Ilk - Leakage Current Test - Voltech AT5600 User Manual

C H A P T E R 1 4 - A T
14.6.36.
A leakage current test is needed for transformers used in certain applications,
mainly medical, where it is an additional safety requirement.
The leakage current to be measured is that which flows between primary
windings and secondary windings under normal operating conditions due to
interwinding capacitance. In a switching power supply, the primary circuits could
be connected directly to the power line supply, and could experience the normal
line voltage as a common signal with respect to ground. This AC signal could
cause a significant leakage current to flow through the transformer to grounded
secondaries.
This test is typically carried out by applying the test voltage between all the primary
terminals shorted together and all the secondary terminals and screen shorted
together.
On selecting "ILK Leakage Current" from the 'available tests' window, the
following dialog box is displayed:
To program the test:
1. Enter the value of voltage for the signal and the required frequency of the
test.
2. Select the integration time required. 'Medium' is the default setting. 'Long'
will give more stable readings (for tighter limits) at the expense of an
increased test time, and 'Short' will test at the maximum speed, but may
give a slightly noisier reading. See 7.3 Explanation of Integration.
3. Select the terminals to be included for both high and low terminals. For
both high and low terminals, select each terminal in turn and click on the
'Add' button at the bottom of the list. Terminals can be removed from the
used list by selecting them and clicking on the 'Remove' button.
4. Select the current limit. There is only a maximum limit for this test.
The Measure button may be used here as outlined in section 14.5.9,
however in most cases the current limit will be determined by the safety
standard to which you are working.
5. Select 'OK'. The test specification will then be displayed in the program
window.
AT5600 User Manual 98-119 issue 14
E D I T O R
ILK – Leakage Current Test
Page 364