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 124
7.18. C2 – Capacitance Match
Where Used
The interwinding capacitance match test calculates the ratio between two
capacitance measurements on two groups of windings. It is measured by
applying a specified AC voltage between two separate windings and the voltage
across and current flow between the two windings is measured to obtain a
complex impedance. This is performed to the two groups in turn.
This test is suitable for switched mode power supply, audio and
telecommunication transformers. It checks that the windings are installed in the
correct positions on the bobbin.
Measurement Conditions
When calculating the capacitance match, the tester performs 2 capacitance
measurements. Firstly, the tester applies an AC voltage between first group of
windings to be tested, usually with all taps on each winding shorted together. It
then measures the voltage between the windings, and the resulting current using
harmonic analysis. Dividing the voltage by the current gives the inter-winding
impedance, from which the capacitance may be calculated. This is then repeated
for the second winding group. The capacitance match is the ratio of first to second
winding group capacitances.
The test voltage can be in the range of 1mV to 5V at a frequency of 20Hz to
3MHz.
The table below gives the recommended test conditions for different values of
average capacitance:
Table 7
Average Capacitance
(Geometric Mean) Preferred test signal
Frequency Voltage
1pF
10pF
100pF
1nF
10nF
→
→
→
→
→
10pF
100pF
1nF
10nF
100nF 100KHz
100KHz
10KHz
1KHz
100Hz 5V
5V
5V
5V
5V
The Test Conditions for Capacitance Match Measurement
When choosing the test conditions, the following potential problems should be
considered: