Voltech AT5600, Руководство пользователя

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C H A P T E R 7 – T E S T S A N D T E S T C O N D I T I O N S
AT5600 User Manual 98-119 issue 14
Page 117
7.14. TRL - Turns Ratio by Inductance
Where Used
The AT5600 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 energizing 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
To do this you will need to know the inductance of the primary and secondary
windings.
The optimum test conditions are chosen for an inductance
value that is between the primary and secondary (
L
m
).
Look up the recommended test signal for this inductance.
Enter the recommended frequency for this inductance as the test frequency.
Where:
L
m
= Intermediate inductance
L
p
= Primary inductance
L
s
= Secondary inductance
V
p
= Primary voltage
V
s
= Secondary voltage
V
m
= Intermediate voltage
N
p
= Primary turns
N
s
= Secondary turns
s p m
L L L

=