TRANSFORMER TESTS VOLTECH AT3600 USER MANUAL
PAGE 7.1.60. VPN 98 - 024 TESTS AND TEST CONDITIONS
1.36. VOC - OPEN CIRCUIT VOLTAGE
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.
Open circuit voltage measurements are the preferred tests for line frequency
transformers, designed to operate over the full extent of the B-H curve, including the
non-linear regions.
(For other transformers, such as pulse transformers and those used in switched mode
power supplies, a measurement of turns ratio is the preferred test.)
Clearly an open circuit voltage test cannot tell you the actual number of turns on a
winding, only the ratio between one winding and the next. You should therefore also
include a magnetising current test in your program, to give confidence that the
absolute number of turns is correct as well as the ratio.
MEASUREMENT CONDITIONS
Open circuit voltage is measured by applying an ac test voltage to a selected winding
(usually a primary winding), and measuring the resulting voltage produced on another
winding.
If, there are several windings to be tested, the program will execute more quickly if
the following points are observed:
Place all the open circuit voltage (VOC) tests consecutively at the same point in the
program.
Use the same energised winding, with the same test voltage and frequency for each
test.
If there is a magnetising current (MAGI) test which has the same energised winding
and the same test voltage and frequency, place this immediately before the first open
circuit voltage test.
SPECIFYING THE TEST LIMITS
The AT3600 offers you three ways to specify the test limits:
Using a normal AC (rms) measurement.
Using a rectified (mean) measurement.
Using a DC (mean) measurement.
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