Center tap

Diagram of center-tapped transformer

In electronics, a center tap (CT) is a contact made to a point halfway along a winding of a transformer or inductor, or along the element of a resistor or a potentiometer. Taps are sometimes used on inductors for the coupling of signals, and may not necessarily be at the half-way point, but rather, closer to one end. A common application of this is in the Hartley oscillator. Inductors with taps also permit the transformation of the amplitude of alternating current (AC) voltages for the purpose of power conversion, in which case, they are referred to as autotransformers, since there is only one winding. An example of an autotransformer is an automobile ignition coil. Potentiometer tapping provides one or more connections along the device's element, along with the usual connections at each of the two ends of the element, and the slider connection.Potentiometer taps allow for circuit functions that would otherwise not be available with the usual construction of just the two end connections and one slider connection.

Volts center tapped

Volts center tapped (VCT) describes the voltage output of a center tapped transformer. For example: A 24 VCT transformer will measure 24 VAC across the outer two taps (winding as a whole), and 12 VAC from each outer tap to the center-tap (half winding). These two 12 VAC supplies are 180 degrees out of phase with each other, thus making it easy to derive positive and negative 12 volt DC power supplies from them.

References

  1. Ballou, Glen (2005). Handbook for Sound Engineers (3 ed.). Focal Press. pp. 411–412. ISBN 0-240-80758-8.
  • F. Langford Smith, The Radiotron Designer's Handbook Third Edition, (1940), The Wireless Press, Sydney, Australia, no ISBN, no Library of Congress card
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