Winding conflgurations in Transformer

Chapter 9.5 Winding conflgurations

Lessons In Electric Circuits Volume II – AC Book
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Lessons In Electric Circuits Volume II – AC Book

  • 240CHAPTER 9. TRANSFORMERSFigure 9.27: Out of phase: primary red to dot, secondary black to dot.Figure 9.28: In phase: primary red to dot, secondary red to dot.• REVIEW:• The phase relationships for voltage and current between primary and secondary circuits of atransformer are direct: ideally, zero phase shift.• The dot convention is a type of polarity marking for transformer windings showing which endof the winding is which, relative to the other windings.9.5Winding configurationsTransformers are very versatile devices. The basic concept of energy transfer between mutual in-ductors is useful enough between a single primary and single secondary coil, but transformers don’thave to be made with just two sets of windings. Consider this transformer circuit: (Figure 250,9.29)Here, three inductor coils share a common magnetic core, magnetically “coupling” or “linking”them together. The relationship of winding turn ratios and voltage ratios seen with a single pair ofmutual inductors still holds true here for multiple pairs of coils. It is entirely possible to assemblea transformer such as the one above (one primary winding, two secondary windings) in which onesecondary winding is a step-down and the other is a step-up. In fact, this design of transformerwas quite common in vacuum tube power supply circuits, which were required to supply low voltagefor the tubes’ filaments (typically 6 or 12 volts) and high voltage for the tubes’ plates (severalhundred volts) from a nominal primary voltage of 110 volts AC. Not only are voltages and currents