Sometimes an electrical device may need an input voltage that is a few percent higher or lower than the supply voltage. A boosting transformer connects the output coil with the input voltage (here, a 120-V AC source) as shown on the left in Figure Q22.21.
(a) Draw the sine waveforms of the input and output coils of the transformer and show how they add to produce the 150-V output.
(b) If the leads from the output coil are connected as shown on the right in Figure Q22.21, a bucking transformer configuration results. (It has this name because two voltages are combined in “opposition” to make the output.) What output voltage would you expect from the circuit on the right in Figure Q22.21? Again draw the sine waveforms of the input and output coils, and the final output waveform. (Note that when the voltages from the input and output coils are combined, you must consider the phases of these voltages relative to each other.) 

Transcribed Image Text:

"Bucking" "Boosting" +. Trans- former Trans- former 30 V 150 V 120 V 30 V 120 V Figure Q22.21