displacement of the windings and a short circuit between adjacent turns. With a transformer that had an impedance of 5% and the secondary short-circuited, the primary and secondary current would automatically limited to 20x normal current. If the impedance were 10% the primary and secondary current would be limited to 10x normal current, and so on within certain limits that need not be explained here.

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Control Transformer, Inc., 3701 Warren Meadville Road, Cortland, OH 44410
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