3.6 Testing Audio Transformers
This transformer is designed for microphone matching, with the outputs
either series or parallel connected to match impedances. The transformer
is terminated with flying leads.
The fixture program allows the test program, and all the test results, to
refer to the transformer terminal names, in this case the colour of the
flying leads.
Recommended measurements for audio transformers
Test
|
Why?
|
| Winding Resistance |
To ensure correct wire size has been used
and that wire has not been over tensioned
during winding. Checks connection to
fixture. |
| Inductance, Q Factor |
Checks for correct primary turns and
proper core assembly. Confirms that the
core is of the correct material and that no
winding shorts have occurred during
winding or assembly. |
| Turns Ratio and Phasing |
Checks that all windings have correct turns
and polarity. |
| Interwinding Capacitance |
Checks that windings have been properly
layered with correct tape thickness
between windings. |
| Leakage Inductance |
Checks that the windings have been
correctly positioned on the bobbin. |
| Insulation Resistance |
Checks insulation e.g. between
secondaries or primary to secondary for
test voltages <850Vdc. |
Note: This Audio transformer has a high permeability iron core.
Inductance is the first test so that inductance is not influenced by any
magnetization of the core that may occur due to resistance tests.