VOLTECH AT3600 USER MANUAL TRANSFORMER TESTS
TESTS AND TEST CONDITIONS VPN 98 - 024 PAGE 7.1.23.
1.12. TRL - TURNS RATIO BY INDUCTANCE
WHERE USED
The AT3600 offers two basic alternative ways to confirm that the transformer has
been assembled properly, with the appropriate number of primary and secondary
turns.
Turns ratio is the preferred test for signal, pulse and switched mode power
transformers, where the normal operating conditions require only small excursions of
the B-H curve, never extending beyond the linear regions.
Where the magnetic coupling between the primary and secondary is poor, it is
preferable to measure the turns ratio by inductance. This test measures the
inductance of both the primary and secondary and calculates the turns ratio from
these measured values.
(For line frequency transformers, designed to operate over the full extent of the B-H
curve, including the non-linear regions, the preferred method is to use an open -
circuit voltage test to check for the correct number of turns on each winding.)
Clearly a turns ratio test cannot tell you the actual number of turns on a winding, only
the ratio between one winding and the next. You should therefore have at least one
inductance test in your program to give confidence that the absolute number of turns
is correct as well as the ratio.
MEASUREMENT CONDITIONS
The inductance of a winding can often depend upon the flux density in the
core/windings. Since during measurement, the flux density will depend upon the
signal energising the winding, it is important that both windings are energized at the
same level. This will ensure that both inductances are measured along the same
region of the B/H curve of the core, to give a true ratio.
SETTING THE TEST PARAMETERS
The simplest method of setting the test parameters is to use the ‘Measure’ button, to
do this you have to program the test from a computer which is connected to the
Auxiliary port of the tester. There are two other methods of inputting the test
parameters, one is to set the primary voltage and frequency and let the editor set the
secondary voltage, and the second is to set both voltages manually.
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