TRANSFORMER TESTS VOLTECH AT3600 USER MANUAL
PAGE 7.1.64. VPN 98 - 024 TESTS AND TEST CONDITIONS
1.38. LVOC – LOW VOLTAGE OPEN CIRCUIT
Measurement
Range
Test
Voltage
Test
Frequency
Basic
Accuracy
100µV to 650V
1mV to 5V 20Hz to 3MHz 0.1%
Where used
The low voltage open circuit test is used to confirm that windings have the correct
ratio of turns between them, and that the phasing of the windings is correct. This test
is used 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 region. On the AT3600 only, a high voltage open circuit test is
available for testing line frequency transformers at their operating point (up to 270V,
1kHz and 2A). See also the test TR – turns ratio.
Measurement conditions
To measure low voltage open circuit, the test signal is applied to one winding called
the energized winding. The voltages across another winding (or the same, energized
winding) is measured. The low voltage open circuit measurement is the rms value of
the voltage measured and can be an ac or a dc voltage.
It is recommended that you choose the winding with the highest number of turns as
the one to be energised.
Choosing test conditions
The recommended test conditions depend on the inductance of the energised winding;
they are given in the table below assuming that the energised winding is the one with
the highest number of turns:
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