M
AVTMTTR25 Rev C April 2008
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TTR25 Functional Test
A customer may want to make sure that the test set is functioning properly before
testing a transformer. Traditionally, for the transformer turns ratio testers, a
customer performed this test by connecting H1-X1 and H2-X2 test leads. The 1:1
turns ratio was expected to be measured. Additionally, the displayed test results
were interpreted as a test set calibration check.
TTR25 test set is designed and optimized for the transformer turns ratio testing. It
uses a mixed analog-digital technique to provide the accurate readings of the
tested transformer turns ratio. The test set measurement approach is based on
high impedance input and output transformer voltage monitoring circuits. The
high impedance of the monitoring circuits is optimized for the accurate
transformer turns ratio testing.
When performing a TTR25 functional test, the H and X test leads interconnect
the input and output monitoring circuits without a transformer being connected.
Such connection cause an impedance mismatch and, as a result of the
mismatch, the displayed turns ratio reading is not exactly 1:1 as it may be
expected. A customer should be aware that a functional test is not a real
transformer turns ratio test. Due to the intrinsic and inevitable impedance
mismatching, the TTR25 functional test readings may be from 0.9980 to 1.0020.
The TTR25 functional test readings do not represent the TTR25 calibration. It
simply shows that the TTR25 test set circuitry functions properly. To check the
TTR25 calibration, a customer should use the Calibration Standards mentioned
in the Calibration section of the manual.
To perform a TTR25 functional test proceed as follows:
1. Turn TTR25 power on (green button on a keypad).
2. Connect H1 lead to X1 lead, and H2 lead to X2 lead.
3. After self-test is complete and start test screen appears, press
◊
to start
testing.
NOTE:
This is not a 1:1 ratio calibration check
due to different
impedances between the instrument's H-side circuitry
and X-side circuitry.
F
WARNING
Keep the leads, which are energized, clear of ground
and personnel.
4. Turn ratio reading on the test results screen should be from +0.9980 to
+1.0020.
