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AVTMMTO3xx Rev 3 Sept 2013
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19. The software will not automatically start testing as a safety precaution. A two step
process is required to energize the test specimen.
20. Additionally, Instrument (Test) Setup can be quickly accessed from this screen in the
event you want to check/change any settings before starting a test.
21. Prev Test – Gives the user the ability to go back only one step in a sequence of steps
that are run. This function will primarily be used during OLTC tap changer
operation.
22. Start – Manual Start of Test, Button will change status as test sequence continues.
23. Next Test – Gives the user the ability to skip forward one step in a sequence of steps
that are run.
24. Exit – Before and After testing, the user has the ability to exit the software without
saving data.
25. MESSAGE WINDOW – Grey area under the function buttons. This window will
constantly flash YELLOW defining the state of the machine as it is operating.
26. High Voltage Winding Resistance – display area for all information measured on the
high voltage side of the transformer.
27. Low Voltage Winding Resistance – display area for all information measured on the
low voltage side of the transformer.
28. Basic sequence of events for a test cycle
a. Start – manual start of test.
b. Charging – Unit drives the winding with voltage and current until the set
current level is reached.
c. Calibration – Once the unit is charged and stable, the unit will perform and
internal calibration to correct for any temperature and offset errors
associated with the hardware at the time of test.
d. Measuring Resistance – The unit will run continuously measuring resistance
and updating the screen. The current and resistance readings are undated
approximately once per second.
i. The stability reading is displayed giving the user an understanding
of how well the transformer resistance readings have stabilized.
100% is an excellent stability reading. After the stability reading
has met the Stability valid value for the stability time period, the
background of the value will turn green.
ii. There are two reasons stability readings may be low. The first is
the software starts the stability value at zero so the user must wait
for a specific amount of time, time for stable reading to assure
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