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 104
7.8. LSB or LPB-Inductance with Bias Current (Series
or Parallel Circuit)
Where Used
With the LSB and LPB tests, the AT5600 offers two further ways to confirm that
the transformer has been assembled properly, with the appropriate number of
turns, the right grade of magnetic material for the core, and the correct air gap if
required.
These tests would normally be used for transformers designed to be used in
applications where a large DC current is flowing through one or more of the
windings.
Measurement Conditions
To measure inductance with bias, the tester firstly applies the programmed bias
current to the winding under test. When this has stabilized, it then applies an AC
voltage across the selected winding and measures the voltage across and the
current through the winding using harmonic analysis. The measured voltage is
divided by the harmonic current to obtain the complex impedance and the
inductance is calculated.
The bias current can be programmed in the range 10mA to 1000mA. The (AC)
test signal can have a frequency between 20Hz and 3MHz, and amplitude from
1mV to 5V.
Usually, the signal frequency and voltage are chosen so that, with the expected
inductance, the resulting signal current is less than 20% of the bias current.
Recommended test signals generally would be the same as given in Section
7.7.2 Table 2, for the normal inductance test. However, if the recommended
levels correspond to too high a signal current, then use a corresponding smaller
test voltage.
It is not normally recommended that the test frequency be increased to reduce the
signal current, as this may lead to other problems, such as those caused by
parasitic inductance and capacitance of the test fixture, and the self-resonant
frequency of the transformer itself.
Please also see
14.6.5 for specific advice on programming the test, and
10.2.14 for test accuracy specification