Introduction to Testing Ferrite Transformers
As electronic products utilise higher frequency
techniques to reduce size and improve efficiency, ferrite cores are used
in an increasing proportion of transformer designs. Transformer
manufacturers must therefore meet a need for smaller transformers designed
to operate at higher frequencies, which introduces additional demands on
both manufacturing and testing methods.
These issues apply to a wide range of common applications
including switched mode power supplies, lighting ballasts, inverter
drives, audio and telecommunications equipment and many more. Today's need
for the proven performance of all components within a product has resulted
in a demand for each and every transformer to be more thoroughly tested
than traditionally expected. In the following pages, we will consider the
range of tests that are appropriate for thorough testing of ferrite
transformer designs and we begin with a review of the components present
in a common transformer.
Schematic of a simple two winding transformer connected
to the four wire Kelvin nodes of an AT series transformer tester.
From the schematic in figure 1, it can be seen that even
the most simple of transformers includes quite a complex combination of
resistive and reactive components. In order to establish with confidence
that a transformer has been manufactured correctly, it is necessary to
execute a range of tests that combine to provide an assurance that the
materials used and manufacturing process executed results in transformers
that meet the design specification.