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TESTS AND TEST CONDITIONS
Choosing Test Limits
The limits may be entered as:
1.
A nominal value together with a percentage tolerance (%)
Enter the nominal Primary to Secondary ratio, together with the
limits as positive and negative percentage values.
2.
An absolute number of turns (#)
When limits are set as +/- an absolute number of turns, the tester
converts these limits to the % type in the following way:
= +/-
(Pri Limit +
(Pri Turns
Sec Limit ) x 100%
Sec Turns )
(You can see the exact result of this conversion by clicking on %
limits in the Editor dialogue once the absolute, #, limits have bee
entered.)
For example, take a typical Switched Mode Power Supply
transformer with windings in the ratio of 200:10.
Typically, a prior measurement of inductance will have confirmed
the correct number of primary turns have been fitted with the correct
cores. Setting absolute limits of 0 on the primary and 1 on the
secondary will result in limits of:
Nominal Ratio: 200/10
=20
Ratio + 1 sec turn
=18.18
Ratio –1 sec turn
= 22.22
Limits calculated by tester = (0/200 + 1/10) x 100%= +/- 10%
The equivalent ratio limits used by tester are:
Upper limit = 22. Lower Limit = 18
VOLTECH ATI USER MANUAL
PAGE 7-61