AC1 Fundamentals Unit 5 – Transformers
Exercise 4 – Transformer Secondary Loading
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to determine the effect of secondary
loading by using a typical transformer. You will verify your results with an oscilloscope.
DISCUSSION
- A ratio of the current through the primary (IP) and the secondary (IS) is called the current
ratio. - The current ratio is equal to the inverse of the voltage and turns ratio.
IS/IP = VP/VS = NP/NS - The relationship between the current and voltage ratio shows that when voltage is stepped up
by a certain factor, the current is stepped down by the same factor. - Transformers are self-regulating devices. The transformer will automatically increase or
decrease the primary current to accommodate for changes in the load (RL). (The load is
placed across the secondary of the transformer.) - In an ideal transformer the power delivered by the primary is equal to the power delivered by
the secondary. - In practical transformers typical efficiency of a transformer is 90% efficient.
% efficiency = (PS/PP) x 100