AC1 Fundamentals Unit 5 – Transformers
Exercise 3 – Transformer Turns and Voltage Ratios
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to determine the turns and voltage
ratios of a transformer by using calculated and measured values. You will verify your results
with an oscilloscope.
DISCUSSION
- A ratio of the number of turns of wire in the primary windings (NP) to the number of turns of
wire in the secondary windings (NS) is called a turns ratio. - The ratio of the primary side voltage (VP) to the secondary side voltage (VS) is equal to the
turns ratio. NP/NS = VP/VS - Transformers that have a larger primary voltage than secondary voltage are called step-down
transformers. - Transformers that have a smaller primary voltage than secondary voltage are called step-up
transformers. - Since ratios are unitless quantities, the voltage ratio is independent of the amplitude of the
applied signal. - The tap on a center-tapped transformer divides the number of turns in half resulting in a
choice of two different turns ratios and voltage ratios.